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A technique for pediatric total skin electron irradiation

A technique for pediatric total skin electron irradiation Background: Total skin electron irradiation (TSEI) is a special radiotherapy technique which has generally been used for treating adult patients with mycosis fungoides. Recently, two infants presented with leukemia cutis isolated to the skin requiring TSEI. This work discusses the commissioning and quality assurance (QA) methods for implementing a modified Stanford technique using a rotating harness system to position sedated pediatric patients treated with electrons to the total skin. Methods and Results: Commissioning of pediatric TSEI consisted of absolute calibration, measurement of dosimetric parameters, and subsequent verification in a pediatric patient sized cylindrical phantom using radiographic film and optically stimulated luminance (OSL) dosimeters. The depth of dose penetration under TSEI treatment condition was evaluated using radiographic film sandwiched in the phantom and demonstrated a 2 cm penetration depth with the maximum dose located at the phantom surface. Dosimetry measurements on the cylindrical phantom and in-vivo measurements from the patients suggested that, the factor relating the skin and calibration point doses (i.e., the B-factor) was larger for the pediatric TSEI treatments as compared to adult TSEI treatments. Custom made equipment, including a rotating plate and harness, was fabricated and added to a standard total body irradiation stand and tested to facilitate patient setup under sedated condition. A pediatric TSEI QA program, consisting of daily output, energy, flatness, and symmetry measurements as well as in-vivo dosimetry verification for the first cycle was developed. With a long interval between pediatric TSEI cases, absolute dosimetry was also repeated as part of the QA program. In-vivo dosimetry for the first two infants showed that a dose of ± 10% of the prescription dose can be achieved over the entire patient body. Conclusion: Though pediatric leukemia cutis and the subsequent need for TSEI are rare, the ability to commission the technique on a modified TBI stand is appealing for clinical implementation and has been successfully used for the treatment of two pediatric patients at our institution. Keywords: Pediatric total skin electron irradiation, Commissioning, Quality assurance, Leukemia cutis Background the skin with a rapid fall-offindosebeyonda shallow Total skin electron irradiation (TSEI) is a special radio- depth to avoid bone marrow toxicity, electron beams therapy technique which aims to deliver a uniform dose delivered to the total body in the energy range of 3-7 to the entire skin of a patient while sparing all other MeV (4-10 MeV at the accelerator beam exit window) organs from a significant amount of radiation. TSEI has have been shown to be successful for treating these historically been used for the treatment of cutaneous T- superficial lesions. First proposed in the early 1950’s, cell lymphoma (mycosis fungoides), but has also been various TSEI treatment techniques have been evaluated extended for the treatment of other cutaneous diseases and clinically implemented [4-10], and a detailed techni- such as Kaposi’s sarcoma and scleromyxodema [1-3]. cal report on the subject has been published for the Due to the ability to achieve therapeutic dose levels to American Association of Physicists in Medicine by the American Institute of Physics [11]. * Correspondence: qinan.bao@utsouthwestern.edu Recently, two pediatric patients with recurrent acute Department of Radiation Oncology, University of Texas Southwestern myelogenous leukemia presenting with leukemia cutis Medical Center, 5801 Forest Park Rd, Dallas, TX 75390, USA (LC) were treated at the University of Texas Full list of author information is available at the end of the article © 2012 Bao et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Bao et al. Radiation Oncology 2012, 7:40 Page 2 of 7 http://www.ro-journal.com/content/7/1/40 Southwestern (UTSW) Medical Center at Dallas using 120.0 TSEI. LC is an extramedullary leukemia where neoplas- 110.0 100.0 tic leukocytes have infiltrated into the skin. Although 90.0 uncommon, this skin manifestation can occur with most 80.0 forms of leukemia. Patients typically present with multi- 70.0 ple raised skin nodules and plaques. The isolated skin 60.0 50.0 condition suggests treatment with superficial electron 40.0 beam irradiation to the total skin and has previously 30.0 been clinically described in case reports [12-15]. 20.0 A particular challenge in implementing a clinical 10.0 0.0 pediatric TSEI program is how to deliver a uniform -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 dose to the total skin of a sedated infant. This report Vertical distance (cm) describes the dosimetric commissioning and quality Figure 1 Combined beam profile at 330 cm SSD. The gantry was assurance (QA) procedures for implementing a clinical directed at ± 20° from the horizontal. TSEI program for the treatment of LC in pediatric patients using a modified Stanford technique [4,16,17]. The commissioning of fabricated setup equipment used mode (6 MeV, 888 MU/min nominal dose rate). A 1.2 to hold sedated pediatric patients in a modified total cm plexiglass scatter plate was placed 25 cm in front of bodyirradiation(TBI) standisalsopresented.Tothe the patient to provide additional electron scattering and best of our knowledge, this is the first report on the to reduce the electron incident energy. commissioning and clinical implementation of pediatric Absolute calibration of the machine output was per- TSEI using this technique. formed for a single dual-field beam, using an Exradin P11 parallel-plate ion chamber under treatment condi- Methods tions (330 cm SSD, 36 × 36 cm field size, 250° and The pediatric TSEI technique described below is based 290° gantry angles) at a depth of d on the horizon- max on a modified Stanford technique, which has been used tal central axis according to AAPM protocol [11]. The for treating adult TSEI patients at our institution. In parallel-plate chamber was first cross-calibrated developing a pediatric TSEI program, the same beam against a NIST-traceable PTW 31013 cylindrical ion configuration of six dual-fields was adopted. Due to the chamber (PTW, Hicksville, NY) in an 18 MeV elec- smaller size of pediatric patients and the sedation tron beam, following AAPM TG-21 [18] and TG-51 requirement for consistent positioning, however, addi- [19] protocols. tional equipment and dosimetric commissioning mea- The entire treatment was delivered to a Rando phan- surements were required. The following section tom (The Phantom Laboratory, Salem, NY). Following describes the measurements used in commissioning our AAPM Report 23 [11], the multiplication factor (B-fac- adult TSEI program and the further steps required for tor) for adult patients, which relates the treatment skin commissioning and performing QA tests for pediatric dose (D ) to the calibration point dose (D ) ,was S w P w TSEI patients. determined using OneDose MOSFETs (Sicel Technolo- gies, Inc., Morrisville, NC) placed on the surface of the Dosimetric commissioning and quality assurance Rando phantom and percent depth dose data. Concep- Adult TSEI field flatness and calibration tually, this factor represents the decrease in dose for At our institution, adult TSEI patients are treated with each single field due to the contribution from the two six dual-fields (anterior, posterior, and four obliques) adjacent fields. The B-factor was used to specify the using gantry angles of ± 20° from the horizontal axis. dose per field per treatment cycle and required monitor These angles are used to achieve a uniform dose (± units (MU) to patients, and was also used as the starting 10%) over a region of more than 170 cm while simulta- point for MU calculations to deliver doses to a pediatric neously reducing the