Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Design and Experiment of Assistive Mechanism for Adjustment of Transrectal Ultrasound Probe

Design and Experiment of Assistive Mechanism for Adjustment of Transrectal Ultrasound Probe Hindawi Applied Bionics and Biomechanics Volume 2020, Article ID 8846073, 13 pages https://doi.org/10.1155/2020/8846073 Research Article Design and Experiment of Assistive Mechanism for Adjustment of Transrectal Ultrasound Probe 1,2 1 1,2 1 1 Jin-Gang Jiang , Hui Zuo, Yong-De Zhang, Zhi-Yuan Huang, Xiao-Wei Guo, and Yong Xu Key Laboratory of Advanced Manufacturing and Intelligent Technology, Ministry of Education, Harbin University of Science and Technology, Harbin 150080, China Robotics & its Engineering Research Center, Harbin University of Science and Technology, Harbin 150080, China Urinary Surgery, The General Hospital of Chinese People’s Liberation Army, Beijing 100039, China Correspondence should be addressed to Jin-Gang Jiang; jiangjingang@hrbust.edu.cn Received 2 April 2020; Revised 9 September 2020; Accepted 3 October 2020; Published 15 October 2020 Academic Editor: Wei Wei Copyright © 2020 Jin-Gang Jiang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Transrectal ultrasound prostate biopsy is the most commonly used method for the diagnosis of prostate cancer. During the operation, the doctor needs to manually adjust the ultrasound probe for repeated adjustments, which is difficult to ensure the efficiency, accuracy, and safety of the operation. This paper presents a passive posture adjusting mechanism of transrectal ultrasound probe. The overall mechanism has 7 degrees of freedom, consisting of a position adjustment module, a posture adjustment module, and an ultrasonic probe rotation and feed module. In order to achieve the centering function, the posture adjustment module is designed based on the double parallelogram. Centering performance is verified based on SimMechanics, and remote center point error of physical prototypes is evaluated. The maximum error of the azimuth remote center point motion and the maximum error of the remote center point motion of the ultrasonic probe are 4 mm and 3.4 mm, respectively, which are less than the anus that can withstand 6 mm. Meanwhile, the analysis of measurement error shows that the random error correlation is weak in different directions, the systematic error confidence intervals of azimuth and elevation angle are less than 2.5 mm, and the maximum relative fixed point error and the maximum relative standard error are 14.73% and 14.98%, respectively. The simulation and testing results have shown the effectiveness and reliability of the propose mechanism. 1. Introduction biopsy. An ultrasound probe is utilized to probe the patient’s rectum and puncture the prostate under ultrasound-guided Nowadays, people are paying attention to their own health guidance when the operation is performed. However, this problems as the significant improvement in people’s living surgery still has the following problems: the entire procedure standards. The American Cancer Society counts the top ten requires the doctor to operate with an ultrasound probe, and cancers with the highest cancer incidence in the United States it is necessary to repeatedly adjust the ultrasound probe, in 2017. Prostate cancer ranks first among all high-risk which may cause fatigue and mood swings; the ultrasound cancers among men, accounting for about one-fifth of the probe needs to be inserted into the patient’s rectum, which total number of male cancer patients; thus, it will cause great will cause damage to the anus when adjusting the posture pain to male patients. At the same time, the mortality rate of of the probe; this surgical procedure requires the cooperation prostate cancer is increasing at a rate of 2% per year and of multiple nurses, resulting in wastage of personnel. More- over, the number of prostate patients is growing, and the showing a trend of rejuvenation [1, 2]. The most critical means of curing prostate cancer is early diagnosis [3–8]. existing medical staff is not enough to complete such a large In the clinic, the most common method for early diagno- workload, and the traditional hand-held method is difficult sis of prostate cancer is transrectal ultrasound prostate to ensure the precision of the puncture intervention because 2 Applied Bionics and Biomechanics and two auxiliary drive legs. The motion-constrained leg is of the special location of the prostate. Therefore, it is neces- sary to study medical devices that assist doctors in prostate designed as a 3RP mechanism, which can realize the rota- scans and biopsy gun puncture interventions. tional motion and axial translational motion of the surgical instrument about the rotation axis [23]. In recent years, minimally invasive interventional robot- ics has gradually become one of the hotspots in the medical From the research status, it can be found that the existing field, and this technology has attracted the attention of RCM can meet the surgical requirements. However, the lack researchers. In 2007, Yan Yu of Thomas Jefferson University of work concerning on a single-bar parallelogram mecha- in the United States developed a prostate seed implantation nism, a crank slider mechanism, or a triangular mechanism is partly due to complicated structure, poor stability, and treatment system based on ultrasound image navigation [9–11], which can automatically or manually use the rota- large space occupation. tion operation to obtain ultrasound images of lesion points. This paper is aimed at studying the ultrasonic probe posi- The American Engineering Research Center and Johns tion and posture adjustment mechanism with centering Hopkins University have jointly developed a robotic system function and passive. The range of motion of the ultrasonic probe, the operable space of the mechanism, and the design that includes ultrasound image navigation and TPS to enable free movement and attitude adjustment of the biopsy needle criteria were obtained accordingly to analyze the surgical in a vertical plane [12, 13]. An ultrasound imaging-guided procedure of prostate biopsy. The mechanism is divided into prostate interventional robot was designed by Kim et al., in functions, and the degree of freedom of each module is which 2-DOF is able to be manually adjusted for posture allocated reasonably according to the design criteria. Next, each module of the mechanism is designed and, a three- adjustment, and two degrees of freedom are used to adjust the movement and rotation of the ultrasound probe [14]. dimensional model of the overall mechanism is drawn. This Vitrani et al. of the University of Pittsburgh designed an study is focused on designing the posture adjustment module artificially operated prostate biopsy probe holder, and its with centering function in design phase. The D-H method is structural is similar to a 6-DOF series manipulator, which utilized to establish the coordinate system of the mechanism, and the joint parameters are obtained. Combined with the uses ultrasound transrectal puncture for good stiffness and stability [15]. The Institute of Intelligent Machines of Harbin simulation results, the positioning error of the remote center University of Science and Technology has designed the point and the analysis of error in the actual surgical operation were tested and analyzed in the experimental part. structure of an all-round prostate robot. This error of each axis of the system is kept within 0.05 mm through experi- The transrectal ultrasound probe position-adjusting RCM will complement a large gap in the passive prostate- ments, which has high repeat positioning accuracy and meet the surgical requirements [16–18]. assisted interventional mechanism in the field of prostate At present, the active prostate interventional robot has intervention. The designed RCM can not only enable doctors to truly liberate their hands during the operation, but also been extensively studied; however, it is difficult to promote and apply because of its complicated system, high cost, and achieve the level of planning and industrialization, improve the efficiency and precision of prostate interventional long training time [19]. In contrast, passive prostate- assisted interventional mechanism has relatively simple surgery, and a more practical motivation for this study is to structure, a short design cycle, low cost, and is easier to promote the development of prostate cancer medicine. promote and apply than active mechanism. The key technology of the passive prostate-assisted inter- 2. Methods ventional mechanism is the centering motion of the transrec- tal ultrasound probe, and the remote center mechanism 2.1. Analysis of Functional Requirements of Adjustment (RCM) can realize the centering motion of the ultrasound Mechanism. Transrectal prostate biopsy is an effective means probe, so that the doctor’s hands are truly liberated. The con- of diagnosing prostate cancer. When the operation is per- cept of the RCM was first proposed by Taylor et al. at Johns formed, the doctor uses an ultrasound probe to probe the Hopkins University in 1995. The designed azimuth rotation patient’s rectum and puncture the prostate under the guid- center and the pitch angle rotation center intersect at the ance of ultrasound images. remote center point, and the posture of the puncture needle can be arbitrarily adjusted in 2-DOF, and the purpose of 2.1.1. Motion Analysis of Ultrasonic Probe. The prostate, adjusting the distal center position is achieved by the expan- which closes to the rectal wall, is located in the abdomen of sion and contraction of the link [20]. The American Com- the rectum. The upper end of the prostatic body has a trans- puter Surgery Systems Research Center and Johns Hopkins verse diameter of about 40 mm, a vertical diameter of about University have developed a renal puncture robot that is able 30 mm, and anteroposterior diameter of about 25 mm. After to be installed on a surgical bed. In this robot, a single-bar filling with water, the volume increases by 25%. The cavity parallelogram RCM mechanism is used to complete the cen- rectal ultrasound probe is invaded through the anus. During tering rotation function during the operation [21]. Jilin Uni- the guided puncture, the rectal ultrasound probe needs to versity developed a mirror arm of a new type of surgical robot perform position adjustment, azimuth adjustment, pitch based on RCM. This RCM uses the crank slider to realize the adjustment, rotation, and feed to achieve multiangle omnidi- centering function of the actuator [22]. Kuo and Dai rectional scanning of the prostate. The rectal anatomy is designed a decoupling RCM based on a parallel arm. The shown in Figure 1. We found that the ampulla space inside mechanism includes a fixed base, a motion restraining leg, the rectum is relatively wide; however, the anal internal Applied Bionics and Biomechanics 3 15-17 cm 11-13 cm 5-6 cm 2.5-3 cm 0 design of the ultrasonic probe posture adjustment mecha- nism needs to be considered as following below criteria: (1) Continuous Motion: The mechanism should continu- ously move, which can drive the ultrasonic probe to smoothly reach the required spatial position and posture (2) Reliable Locking: In order to the safety and position- ing accuracy of the operation, the mechanism needs to be securely locked when the ultrasonic probe Rectum Internal External Anal moves to a proper posture ampulla sphincter sphincter canal (3) The positioning mechanism and the posture adjust- Figure 1: Rectum anatomy graph. ment mechanism are not interfere with each other and are completely decoupled (4) The working range is able to cover all prostate areas Urethra without blind spots Pubic (5) The structure is simple and reliable, and the Bladder manufacturing is easy obtained Prostate Seminal Puncture