Total Skin Electron Irradiation Technique Research Articles

Development of an Intensity Modulated Total Skin Electron Irradiation Technique

During total skin electron irradiation (TSEI) of the pot-bellied patients, the anterior skin areas other than the abdominal area move away from the treatment machine and receive a different dose than that of the prescribed. In this study intensity modulated total skin electron irradiation (IM-TSEI) technique is developed to eliminate the dose irregularity in anterior skin areas. Tissue equivalence of a black ABS filament for 3D printer was determined. Abdominal phantoms of different thicknesses (3-6-9-12-15 cm) were created by a 3D printer. Characteristics of IM-TSEI technique were defined by determining the properties of Stanford technique. In this technique a new angle pair, 12FF and treatment time were determined based on the thickness of the abdominal region at the anterior beam positions and SSD was adjusted on the sternum point. Since there were no contour irregularities in the posterior treatment positions SSD was adjusted to the posterior waist point as in the Stanford technique, and the treatment angle pair and treatment time which created a homogeneous profile were used. The parameters affected by abdominal thickness were determined and depth-dependent dose change measurements were performed. IM-TSEI application parameters for different abdominal thicknesses were determined by combined dose measurements and calculation of treatment times. Quality assurance was done by TLD skin dose and intra-phantom film measurements for each abdominal thickness added on an anthropomorphic human phantom. Non-parametric two related Wilcoxon signed rank test was used for statistical analysis, p value <0.05 was considered significant. Average percent doses of IM-TSEI and TSEI profiles were 99.7% and 101.5%(p = 0.006), 100% and 96.5%(p = 0.000), 98.7% and 94.7% (p = 0.000), 99.8% and 94.4% (p = 0.000), 98.9% and 93% (p = 0.000) for 3,6,9,12,15 cm thicknesses respectively in favor of IM-TSEI. More homogeneous doses were obtained with IM-TSEI technique. Average skin doses of IM-TSEI and TSEI were 0.971 and 0.998 Gy for 3 cm (p = 0.088), 1.046 and 1.044 Gy for 6 cm (p = 0.737), 1.019 and 1.075 Gy for 9 cm (p = 0.013) , 1.009 and 1.073 Gy for 12 cm (p = 0.007), 1.023 and 1.081 Gy for 15 cm (p = 0.014) respectively. Absolute dose difference between anterior body regions and the treatment dose for IM-TSEI and TSEI were 2.94% and 4.24%, 11.65% and 11.46%, 9.04% and 17.12%, 9.98% and 19.30%, 7.42% and 16.52% for 3,6,9,12,15 cm thicknesses respectively. In IM-TSEI technique the absolute dose differences between the prescribed dose and anterior body region and the average skin dose were lower at abdominal thicknesses of 9 cm and above. TLD measurements also revealed that IM-TSEI technique corrected the dose irregularity in anterior body surface due to abdominal thickness. Although IM-TSEI technique can be used safely in all abdominal thicknesses, it is more advantageous than Stanford technique in abdominal thicknesses of 9 cm and above, so it can be used in pot-bellied patients.