total body dose from the mostly patient sized phantom described below. forward peaked contaminant bremsstrahlung photons. The combined beam profile, shown in Figure 1, was Phantom measurements for pediatric TSEI commissioning measured at the surface of solid water stacks (1 mm Since the pediatric patient size is much smaller than the intrinsic ion chamber buildup) using an Exradin P11 adult patient, it is necessary to determine whether the parallel-plate ion chamber (Standard Imaging, Middle- B-factor for the adult patient is applicable to the pedia- ton, WI)atadistance of 330cmSSD fromaVarian tric patient. A custom made cylindrical acrylic phantom Clinac 21EX linear accelerator (Varian Medical Systems, of 20 cm diameter and 25 cm height was used for this Palo Alto, CA) operating under the high dose rate TSE evaluation. Two aluminum oxide (Al O )MicroStar 2 3 Relative Dose (%) Bao et al. Radiation Oncology 2012, 7:40 Page 3 of 7 http://www.ro-journal.com/content/7/1/40 nanoDot™ optically stimulated luminescent (OSL) dosi- used to apply a calibration curve to assess the depth meters (Landauer Inc., Glenwood, IL) were placed on dose distribution, dose profile, and isodose curves. each of four locations (anterior, posterior, left lateral, and right lateral) at the surface of the phantom and Treatment design aligned with the central axis. A surface dose of 50 cGy Equipment was delivered by manually rotating the phantom at 60° In order to position sedated pediatric patients into the six steps through each of the six TSEI positions. The required angles required for TSEI, a rotating plate/harness required number of MUs was calculated using the B- system was constructed and attached to a custom made factor for the adult patient. The dose received by the frame used for Total Body Irradiation (TBI) treatments OSL nanoDots were read out using a MicroStar OSL (Figure 2). A central bar was mounted on top of the TBI reader with a luminescence-to-dose calibration curve frame and an aluminum rotating plate was attached to the applied. bar. Holes were drilled on the outer rim of the rotating XV film was sandwiched in the cylindrical acrylic plate at 120 degrees increments to facilitate patient posi- phantom at mid-phantom height. The excess film was tioning at 60° interval for the 6 positions. A bolt is used to cut in a darkroom so that the film edges conformed to index the rotating plate to the top central bar for each dif- the circular surface of the phantom. 3 M Scotch black ferent position to ensure the positioning accuracy. The duct tape was wrapped around the phantom over the entire plate can be moved along the central bar, which is film edge to ensure the film was light-tight. The film parallel to the beam axis, to maintain a constant patient to plane was aligned with the horizontal central axis hori- spoiler distance of 25 cm at the central beam axis for each zontal plane and a 50 cGy surface dose was delivered position over the course of the treatment. using the same technique as described above. The film A custom made harness was sewn to hold the patient was then developed and scanned using a Vidar VXR vertically. The harness only covers the trunk of the Dosimetry Pro film digitizer (VIDAR Systems Corpora- patient body, leaving arms and legs uncovered. The har- tion, Herndon, VA). RIT113V5.2 software (Radiological ness attaches to the rotating plate with four belts which Imaging Technology, Inc., Colorado Springs, CO) was loop through carabiner clips. The lengths of the belts (a) (b) rotating plate carabiner clips harness Figure 2 The patient in treatment positions for (a) PA and (b) RAO locations. Bao et al. Radiation Oncology 2012, 7:40 Page 4 of 7 http://www.ro-journal.com/content/7/1/40 were constructed such that the patient umbilicus is cen- As part of routine quality assurance tests, OSL dosi- tered along the horizontal beam axis. The harness was meters were placed on the patient’sskinatmultiple made from a single layer cloth to minimize the attenua- locations. Doses for the first two days of treatment were tion of the electron beam yet maintain enough strength measured and combined to give the total dose delivered to support an infant. To ensure patient safety during during one cycle, and this was compared against the treatment, the strength of the harness was verified by prescription dose of 200 cGy per cycle. Based on the placing weights inside the harness while hanging on the OSL measurements, the B-factor and the required MUs were adjusted if needed in order to meet our absolute rotating plate for at least one hour. dose and dose uniformity criteria. Treatment procedure Two patients (17 months and 12 months old) have been Results treated since commissioning this pediatric TSEI technique. Phantom measurements for pediatric TSEI commissioning Each patient was scheduled to receive 16 Gy over the Two nanoDots were placed on each of four locations on entire treatment course for 8 cycles as described in case the cylindrical acrylic phantom and uniformly irradiated reports [13,14]. Each cycle consists of two treatment days to a nominal dose of 50 cGy, based on the adult TSEI with three dual-fields each: AP, LPO, RPO on the first day B-factor of 2.414, using the six dual-field technique. and PA, LAO, RAO on the second day. During treatment Each nanoDot was read out 3 times and the average of days, morning machine output quality assurance was per- the 3 readings is shown in Table 1. formed using the high dose rate TSE delivery mode using Thedosedelivered to thesurface ofthe20cmdia- a Daily QA3 detector array (Sun Nuclear Corporation, meter phantom was measured to be 53.7 cGy on aver- Melbourne, FL) to verify output consistency. age at the four locations around the phantom Prior to each treatment, the stand was moved into a periphery, 7.3% higher than the nominally delivered preset position and the source-to-spoiler distance was dose. Given the intrinsic 5% accuracy of the OSL dosi- measured to ensure the correct stand position. The meters, the dose uniformity requirement, and the fact patient was anesthetized and placed within the harness that these measurements were not patient specific, the while on a gurney. The patient was monitored for B-factor was not adjusted for subsequent patient MU hemodynamic status, pulse oximetry, and nasal end tidal calculations. carbon dioxide levels during the entire treatment. The While the OSL dosimeters were used for absolute patient was carefully lifted into place while the harness dose measurements, film was used for relative dose belts were clipped onto the carabiners attached to the measurements because a batch specific calibration curve rotating plate. The patient’sheadwaseithersupported and carefully controlled development conditions were by a piece of acrylic plate placed opposite of the beam not used. Figure 3a shows the dose distribution on a or taped in place to the harness belts. Patient arms were central axial slice of the 20 cm diameter cylindrical positioned in similar positions as for adult TSEI patients phantom measured by KODAK X-OMAT V (XV) film using Velcro strips which were looped around the TBI following the delivery of the MUs calculated to deliver frame and attached to a Styrofoam pad taped to the 50 cGy. Two orthogonal lines were drawn using RIT patient’s hand opposite of the beam (Figure 2). After the software and the profiles are shown in Figure 3b. Based patient AP position was set, the distance from the on the dose profile of the film, it can be seen that the patient to the spoiler was measured, and the rotating periphery of the film was uniformly irradiated from the plate was moved along the bars of the TBI stand to the degraded 6 MeV electron beams. The penetration of desired 25 cm spoiler-to-patient distance. The required electrons after the spoiler has a maximum range of number of MUs was delivered and then the patient was approximately 2 cm, with the maximum dose occurring rotated to each posterior oblique position for each