frame 2.2. Design of Position and Posture of Adjustment vesicle Mechanism. In order to meet the needs of different scanning Biopsy gun Rectum range of prostate tissue by ultrasound probe during opera- Range tion, the position adjustment function, posture adjustment function, rotation, and feed function of the ultrasonic probe should be realized. The 3-DOF spatial positioning mecha- Rotation center Ultrasound probe nism, 2-DOF posture adjustment mechanism, and 2-DOF Figure 2: Motion scope of ultrasonic probe. ultrasonic probe rotation and feed mechanism are adopted. The motion relationship between the three mechanisms is completely decoupled. The transrectal ultrasound probe sphincter is muscle and its space is narrow, and the position position and posture adjustment mechanism are composed is fixed. of a position adjustment module, a posture adjustment mod- The ultrasound probe pass through the anal canal to ule, an ultrasonic probe rotation, and a feed module and a reach the ampulla of the rectum, and the ultrasound probe bottom clamping device. From the perspective of degree of contacts with the internal sphincter of the anus at the anal freedom, this adjustment mechanism is a 7-DOF robot. Joint canal. Therefore, the ultrasound probe should always swing 7 is only a moving joint, and the other joints are rotating with the center of the anus peripheral as the center of rotation joints in the mechanism. The joints 1 to 4 constitute a position to avoid damage to the rectum and increase the patient’s pain adjustment module; joint 5 and joint 6 constitute a posture when scanning the prostate. Figure 2 shows that the resulting adjustment module; joint 7 is utilized to realize the penetration range of motion is a conical space. movement of the ultrasonic probe along the peripheral center of the anus, and the joint 8 is utilized to realize the rotation of 2.1.2. Analysis of Mechanism Operational Space. During the the ultrasonic probe around its own axis. Figure 4 shows sche- prostate biopsy operation, the patient adopts the left lateral matic diagram of each module of the adjustment mechanism. position. In order to prevent the ultrasound probe from The centering function is implemented by the posture interfering with the bed during adjustment, the patient keeps adjustment module. We need to consider the centering effect knee-shouldered and the buttocks are positioned the bed- and the implementation of the centering function; therefore, side. The posture of the patient is shown in Figure 3. The the design of posture adjustment module is focused in design ° ° longitudinal axis of the trunk is 30 ~45 to the edge of the phase. bed, the angle between the thigh and the edge of the bed is Due to the size and weight of the posture adjustment ° ° 45 ~60 , and the distance between the prostate and the bed module affect the size of the position adjustment module, is 150~250 mm. The anus is able to be exposed according the specific structural size of the posture adjustment module to the position of left knee flexing. Furthermore, it is conve- is calculated in this section. For the posture adjustment mod- nient for the ultrasound probe to be invaded from the ule, the 2-DOF structure is chosen. In order to make the rectum. ultrasound probe move in two directions around the center of the anus, an RCM mechanism is considered. The posture 2.1.3. Design Guidelines of Position and Posture Adjustment adjustment module adopts an RCM mechanism based on Mechanism. According to the surgical characteristics of double parallelograms, and its schematic diagram is shown in Figure 5. Double parallelograms are ▱ADCF and ▱BCIJ. transrectal ultrasound probe prostate biopsy surgery, the 2.5-3 cm 4 Applied Bionics and Biomechanics Trunk longitudinal axis 150~250mm Thigh Bed surface Operable Red edge space Figure 3: Operational space. Joint 4 Joint 5 Joint 1 Joint 3 Joint 2 Joint 7 Joint 6 Joint 8 DOF simplified diagram Partial enlarged detail Forearm Posture adjustment mechanism Main arm linkage Bearing Patient Joint 1 Surgery table Disc spring Joint 4 Bearing Forearm shaft Locating ring Column Position adjustment module Transverse linkage Ultrasound Rotary Fixed Polished Installation Column Forearm probe cylinder ring pole block Connecting set Stopper Tension spring Manually Clamping tightened disc Connecting bolt seat Bracket Vertical linkage Manually Probe rotation and feed module tightened Surgery table installation platform Hand tighten bolt Rotating ring Rubber clamping block bolt Bottom clamping device Ultrasonic probe rotation and feed module Posture adjustment module Figure 4: Schematic diagram of the position adjustment mechanism of the transrectal ultrasound probe and each module structure diagram. When the doctor performs the operation, the fixed point In order to conveniently describe the characteristics of the mechanism, a local coordinate system is established in H is always at the center point of the anus, and the AD rod is Figure 5. When the link DF swings the angle α around the vertically above the patient’s ankle. The length DH must be point D, the double parallelogram mechanism has the follow- greater than half the width of the patient’s ankle to prevent ing characteristics: the posture adjustment module from interfering with the patient’s body. According to the size of the human body, (1) Parallel Characteristics: AD//BI//CJ and AC//DF//IJ the width of the crotch is generally 300 mm~420 mm, so the length of DH needs to satisfy the equation: (2) Centering Characteristics: The position of the inter- section H of the AD extension line and the JI exten- l > 210mm: ð1Þ sion line is always unchanged DH 60 Applied Bionics and Biomechanics 5 Fixed end Vertical section Prostate Z Lateral link AE Transverse section Vertical link Anal Probe rotation and peripheral feed module Probe front center point mounting platform initial position Figure 5: Schematic diagram of posture adjustment module. We choosel = 220mm and l = 30mm, and then, the DH AD Unit: mm length of the longitudinal link is as follows: Figure 6: Analysis of swing angle of ultrasonic probe. l = 250mm: ð2Þ BI β OM 28 tan ≥ = , The size of the vertical plane of the anus peripheral center 2 OH 88 ð6Þ point is 120 mm away from the buttocks. In order to prevent γ PK 25 the longitudinal link BI from interfering with the patient’s tan ≥ = : 2 HK 60 body, the length HI needs to satisfy the equation: ∘ ∘ l > 120mm ð3Þ Solving result is β ≥ 35:4 , γ ≥ 45:3 . HI 2.3. Simulation Analysis of the Motion Performance of Taking into account the ultrasonic probe rotation and the Adjustment Mechanism. The principle design of the ultra- size occupied by the feed module, we choose l = 200mm, DI sonic probe position and posture adjustment mechanism l = 30mm, the length of the transverse link is: IJ determines the overall configuration of the mechanism, so that the designed mechanism is able to meet the working requirements, which meet the scanning range of the ultra- l = 230mm ð4Þ AC sound probe during the operation to completely cover every part of the prostate. Therefore, it is necessary to utilize kine- According to the physiological characteristics of the matics to analyze the mechanism to solve the motion space of human body, the space occupied by the prostate is generally the mechanism and the centering effect when the ultrasonic 40 mm × 30 mm × 25 mm, and Figure 6 shows the spatial probe finishes the adjustment of posture. state of the prostate in the left lateral position and the spatial analysis of the angle of the ultrasound probe scanning the 2.3.1. Coordinate System Establishment and Joint Parameters. prostate. The azimuth angle β is the swing angle of the ultra- According to the structure of the ultrasonic probe position sonic probe in the transverse section, and the pitch angle γ is and posture adjustment mechanism, a schematic diagram the swing angle of the ultrasonic probe in the longitudinal of the mechanism is established, as shown in Figure 7. This section. Due to the distance HK from the peripheral center mechanism is a six-bar linkage consisting of two parallelo- point H of the anus to the surface of the prostate is 60 mm, grams because of the posture adjustment module is not a the volume of the prostate is increased by 25% after filling simple open-loop kinematic chain. with water, and the volume of the prostate is 50 mm × 40 In this mechanism, the rod 6 and the rod 7 are, respec- mm × 40 mm when calculating the swing angle of the ultra- tively, the probe rotation and feed module mounting plat- sonic probe. form and the feeding platform, and the rod 8 is an Therefore, PK = 25mm, MK = NK = 40mm, OM = OK ultrasonic probe. The coordinate system origin o of the pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 rod 6 is established at the remote center point based on the = 1/2MN = 1/2 MK + NK = 28mm, analysis of the mechanism characteristics. The coordinate system origin o of the rod 7 is established at the end of the OH = HK + OK = 88mm: ð5Þ feed platform, and the coordinate system origin o of the rod 8 is established at the end of the ultrasonic probe, and In order for the ultrasound probe to cover the entire area the directions of the x -axis and the x -axis are along the 6 7 of the prostate, the beta and gamma angles should satisfy the ultrasonic probe axis x . Therefore, the system is regarded following equation: as a simple open-loop kinematic chain to discuss and 40 gan3 6 Applied Bionics and Biomechanics Rod 3 Rod 4 Rod 5 a a 3 4 Rod 1 4 1 𝜃 𝜃 X 2 3 Y 5 Rod 2 7 Rod 7 Rod 6 Rod 0 O X 0 0 Figure 7: The kinematics coordinate system. Table 1: D-H parameters of manipulator. Rod i 12 3 45 6 7 8 a ( ) 0 29.5 200 29.5 250 300 a 190 i−1 α ( ) 0 -90 0 90 0 90 0 i−1 d (mm) 445 0 0 0 0 0 0 0 θ θ −θ θ θ θ θ ( ) 00 1 2 2 4 5 6 Joint sub Joint 2 drive F F1 f(x)=0 World F drive Revolute11 gan2_xia F2 A1 Revolute10 F B F2 F1 Arm F1 F F F B F drive F1 q B F F1 B F Transform Column Revolute1 gan1 q Conn1 Revolute8 gan2_shang Revolute9 gan4 Conn1 F2 Azimuth angle B B Conn3 F F1 F F1 F F F device F1 Conn2 q q Conn4 gan5_liban Revolute7 Revolute2 Brake Conn5 Conn1 Pitch angle Subsystem device F1-probe handheld Conn1 F1 F2-probe end Probe feed F2 device B F1 Tantouliankuai F F Conn1 q F2 Conn1 Conn1 Prismatic Tantou joint xyz x1y1z1 Figure 8: SimMechanics model of ultrasonic probe position adjustment mechanism. Table 2: Posture simulation parameters of ultrasonic probe at research; furthermore, the D-H method is utilized to solve 0 mm, 30 mm, and 60 mm feeding. the kinematics of the mechanism. ° ° ° ° ° ° θ ( ) θ ( ) θ ( ) θ ( ) θ ( ) α ( ) The base coordinate system is o x y z , and d , a , a , a , 1 2 4 5 6 7 0 0 0 0 1 1 2 3 a , a , and a are the rod lengths of the respective links, and -30 20 80 -20~20 -25~25 0 4 6 7 θ , θ , θ , and θ are the rotation angles of the respective 1 2 3 4 Conn1 Conn1 Applied Bionics and Biomechanics 7 X:381 500 100 Y:2.461 400 Z:210.8 (0,0,0) –100 X:479.2 X:2787 –200 Y:–274.6 Y:–280 Z:324 Z:306.6 –100 (0,0,0) –300 –200 Y –400 0 200 400 600 –400 (a) (b) 500 500 X:287.8 X:324.1 X:471 Y:–268.5 Y:–278 Y:–270.8 Z:342.2 Z:342.9 Z:339.2 X:381 X:324.7 Y:2.461 Y:–307.9 Z:210.8 Z:213.4 X:326.7 X:290.1 X:475.3 Y:–280 0 Y:–272.5 Y:–271.6 (0,0,0) Z:81.05 (0,0,0) Z:85.53 Z:86.61 –100 –100 200 0 –200 –400 0 200 400 600 (c) (d) Figure 9: Posture of ultrasonic probe at 0 mm feeding: (a) three-dimensional map; (b) xoy plane projection; (c) yoz plane projection; and (d) xoz plane projection. rotary joints of the position adjustment mechanism, (2) The rigid body modules respectively represent 13 respectively. movable members of the posture adjustment Due to the rod 2 that constitutes a parallelogram struc- mechanism ture, θ = −θ , θ , θ are the azimuth and pitching angles of 3 2 5 6 (3) The rotary joints respectively represent the move- the RCM mechanism, a is the feed distance of the ultrasonic ment relationship between the members as rotation probe along the x -axis, and α is the rotation angle of the 8 7 ultrasonic probe. According to the designed requirements, (4) The moving joints represent the rotation and the organization has a total of 7 degrees of freedom, and advancement of the ultrasonic probe the joint parameters are shown in Table 1. (5) The movement constraint of the module relative to the posture adjustment module is provided 2.3.2. Simulation of Centering Effect Based on SimMechanics. According to the mechanism diagram and the connecting (6) The drive modules are respectively added to the rod parameters drawn in Figure 7 and Table 1, the physical corresponding joints model of the ultrasonic probe posture adjustment mecha- (7) The sensor modules respectively record the coordi- nism is established in the SimMechanics toolbox, the end nate positions that the end position of the ultrasonic track of the ultrasonic probe is tracked, and we output the probe and the position of reached handheld recorded position coordinates to Workspace for drawing 3D graphics. The posture adjustment module enables the ultrasonic The model established for the ultrasonic probe pose probe to realize the centering function of swinging around adjustment mechanism in the SimMechanics toolbox is a certain point and simulates the centering effect of the ultra- shown in Figure 8. The SimMechanics model mainly sonic probe. Table 2 shows the setting parameters. includes a ground module, 13 rigid body modules, 12 rotary joint modules, 1 moving joint module, 6 drive modules, and 2 sensor modules. 