Total skin electron therapy (TSET): Monte Carlo Simulation and implementation

Introduction: Total skin electron irradiation technique is used in treatment of the mycosis fungoid. The implementation of this technique requires non-standard measurements and complex dosimetry methods. Operating procedures for total skin electron irradiation and its dosimetry vary in different radiation therapy centers in the world. In this article, validation of TSET technique dosimetry data by Monte Carlo simulation is done. Materials and Methods: The electron beam characteristic of RTSEI for the only electron accelerator, located at the radiation center of the Seyed Alshohada Hospital of Isfahan (NEPTUN 10PC) determined by performing Monte Carlo simulations and using EGSnrc-based codes (BEAMnrc and DOSXYZnrc). For the best uniformity of the vertical profile, the optimal angle of gantry was defined at SSD=300 cm. The effect of the degrader plane that is located at a distance of 20 cm from the patient surface, was evaluated on the amount of energy reduction of the beam, the opening of the electron beam field and the homogeneity of the dose distribution. The transversal dose distribution from the whole treatment with Rotational technique was simulated in a CT- based anthropomorphic phantom. Also, the percentage depth dose in the head, neck, thorax, abdomen and legs was obtained for RTSET technique. TSET dosimetry requires measurements in nonreference conditions. Because of the complexity of the required measurements for the commissioning process of this technique, different dosimetric systems were employed such as radiochromic films (EBT3) and an ionization chamber. In particular, for dual-field beams irradiation, the optimal tilt angle was investigated and the dose distribution in the treatment plane was measured by radiochromic films. Dose distributions and percentage depth dose measurements for a total skin electron therapy were measured in an anthropomorphic phantom. Results: The optimal angle of 20o would give the most uniform total profile and the use of a 0.8 cm PMMA degrader in front of the patient leads to a homogeneous distribution of the dose in all directions (the mean relative dose value was 97%±5%, normalizing to 100% at the calibration point level). The percentage depth dose curves in different organs of anthropomorphic phantom for RTSEI indicates that the depth of maximum dose is on the surface of the phantom, Isodose curve of 80% is formed at a depth less than 4 mm and at the depth less than 1.5 mm, the dose decreases to 20% of the maximum dose. Conclusion: The main purpose of this study was to commission and optimize a TSET technique for the treatment of mycosis fungiodes with the NEPTUN 10PC linear accelerator. This was done through an extensive set of measurements and a large number of MC simulations. The results of Monte Carlo calculations were found to be in general agreement with the measurements, providing a promising tool for further studies of dose distribution calculations in TSEI.

Monte Carlo study and design of system for implementation of Rotational Total Skin Electron Irradiation technique

Total skin electron irradiation technique is used in treatment of the mycosis fungoid. The implementation of this technique requires non-standard measurements and complex dosimetry methods. Depending on the linear accelerator (Linac) type, bunker size, room dimensions and dosimetry equipment, the design of instruments for appropriate set up and implementation of TSEI in different radiation therapy centers varies. The studies which have been done in this article provide an introduction to the implementing of this method for the first time in Iran and its results can be used for the centers with similar specifications in the world. This article determined the electron beam characteristic of TSEI for the only electron accelerator, located at the radiation center of the Seyed Alshohada Hospital of Isfahan (NEPTUN 10PC), by performing Monte Carlo simulations and using EGSnrc-based codes (BEAMnrc and DOSXYZnrc). For the best uniformity of the vertical profile, the optimal angle of gantry was defined at SSD=350 cm. The effect of the degrader plane that is located at a distance of 20 cm from the patient surface, was evaluated on the amount of energy reduction of the beam, the opening of the electron beam field and the homogeneity of the dose distribution. The transversal dose distribution from the whole treatment with Stanford technique (six dual fields) and Rotational technique was simulated in a CT-based anthropomorphic phantom. Also, the percentage depth dose in the head, neck, thorax, abdomen and legs was obtained for both methods. The simulation results show that the 20̂ angle between the horizontal and the beam central axis is optimal in order to provide the best vertical dose uniformity. The mean energy decreases from 6.1 MeV (the exit window) to 3 MeV (the treatment surface) by placing a degrader with 0.8 cm thickness in front of the treatment plane. FWHM of the angular distribution of the electron beam increased from 15̂ at SSD=100 cm to more than 30̂ on the treatment surface by traversing the PMMA degrader. The MC calculated percentage depth dose curves in different organs of anthropomorphic phantom for RTSEI indicates that the depth of maximum dose is on the surface of the phantom and Isodose curve of 80% is formed at a depth less than 4 mm. the results also show, with the degrader plane in front of the patient, the degree of homogeneity of the dose distribution for both Stanford and rotational techniques is the same.

Failure modes and effects analysis of total skin electron irradiation technique.

Total skin electron irradiation (TSEI) is a radiotherapy technique which consists of an homogeneous body surface irradiation by electrons. This treatment requires very strict technical and dosimetric conditions, requiring the implementation of multiple controls. Recently, the Task Group 100 report of the AAPM has recommended adapting the quality assurance program of the facility to the risks of their processes. A multidisciplinary team evaluated the potential failure modes (FMs) of every process step, regardless of the management tools applied in the installation. For every FM, occurrence (O), severity (S) and detectability (D) by consensus was evaluated, which resulted in the risk priority number (RPN), which permitted the ranking of the FMs. Subsequently, all the management tools used, related to the TSEI process, were examined and the FMs were reevaluated, to analyze the effectiveness of these tools and to propose new management tools to cover the greater risk FMs. 361 FMs were identified, 103 of which had RPN ≥80, initially, and 41 had S≥8. Taking this into account the quality management tools FMs were reevaluated and only 30 FMs had RPN≥80. The study of these 30 FMs emphasized that the FMs that involved greater risk were related to the diffuser screen placement and the patient's position during treatment. The quality assurance program of the facility has been adapted to the risk of this treatment process, following the guidelines proposed by the TG-100. However, clinical experience continually reveals new FMs, so the need for periodic risk analysis is required.