sub- at the surface of the phantom. The cold surface dose sequent delivery to complete the first half of the cycle. artifact on the right-hand side of the horizontal profile Table 1 OSL detector measured dose on 20 cm diameter cylindrical phantom following delivery of a prescribed 50 cGy OSL Detector Location NanoDot 1 Dose (cGy) NanoDot 2 Dose (cGy) Average Dose (cGy) % Diff from Prescription AP 54.3 53.3 53.8 7.6 Lt Lat 53.5 54.4 54.0 8.0 PA 53.9 53.1 53.5 7.0 Rt Lat 54.5 52.4 53.4 6.8 Average 53.7 7.3 Bao et al. Radiation Oncology 2012, 7:40 Page 5 of 7 http://www.ro-journal.com/content/7/1/40 reasonable that the B-factor increases compared to the (a) (b) adult TSEI technique. For the six dual-field beam arrangement, the dose contribution at any one location is primarily from three of the six dual-fields. For exam- ple, the dose contribution to the umbilicus point is pri- marily from the AP, LAO and RAO beams. The AP beam will contribute the same amount of dose to the umbilicus point regardless of the patient size, but for a smaller diameter phantom or patient at the same SSD, the two oblique beams will contribute more dose to the umbilicus point, resulting in a higher B-factor. This inverse relationship of B-factor with patient diameter Figure 3 Film measurement for the composite TSEI beam.(a) An XV film was uniformly irradiated with 50 cGy dose and (b) two has been reported previously [20]. orthogonal profiles indicates the dose penetration of the TSEI beam. Following adjustment of the MUs, in-vivo dosimetry using OSL detectors was repeated as a second check on selected locations of the patient during the second cycle is believed to be caused by misalignment of the film (days 3 and 4). Of the five locations measured, the aver- edge with the cylindrical phantom edge. Perfect align- aged dose was 201.9 cGy, which was 1.0% higher than ment was difficult to obtain when cutting and matching the prescription dose and within our accepted tolerance the film with the phantom in a dark-room. (Table 3). Therefore the new B-factor and the calculated MUs were used for the remainder of the treatment Patient in-vivo dosimetry course. During the first two treatment days (first cycle) of the For the second pediatric TSEI patient, the adjusted B- first pediatric TSEI patient, patient specific in-vivo dosi- factor determined from phantom and in-vivo measure- metry using OSL detectors was performed for different ments in the first patient was used for MU calculations. locations on the body surface to verify dose calculations In-vivo dosimetry was performed as in the previous and the B-factor. The resulting dose measurements are patient as part of patient-specific TSEI QA. The average summarized in Table 2. The average dose was 222.2 dose determined by the OSL detectors was 198.3 cGy, cGy over all measured locations, 11.1% higher on aver- 0.8% lower than the prescription. Based on these results, age than the prescription dose. This value was consis- no adjustment was made to the dose calculations or tent with the 7.3% higher dose measured on the patient setup. However, with this patient, individual cylindrical phantom, thus the value of the B-factor was regions including the top of the head and the inner increased by 10% (from 2.414 to 2.655) and the MUs thighs exceeded our ± 10% dose uniformity criteria. prescribed for each beam were correspondingly After discussing with the ain’s physician, an electron decreased by 10%. Due to the smaller diameter of the boost was concurrently administered to the top of the 20 cm cylindrical phantom and pediatric patients, it is Table 2 OSL detector dose measurements for cycle one of first patient OSL Detector AP + LPO + RPO Day 1 Dose PA + LAO + RAO Day 2 Dose Total Dose % Diff from Location (cGy) (cGy) (cGy) Prescription Forehead 106.2 119.1 225.3 12.7 Posterior of head 152.1 96.2 248.3 24.2 Sternum 78.9 136.9 215.8 7.9 Posterior of sternum 137.8 85.9 223.7 11.9 Umbilicus 80.5 132.7 213.2 6.6 Posterior of Umbilicus 146.9 78.7 225.6 12.8 Left thigh 75.8 139.1 214.9 7.5 Posterior Left Thigh 145.9 81.5 227.4 13.7 Right thigh 77.1 133.7 210.8 5.4 Posterior Right Thigh 130.0 86.5 216.5 8.3 Right Foot 84.6 141.6 226.2 13.1 Bottom of Right Foot 135.9 82.6 218.5 9.3 Average 222.2 11.1 Bao et al. Radiation Oncology 2012, 7:40 Page 6 of 7 http://www.ro-journal.com/content/7/1/40 Table 3 OSL detector dose measurements for cycle two of first patient for reduced MUs OSL Detector AP + LPO + RPO Day 3 Dose PA + LAO + RAO Day 4 Dose Total Dose % Diff from Location (cGy) (cGy) (cGy) Prescription Forehead 96.1 117.2 213.3 6.6 Posterior of Head 121.9 84 205.9 3.0 Umbilicus 79.1 117.3 196.3 18 Posterior of Umbilicus 125.6 72.6 198.2 09 Back of Right Hand 70.5 125.3 195.7 21 Average 201.9 1.0 patient’s head, which had visible lesions, for the second platform in unison with an oxygen airway, IVs, and half of the treatment course based on under dosage of other lines for different beam positions. this region. Although commissioning showed overall surface dose uniformity within ± 10% in the plane perpendicular to Discussion the central axis for an adult patient’s dimensions, there In this work we present the commissioning and quality are many locations which could possibly exceed this assurance processes used to successfully implement a uniformity criterion. Due primarily to surface irregulari- ties, this has also been observed in patients treated by pediatric TSEI program at UTSW. With this modified TSEI for mycosis fungoides. Surface cavities can receive Stanford technique, the sedated pediatric patient is less dose than flat or convex surfaces, while higher secured by a custom made harness and rotational sys- tem attached to a common TBI stand. Though pediatric doses may occur in areas with body protrusions [21,22]. leukemia cutis and the subsequent need for TSEI are With the patient setup described in this work, in-vivo rare, the ability to commission the technique on a modi- dosimetry demonstrated that under dose regions can fied TBI stand is appealing for clinical implementation. occur when the skin is shielded by other body parts To the best of our knowledge this is the first complete (inner thigh and leg regions), when the skin is shielded description of the commissioning and QA of pediatric by patient vital sign monitoring equipment (beneath the TSEI using a modified Stanford technique. Rubin et al. blood pressure cuff), and at the top of the head. The [12] use a similar pediatric TSEI technique for the treat- inner thigh region underdose may be improved with the ment of acute monoblastic leukemia; however, it is pre- use of additional straps to separate the legs; however, a sented as a medical case report with an incomplete boost to the perineum region may still be needed at the description of the irradiation technique and the com- discretion of the physician. In both UTSW clinical missioning and QA methods. Pepek et al. [13] also pre- cases, every attempt was made to move oxygen tube and sent a medical case report for the treatment of leukemia monitoring wires out of the treatment fields and away cutis in pediatric patients. In this work they provide a from the patient. The position of the blood pressure brief description of the irradiation technique, which is cuff was moved throughout the course of treatment to based on a rotating platform at extended distances. The average out the shielding effect. As recommended in pediatricpatientswereofagewheretheywereableto AAPM Report No. 23 [11], the use of boost fields stand on their own in the required positions over the required clinical judgment. Based on in-vivo dosimetry, course of the treatment, thus removing the need for the physician elected for a 6 MeV electron boost to the top of the head for the second patient with a 1 cm sedation and a rotating harness system. Earley et al. [7] describe, to date, the most complete description of the bolus since this region was under dosed during TSEI commissioning of a pediatric TSEI technique