3. Results (1) “World” indicates the position of the base coordinate 3.1. Simulation Results of Centering Effect. The simulation system, which is located on the bottom surface of the results when the feed distance a =0 mm are shown in column Figure 9. The posture adjustment module allows the Z Y 8 Applied Bionics and Biomechanics X:380.7 Y:32.5 100 Z:209 X:381 Y:2.461 (0,0,0) Z:210.8 –100 0 –200 (0,0,0) –100 –300 X:378.5 –200 Y:–273.4 –400 Y Z:283.2 –400 0 100 200 300 400 500 600 (a) (b) 500 500 X:46.39 X:302.4 400 Y:–242.2 Y:–244 Z:331.2 Z:331 X:318 Y:32.1 300 X:320.4 Z:211 Y:–276.4 Z:208.2 X:381 Y:2.461 X:297.1 X:462.9 Z:210.8 Y:–246.8 Y:–246.3 0 Z:98.51 Z:98.61 (0,0,0) (0,0,0) –100 –100 0 100 200 300 400 500 600 200 100 0 –100 –200 –300 –400 (c) (d) Figure 10: Posture of ultrasonic probe at 30 mm feeding: (a) three-dimensional map; (b) xoy plane projection; (c) yoz plane projection; and (d) xoz plane projection. ultrasonic probe to realize the centering function of swinging ing to the remote center point after feeding 30 mm, which around a certain point, and the effectiveness of centering the meets the design requirements. We changed the feed distance ultrasonic probe is simulated. The parameter settings are of the ultrasonic probe to a =60 mm, while leaving the shown in Table 2. parameters of the other joints unchanged, and the posture The simulation results when the feed distance a =0 mm change of the ultrasonic probe was simulated. The simulation are shown in Figure 9. The color line segments in the figure results are shown in Figure 11. It can be seen in the figure that represent the posture of the ultrasonic probe at different joint the coordinates of the intersections of all the line segments angles. The position coordinates of the remote center point intersecting in space remain at (381.000, 2.461, and of the mechanism are (381.000, 2.461, and 210.800) when 210.800). This means that the azimuth and pitching angles ° ° ° θ = −30 , θ =20 , and θ =80 . The scanning end of the of the ultrasonic probe remain changed according to the 1 2 4 ultrasonic probe is always at the remote center point of the remote center point after feeding 60 mm, which also meets mechanism, and a cone-shaped space with the point as a the design requirements. vertex is formed when the azimuth and pitching angles are The results of the simulation of the ultrasonic probe at adjusted according to a given angle. feed rates of 0 mm, 30 mm, and 60 mm, respectively, showed The omnidirectional scan of the prostate can be com- that the ultrasonic probe can achieve a very stable centering pleted when the doctor inserts the ultrasound probe into effect at different feed rates and can be used for surgery. the rectum and adjusts the azimuth, pitching angle, and the angle of rotation of the ultrasound probe. The joint parame- 3.2. Experiment Results of Centering Effect ters of the position adjustment module and the posture adjustment module are not changed in order to observe the 3.2.1. Physical Prototype of the Posture Adjustment change in the posture after the ultrasonic probe is fed. The Mechanism of Ultrasonic Probe. Many interference factors feed distance of the ultrasonic probe was changed to a =30 exist because the mechanism is operated during the actual operation. This experimental section describes the simula- mm. The simulation results obtained are shown in Figure 10. Measurements showed that the coordinates of this point tion of the actual surgical environment and operation pro- remained at (381.000, 2.461, and 210.800). The ultrasonic cess. The range and continuity of each joint, reliable locking probe still changed the azimuth and pitching angles accord- ability, position adjustment mechanism working space and Z Y Applied Bionics and Biomechanics 9 X:378 Y:59.33 Z:228.3 X:381 Y:2.461 (0,0,0) Z:210.8 –100 –200 (0,0,0) X:374.9 –100 600 –300 200 Y:–246.6 0 Z:266.3 –200 200 –400 0 –400 100 200 300 400 500 600 (a) (b) 500 500 X:457.2 400 X:381 X:306.3 Y:–216.3 Y:–218.3 Y:2.461 Z:317.5 Z:210.8 Z:314.8 X:360.6 300 300 Y:58.66 Z:20.5 X:319.3 Y:–245.4 Z:213.8 X:302.8 X:456.8 Y:–219 Y:–219.3 Z:110.2 Z:109.5a (0,0,0) (0,0,0) –100 –100 200 100 0 –100 –200 –300 –400 100 200 300 400 500 600 (c) (d) Figure 11: Posture of ultrasonic probe at 60 mm feeding: (a) three-dimensional map; (b) xoy plane projection; (c) yoz plane projection; and (d) xoz plane projection. Transrectal The RCM performance comprises the displacement ultrasound probe range of the remote center point of the mechanism in the posture adjustment mechanism space when the ultrasonic probe performs posture adjust- ment. The RCM performance can be evaluated by measuring the error between the spatial fixed point and the remote cen- ter marked point under the existing experimental conditions. Patient A fixed point in space measures only the error of the remote center point in the two-dimensional (2D) plane because the position change of the remote center point is 3D in space. Therefore, in this section, we describe two sets of experi- Figure 12: Physical prototype of the posture adjustment ments performed to measure the error, which is caused by mechanism of ultrasonic probe. changing the azimuth or pitching angle, separately. positioning ability, mechanism static stiffness, RCM posture (1) Azimuth Remote Center Point Motion Error Measure- adjustment, and centering motion performance were tested ° ° ° ° ° ment. The azimuth angles θ (-40 , -20 ,0 ,20 , and 40 ) were to verify the rationality of these mechanisms. Figure 12 shows adjusted under different feed rates a (0 mm, 30 mm, and the physical prototype of the mechanism. 60 mm). The mechanism was adjusted to a certain position, 3.2.2. Remote Center Point Error Measurement. The doctor and then, the joints of the position adjustment mechanism adjusts the azimuth and pitching angle of the ultrasound were locked. The pitch angle of the ultrasonic probe was θ ° ° probe to omnidirectionally scan the prostate. To ensure the =0 , and the rotation angle of the ultrasonic probe α =0 . safety of the operation and reduce the damage caused to the Because the azimuth is adjusted to the angle change in the patient by the ultrasonic probe, the ultrasonic probe needs horizontal plane, the wooden board with the coordinate to achieve a centering motion around the center of the anus. paper was fixed directly below the ultrasonic probe (the scale Therefore, it was necessary to test the RCM of the posture of the coordinate paper was 1 mm), and then, the position of adjustment module to examine whether it meets the surgical the remote center point was marked on the ultrasonic probe; requirements. a laser was used to illuminate the remote center point as a Z Y 10 Applied Bionics and Biomechanics Fixed spatial point Fixed spatial point (a) (b) Figure 13: Measurement of azimuth remote center point error: (a) overall view; (b) partial magnification view. 18 Because the azimuth is adjusted to the angle change in the vertical plane, the wooden board with the coordinate paper was fixed directly below the ultrasonic probe (the scale of the coordinate paper was 1 mm), and then, the position of the remote center point was marked on the ultrasonic probe; a laser was used to illuminate the remote center point as a 13 fixed spatial point. Finally, the position of the fixed spatial point was marked on the coordinate paper. Figure 15 shows the experimental process. The obtained experimental data are shown in Figure 16. The measurement of the points marked on the coordi- 8 nate paper showed that the distance between the subsequent remote center points and the fixed spatial point is less than 3.4 mm, and the deformation of the anus is about 6 mm. Therefore, the accuracy of the remote center point meets 0 12 3 4 5 6 7 89 10 11 12 13 14 15 16 17 18 the surgical requirements under the change in the pitch X (mm) angle. a = 0 mm a = 60 mm 6 6 a = 30 mm Fixed point 4. Discussion Figure 14: Remote center point error under the motion of azimuth angle. The positioning error of the remote center point is related to the entire mechanism and is composed mainly of systematic error and random error. fixed spatial point. Finally, the position of the fixed spatial The systematic error is composed of multiple error fac- point was marked on the coordinate paper. Figure 13 shows tors with deterministic changes [24–26]. Therefore, we used experimental process. the measured mean and variance to consider the systematic error, and, in order to avoid the error estimation bias caused The experimental data were obtained by means of multi- by the small number of sample repetitions, the confidence ple measurements. The experimental results are shown in interval was used to state the systematic error limit. Then, Figure 14. The points marked on the coordinate paper were we defined the safety factor ask and ½x − k s, x + k s as the 1 1 1 enlarged and measured. The distance between the subse- confidence interval forμ, whereμis the mean, s is the mea- quent remote center point and the fixed spatial point is less surement variance, andxis the unbiased estimator ofμ.In than 4 mm, and the deformation of the anus is about 6 mm. addition, in order to determine the relative error, the relative Therefore, the accuracy of the remote center point under fixed point error and the relative standard deviation (RSD) the azimuth angle meets the surgical requirements. were used as the evaluation indexes in each direction. The relative fixed point errorε is the error of the measured mean (2) Pitch Angle Remote Center Point Motion Error Measure- 0 ° ° ° ° ° value with respect to the fixed point. It takes the relative error ment. The pitch angles θ (-24 , -12 ,0 ,12 , and 24 ) were of the x-axis coordinates as an example, which is expressed as adjusted under different feed rates a (0 mm, 30 mm, and 60 mm). The mechanism was adjusted to a certain position, and then, the joints of the position adjustment mechanism x − x jj were locked. The pitch angle of the ultrasonic probe was θ ε = × 100%, ð7Þ ° ° =0 , and the rotation angle of the ultrasonic probe α =0 . 