SU‐F‐T‐248: FMEA Risk Analysis Implementation (AAPM TG‐100) in Total Skin Electron Irradiation Technique

Purpose:Total Skin Electron Irradiation (TSEI) is a radiotherapy treatment which involves irradiating the entire body surface as homogeneously as possible. It is composed of an extensive multi‐step technique in which quality management requires high consumption of resources and a fluid communication between the involved staff, necessary to improve the safety of treatment. The TG‐100 proposes a new perspective of quality management in radiotherapy, presenting a systematic method of risk analysis throughout the global flow of the stages through the patient. The purpose of this work has been to apply TG‐100 approach to the TSEI procedure in our institution.Methods:A multidisciplinary team specifically targeting TSEI procedure was formed, that met regularly and jointly developed the process map (PM), following TG‐100 guidelines of the AAPM. This PM is a visual representation of the temporal flow of steps through the patient since start until the end of his stay in the radiotherapy service.Results:This is the first stage of the full risk analysis, which is being carried out in the center. The PM provides an overview of the process and facilitates the understanding of the team members who will participate in the subsequent analysis. Currently, the team is implementing the analysis of failure modes and effects (FMEA). The failure modes of each of the steps have been identified and assessors are assigning a value of severity (S), frequency of occurrence (O) and lack of detection (D) individually. To our knowledge, this is the first PM made for the TSEI. The developed PM can be useful for those centers that intend to implement the TSEI technique.Conclusion:The PM of TSEI technique has been established, as the first stage of full risk analysis, performed in a reference center in this treatment.

EP-1392: Validation of total skin electron irradiation technique dosimetry data by Monte Carlo simulation

EP-1392: Validation of total skin electron irradiation technique dosimetry data by Monte Carlo simulation

EP-1479: In vivo dosimetry with MOSFET and EBT3Æ film for total skin electron irradiation technique

EP-1479: In vivo dosimetry with MOSFET and EBT3Æ film for total skin electron irradiation technique

Advantages and implications of high dose rate (HDR) total skin electron irradiation (TSEI) for the management of Mycosis Fungoides. Indian experience

BackgroundMycosis Fungoides (MF) is an indolent lymphoproliferative disorder affecting dermis caused by abnormal proliferation of CD4+ T-cells. Radiation therapy is the most effective modality of treatment for MF which offers cure in limited stage disease and desirable palliation in advance stage disease. Treating entire skin having many curved surfaces and folds with radiation is the real challenge for the radiation oncologist. Many techniques, dose schedules and modifications in total skin electron irradiation (TSEI) have been tried since 1950s. TSEI treatment is a very time consuming, inconvenient and physically challenging to both patient as well as oncologist. AimAt our center TSEI was performed since 1983 with conventional linear accelerator where the treatment time was prolonged beyond two hours, which was very difficult or the patient, oncologist, technical officer and eating away the machine time hampering the treatment of other patients. From 1998 we shifted to high dose rate (HDR) mode, in order to bring down the treatment time of a single patient every day from two and half hour to 15min. The reduction of treatment time increases patient compliance and at the same time saved machine time. Materials and methodsBetween 1998 and 2003, eleven pathological diagnosed MF patients were treated using HDR TSEI. All the patients were male between 40 and 70 years of age, who had the history of having the disease for 7–22 months. Four patients had T2 and seven patients had T3 stage disease with more than 90% skin surface involvement. TSEI was performed with 4MeV electrons with a daily fraction size of 120cGy to a total dose of 36Gy. At the end of 36Gy, boost dose of 10Gy was delivered to self shielding regions like sole, scalp and perineum. Considering the treatment related toxicities and consequent treatment interruptions, in the first seven patients, the last four patients were treated using similar HDR TSEI technique with modified treatment schedule, where the treatment was given on an alternate day basis following 2nd week of initiation of treatment. ResultsThe patients were followed over a period of 144 months with a median of 72 months. Nine patients are alive without any evidence of disease, one patient relapsed and one died due to progression of disease. The most common radiation related morbidities are erythema, skin blisters, various degree of desquamations, swelling of joints (specially small joints) etc. which are controlled by treatment interruptions and conservative measures. By modifying the treatment schedule, the incidence of toxicity as well as treatment interruptions were brought down. ConclusionsWe can conclude that HDR-TSEI is an excellent and safe therapeutic modality for the patients with MF both curative as well as palliative without any added toxicity profile, provided patient positioning is done properly.