for the and this was the location of the isolated skin lesions. treatment of a sedated acute myelocytic leukemia When performing in-vivo dosimetry measurements to patient. In this technique, the sedated patient is placed verify that the prescribed dose is delivered correctly and on a platform that is carried to the floor for AP and PA confirm dose uniformity, the choice of detector is impor- beams and the treatment couch for oblique beams (with tant to consider. Thermoluminescent dosimeters have the gantry moved to different angles). Beam profiles been the most commonly used for TSEI treatments due were acquired at a 200 cm distance for 6 MeV electrons to the small volume minimizing the effect of dose gradi- to assess uniformity. From the authors’ description, it ents across the dosimeter. OSL dosimeters have recently seems the rotating harness system and irradiation tech- been introduced for clinical dose measurements and have nique described in our work would facilitate a faster been implemented in clinical TSEI programs [23]. OSL total treatment time without having to move a patient dosimeters were used for in-vivo measurements due to Bao et al. Radiation Oncology 2012, 7:40 Page 7 of 7 http://www.ro-journal.com/content/7/1/40 4. Karzmark CJ: Large-field superficial electron therapy with linear their ease of use and quick readout with the MicroStar accelerators. Br J Radiol 1964, 37:302-305. reader system. 5. Wu JM, Yeh SA, Hsiao KY, Chao MM, Hargrove I: A conceptual design of Patient safety is of utmost important over the course rotating board technique for delivering total skin electron therapy. Med Phys 2010, 37:1449-1458. of treatment and was of primary consideration in the 6. Podgorsak EB, Pla C, Pla M, Lefebvre PY, Heese R: Physical aspects of a commissioning process. It is crucial for the sedated rotational total skin electron irradiation. Med Phys 1983, 10:159-168. patient in the harness system to remain in the same 7. Earley L, Moeller J, O’Rear J, Leavitt DD: A method for total skin electron treatment for infants. Med Dosim 1995, 20:243-248. position while the treatment team is outside of the 8. Wu JM, Leung SW, Wang CJ, Chui CS: Lying-on position of total skin vault. During commissioning, filled water jugs were electron therapy. Int J Radiat Oncol Biol Phys 1997, 39:521-528. placed in the harness system to demonstrate structural 9. Peters VG, Jaywant SM: Implementation of total skin electron therapy using an optional high dose rate mode on a conventional linear integrity. Velcro straps as well as paper tape were on accelerator. Med Dosim 1995, 20:99-104. hand in abundance to set a consistent position. At every 10. Trump JG, Wright KA, Evans WW, Anson JH, Hare HF, Fromer JL, Jacque G, treatment, a team including an anesthesiologist, nurse, Horne KW: High energy electrons for the treatment of extensive superficial malignant lesions. The American journal of roentgenology, medical physicist, and radiation therapist were present radium therapy, and nuclear medicine 1953, 69:623-629. to secure the patient, monitor the patient, verify treat- 11. Karzmark CJ, Anderson J, Fessenden P, Svensson G, Buffa A, Khan FM, ment settings and setup, and deliver the required radia- Wright KA: Total skin electron therapy: technique and dosimetry. Report of Task Group 30. 1987. tion dose. In addition to in-vivo dosimetry, machine QA 12. Rubin CM, Arthur DC, Meyers G, McClain KL, Kim TH, Woods WG: Leukemia procedures were implemented and performed on each cutis treated with total skin irradiation. Cancer 1985, 55:2649-2652. treatment day to verify proper operation in TSEI mode. 13. Pepek JM, Paulino AC, Briones MA, Marcus RB Jr, Esiashvili N: Role of total skin electron beam therapy for leukemia cutis in pediatric patients. This consisted of checks for output, energy, symmetry, Pediatr Blood Cancer 2008, 50:1054-1055. and flatness constancy. Due to the infrequent use of this 14. Majdzadeh N, Jain SK, Murphy MC, Dugas JP, Hager F, Abdulrahman R: treatment technique it is important, as part of the QA Total skin electron beam radiation in a pediatric patient with leukemia cutis: A case report. Journal of Pediatric Hematology/Oncology . protocol, to verify any changes in the system over time 15. Dusenbery KE, Howells WB, Arthur DC, Alonzo T, Lee JW, Kobrinsky N, which would affect the patient dose, including the abso- Barnard DR, Wells RJ, Buckley JD, Lange BJ, Woods WG: Extramedullary lute output calibration and B-factor. At our clinic, the leukemia in children with newly diagnosed acute myeloid leukemia: a report from the children’s cancer group. Journal of Pediatric Hematology/ second pediatric TSEI case for LC occurred approxi- Oncology 2003, 25:760-768. mately one year following the first case. Prior to the 16. Karzmark CJ, Loevinger R, Steele RE, Weissbluth M: A technique for large- first treatment day of the second pediatric case, a cali- field, superficial electron therapy. Radiology 1960, 74:633-644. 17. Karzmark CJ: Physical aspects of whole-body superficial therapy with brated parallel plate ionization chamber was used for electrons. Front Radiat Ther Oncol 1968, 2:36-54. absolute dosimetry in TSEI mode and the output for 18. A protocol for the determination of absorbed dose from high-energy this mode was adjusted to the value used for initial photon and electron beams. Task Group 21, Radiation Therapy Committee, AAPM. Med Phys 1983, 10:741-771. commissioning. 19. Almond PR, Biggs PJ, Coursey BM, Hanson WF, Huq MS, Nath R, Rogers DW: AAPM’s TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys 1999, 26:1847-1870. Author details 20. Van Der Merwe DG: Total skin electron therapy: A technique which can Department of Radiation Oncology, University of Texas Southwestern be implemented on a conventional electron linear accelerator. Medical Center, 5801 Forest Park Rd, Dallas, TX 75390, USA. Mary Bird International Journal of Radiation Oncology Biology Physics 1993, 27:391-396. Perkins Cancer Center, 4950 Essen Lane, Baton Rouge, LA 70809, USA. 21. Niroomand-Rad A, Gillin MT, Komaki R, Kline RW, Grimm DF: Dose Department of Physics and Astronomy, Louisiana State University, 202 distribution in total skin electron beam irradiation using the six-field Nicholson Hall, Baton Rouge, LA 70803, USA. technique. Int J Radiat Oncol Biol Phys 1986, 12:415-419. 22. Khan FM: Electron beam therapy. The Physics of Radiation Therapy. 4 Authors’ contributions edition. Philadelphia, PA: Lippincott Williams & Wilkins; 2009, 299-306. QB, JPD and FHH conducted the phantom measurement, initial 23. Esquivel C, Smith MS, Stathakis S, Gutierrez A, Shi C, Papanikolaou N: Total commissioning of the setup, and treated the first patient. QB, BAH and FHH skin electron therapy skin dose validation using optically stimulated treated the second patient. QB and BAH drafted the manuscript. TDS luminescent dosimeters [abstract]. AAPM Annual Meeting 2009, ID10746. oversaw the whole procedure. All authors read and approved the final manuscript. doi:10.1186/1748-717X-7-40 Cite this article as: Bao et al.: A technique for pediatric total skin Competing interests electron irradiation. Radiation Oncology 2012 7:40. The authors declare that they have no competing interests. Received: 19 December 2011 Accepted: 20 March 2012 Published: 20 March 2012 References 1. Jones G, Wilson LD, Fox-Goguen L: Total skin electron beam radiotherapy for patients who have mycosis fungoides. Hematol Oncol Clin North Am 2003, 17:1421-1434. 2. Nisce LZ, Safai B, Poussin-Rosillo H: Once weekly total and subtotal skin electron beam therapy for Kaposi’s sarcoma. Cancer 1981, 47:640-644. 3. Leung SW, Hsu HC, Huang PH: Total skin electron beam irradiation in scleromyxoedema. Br J Radiol 1998, 71:84-86. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiation Oncology Springer Journals

A technique for pediatric total skin electron irradiation

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Copyright © 2012 by Bao et al; licensee BioMed Central Ltd.