0 Y (mm) Applied Bionics and Biomechanics 11 Fixed spatial point Fixed spatial point (a) (b) Figure 15: Measurement of pitching center point error: (a) overall view; (b) partial magnification view. ∑ x − x y − y ðÞðÞ i=1 i i r = qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi : ð9Þ n n 2 2 ∑ ðÞ x − x ∑ ðÞ y − y i=1 i i=1 According to the theory of the above error analysis, the 10 confidence interval was taken as 90%, and the measured mean value, relative fixed point error, relative standard error, confidence interval, and 2D variable relative parameters were calculated. The azimuth error calculation results are shown in Table 3. As shown in Table 3, for the same probe feed distance, the width of the confidence interval between the x direction and the y direction is close, and both are stable at approxi- mately 2.3 mm, indicating that the positioning performance 01 2 3 45 6 7 8 9 10 11 12 13 14 15 16 17 18 is relatively stable. The relative fixed point error and RSD X (mm) in different feed directions are basically stable in the x direc- a = 60 mm a = 0 mm 6 tion, and the relative fixed point error is larger in the y direc- a = 30 mm Fixed point tion, except in the case of the 0 mm feed distance. However, for the remaining feed distances, the error remains stable Figure 16: Remote center point error under the motion of pitching below 15%, and the error can be controlled within 1.8 mm. angle. The relative error parameters of the x and y directions under different feed distances are relatively low, indicating that the where x = ∑ x /n, andx is the x-axis coordinate value of the i=1 i 0 correlation between the two parameters is not strong. It is fixed point. proved that the measurement value in the y direction cannot The RSD can be used to verify the precision of the be determined by measuring the x direction. The results measurement results: show that the azimuth centering performance is stable, and the accuracy meets the requirements. Similarly, an error analysis of the remote center point measurement data was RSD = × 100%: ð8Þ performed. The analysis results are shown in Table 4. 5. Conclusions Most random errors follow a normal distribution. To reflect the spatial relationship of random stochastic processes This study is aimed at designing a passive ultrasound probe in different spatial locations, the value of the random error position and posture adjustment mechanism to assist doctors parameters ranged from -1 to 1 [27, 28]. The x and y direc- performing prostate scans and puncture interventions. In tion and the x and z directions of the azimuth and pitching this paper, the forward kinematics analysis of the mecha- angles were used as the positioning quality indicators as nism, the simulation of the centering effect, the development two sets of 2D random variables. The correlation coefficient of the physical prototype, and related experimental research between 2D variables is defined as were presented. The main findings are as follows. Y (mm) 12 Applied Bionics and Biomechanics Table 3: Analysis result of azimuth angle of remote center point error. x direction y direction Probe feed x and y directional random error Confidence Confidence distance/mm μ (mm) ε relative parameter (%) RSD (%) μ (mm) ε (%) RSD (%) 0 0 interval interval 0 8.30 7.78 14.40 (7.15, 9.44) 13.26 10.50 7.50 [12.30, 14.21] 0.342 30 8.40 6.67 12.80 (7.36, 9.43) 11.86 1.16 14.41 (11.22, 13.49) 0.758 60 9.54 6.00 12.50 (8.38, 10.69) 12.30 2.50 10.50 (11.05, 13.54) 0.840 Table 4: Analysis result of pitching angle of remote center point error. x direction z direction Probe feed x and z directional random error Confidence Confidence distance/mm μ (mm) ε (%) RSD (%) μ (mm) ε (%) RSD (%) relative parameter 0 0 interval interval 0 8.72 14.73 12.97 (7.56, 9.95) 9.58 8.76 11.69 (8.50, 10.65) 0.741 30 7.46 1.84 14.98 (6.45, 8.46) 10.20 2.85 11.56 (9.16, 11.23) -0.873 60 7.30 3.94 7.80 (6.75, 8.84) 8.90 15.23 9.10 (8.12, 10.67) 0.108 (1) The moving shape of the ultrasonic probe is the con- Conflicts of Interest ical space around the center of rotation of the anus. Authors declare that there is no conflict of interest. The design requirements are determined by analyz- ing the surgical procedure; the posture adjustment module is designed such that the double parallel Acknowledgments quadrilateral RCM mechanism allows the ultrasonic probe to achieve the centering function This research was supported by the National Natural Science Foundation of China (Grant No. 51675142), the Fundamen- (2) SimMechanics was used to simulate the effectiveness tal Research Foundation for Universities of Heilongjiang of centering the ultrasonic probe when adjusting the Province (Grant No. LGYC2018JQ016), the Key Project of posture under different feed distances. The study the Natural Science Foundation of Heilongjiang Province results showed that the ultrasonic probe is centered (No. ZD2018013), and the University Nursing Program for and stable, which verifies that the position adjustment Young Scholars with Creative Talents in Heilongjiang of the ultrasonic probe meets the design requirements Province (Grant No. UNPYSCT-2017082). (3) A physical prototype was developed and debugged. The effectiveness of the centering of the remote cen- References ter point was measured when adjusting the posture of the ultrasonic probe, and the displacement range [1] R. L. Siegel, K. D. Miller, and A. Jemal, “Cancer statistics, of the remote center point in space was obtained. 2020,” Ca A Cancer Journal for Clinicians, vol. 70, no. 1, The experimental results show that the maximum pp. 7–30, 2020. error of the azimuth remote center point motion [2] K. A. Cronin, A. J. Lake, S. Scott et al., “Annual Report to the and the maximum error of the remote center point Nation on the Status of Cancer, part I: National cancer statis- motion of the ultrasonic probe are 4 mm and tics,” Cancer, vol. 124, no. 13, pp. 2785–2800, 2018. 3.4 mm, respectively, that is, less than a 6 mm anus [3] Z. F. Ma, “How to find prostate cancer early,” Health Guide, can withstand. The random error correlation in dif- vol. 21, no. 2, pp. 14-15, 2015. ferent directions is weak, the systematic error confi- [4] C. H. Pernar, E. M. Ebot, K. M. Wilson, and L. A. Mucci, “The dence intervals of the azimuth and elevation angle epidemiology of prostate cancer,” Cold Spring Harbor Perspec- are less than 2.5 mm, and the maximum relative fixed tives in Medicine, vol. 8, no. 12, p. a030361, 2018. point error and the maximum relative standard error [5] K. J. Harrington, C. Spitzweg, A. R. Bateman, J. C. Morris, and are 14.73% and 14.98%, respectively R. G. Vile, “Gene therapy for prostate cancer: current status and future prospects,” Journal of Urology, vol. 166, no. 4, The system meets the surgical requirements of a pas- pp. 1220–1233, 2001. sive medical mechanism to be applied in actual surgical [6] M. M. Pomerantz, M. L. Freedman, and P. W. Kantoff, procedures. “Genetic determinants of prostate cancer risk,” BJU Interna- tional, vol. 100, no. 2, pp. 241–243, 2018. [7] D. D. Sjoberg, A. J. Vickers, M. Assel et al., “Twenty-year risk Data Availability of prostate cancer death by midlife prostate-specific antigen and a panel of four kallikrein markers in a large population- The data used to support the findings of this study are based cohort of healthy men,” European Urology, vol. 73, available from the corresponding author upon request. no. 6, pp. 941–948, 2018. Applied Bionics and Biomechanics 13 [24] M. Yi, X. J. Zou, L. F. Luo et al., “Error analysis of dynamic [8] J. Jiang, Z. Min, Y. Zhang, X. Guo, and Y. Xu, “Design and performance evaluation of passive interlocking posture adjust- localization tests based on binocular stereo vision on litchi ment mechanism for transrectal ultrasound probe,” Journal of harvesting manipulator,” Transactions of the Chinese Society Mechanics in Medicine and Biology, vol. 19, no. 7, article of Agricultural Engineering (Transactions of the CSAE), vol. 32, no. 5, pp. 50–56, 2016. 1940035, 2019. [9] K. G. Yan, T. Podder, Y. Yu, T.-I. Liu, C. W. S. Cheng, and [25] H. Wei and C. Cheng, “The error analysis of the localization W. S. Ng, “Flexible needle-tissue interaction modeling with result caused by the installation errors of a seabed array of depth-varying mean parameter: preliminary study,” IEEE magnetometers,” in 2016 IEEE Chinese Guidance, Navigation Transactions on Biomedical Engineering, vol. 56, no. 2, and Control Conference (CGNCC), pp. 16–19, Nanjing, China, pp. 255–262, 2009. 2017. [10] Y. Yu, T. K. Podder, Y. D. Zhang et al., “Robotic system for [26] Y. Cheng, S. Yin, X. Wang, L. An, and H. Liu, “Design and prostate brachytherapy,” Brachytherapy, vol. 7, no. 6, analysis of double-side meshing and dual-phase driving timing pp. 100-101, 2010. silent chain system,” Strojniski Vestnik - Journal of Mechanical Engineering, vol. 62, no. 2, pp. 127–136, 2016. [11] Y. Yu, T. Podder, Y. Zhang et al., “Robot-assisted prostate brachytherapy,” in International Conference on Medical Image [27] M. Pola and P. Bezoušek, “Pseudorange error analysis for Computing & Computer-assisted Intervention, pp. 41–49, precise indoor positioning system,” Journal of Electrical Copenhagen, Denmark, 2006. Engineering, vol. 68, no. 3, pp. 206–211, 2017. [12] M. A. Meltsner, N. J. Ferrier, and B. R. Thomadsen, “Observa- [28] J. Chang, A. Delaigle, P. Hall, and C. Y. Tang, “A frequency tions on rotating needle insertions using a brachytherapy domain analysis of the error distribution from noisy high- robot,” Physics in Medicine & Biology, vol. 52, no. 19, frequency data,” Biometrika, vol. 105, no. 2, pp. 353–369, 2018. pp. 6027–6037, 2007. [13] G. Fichtinger, J. P. Fiene, C. W. Kennedy et al., “Robotic assis- tance for ultrasound-guided prostate brachytherapy,” Medical Image Analysis, vol. 12, no. 5, pp. 535–545, 2008. [14] C. Kim, F. Schäfer, D. Chang, and D. Petrisor, “Robot for ultrasound-guided prostate imaging and intervention,” in 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems, pp. 943–948, San Francisco, CA, USA, 2011. [15] M.-A. Vitrani, M. Baumann, D. Reversat, G. Morel, A. Moreau-Gaudry, and P. Mozer, “Prostate biopsies assisted by comanipulated probe-holder: first in man,” International Journal of Computer Assisted Radiology and Surgery, vol. 11, no. 6, pp. 1153–1161, 2016. [16] J. Y. Li, Design on Control System of Five Degrees of Freedom Prostate Biopsy Robot, Harbin University of Science and Tech- nology, 2013. [17] Y. D. Zhang, J. C. Peng, Z. Liu, J. G. Jiang, and Y. J. Zhao, “Research on the segmentation method of prostate magnetic resonance image based on level set,” Chinese Journal of Scientific Instrument, vol. 38, no. 2, pp. 416–424, 2017. [18] Y. D. Zhang, W. X. Zhang, Y. Liang, and Y. Xu, “Research on mechanism and strategy of high accuracy puncture of prostate,” Chinese Journal of Scientific Instrument, vol. 38, no. 6, pp. 1405–1412, 2017. [19] M. E. Karar, “A simulation study of adaptive force controller for medical robotic liver ultrasound guidance,” Arabian Jour- nal for Science and Engineering, vol. 43, no. 8, pp. 4229– 4238, 2018. [20] R. H. Taylor, J. Funda, B. Eldridge et al., “A telerobotic assis- tant for laparoscopic surgery,” IEEE Engineering in Medicine and Biology Magazine, vol. 14, no. 3, pp. 279–288, 1993. [21] E. M. Boctor, R. J. Webster III, H. Mathieu, A. M. Okamura, and G. Fichtinger, “Virtual remote center of motion control for needle placement robots,” Computer Aided Surgery, vol. 9, no. 5, pp. 175–183, 2010. [22] G. Y. Dong, The Design and Research of the Robot Arm for Celiac Minimally Invasive Surgery, Jil-in University, 2016. [23] C. H. Kuo and J. S. Dai, “Kinematics of a fully-decoupled remote center-of-motion parallel manipulator for minimally invasive surgery,” Journal of Medical Devices, vol. 6, no. 2, pp. 211–214, 2012. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Applied Bionics and Biomechanics Hindawi Publishing Corporation

Design and Experiment of Assistive Mechanism for Adjustment of Transrectal Ultrasound Probe

Loading next page...