SU‐GG‐T‐266: Implementation of Total Skin Electron Irradiation (TSEI) Using High Dose Rate Mode at Siriraj Hospital

Purpose: To implement and commissioning of applied Stanford total skin electron irradiation (TSEI) technique using standard linear accelerator at our institute. Method and Materials: Patient was treated in six different upright patient positions using dual angle fields. This study was carried out on Varian 23EX linear accelerator with 6 MeV, 36×36 cm2 field size at collimator in HDTSe mode at a SSD of 400 cm behind a beam degrader. The dosimetric characteristics were verified experimentally using a parallel plate ion chamber, electron diodes, and TLD‐100 chip and rod types. The delivered dose is 36 Gy in 9 weeks. The basic dosimetric parameter consists of beam profile, depth dose curve and electron beam output in the treatment plane. The output and depth dose curve was measured by PTW23343 Markus chamber in solid phantom. Delivered dose from six dual fields technique in treatment position was verified on round phantom by TLD‐100. Results: The uniform vertical profile was obtained for gantry angulations of ± 17.5 degree above and below horizontal within 10% of the prescribed dose. The depth dose curve shows maximum dose at skin surface. The mean energy is 2.09 MeV with beam degrader 1 cm thick. The dose uniformity from six dual fields on round phantom is within 10%. The average measured skin dose in the anterior and posterior at the level of head, chest and pelvis on rando phantom is within 10% of prescribed point. Total X‐ray contamination in the rando phantom is about 1.35% of the delivered dose. Conclusion: The TSEI technique using six dual fields applied Stanford technique produced a uniformity at the whole patient's surface cannot be better than 15% of the prescribed dose because of variable skin distance, self‐shielding, and differences in curvature.

SU‐FF‐T‐387: Rotational Total Skin Electron Irradiation Using a Commercially Available Linear Accelerator with a High Dose Rate Total Body Electron Mode

Purpose: During the past 25 years, 185 patients have been treated with a rotational total skin electron irradiation (RTSEI) technique in our center. To modernize the technique we recently transferred it from a linac (Varian Clinac‐18) with a custom modified beam line to a linac (Varian 21EX) with a commercially available electron mode intended for total skin electron irradiation. Methods and Materials: The new technique uses a “high dose rate” mode and a “high dose per Monitor Unit” mode in conjunction with a custom‐made flattening filter to produce a uniform beam at an extended SSD of 378 cm. The accessory tray holds the custom‐made flattening filter and automatically selects the beam energy (6 MeV) and high dose rate (888 MU/min) while moving the collimators to the maximum 40 × 40 cm2 field size. Beam parameters are monitored using the record‐and‐verify (VARIS) system. Results: Reference dosimetry for the stationary and rotational electron fields was performed to allow delivery of the prescription dose using the linac's transmission ionization chamber. Patients are treated on a rotating platform with a high dose rate rotational electron beam having a zmax at the skin surface, an R50 at 15 mm and a bremsstrahlung contamination of the order of 3%. The nominal dose rate to water at zmax (surface) for the rotational technique was determined to be 24.1 cGy/1000 MU, and beam delivery is monitored with a secondary Farmer‐type ionization chamber located near the patient in the treatment field. Conclusions: Treatment times with the rotational total skin electron irradiation technique at an SSD of 378 cm for a daily dose of 2.0 Gy are of the order of 9.5 minutes and to date we have treated 15 patients with this technique.