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Medicine & Public Health; Oncology; Radiotherapy
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1748-717X
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10.1186/1748-717X-7-40
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22433063
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Abstract

Background: Total skin electron irradiation (TSEI) is a special radiotherapy technique which has generally been used for treating adult patients with mycosis fungoides. Recently, two infants presented with leukemia cutis isolated to the skin requiring TSEI. This work discusses the commissioning and quality assurance (QA) methods for implementing a modified Stanford technique using a rotating harness system to position sedated pediatric patients treated with electrons to the total skin. Methods and Results: Commissioning of pediatric TSEI consisted of absolute calibration, measurement of dosimetric parameters, and subsequent verification in a pediatric patient sized cylindrical phantom using radiographic film and optically stimulated luminance (OSL) dosimeters. The depth of dose penetration under TSEI treatment condition was evaluated using radiographic film sandwiched in the phantom and demonstrated a 2 cm penetration depth with the maximum dose located at the phantom surface. Dosimetry measurements on the cylindrical phantom and in-vivo measurements from the patients suggested that, the factor relating the skin and calibration point doses (i.e., the B-factor) was larger for the pediatric TSEI treatments as compared to adult TSEI treatments. Custom made equipment, including a rotating plate and harness, was fabricated and added to a standard total body irradiation stand and tested to facilitate patient setup under sedated condition. A pediatric TSEI QA program, consisting of daily output, energy, flatness, and symmetry measurements as well as in-vivo dosimetry verification for the first cycle was developed. With a long interval between pediatric TSEI cases, absolute dosimetry was also repeated as part of the QA program. In-vivo dosimetry for the first two infants showed that a dose of ± 10% of the prescription dose can be achieved over the entire patient body. Conclusion: Though pediatric leukemia cutis and the subsequent need for TSEI are rare, the ability to commission the technique on a modified TBI stand is appealing for clinical implementation and has been successfully used for the treatment of two pediatric patients at our institution. Keywords: Pediatric total skin electron irradiation, Commissioning, Quality assurance, Leukemia cutis Background the skin with a rapid fall-offindosebeyonda shallow Total skin electron irradiation (TSEI) is a special radio- depth to avoid bone marrow toxicity, electron beams therapy technique which aims to deliver a uniform dose delivered to the total body in the energy range of 3-7 to the entire skin of a patient while sparing all other MeV (4-10 MeV at the accelerator beam exit window) organs from a significant amount of radiation. TSEI has have been shown to be successful for treating these historically been used for the treatment of cutaneous T- superficial lesions. First proposed in the early 1950’s, cell lymphoma (mycosis fungoides), but has also been various TSEI treatment techniques have been evaluated extended for the treatment of other cutaneous diseases and clinically implemented [4-10], and a detailed techni- such as Kaposi’s sarcoma and scleromyxodema [1-3]. cal report on the subject has been published for the Due to the ability to achieve therapeutic dose levels to American Association of Physicists in Medicine by the American Institute of Physics [11]. * Correspondence: qinan.bao@utsouthwestern.edu Recently, two pediatric patients with recurrent acute Department of Radiation Oncology, University of Texas Southwestern myelogenous leukemia presenting with leukemia cutis Medical Center, 5801 Forest Park Rd, Dallas, TX 75390, USA (LC) were treated at the University of Texas Full list of author information is available at the end of the article © 2012 Bao et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Bao et al. Radiation Oncology 2012, 7:40 Page 2 of 7 http://www.ro-journal.com/content/7/1/40 Southwestern (UTSW) Medical Center at Dallas using 120.0 TSEI. LC is an extramedullary leukemia where neoplas- 110.0 100.0 tic leukocytes have infiltrated into the skin. Although 90.0 uncommon, this skin manifestation can occur with most 80.0 forms of leukemia. Patients typically present with multi- 70.0 ple raised skin nodules and plaques. The isolated skin 60.0 50.0 condition suggests treatment with superficial electron 40.0 beam irradiation to the total skin and has previously 30.0 been clinically described in case reports [12-15]. 20.0 A particular challenge in implementing a clinical 10.0 0.0 pediatric TSEI program is how to deliver a uniform -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 dose to the total skin of a sedated infant. This report Vertical distance (cm) describes the dosimetric commissioning and quality Figure 1 Combined beam profile at 330 cm SSD. The gantry was assurance (QA) procedures for implementing a clinical directed at ± 20° from the horizontal. TSEI program for the treatment of LC in pediatric patients using a modified Stanford technique [4,16,17]. The commissioning of fabricated setup equipment used mode (6 MeV, 888 MU/min nominal dose rate). A 1.2 to hold sedated pediatric patients in a modified total cm plexiglass scatter plate was placed 25 cm in front of bodyirradiation(TBI) standisalsopresented.Tothe the patient to provide additional electron scattering and best of our knowledge, this is the first report on the to reduce the electron incident energy. commissioning and clinical implementation of pediatric Absolute calibration of the machine output was per- TSEI using this technique. formed for a single dual-field beam, using an Exradin P11 parallel-plate ion chamber under treatment condi- Methods tions (330 cm SSD, 36 × 36 cm field size, 250° and The pediatric TSEI technique described below is based 290° gantry angles) at a depth of d on the horizon- max on a modified Stanford technique, which has been used tal central axis according to AAPM protocol [11]. The for treating adult TSEI patients at our institution. In parallel-plate chamber was first cross-calibrated developing a pediatric TSEI program, the same beam against a NIST-traceable PTW 31013 cylindrical ion configuration of six dual-fields was adopted. Due to the chamber (PTW, Hicksville, NY) in an 18 MeV elec- smaller size of pediatric patients and the sedation tron beam, following AAPM TG-21 [18] and TG-51 requirement for consistent positioning, however, addi- [19] protocols. tional equipment and dosimetric commissioning mea- The entire treatment was delivered to a Rando phan- surements were required. The following section tom (The Phantom Laboratory, Salem, NY). Following describes the measurements used in commissioning our AAPM Report 23 [11], the multiplication factor (B-fac- adult TSEI program and the further steps required for tor) for adult patients, which relates the treatment skin commissioning and performing QA tests for pediatric dose (D ) to the calibration point dose (D ) ,was S w P w TSEI patients. determined using OneDose MOSFETs (Sicel Technolo- gies, Inc., Morrisville, NC) placed on the surface of the Dosimetric commissioning and quality assurance Rando phantom and percent depth dose data. Concep- Adult TSEI field flatness and calibration tually, this factor represents the decrease in dose for At our institution, adult TSEI patients are treated with each single field due to the contribution from the two six dual-fields (anterior, posterior, and four obliques) adjacent fields. The B-factor was used to specify the using gantry angles of ± 20° from the horizontal axis. dose per field per treatment cycle and required monitor These angles are used to achieve a uniform dose (± units (MU) to patients, and