 
/lp/hindawi-publishing-corporation/design-and-experiment-of-assistive-mechanism-for-adjustment-of-BfLFXri5x0
Publisher
Hindawi Publishing Corporation
Copyright
Copyright © 2020 Jin-Gang Jiang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ISSN
1176-2322
eISSN
1754-2103
DOI
10.1155/2020/8846073
Publisher site
See Article on Publisher Site

Abstract

Hindawi Applied Bionics and Biomechanics Volume 2020, Article ID 8846073, 13 pages https://doi.org/10.1155/2020/8846073 Research Article Design and Experiment of Assistive Mechanism for Adjustment of Transrectal Ultrasound Probe 1,2 1 1,2 1 1 Jin-Gang Jiang , Hui Zuo, Yong-De Zhang, Zhi-Yuan Huang, Xiao-Wei Guo, and Yong Xu Key Laboratory of Advanced Manufacturing and Intelligent Technology, Ministry of Education, Harbin University of Science and Technology, Harbin 150080, China Robotics & its Engineering Research Center, Harbin University of Science and Technology, Harbin 150080, China Urinary Surgery, The General Hospital of Chinese People’s Liberation Army, Beijing 100039, China Correspondence should be addressed to Jin-Gang Jiang; jiangjingang@hrbust.edu.cn Received 2 April 2020; Revised 9 September 2020; Accepted 3 October 2020; Published 15 October 2020 Academic Editor: Wei Wei Copyright © 2020 Jin-Gang Jiang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Transrectal ultrasound prostate biopsy is the most commonly used method for the diagnosis of prostate cancer. During the operation, the doctor needs to manually adjust the ultrasound probe for repeated adjustments, which is difficult to ensure the efficiency, accuracy, and safety of the operation. This paper presents a passive posture adjusting mechanism of transrectal ultrasound probe. The overall mechanism has 7 degrees of freedom, consisting of a position adjustment module, a posture adjustment module, and an ultrasonic probe rotation and feed module. In order to achieve the centering function, the posture adjustment module is designed based on the double parallelogram. Centering performance is verified based on SimMechanics, and remote center point error of physical prototypes is evaluated. The maximum error of the azimuth remote center point motion and the maximum error of the remote center point motion of the ultrasonic probe are 4 mm and 3.4 mm, respectively, which are less than the anus that can withstand 6 mm. Meanwhile, the analysis of measurement error shows that the random error correlation is weak in different directions, the systematic error confidence intervals of azimuth and elevation angle are less than 2.5 mm, and the maximum relative fixed point error and the maximum relative standard error are 14.73% and 14.98%, respectively. The simulation and testing results have shown the effectiveness and reliability of the propose mechanism. 1. Introduction biopsy. An ultrasound probe is utilized to probe the patient’s rectum and puncture the prostate under ultrasound-guided Nowadays, people are paying attention to their own health guidance when the operation is performed. However, this problems as the significant improvement in people’s living surgery still has the following problems: the entire procedure standards. The American Cancer Society counts the top ten requires the doctor to operate with an ultrasound probe, and cancers with the highest cancer incidence in the United States it is necessary to repeatedly adjust the ultrasound probe, in 2017. Prostate cancer ranks first among all high-risk which may cause fatigue and mood swings; the ultrasound cancers among men, accounting for about one-fifth of the probe needs to be inserted into the patient’s rectum, which total number of male cancer patients; thus, it will cause great will cause damage to the anus when adjusting the posture pain to male patients. At the same time, the mortality rate of of the probe; this surgical procedure requires the cooperation prostate cancer is increasing at a rate of 2% per year and of multiple nurses, resulting in wastage of personnel. More- over, the number of prostate patients is growing, and the showing a trend of rejuvenation [1, 2]. The most critical means of curing prostate cancer is early diagnosis [3–8]. existing medical staff is not enough to complete such a large In the clinic, the most common method for early diagno- workload, and the traditional hand-held method is difficult sis of prostate cancer is transrectal ultrasound prostate to ensure the precision of the puncture intervention because 2 Applied Bionics and Biomechanics and two auxiliary drive legs. The motion-constrained leg is of the special location of the prostate. Therefore, it is neces- sary to study medical devices that assist doctors in prostate designed as a 3RP mechanism, which can realize the rota- scans and biopsy gun puncture interventions. tional motion and axial translational motion of the surgical instrument about the rotation axis [23]. In recent years, minimally invasive interventional robot- ics has gradually become one of the hotspots in the medical From the research status, it can be found that the existing field, and this technology has attracted the attention of RCM can meet the surgical requirements. However, the lack researchers. In 2007, Yan Yu of Thomas Jefferson University of work concerning on a single-bar parallelogram mecha- in the United States developed a prostate seed implantation nism, a crank slider mechanism, or a triangular mechanism is partly due to complicated structure, poor stability, and treatment system based on ultrasound image navigation [9–11], which can automatically or manually use the rota- large space occupation. tion operation to obtain ultrasound images of lesion points. This paper is aimed at studying the ultrasonic probe posi- The American Engineering Research Center and Johns tion and posture adjustment mechanism with centering Hopkins University have jointly developed a robotic system function and passive. The range of motion of the ultrasonic probe, the operable space of the mechanism, and the design that includes ultrasound image navigation and TPS to enable free movement and attitude adjustment of the biopsy needle criteria were obtained accordingly to analyze the surgical in a vertical plane [12, 13]. An ultrasound imaging-guided procedure of prostate biopsy. The mechanism is divided into prostate interventional robot was designed by Kim et al., in functions, and the degree of freedom of each module is which 2-DOF is able to be manually adjusted for posture allocated reasonably according to the design criteria. Next, each module of the mechanism is designed and, a three- adjustment, and two degrees of freedom are used to adjust the movement and rotation of the ultrasound probe [14]. dimensional model of the overall mechanism is drawn. This Vitrani et al. of the University of Pittsburgh designed an study is focused on designing the posture adjustment module artificially operated prostate biopsy probe holder, and its with centering function in design phase. The D-H method is structural is similar to a 6-DOF series manipulator, which utilized to establish the coordinate system of the mechanism, and the joint parameters are obtained. Combined with the uses ultrasound transrectal puncture for good stiffness and stability [15]. The Institute of Intelligent Machines of Harbin simulation results, the positioning error of the remote center University of Science and Technology has designed the point and the analysis of error in the actual surgical operation were tested and analyzed in the experimental part. structure of an all-round prostate robot. This error of each axis of the system is kept within 0.05 mm through experi- The transrectal ultrasound probe position-adjusting RCM will complement a large gap in the passive prostate- ments, which has high repeat positioning accuracy and meet the surgical requirements [16–18]. assisted interventional mechanism in the field of prostate At present, the active prostate interventional robot has intervention. The designed RCM can not only enable doctors to truly liberate their hands during the operation, but also been extensively studied; however, it is difficult to promote and apply because of its complicated system, high cost, and achieve the level of planning and industrialization, improve the efficiency and precision of prostate interventional long training time [19]. In contrast, passive prostate- assisted interventional mechanism has relatively simple surgery, and a more practical motivation for this study is to structure, a short design cycle, low cost, and is easier to promote the development of prostate cancer medicine. promote and apply than active mechanism. The key technology of the passive prostate-assisted inter- 2. Methods ventional mechanism is the centering motion of the transrec- tal ultrasound probe, and the remote center mechanism 2.1. Analysis of Functional Requirements of Adjustment (RCM) can realize the centering motion of the ultrasound Mechanism. Transrectal prostate biopsy is an effective means probe, so that the doctor’s hands are truly liberated. The con- of diagnosing prostate cancer. When the operation is per- cept of the RCM was first proposed by Taylor et al. at Johns formed, the doctor uses an ultrasound probe to probe the Hopkins University in 1995. The designed azimuth rotation patient’s rectum and puncture the prostate under the guid- center and the pitch angle rotation center intersect at the ance of ultrasound images. remote center point, and the posture of the puncture needle can be arbitrarily adjusted in 2-DOF, and the purpose of 2.1.1. Motion Analysis of Ultrasonic Probe. The prostate, adjusting the distal center position is achieved by the expan- which closes to the rectal wall, is located in the abdomen of sion and contraction of the link [20]. The American Com- the rectum. The upper end of the prostatic body has a trans- puter Surgery Systems Research Center and Johns Hopkins verse diameter of about 40 mm, a vertical diameter of about University have developed a renal puncture robot that is able 30 mm, and anteroposterior diameter of about 25 mm. After to be installed on a surgical bed. In this robot, a single-bar filling with water, the volume increases by 25%. The cavity parallelogram RCM mechanism is used to complete the cen- rectal ultrasound probe is invaded through the anus. During tering rotation function during the operation [21]. Jilin Uni- the guided puncture, the rectal ultrasound probe needs to versity developed a mirror arm of a new type of surgical robot perform position adjustment, azimuth adjustment, pitch based on RCM. This RCM uses the crank slider to realize the adjustment, rotation, and feed to achieve multiangle omnidi- centering function of the actuator [22]. Kuo and Dai rectional scanning of the prostate. The rectal anatomy is designed a decoupling RCM based on a parallel arm. The shown in Figure 1. We found that the ampulla space inside mechanism includes a fixed base, a motion restraining leg, the rectum is relatively wide; however, the anal internal Applied Bionics and Biomechanics 3 15-17 cm 11-13 cm 5-6 cm 2.5-3 cm 0 design of the ultrasonic probe posture adjustment mecha- nism needs to be considered as following below criteria: (1) Continuous Motion: The mechanism should continu- ously move, which can drive the ultrasonic probe to smoothly reach the required spatial position and posture (2) Reliable Locking: In order to the safety and position- ing accuracy of the operation, the mechanism needs to be securely locked when the ultrasonic probe Rectum Internal External Anal moves to a proper posture ampulla sphincter sphincter canal (3) The positioning mechanism and the posture adjust- Figure 1: Rectum anatomy graph. ment mechanism are not interfere with each other and are completely decoupled (4) The working range is able to cover all prostate areas Urethra without blind spots