Variation of electron beam uniformity with beam angulation and scatterer position for total skin irradiation with the stanford technique

Purpose : The influence of different scatterer-degraders and beam angulations on beam uniformity for total skin electron irradiation using the six dual beam Stanford technique is investigated. Methods and Materials : The 6 MeV high dose rate total skin electron irradiation mode on a linear accelerator was used. Beam profiles and percentage depth doses in the patient plane for single, dual, and six dual beams were measured for different dual beam angulations and acrylic scatterer-degraders of different thicknesses mounted on the treatment head or in front of the patient in the treatment plane. Results : It is demonstrated that, with the same electron nominal energy, total skin irradiation techniques with different beam penetrations can be obtained by inserting various beam scatterer-degraders into the beam, either mounted on the accelerator head or close to the patient. For our patient treatment, a beam penetration was selected so that the 80% dose lay at 8–9 mm and the 50% dose at 15–16 mm depth. This was achieved by mounting a 0.32-cm thick acrylic beam scatterer-degrader on the accelerator head. A uniform vertical profile was obtained for gantry angulations of ±21°. Conclusions : To implement a total skin electron irradiation technique using the Stanford method, the required depth of penetration needs to be selected. Based on this, the appropriate combination of scatterer-degraders and dual beam angulations to produce a uniform beam in the treatment plane needs to be determined. Different techniques with different beam penetrations can be developed using the same high dose rate mode on the linear accelerator by a proper choice of scatterer-degraders and beam angulations.

Clinical experience with a single field rotational total skin electron irradiation technique for cutaneous T-cell lymphoma

Between October 1981 and December 1989, 44 patients with cutaneous T-cell lymphoma (CTCL) were treated with a single field rotational total skin electron irradiation (RTSEI) technique developed in the McGill University, Department of Radiation Oncology. Only 11 (25%) of the 44 patients had received no prior treatment. Three-quarters ( 33 44 ) had advanced (T 3 or T 4) disease. Complete responses were seen in ( 32 44 (73%) of patients (91% T 2, 71% T 3 and 58% T 4), but only ( 3 11 , (27%) of patients with T 2 disease and ( 3 21 (14%) of patients with T 3 disease remain in continuous complete remission in the skin, after median intervals of 58 and 35 months, respectively. Median cause-specific survival for the whole group is 43 months and survival at 5 years is 38%. Survival was significantly better for patients with T 2 disease than for patients with T 3 disease (relative risk 4.3; 95% CI 1.4–13.2) and patients with T 4 disease (relative risk 3.1; 95% CI 0.8–12.1). The RTSEI technique used at McGill has depth-dose characteristics and photon contamination similar to other commonly used TSEI techniques. It is relatively simple and provides a homogenous dose distribution over the entire skin surface in a short treatment time. Results of treatment are similar to those obtained with other techniques. For T 2 disease, TSEI is an effective treatment modality with a possibility of long-term tumor control. For more advanced disease, more aggressive treatment, which may include TSEI, is necessary.

Total skin electron arc irradiation using a reclined patient position

Several techniques for the treatment of the total skin of the patient using electron beams have been described in the literature. However, most techniques presuppose that the patient is capable of maintaining a standing position for the duration of the treatment. For patients either weakened by disease or those suffering from a loss of limbs, this is often an unrealistic expectation. We will describe a total skin electron irradiation technique that allows the patient to remain in a reclined position without sacrificing dose uniformity. This technique uses two symmetric ±48° arc electron beams to provide a field uniformity of ±5% over a range of ∼250 cm X 45 cm. Six patient positions are used to provide a uniform dose around the periphery of the patient. A description of the treatment technique along with details of the dosimetry are given.

Calculation of surface dose in rotational total skin electron irradiation.

A single-field rotational total skin electron irradiation technique has recently been developed at the McGill University for treatment of skin malignancies. The dose received by a given surface point during rotation in a uniform large electron field depends on the radius of rotation of the surface point, on the local radius of curvature of the contour in the vicinity of the point of interest, and on the shadows cast by limbs (arms upon trunk or head and neck, and legs upon each other). A method for calculating the surface dose distribution on a patient is presented accounting for the various parameters affecting the dose. A series of measurements were performed with polystyrene and a humanoid phantom, and an excellent agreement between measured and calculated dose distributions was obtained.

Clinical aspects of a rotational total skin electron irradiation.

A simple rotational total skin electron irradiation technique utilising a single large field electron beam is presented. Clinical and technical aspects of the technique are discussed and treatment results for the first 10 patients treated for widespread mycosis fungoides reported. The technique is simple and well tolerated by patients, and can easily be implemented in centres utilising electron beam radiotherapy.