was also used as the starting 10%) over a region of more than 170 cm while simulta- point for MU calculations to deliver doses to a pediatric neously reducing the total body dose from the mostly patient sized phantom described below. forward peaked contaminant bremsstrahlung photons. The combined beam profile, shown in Figure 1, was Phantom measurements for pediatric TSEI commissioning measured at the surface of solid water stacks (1 mm Since the pediatric patient size is much smaller than the intrinsic ion chamber buildup) using an Exradin P11 adult patient, it is necessary to determine whether the parallel-plate ion chamber (Standard Imaging, Middle- B-factor for the adult patient is applicable to the pedia- ton, WI)atadistance of 330cmSSD fromaVarian tric patient. A custom made cylindrical acrylic phantom Clinac 21EX linear accelerator (Varian Medical Systems, of 20 cm diameter and 25 cm height was used for this Palo Alto, CA) operating under the high dose rate TSE evaluation. Two aluminum oxide (Al O )MicroStar 2 3 Relative Dose (%) Bao et al. Radiation Oncology 2012, 7:40 Page 3 of 7 http://www.ro-journal.com/content/7/1/40 nanoDot™ optically stimulated luminescent (OSL) dosi- used to apply a calibration curve to assess the depth meters (Landauer Inc., Glenwood, IL) were placed on dose distribution, dose profile, and isodose curves. each of four locations (anterior, posterior, left lateral, and right lateral) at the surface of the phantom and Treatment design aligned with the central axis. A surface dose of 50 cGy Equipment was delivered by manually rotating the phantom at 60° In order to position sedated pediatric patients into the six steps through each of the six TSEI positions. The required angles required for TSEI, a rotating plate/harness required number of MUs was calculated using the B- system was constructed and attached to a custom made factor for the adult patient. The dose received by the frame used for Total Body Irradiation (TBI) treatments OSL nanoDots were read out using a MicroStar OSL (Figure 2). A central bar was mounted on top of the TBI reader with a luminescence-to-dose calibration curve frame and an aluminum rotating plate was attached to the applied. bar. Holes were drilled on the outer rim of the rotating XV film was sandwiched in the cylindrical acrylic plate at 120 degrees increments to facilitate patient posi- phantom at mid-phantom height. The excess film was tioning at 60° interval for the 6 positions. A bolt is used to cut in a darkroom so that the film edges conformed to index the rotating plate to the top central bar for each dif- the circular surface of the phantom. 3 M Scotch black ferent position to ensure the positioning accuracy. The duct tape was wrapped around the phantom over the entire plate can be moved along the central bar, which is film edge to ensure the film was light-tight. The film parallel to the beam axis, to maintain a constant patient to plane was aligned with the horizontal central axis hori- spoiler distance of 25 cm at the central beam axis for each zontal plane and a 50 cGy surface dose was delivered position over the course of the treatment. using the same technique as described above. The film A custom made harness was sewn to hold the patient was then developed and scanned using a Vidar VXR vertically. The harness only covers the trunk of the Dosimetry Pro film digitizer (VIDAR Systems Corpora- patient body, leaving arms and legs uncovered. The har- tion, Herndon, VA). RIT113V5.2 software (Radiological ness attaches to the rotating plate with four belts which Imaging Technology, Inc., Colorado Springs, CO) was loop through carabiner clips. The lengths of the belts (a) (b) rotating plate carabiner clips harness Figure 2 The patient in treatment positions for (a) PA and (b) RAO locations. Bao et al. Radiation Oncology 2012, 7:40 Page 4 of 7 http://www.ro-journal.com/content/7/1/40 were constructed such that the patient umbilicus is cen- As part of routine quality assurance tests, OSL dosi- tered along the horizontal beam axis. The harness was meters were placed on the patient’sskinatmultiple made from a single layer cloth to minimize the attenua- locations. Doses for the first two days of treatment were tion of the electron beam yet maintain enough strength measured and combined to give the total dose delivered to support an infant. To ensure patient safety during during one cycle, and this was compared against the treatment, the strength of the harness was verified by prescription dose of 200 cGy per cycle. Based on the placing weights inside the harness while hanging on the OSL measurements, the B-factor and the required MUs were adjusted if needed in order to meet our absolute rotating plate for at least one hour. dose and dose uniformity criteria. Treatment procedure Two patients (17 months and 12 months old) have been Results treated since commissioning this pediatric TSEI technique. Phantom measurements for pediatric TSEI commissioning Each patient was scheduled to receive 16 Gy over the Two nanoDots were placed on each of four locations on entire treatment course for 8 cycles as described in case the cylindrical acrylic phantom and uniformly irradiated reports [13,14]. Each cycle consists of two treatment days to a nominal dose of 50 cGy, based on the adult TSEI with three dual-fields each: AP, LPO, RPO on the first day B-factor of 2.414, using the six dual-field technique. and PA, LAO, RAO on the second day. During treatment Each nanoDot was read out 3 times and the average of days, morning machine output quality assurance was per- the 3 readings is shown in Table 1. formed using the high dose rate TSE delivery mode using Thedosedelivered to thesurface ofthe20cmdia- a Daily QA3 detector array (Sun Nuclear Corporation, meter phantom was measured to be 53.7 cGy on aver- Melbourne, FL) to verify output consistency. age at the four locations around the phantom Prior to each treatment, the stand was moved into a periphery, 7.3% higher than the nominally delivered preset position and the source-to-spoiler distance was dose. Given the intrinsic 5% accuracy of the OSL dosi- measured to ensure the correct stand position. The meters, the dose uniformity requirement, and the fact patient was anesthetized and placed within the harness that these measurements were not patient specific, the while on a gurney. The patient was monitored for B-factor was not adjusted for subsequent patient MU hemodynamic status, pulse oximetry, and nasal end tidal calculations. carbon dioxide levels during the entire treatment. The While the OSL dosimeters were used for absolute patient was carefully lifted into place while the harness dose measurements, film was used for relative dose belts were clipped onto the carabiners attached to the measurements because a batch specific calibration curve rotating plate. The patient’sheadwaseithersupported and carefully controlled development conditions were by a piece of acrylic plate placed opposite of the beam not used. Figure 3a shows the dose distribution on a or taped in place to the harness belts. Patient arms were central axial slice of the 20 cm diameter cylindrical positioned in similar positions as for adult TSEI patients phantom measured by KODAK X-OMAT V (XV) film using Velcro strips which were looped around the TBI following the delivery of the MUs calculated to deliver frame and attached to a Styrofoam pad taped to the 50 cGy. Two orthogonal lines were drawn using RIT patient’s hand opposite of the beam (Figure 2). After the software and the profiles are shown in Figure 3b. Based patient AP position was set, the distance from the on the dose profile of the film, it can be seen that the patient to the spoiler was measured, and the rotating periphery of the film was uniformly irradiated from the plate was moved along the bars of the TBI stand to the degraded 6 MeV electron beams. The penetration of desired 25 cm spoiler-to-patient distance. The required electrons after the spoiler has a maximum range of number of MUs