Pubic (5) The structure is simple and reliable, and the Bladder manufacturing is easy obtained Prostate Seminal Puncture frame 2.2. Design of Position and Posture of Adjustment vesicle Mechanism. In order to meet the needs of different scanning Biopsy gun Rectum range of prostate tissue by ultrasound probe during opera- Range tion, the position adjustment function, posture adjustment function, rotation, and feed function of the ultrasonic probe should be realized. The 3-DOF spatial positioning mecha- Rotation center Ultrasound probe nism, 2-DOF posture adjustment mechanism, and 2-DOF Figure 2: Motion scope of ultrasonic probe. ultrasonic probe rotation and feed mechanism are adopted. The motion relationship between the three mechanisms is completely decoupled. The transrectal ultrasound probe sphincter is muscle and its space is narrow, and the position position and posture adjustment mechanism are composed is fixed. of a position adjustment module, a posture adjustment mod- The ultrasound probe pass through the anal canal to ule, an ultrasonic probe rotation, and a feed module and a reach the ampulla of the rectum, and the ultrasound probe bottom clamping device. From the perspective of degree of contacts with the internal sphincter of the anus at the anal freedom, this adjustment mechanism is a 7-DOF robot. Joint canal. Therefore, the ultrasound probe should always swing 7 is only a moving joint, and the other joints are rotating with the center of the anus peripheral as the center of rotation joints in the mechanism. The joints 1 to 4 constitute a position to avoid damage to the rectum and increase the patient’s pain adjustment module; joint 5 and joint 6 constitute a posture when scanning the prostate. Figure 2 shows that the resulting adjustment module; joint 7 is utilized to realize the penetration range of motion is a conical space. movement of the ultrasonic probe along the peripheral center of the anus, and the joint 8 is utilized to realize the rotation of 2.1.2. Analysis of Mechanism Operational Space. During the the ultrasonic probe around its own axis. Figure 4 shows sche- prostate biopsy operation, the patient adopts the left lateral matic diagram of each module of the adjustment mechanism. position. In order to prevent the ultrasound probe from The centering function is implemented by the posture interfering with the bed during adjustment, the patient keeps adjustment module. We need to consider the centering effect knee-shouldered and the buttocks are positioned the bed- and the implementation of the centering function; therefore, side. The posture of the patient is shown in Figure 3. The the design of posture adjustment module is focused in design ° ° longitudinal axis of the trunk is 30 ~45 to the edge of the phase. bed, the angle between the thigh and the edge of the bed is Due to the size and weight of the posture adjustment ° ° 45 ~60 , and the distance between the prostate and the bed module affect the size of the position adjustment module, is 150~250 mm. The anus is able to be exposed according the specific structural size of the posture adjustment module to the position of left knee flexing. Furthermore, it is conve- is calculated in this section. For the posture adjustment mod- nient for the ultrasound probe to be invaded from the ule, the 2-DOF structure is chosen. In order to make the rectum. ultrasound probe move in two directions around the center of the anus, an RCM mechanism is considered. The posture 2.1.3. Design Guidelines of Position and Posture Adjustment adjustment module adopts an RCM mechanism based on Mechanism. According to the surgical characteristics of double parallelograms, and its schematic diagram is shown in Figure 5. Double parallelograms are ▱ADCF and ▱BCIJ. transrectal ultrasound probe prostate biopsy surgery, the 2.5-3 cm 4 Applied Bionics and Biomechanics Trunk longitudinal axis 150~250mm Thigh Bed surface Operable Red edge space Figure 3: Operational space. Joint 4 Joint 5 Joint 1 Joint 3 Joint 2 Joint 7 Joint 6 Joint 8 DOF simplified diagram Partial enlarged detail Forearm Posture adjustment mechanism Main arm linkage Bearing Patient Joint 1 Surgery table Disc spring Joint 4 Bearing Forearm shaft Locating ring Column Position adjustment module Transverse linkage Ultrasound Rotary Fixed Polished Installation Column Forearm probe cylinder ring pole block Connecting set Stopper Tension spring Manually Clamping tightened disc Connecting bolt seat Bracket Vertical linkage Manually Probe rotation and feed module tightened Surgery table installation platform Hand tighten bolt Rotating ring Rubber clamping block bolt Bottom clamping device Ultrasonic probe rotation and feed module Posture adjustment module Figure 4: Schematic diagram of the position adjustment mechanism of the transrectal ultrasound probe and each module structure diagram. When the doctor performs the operation, the fixed point In order to conveniently describe the characteristics of the mechanism, a local coordinate system is established in H is always at the center point of the anus, and the AD rod is Figure 5. When the link DF swings the angle α around the vertically above the patient’s ankle. The length DH must be point D, the double parallelogram mechanism has the follow- greater than half the width of the patient’s ankle to prevent ing characteristics: the posture adjustment module from interfering with the patient’s body. According to the size of the human body, (1) Parallel Characteristics: AD//BI//CJ and AC//DF//IJ the width of the crotch is generally 300 mm~420 mm, so the length of DH needs to satisfy the equation: (2) Centering Characteristics: The position of the inter- section H of the AD extension line and the JI exten- l > 210mm: ð1Þ sion line is always unchanged DH 60 Applied Bionics and Biomechanics 5 Fixed end Vertical section Prostate Z Lateral link AE Transverse section Vertical link Anal Probe rotation and peripheral feed module Probe front center point mounting platform initial position Figure 5: Schematic diagram of posture adjustment module. We choosel = 220mm and l = 30mm, and then, the DH AD Unit: mm length of the longitudinal link is as follows: Figure 6: Analysis of swing angle of ultrasonic probe. l = 250mm: ð2Þ BI β OM 28 tan ≥ = , The size of the vertical plane of the anus peripheral center 2 OH 88 ð6Þ point is 120 mm away from the buttocks. In order to prevent γ PK 25 the longitudinal link BI from interfering with the patient’s tan ≥ = : 2 HK 60 body, the length HI needs to satisfy the equation: ∘ ∘ l > 120mm ð3Þ Solving result is β ≥ 35:4 , γ ≥ 45:3 . HI 2.3. Simulation Analysis of the Motion Performance of Taking into account the ultrasonic probe rotation and the Adjustment Mechanism. The principle design of the ultra- size occupied by the feed module, we choose l = 200mm, DI sonic probe position and posture adjustment mechanism l = 30mm, the length of the transverse link is: IJ determines the overall configuration of the mechanism, so that the designed mechanism is able to meet the working requirements, which meet the scanning range of the ultra- l = 230mm ð4Þ AC sound probe during the operation to completely cover every part of the prostate. Therefore, it is necessary to utilize kine- According to the physiological characteristics of the matics to analyze the mechanism to solve the motion space of human body, the space occupied by the prostate is generally the mechanism and the centering effect when the ultrasonic 40 mm × 30 mm × 25 mm, and Figure 6 shows the spatial probe finishes the adjustment of posture. state of the prostate in the left lateral position and the spatial analysis of the angle of the ultrasound probe scanning the 2.3.1. Coordinate System Establishment and Joint Parameters. prostate. The azimuth angle β is the swing angle of the ultra- According to the structure of the ultrasonic probe position sonic probe in the transverse section, and the pitch angle γ is and posture adjustment mechanism, a schematic diagram the swing angle of the ultrasonic probe in the longitudinal of the mechanism is established, as shown in Figure 7. This section. Due to the distance HK from the peripheral center mechanism is a six-bar linkage consisting of two parallelo- point H of the anus to the surface of the prostate is 60 mm, grams because of the posture adjustment module is not a the volume of the prostate is increased by 25% after filling simple open-loop kinematic chain. with water, and the volume of the prostate is 50 mm × 40 In this mechanism, the rod 6 and the rod 7 are, respec- mm × 40 mm when calculating the swing angle of the ultra- tively, the probe rotation and feed module mounting plat- sonic probe. form and the feeding platform, and the rod 8 is an Therefore, PK = 25mm, MK = NK = 40mm, OM = OK ultrasonic probe. The coordinate system origin o of the pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 rod 6 is established at the remote center point based on the = 1/2MN = 1/2 MK + NK = 28mm, analysis of the mechanism characteristics. The coordinate system origin o of the rod 7 is established at the end of the OH = HK + OK = 88mm: ð5Þ feed platform, and the coordinate system origin o of the rod 8 is established at the end of the ultrasonic probe, and In order for the ultrasound probe to cover the entire area the directions of the x -axis and the x -axis are along the 6 7 of the prostate, the beta and gamma angles should satisfy the ultrasonic probe axis x . Therefore, the system is regarded following equation: as a simple open-loop kinematic chain to discuss and 40 gan3 6 Applied Bionics and Biomechanics Rod 3 Rod 4 Rod 5 a a 3 4 Rod 1 4 1 𝜃 𝜃 X 2 3 Y 5 Rod 2 7 Rod 7 Rod 6 Rod 0 O X 0 0 Figure 7: The kinematics coordinate system. Table 1: D-H parameters of manipulator. Rod i 12 3 45 6 7 8 a ( ) 0 29.5 200 29.5 250 300 a 190 i−1 α ( ) 0 -90 0 90 0 90 0 i−1 d (mm) 445 0 0 0 0 0 0 0 θ θ −θ θ θ θ θ ( ) 00 1 2 2 4 5 6 Joint sub Joint 2 drive F F1 f(x)=0 World F drive Revolute11 gan2_xia F2 A1 Revolute10 F B F2 F1 Arm F1 F F F B F drive F1 q B F F1 B F Transform Column Revolute1 gan1 q Conn1 Revolute8 gan2_shang Revolute9 gan4 Conn1 F2 Azimuth angle B B Conn3 F F1 F F1 F F F device F1 Conn2 q q Conn4 gan5_liban Revolute7 Revolute2 Brake Conn5 Conn1 Pitch angle Subsystem device F1-probe handheld Conn1 F1 F2-probe end Probe feed F2 device B F1 Tantouliankuai F F Conn1 q F2 Conn1 Conn1 Prismatic Tantou joint xyz x1y1z1 Figure 8: SimMechanics model of ultrasonic probe position adjustment mechanism. Table 2: Posture simulation parameters of ultrasonic probe at research; furthermore, the D-H method is utilized to solve 0 mm, 30 mm, and 60 mm feeding. the kinematics of the mechanism. ° ° ° ° ° ° θ ( ) θ ( ) θ ( ) θ ( ) θ ( ) α ( ) The base coordinate system is o x y z , and d , a , a , a , 1 2 4 5 6 7 0 0 0 0 1 1 2 3 a , a , and a are the rod lengths of the respective links, and -30 20 80 -20~20 -25~25 0 4 6 7 θ , θ , θ , and θ are the rotation angles of the respective 1 2 3 4 Conn1 Conn1 Applied Bionics and Biomechanics 7 X:381 500 100 Y:2.461 400 Z:210.8 (0,0,0) –100 X:479.2 X:2787 –200 Y:–274.6 Y:–280 Z:324 Z:306.6 –100 (0,0,0) –300 –200 Y –400 0 200 400 600 –400 (a) (b) 500 500 X:287.8 X:324.1 X:471 Y:–268.5 Y:–278 Y:–270.8 Z:342.2 Z:342.9 Z:339.2 X:381 X:324.7 Y:2.461 Y:–307.9 Z:210.8 Z:213.4 X:326.7 X:290.1 X:475.3 Y:–280 0 Y:–272.5 Y:–271.6 (0,0,0) Z:81.05 (0,0,0) Z:85.53 Z:86.61 –100 –100 200 0 –200 –400 0 200 400 600 (c) (d) Figure 9: Posture of ultrasonic probe at 0 mm feeding: (a) three-dimensional map; (b) xoy plane projection; (c) yoz plane projection; and (d) xoz plane projection. rotary joints of the position adjustment mechanism, (2) The rigid body modules respectively represent 13 respectively. movable members of the posture adjustment Due to the rod 2 that constitutes a parallelogram struc- mechanism ture, θ = −θ , θ , θ are the azimuth and pitching angles of 3 2 5 6 (3) The rotary joints respectively represent the move- the RCM mechanism, a is the feed distance of the ultrasonic ment relationship between the members as rotation probe along the x -axis, and α is the rotation angle of the 8 7 ultrasonic probe. According to the designed requirements, (4) The moving joints represent the rotation and the organization has a total of 7 degrees of freedom, and advancement of the ultrasonic probe the joint parameters are shown in Table 1. (5) The movement constraint of the module relative to the posture adjustment module is provided 2.3.2. Simulation of Centering Effect Based on SimMechanics. According to the mechanism diagram and the connecting (6) The drive modules are respectively added to the rod parameters drawn in Figure 7 and Table 1, the physical corresponding joints model of the ultrasonic probe posture adjustment mecha- (7) The sensor modules respectively record the coordi- nism is established in the SimMechanics toolbox, the end nate positions that the end position of the ultrasonic track of the ultrasonic probe is tracked, and we output the probe and the position of reached handheld recorded position coordinates to Workspace for drawing 3D graphics. The posture adjustment module enables the ultrasonic The model established for the ultrasonic probe pose probe to realize the centering function of swinging around adjustment mechanism in the SimMechanics toolbox is a certain point and simulates the centering effect of the ultra- shown in Figure 8. The SimMechanics model mainly sonic probe. Table 2 shows the setting parameters. includes a ground module, 13 rigid body modules, 12 rotary joint modules, 1 moving joint module, 6 drive modules, and 2 sensor modules. 