was delivered and then the patient was approximately 2 cm, with the maximum dose occurring rotated to each posterior oblique position for each sub- at the surface of the phantom. The cold surface dose sequent delivery to complete the first half of the cycle. artifact on the right-hand side of the horizontal profile Table 1 OSL detector measured dose on 20 cm diameter cylindrical phantom following delivery of a prescribed 50 cGy OSL Detector Location NanoDot 1 Dose (cGy) NanoDot 2 Dose (cGy) Average Dose (cGy) % Diff from Prescription AP 54.3 53.3 53.8 7.6 Lt Lat 53.5 54.4 54.0 8.0 PA 53.9 53.1 53.5 7.0 Rt Lat 54.5 52.4 53.4 6.8 Average 53.7 7.3 Bao et al. Radiation Oncology 2012, 7:40 Page 5 of 7 http://www.ro-journal.com/content/7/1/40 reasonable that the B-factor increases compared to the (a) (b) adult TSEI technique. For the six dual-field beam arrangement, the dose contribution at any one location is primarily from three of the six dual-fields. For exam- ple, the dose contribution to the umbilicus point is pri- marily from the AP, LAO and RAO beams. The AP beam will contribute the same amount of dose to the umbilicus point regardless of the patient size, but for a smaller diameter phantom or patient at the same SSD, the two oblique beams will contribute more dose to the umbilicus point, resulting in a higher B-factor. This inverse relationship of B-factor with patient diameter Figure 3 Film measurement for the composite TSEI beam.(a) An XV film was uniformly irradiated with 50 cGy dose and (b) two has been reported previously [20]. orthogonal profiles indicates the dose penetration of the TSEI beam. Following adjustment of the MUs, in-vivo dosimetry using OSL detectors was repeated as a second check on selected locations of the patient during the second cycle is believed to be caused by misalignment of the film (days 3 and 4). Of the five locations measured, the aver- edge with the cylindrical phantom edge. Perfect align- aged dose was 201.9 cGy, which was 1.0% higher than ment was difficult to obtain when cutting and matching the prescription dose and within our accepted tolerance the film with the phantom in a dark-room. (Table 3). Therefore the new B-factor and the calculated MUs were used for the remainder of the treatment Patient in-vivo dosimetry course. During the first two treatment days (first cycle) of the For the second pediatric TSEI patient, the adjusted B- first pediatric TSEI patient, patient specific in-vivo dosi- factor determined from phantom and in-vivo measure- metry using OSL detectors was performed for different ments in the first patient was used for MU calculations. locations on the body surface to verify dose calculations In-vivo dosimetry was performed as in the previous and the B-factor. The resulting dose measurements are patient as part of patient-specific TSEI QA. The average summarized in Table 2. The average dose was 222.2 dose determined by the OSL detectors was 198.3 cGy, cGy over all measured locations, 11.1% higher on aver- 0.8% lower than the prescription. Based on these results, age than the prescription dose. This value was consis- no adjustment was made to the dose calculations or tent with the 7.3% higher dose measured on the patient setup. However, with this patient, individual cylindrical phantom, thus the value of the B-factor was regions including the top of the head and the inner increased by 10% (from 2.414 to 2.655) and the MUs thighs exceeded our ± 10% dose uniformity criteria. prescribed for each beam were correspondingly After discussing with the ain’s physician, an electron decreased by 10%. Due to the smaller diameter of the boost was concurrently administered to the top of the 20 cm cylindrical phantom and pediatric patients, it is Table 2 OSL detector dose measurements for cycle one of first patient OSL Detector AP + LPO + RPO Day 1 Dose PA + LAO + RAO Day 2 Dose Total Dose % Diff from Location (cGy) (cGy) (cGy) Prescription Forehead 106.2 119.1 225.3 12.7 Posterior of head 152.1 96.2 248.3 24.2 Sternum 78.9 136.9 215.8 7.9 Posterior of sternum 137.8 85.9 223.7 11.9 Umbilicus 80.5 132.7 213.2 6.6 Posterior of Umbilicus 146.9 78.7 225.6 12.8 Left thigh 75.8 139.1 214.9 7.5 Posterior Left Thigh 145.9 81.5 227.4 13.7 Right thigh 77.1 133.7 210.8 5.4 Posterior Right Thigh 130.0 86.5 216.5 8.3 Right Foot 84.6 141.6 226.2 13.1 Bottom of Right Foot 135.9 82.6 218.5 9.3 Average 222.2 11.1 Bao et al. Radiation Oncology 2012, 7:40 Page 6 of 7 http://www.ro-journal.com/content/7/1/40 Table 3 OSL detector dose measurements for cycle two of first patient for reduced MUs OSL Detector AP + LPO + RPO Day 3 Dose PA + LAO + RAO Day 4 Dose Total Dose % Diff from Location (cGy) (cGy) (cGy) Prescription Forehead 96.1 117.2 213.3 6.6 Posterior of Head 121.9 84 205.9 3.0 Umbilicus 79.1 117.3 196.3 18 Posterior of Umbilicus 125.6 72.6 198.2 09 Back of Right Hand 70.5 125.3 195.7 21 Average 201.9 1.0 patient’s head, which had visible lesions, for the second platform in unison with an oxygen airway, IVs, and half of the treatment course based on under dosage of other lines for different beam positions. this region. Although commissioning showed overall surface dose uniformity within ± 10% in the plane perpendicular to Discussion the central axis for an adult patient’s dimensions, there In this work we present the commissioning and quality are many locations which could possibly exceed this assurance processes used to successfully implement a uniformity criterion. Due primarily to surface irregulari- ties, this has also been observed in patients treated by pediatric TSEI program at UTSW. With this modified TSEI for mycosis fungoides. Surface cavities can receive Stanford technique, the sedated pediatric patient is less dose than flat or convex surfaces, while higher secured by a custom made harness and rotational sys- tem attached to a common TBI stand. Though pediatric doses may occur in areas with body protrusions [21,22]. leukemia cutis and the subsequent need for TSEI are With the patient setup described in this work, in-vivo rare, the ability to commission the technique on a modi- dosimetry demonstrated that under dose regions can fied TBI stand is appealing for clinical implementation. occur when the skin is shielded by other body parts To the best of our knowledge this is the first complete (inner thigh and leg regions), when the skin is shielded description of the commissioning and QA of pediatric by patient vital sign monitoring equipment (beneath the TSEI using a modified Stanford technique. Rubin et al. blood pressure cuff), and at the top of the head. The [12] use a similar pediatric TSEI technique for the treat- inner thigh region underdose may be improved with the ment of acute monoblastic leukemia; however, it is pre- use of additional straps to separate the legs; however, a sented as a medical case report with an incomplete boost to the perineum region may still be needed at the description of the irradiation technique and the com- discretion of the physician. In both UTSW clinical missioning and QA methods. Pepek et al. [13] also pre- cases, every attempt was made to move oxygen tube and sent a medical case report for the treatment of leukemia monitoring wires out of the treatment fields and away cutis in pediatric patients. In this work they provide a from the patient. The position of the blood pressure brief description of the irradiation technique, which is cuff was moved throughout the course of treatment to based on a rotating platform at extended distances. The average out the shielding effect. As recommended in pediatricpatientswereofagewheretheywereableto AAPM Report No. 23 [11], the use of boost fields stand on their own in the required positions over the required clinical judgment. Based on in-vivo dosimetry, course of the treatment, thus removing the need for the physician elected for a 6 MeV electron boost to the top of the head for the second patient with a 1 cm sedation and a rotating harness system. Earley et al. [7] describe, to date, the most complete description of the bolus since this region was under dosed during TSEI commissioning of a pediatric TSEI technique for the and this was the location of the isolated skin lesions. treatment of a sedated acute myelocytic leukemia When performing in-vivo dosimetry measurements to patient. In this technique, the sedated patient is placed verify that the prescribed dose is delivered correctly and on a platform that is carried to the floor for AP and PA confirm dose uniformity, the choice of detector is impor- beams and the treatment couch for oblique beams (with tant to consider. Thermoluminescent dosimeters have the gantry moved to different angles). Beam profiles been the most commonly used for TSEI treatments due were acquired at a 200 cm distance for 6 MeV electrons to the small volume minimizing the effect of dose gradi- to assess uniformity. From the authors’ description, it ents across the dosimeter. OSL dosimeters have recently seems the rotating harness system and irradiation tech- been introduced for clinical dose measurements and have nique described in our work would facilitate a faster been implemented in clinical TSEI programs [23]. OSL total treatment time without having to move a patient dosimeters were used for in-vivo measurements due to Bao et al. Radiation Oncology 2012, 7:40 Page 7 of 7 http://www.ro-journal.com/content/7/1/40 4. Karzmark CJ: Large-field superficial electron therapy with linear their ease of use and quick readout with the MicroStar accelerators. Br J Radiol 1964, 37:302-305. reader system. 5. Wu JM, Yeh SA, Hsiao KY, Chao MM, Hargrove I: A conceptual design of Patient safety is of utmost important over the course rotating board technique for delivering total skin electron therapy. Med Phys 2010, 37:1449-1458. of treatment and was of primary consideration in the 6. Podgorsak EB, Pla C, Pla M, Lefebvre PY, Heese R: Physical aspects of a commissioning process. It is crucial for the sedated rotational total skin electron irradiation. Med Phys 1983, 10:159-168. patient in the harness system to remain in the same 7. Earley L, Moeller J, O’Rear J, Leavitt DD: A method for total skin electron treatment for infants. Med Dosim 1995, 20:243-248. position while the treatment team is outside of the 8. Wu JM, Leung SW, Wang CJ, Chui CS: Lying-on position of total skin vault. During commissioning, filled water jugs were electron therapy. Int J Radiat Oncol Biol Phys 1997, 39:521-528. placed in the harness system to demonstrate structural 9. Peters VG, Jaywant SM: Implementation of total skin electron therapy using an optional high dose rate mode on a conventional linear integrity. Velcro straps as well as paper tape were on accelerator. Med Dosim 1995, 20:99-104. hand in abundance to set a consistent position. At every 10. Trump JG, Wright KA, Evans WW, Anson JH, Hare HF, Fromer JL, Jacque G, treatment, a team including an anesthesiologist, nurse, Horne KW: High energy electrons for the treatment of extensive superficial malignant lesions. The American journal of roentgenology, medical physicist, and radiation therapist were present radium therapy, and nuclear medicine 1953, 69:623-629. to secure the patient, monitor the patient, verify treat- 11. Karzmark CJ, Anderson J, Fessenden P, Svensson G, Buffa A, Khan FM, ment settings and setup, and deliver the required radia- Wright KA: Total skin electron therapy: technique and dosimetry. Report of Task Group 30. 1987. tion dose. In addition to in-vivo dosimetry, machine QA 12. Rubin CM, Arthur DC, Meyers G, McClain KL, Kim TH, Woods WG: Leukemia procedures were implemented and performed on each cutis treated with total skin irradiation. Cancer 1985, 55:2649-2652. treatment day to verify proper operation in TSEI mode. 13. Pepek JM, Paulino AC, Briones MA, Marcus RB Jr, Esiashvili N: Role of total skin electron beam therapy for leukemia cutis in pediatric patients. This consisted of checks for output, energy, symmetry, Pediatr Blood Cancer 2008, 50:1054-1055. and flatness constancy. Due to the infrequent use of this 14. Majdzadeh N, Jain SK, Murphy MC, Dugas JP, Hager F, Abdulrahman R: treatment technique it is important, as part of the QA Total skin electron beam radiation in a pediatric patient with leukemia cutis: A case report. Journal of Pediatric Hematology/Oncology . protocol, to verify any changes in the system over time 15. Dusenbery KE, Howells WB, Arthur DC, Alonzo T, Lee JW, Kobrinsky N, which would affect the patient dose, including the abso- Barnard DR, Wells RJ, Buckley JD, Lange BJ, Woods WG: Extramedullary lute output calibration and B-factor. At our clinic, the leukemia in children with newly diagnosed acute myeloid leukemia: a report from the children’s cancer group. Journal of Pediatric Hematology/ second pediatric TSEI case for LC occurred approxi- Oncology 2003, 25:760-768. mately one year following the first case. Prior to the 16. Karzmark CJ, Loevinger R, Steele RE, Weissbluth M: A technique for large- first treatment day of the second pediatric case, a cali- field, superficial electron therapy. Radiology 1960, 74:633-644. 17. Karzmark CJ: Physical aspects of whole-body superficial therapy with brated parallel plate ionization chamber was used for electrons. Front Radiat Ther Oncol 1968, 2:36-54. absolute dosimetry in TSEI mode and the output for 18. A protocol for the determination of absorbed dose from high-energy this mode was adjusted to the value used for initial photon and electron beams. Task Group 21, Radiation Therapy Committee, AAPM. Med Phys 1983, 10:741-771. commissioning. 19. Almond PR, Biggs PJ, Coursey BM, Hanson WF, Huq MS, Nath R, Rogers DW: AAPM’s TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys 1999, 26:1847-1870. Author details 20. Van Der Merwe DG: Total skin electron therapy: A technique which can Department of Radiation Oncology, University of Texas Southwestern be implemented on a conventional electron linear accelerator. Medical Center, 5801 Forest Park Rd, Dallas, TX 75390, USA. Mary Bird International Journal of Radiation Oncology Biology Physics 1993, 27:391-396. Perkins Cancer Center, 4950 Essen Lane, Baton Rouge, LA 70809, USA. 21. Niroomand-Rad A, Gillin MT, Komaki R, Kline RW, Grimm DF: Dose Department of Physics and Astronomy, Louisiana State University, 202 distribution in total skin electron beam irradiation using the six-field Nicholson Hall, Baton Rouge, LA 70803, USA. technique. Int J Radiat Oncol Biol Phys 1986, 12:415-419. 22. Khan FM: Electron beam therapy. The Physics of Radiation Therapy. 4 Authors’ contributions edition. Philadelphia, PA: Lippincott Williams & Wilkins; 2009, 299-306. QB, JPD and FHH conducted the phantom measurement, initial 23. Esquivel C, Smith MS, Stathakis S, Gutierrez A, Shi C, Papanikolaou N: Total commissioning of the setup, and treated the first patient. QB, BAH and FHH skin electron therapy skin dose validation using optically stimulated treated the second patient. QB and BAH drafted the manuscript. TDS luminescent dosimeters [abstract]. AAPM Annual Meeting 2009, ID10746. oversaw the whole procedure. All authors read and approved the final manuscript. doi:10.1186/1748-717X-7-40 Cite this article as: Bao et al.: A technique for pediatric total skin Competing interests electron irradiation. Radiation Oncology 2012 7:40. The authors declare that they have no competing interests. Received: 19 December 2011 Accepted: 20 March 2012 Published: 20 March 2012 References 1. Jones G, Wilson LD, Fox-Goguen L: Total skin electron beam radiotherapy for patients who have mycosis fungoides. Hematol Oncol Clin North Am 2003, 17:1421-1434. 2. Nisce LZ, Safai B, Poussin-Rosillo H: Once weekly total and subtotal skin electron beam therapy for Kaposi’s sarcoma. Cancer 1981, 47:640-644. 3. Leung SW, Hsu HC, Huang PH: Total skin electron beam irradiation in scleromyxoedema. Br J Radiol 1998, 71:84-86.

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Radiation OncologySpringer Journals

Published: Mar 20, 2012

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