3. Results (1) “World” indicates the position of the base coordinate 3.1. Simulation Results of Centering Effect. The simulation system, which is located on the bottom surface of the results when the feed distance a =0 mm are shown in column Figure 9. The posture adjustment module allows the Z Y 8 Applied Bionics and Biomechanics X:380.7 Y:32.5 100 Z:209 X:381 Y:2.461 (0,0,0) Z:210.8 –100 0 –200 (0,0,0) –100 –300 X:378.5 –200 Y:–273.4 –400 Y Z:283.2 –400 0 100 200 300 400 500 600 (a) (b) 500 500 X:46.39 X:302.4 400 Y:–242.2 Y:–244 Z:331.2 Z:331 X:318 Y:32.1 300 X:320.4 Z:211 Y:–276.4 Z:208.2 X:381 Y:2.461 X:297.1 X:462.9 Z:210.8 Y:–246.8 Y:–246.3 0 Z:98.51 Z:98.61 (0,0,0) (0,0,0) –100 –100 0 100 200 300 400 500 600 200 100 0 –100 –200 –300 –400 (c) (d) Figure 10: Posture of ultrasonic probe at 30 mm feeding: (a) three-dimensional map; (b) xoy plane projection; (c) yoz plane projection; and (d) xoz plane projection. ultrasonic probe to realize the centering function of swinging ing to the remote center point after feeding 30 mm, which around a certain point, and the effectiveness of centering the meets the design requirements. We changed the feed distance ultrasonic probe is simulated. The parameter settings are of the ultrasonic probe to a =60 mm, while leaving the shown in Table 2. parameters of the other joints unchanged, and the posture The simulation results when the feed distance a =0 mm change of the ultrasonic probe was simulated. The simulation are shown in Figure 9. The color line segments in the figure results are shown in Figure 11. It can be seen in the figure that represent the posture of the ultrasonic probe at different joint the coordinates of the intersections of all the line segments angles. The position coordinates of the remote center point intersecting in space remain at (381.000, 2.461, and of the mechanism are (381.000, 2.461, and 210.800) when 210.800). This means that the azimuth and pitching angles ° ° ° θ = −30 , θ =20 , and θ =80 . The scanning end of the of the ultrasonic probe remain changed according to the 1 2 4 ultrasonic probe is always at the remote center point of the remote center point after feeding 60 mm, which also meets mechanism, and a cone-shaped space with the point as a the design requirements. vertex is formed when the azimuth and pitching angles are The results of the simulation of the ultrasonic probe at adjusted according to a given angle. feed rates of 0 mm, 30 mm, and 60 mm, respectively, showed The omnidirectional scan of the prostate can be com- that the ultrasonic probe can achieve a very stable centering pleted when the doctor inserts the ultrasound probe into effect at different feed rates and can be used for surgery. the rectum and adjusts the azimuth, pitching angle, and the angle of rotation of the ultrasound probe. The joint parame- 3.2. Experiment Results of Centering Effect ters of the position adjustment module and the posture adjustment module are not changed in order to observe the 3.2.1. Physical Prototype of the Posture Adjustment change in the posture after the ultrasonic probe is fed. The Mechanism of Ultrasonic Probe. Many interference factors feed distance of the ultrasonic probe was changed to a =30 exist because the mechanism is operated during the actual operation. This experimental section describes the simula- mm. The simulation results obtained are shown in Figure 10. Measurements showed that the coordinates of this point tion of the actual surgical environment and operation pro- remained at (381.000, 2.461, and 210.800). The ultrasonic cess. The range and continuity of each joint, reliable locking probe still changed the azimuth and pitching angles accord- ability, position adjustment mechanism working space and Z Y Applied Bionics and Biomechanics 9 X:378 Y:59.33 Z:228.3 X:381 Y:2.461 (0,0,0) Z:210.8 –100 –200 (0,0,0) X:374.9 –100 600 –300 200 Y:–246.6 0 Z:266.3 –200 200 –400 0 –400 100 200 300 400 500 600 (a) (b) 500 500 X:457.2 400 X:381 X:306.3 Y:–216.3 Y:–218.3 Y:2.461 Z:317.5 Z:210.8 Z:314.8 X:360.6 300 300 Y:58.66 Z:20.5 X:319.3 Y:–245.4 Z:213.8 X:302.8 X:456.8 Y:–219 Y:–219.3 Z:110.2 Z:109.5a (0,0,0) (0,0,0) –100 –100 200 100 0 –100 –200 –300 –400 100 200 300 400 500 600 (c) (d) Figure 11: Posture of ultrasonic probe at 60 mm feeding: (a) three-dimensional map; (b) xoy plane projection; (c) yoz plane projection; and (d) xoz plane projection. Transrectal The RCM performance comprises the displacement ultrasound probe range of the remote center point of the mechanism in the posture adjustment mechanism space when the ultrasonic probe performs posture adjust- ment. The RCM performance can be evaluated by measuring the error between the spatial fixed point and the remote cen- ter marked point under the existing experimental conditions. Patient A fixed point in space measures only the error of the remote center point in the two-dimensional (2D) plane because the position change of the remote center point is 3D in space. Therefore, in this section, we describe two sets of experi- Figure 12: Physical prototype of the posture adjustment ments performed to measure the error, which is caused by mechanism of ultrasonic probe. changing the azimuth or pitching angle, separately. positioning ability, mechanism static stiffness, RCM posture (1) Azimuth Remote Center Point Motion Error Measure- adjustment, and centering motion performance were tested ° ° ° ° ° ment. The azimuth angles θ (-40 , -20 ,0 ,20 , and 40 ) were to verify the rationality of these mechanisms. Figure 12 shows adjusted under different feed rates a (0 mm, 30 mm, and the physical prototype of the mechanism. 60 mm). The mechanism was adjusted to a certain position, 3.2.2. Remote Center Point Error Measurement. The doctor and then, the joints of the position adjustment mechanism adjusts the azimuth and pitching angle of the ultrasound were locked. The pitch angle of the ultrasonic probe was θ ° ° probe to omnidirectionally scan the prostate. To ensure the =0 , and the rotation angle of the ultrasonic probe α =0 . safety of the operation and reduce the damage caused to the Because the azimuth is adjusted to the angle change in the patient by the ultrasonic probe, the ultrasonic probe needs horizontal plane, the wooden board with the coordinate to achieve a centering motion around the center of the anus. paper was fixed directly below the ultrasonic probe (the scale Therefore, it was necessary to test the RCM of the posture of the coordinate paper was 1 mm), and then, the position of adjustment module to examine whether it meets the surgical the remote center point was marked on the ultrasonic probe; requirements. a laser was used to illuminate the remote center point as a Z Y 10 Applied Bionics and Biomechanics Fixed spatial point Fixed spatial point (a) (b) Figure 13: Measurement of azimuth remote center point error: (a) overall view; (b) partial magnification view. 18 Because the azimuth is adjusted to the angle change in the vertical plane, the wooden board with the coordinate paper was fixed directly below the ultrasonic probe (the scale of the coordinate paper was 1 mm), and then, the position of the remote center point was marked on the ultrasonic probe; a laser was used to illuminate the remote center point as a 13 fixed spatial point. Finally, the position of the fixed spatial point was marked on the coordinate paper. Figure 15 shows the experimental process. The obtained experimental data are shown in Figure 16. The measurement of the points marked on the coordi- 8 nate paper showed that the distance between the subsequent remote center points and the fixed spatial point is less than 3.4 mm, and the deformation of the anus is about 6 mm. Therefore, the accuracy of the remote center point meets 0 12 3 4 5 6 7 89 10 11 12 13 14 15 16 17 18 the surgical requirements under the change in the pitch X (mm) angle. a = 0 mm a = 60 mm 6 6 a = 30 mm Fixed point 4. Discussion Figure 14: Remote center point error under the motion of azimuth angle. The positioning error of the remote center point is related to the entire mechanism and is composed mainly of systematic error and random error. fixed spatial point. Finally, the position of the fixed spatial The systematic error is composed of multiple error fac- point was marked on the coordinate paper. Figure 13 shows tors with deterministic changes [24–26]. Therefore, we used experimental process. the measured mean and variance to consider the systematic error, and, in order to avoid the error estimation bias caused The experimental data were obtained by means of multi- by the small number of sample repetitions, the confidence ple measurements. The experimental results are shown in interval was used to state the systematic error limit. Then, Figure 14. The points marked on the coordinate paper were we defined the safety factor ask and ½x − k s, x + k s as the 1 1 1 enlarged and measured. The distance between the subse- confidence interval forμ, whereμis the mean, s is the mea- quent remote center point and the fixed spatial point is less surement variance, andxis the unbiased estimator ofμ.In than 4 mm, and the deformation of the anus is about 6 mm. addition, in order to determine the relative error, the relative Therefore, the accuracy of the remote center point under fixed point error and the relative standard deviation (RSD) the azimuth angle meets the surgical requirements. were used as the evaluation indexes in each direction. The relative fixed point errorε is the error of the measured mean (2) Pitch Angle Remote Center Point Motion Error Measure- 0 ° ° ° ° ° value with respect to the fixed point. It takes the relative error ment. The pitch angles θ (-24 , -12 ,0 ,12 , and 24 ) were of the x-axis coordinates as an example, which is expressed as adjusted under different feed rates a (0 mm, 30 mm, and 60 mm). The mechanism was adjusted to a certain position, and then, the joints of the position adjustment mechanism x − x jj were locked. The pitch angle of the ultrasonic probe was θ ε = × 100%, ð7Þ ° ° =0 , and the rotation angle of the ultrasonic probe α =0 . 0 Y (mm) Applied Bionics and Biomechanics 11 Fixed spatial point Fixed spatial point (a) (b) Figure 15: Measurement of pitching center point error: (a) overall view; (b) partial magnification view. ∑ x − x y − y ðÞðÞ i=1 i i r = qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi : ð9Þ n n 2 2 ∑ ðÞ x − x ∑ ðÞ y − y i=1 i i=1 According to the theory of the above error analysis, the 10 confidence interval was taken as 90%, and the measured mean value, relative fixed point error, relative standard error, confidence interval, and 2D variable relative parameters were calculated. The azimuth error calculation results are shown in Table 3. As shown in Table 3, for the same probe feed distance, the width of the confidence interval between the x direction and the y direction is close, and both are stable at approxi- mately 2.3 mm, indicating that the positioning performance 01 2 3 45 6 7 8 9 10 11 12 13 14 15 16 17 18 is relatively stable. The relative fixed point error and RSD X (mm) in different feed directions are basically stable in the x direc- a = 60 mm a = 0 mm 6 tion, and the relative fixed point error is larger in the y direc- a = 30 mm Fixed point tion, except in the case of the 0 mm feed distance. However, for the remaining feed distances, the error remains stable Figure 16: Remote center point error under the motion of pitching below 15%, and the error can be controlled within 1.8 mm. angle. The relative error parameters of the x and y directions under different feed distances are relatively low, indicating that the where x = ∑ x /n, andx is the x-axis coordinate value of the i=1 i 0 correlation between the two parameters is not strong. It is fixed point. proved that the measurement value in the y direction cannot The RSD can be used to verify the precision of the be determined by measuring the x direction. The results measurement results: show that the azimuth centering performance is stable, and the accuracy meets the requirements. Similarly, an error analysis of the remote center point measurement data was RSD = × 100%: ð8Þ performed. The analysis results are shown in Table 4. 5. Conclusions Most random errors follow a normal distribution. To reflect the spatial relationship of random stochastic processes This study is aimed at designing a passive ultrasound probe in different spatial locations, the value of the random error position and posture adjustment mechanism to assist doctors parameters ranged from -1 to 1 [27, 28]. The x and y direc- performing prostate scans and puncture interventions. In tion and the x and z directions of the azimuth and pitching this paper, the forward kinematics analysis of the mecha- angles were used as the positioning quality indicators as nism, the simulation of the centering effect, the development two sets of 2D random variables. The correlation coefficient of the physical prototype, and related experimental research between 2D variables is defined as were presented. The main findings are as follows. Y (mm) 12 Applied Bionics and Biomechanics Table 3: Analysis result of azimuth angle of remote center point error. x direction y direction Probe feed x and y directional random error Confidence Confidence distance/mm μ (mm) ε relative parameter (%) RSD (%) μ (mm) ε (%) RSD (%) 0 0 interval interval 0 8.30 7.78 14.40 (7.15, 9.44) 13.26 10.50 7.50 [12.30, 14.21] 0.342 30 8.40 6.67 12.80 (7.36, 9.43) 11.86 1.16 14.41 (11.22, 13.49) 0.758 60 9.54 6.00 12.50 (8.38, 10.69) 12.30 2.50 10.50 (11.05, 13.54) 0.840 Table 4: Analysis result of pitching angle of remote center point error. x direction z direction Probe feed x and z directional random error Confidence Confidence distance/mm μ (mm) ε (%) RSD (%) μ (mm) ε (%) RSD (%) relative parameter 0 0 interval interval 0 8.72 14.73 12.97 (7.56, 9.95) 9.58 8.76 11.69 (8.50, 10.65) 0.741 30 7.46 1.84 14.98 (6.45, 8.46) 10.20 2.85 11.56 (9.16, 11.23) -0.873 60 7.30 3.94 7.80 (6.75, 8.84) 8.90 15.23 9.10 (8.12, 10.67) 0.108 (1) The moving shape of the ultrasonic probe is the con- Conflicts of Interest ical space around the center of rotation of the anus. Authors declare that there is no conflict of interest. The design requirements are determined by analyz- ing the surgical procedure; the posture adjustment module is designed such that the double parallel Acknowledgments quadrilateral RCM mechanism allows the ultrasonic probe to achieve the centering function This research was supported by the National Natural Science Foundation of China (Grant No. 51675142), the Fundamen- (2) SimMechanics was used to simulate the effectiveness tal Research Foundation for Universities of Heilongjiang of centering the ultrasonic probe when adjusting the Province (Grant No. LGYC2018JQ016), the Key Project of posture under different feed distances. The study the Natural Science Foundation of Heilongjiang Province results showed that the ultrasonic probe is centered (No. ZD2018013), and the University Nursing Program for and stable, which verifies that the position adjustment Young Scholars with Creative Talents in Heilongjiang of the ultrasonic probe meets the design requirements Province (Grant No. UNPYSCT-2017082). (3) A physical prototype was developed and debugged. The effectiveness of the centering of the remote cen- References ter point was measured when adjusting the posture of the ultrasonic probe, and the displacement range [1] R. L. Siegel, K. D. Miller, and A. Jemal, “Cancer statistics, of the remote center point in space was obtained. 2020,” Ca A Cancer Journal for Clinicians, vol. 70, no. 1, The experimental results show that the maximum pp. 7–30, 2020. error of the azimuth remote center point motion [2] K. A. Cronin, A. J. Lake, S. Scott et al., “Annual Report to the and the maximum error of the remote center point Nation on the Status of Cancer, part I: National cancer statis- motion of the ultrasonic probe are 4 mm and tics,” Cancer, vol. 124, no. 13, pp. 2785–2800, 2018. 3.4 mm, respectively, that is, less than a 6 mm anus [3] Z. F. Ma, “How to find prostate cancer early,” Health Guide, can withstand. The random error correlation in dif- vol. 21, no. 2, pp. 14-15, 2015. ferent directions is weak, the systematic error confi- [4] C. H. Pernar, E. M. Ebot, K. M. Wilson, and L. A. Mucci, “The dence intervals of the azimuth and elevation angle epidemiology of prostate cancer,” Cold Spring Harbor Perspec- are less than 2.5 mm, and the maximum relative fixed tives in Medicine, vol. 8, no. 12, p. a030361, 2018. point error and the maximum relative standard error [5] K. J. Harrington, C. Spitzweg, A. R. Bateman, J. C. Morris, and are 14.73% and 14.98%, respectively R. G. Vile, “Gene therapy for prostate cancer: current status and future prospects,” Journal of Urology, vol. 166, no. 4, The system meets the surgical requirements of a pas- pp. 1220–1233, 2001. sive medical mechanism to be applied in actual surgical [6] M. M. Pomerantz, M. L. Freedman, and P. W. Kantoff, procedures. “Genetic determinants of prostate cancer risk,” BJU Interna- tional, vol. 100, no. 2, pp. 241–243, 2018. [7] D. D. Sjoberg, A. J. Vickers, M. Assel et al., “Twenty-year risk Data Availability of prostate cancer death by midlife prostate-specific antigen and a panel of four kallikrein markers in a large population- The data used to support the findings of this study are based cohort of healthy men,” European Urology, vol. 73, available from the corresponding author upon request. no. 6, pp. 941–948, 2018. Applied Bionics and Biomechanics 13 [24] M. Yi, X. J. Zou, L. F. Luo et al., “Error analysis of dynamic [8] J. Jiang, Z. Min, Y. Zhang, X. Guo, and Y. Xu, “Design and performance evaluation of passive interlocking posture adjust- localization tests based on binocular stereo vision on litchi ment mechanism for transrectal ultrasound probe,” Journal of harvesting manipulator,” Transactions of the Chinese Society Mechanics in Medicine and Biology, vol. 19, no. 7, article of Agricultural Engineering (Transactions of the CSAE), vol. 32, no. 5, pp. 50–56, 2016. 1940035, 2019. [9] K. G. Yan, T. Podder, Y. Yu, T.-I. Liu, C. W. S. Cheng, and [25] H. Wei and C. Cheng, “The error analysis of the localization W. S. Ng, “Flexible needle-tissue interaction modeling with result caused by the installation errors of a seabed array of depth-varying mean parameter: preliminary study,” IEEE magnetometers,” in 2016 IEEE Chinese Guidance, Navigation Transactions on Biomedical Engineering, vol. 56, no. 2, and Control Conference (CGNCC), pp. 16–19, Nanjing, China, pp. 255–262, 2009. 2017. [10] Y. Yu, T. K. Podder, Y. D. Zhang et al., “Robotic system for [26] Y. Cheng, S. Yin, X. Wang, L. An, and H. Liu, “Design and prostate brachytherapy,” Brachytherapy, vol. 7, no. 6, analysis of double-side meshing and dual-phase driving timing pp. 100-101, 2010. silent chain system,” Strojniski Vestnik - Journal of Mechanical Engineering, vol. 62, no. 2, pp. 127–136, 2016. [11] Y. Yu, T. Podder, Y. Zhang et al., “Robot-assisted prostate brachytherapy,” in International Conference on Medical Image [27] M. Pola and P. Bezoušek, “Pseudorange error analysis for Computing & Computer-assisted Intervention, pp. 41–49, precise indoor positioning system,” Journal of Electrical Copenhagen, Denmark, 2006. Engineering, vol. 68, no. 3, pp. 206–211, 2017. [12] M. A. Meltsner, N. J. Ferrier, and B. R. Thomadsen, “Observa- [28] J. Chang, A. Delaigle, P. Hall, and C. Y. Tang, “A frequency tions on rotating needle insertions using a brachytherapy domain analysis of the error distribution from noisy high- robot,” Physics in Medicine & Biology, vol. 52, no. 19, frequency data,” Biometrika, vol. 105, no. 2, pp. 353–369, 2018. pp. 6027–6037, 2007. [13] G. Fichtinger, J. P. Fiene, C. W. Kennedy et al., “Robotic assis- tance for ultrasound-guided prostate brachytherapy,” Medical Image Analysis, vol. 12, no. 5, pp. 535–545, 2008. [14] C. Kim, F. Schäfer, D. Chang, and D. Petrisor, “Robot for ultrasound-guided prostate imaging and intervention,” in 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems, pp. 943–948, San Francisco, CA, USA, 2011. [15] M.-A. Vitrani, M. Baumann, D. Reversat, G. Morel, A. Moreau-Gaudry, and P. Mozer, “Prostate biopsies assisted by comanipulated probe-holder: first in man,” International Journal of Computer Assisted Radiology and Surgery, vol. 11, no. 6, pp. 1153–1161, 2016. [16] J. Y. Li, Design on Control System of Five Degrees of Freedom Prostate Biopsy Robot, Harbin University of Science and Tech- nology, 2013. [17] Y. D. Zhang, J. C. Peng, Z. Liu, J. G. Jiang, and Y. J. Zhao, “Research on the segmentation method of prostate magnetic resonance image based on level set,” Chinese Journal of Scientific Instrument, vol. 38, no. 2, pp. 416–424, 2017. [18] Y. D. Zhang, W. X. Zhang, Y. Liang, and Y. Xu, “Research on mechanism and strategy of high accuracy puncture of prostate,” Chinese Journal of Scientific Instrument, vol. 38, no. 6, pp. 1405–1412, 2017. [19] M. E. Karar, “A simulation study of adaptive force controller for medical robotic liver ultrasound guidance,” Arabian Jour- nal for Science and Engineering, vol. 43, no. 8, pp. 4229– 4238, 2018. [20] R. H. Taylor, J. Funda, B. Eldridge et al., “A telerobotic assis- tant for laparoscopic surgery,” IEEE Engineering in Medicine and Biology Magazine, vol. 14, no. 3, pp. 279–288, 1993. [21] E. M. Boctor, R. J. Webster III, H. Mathieu, A. M. Okamura, and G. Fichtinger, “Virtual remote center of motion control for needle placement robots,” Computer Aided Surgery, vol. 9, no. 5, pp. 175–183, 2010. [22] G. Y. Dong, The Design and Research of the Robot Arm for Celiac Minimally Invasive Surgery, Jil-in University, 2016. [23] C. H. Kuo and J. S. Dai, “Kinematics of a fully-decoupled remote center-of-motion parallel manipulator for minimally invasive surgery,” Journal of Medical Devices, vol. 6, no. 2, pp. 211–214, 2012.

Journal

Applied Bionics and BiomechanicsHindawi Publishing Corporation

Published: Oct 15, 2020

References