Rotational Total Skin Electron Irradiation Research Articles

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.

SU‐F‐T‐70: A High Dose Rate Total Skin Electron Irradiation Technique with A Specific Inter‐Film Variation Correction Method for Very Large Electron Beam Fields

Purpose:Rotational total skin electron irradiation (RTSEI) is used in the treatment of cutaneous T‐cell lymphoma. Due to inter‐film uniformity variations the dosimetry measurement of a large electron beam of a very low energy is challenging. This work provides a method to improve the accuracy of flatness and symmetry for a very large treatment field of low electron energy used in dual beam RTSEI.Methods:RTSEI is delivered by dual angles field a gantry of ±20 degrees of 270 to cover the upper and the lower halves of the patient body with acceptable beam uniformity. The field size is in the order of 230cm in vertical height and 120 cm in horizontal width and beam energy is a degraded 6 MeV (6 mm of PMMA spoiler). We utilized parallel plate chambers, Gafchromic films and OSLDs as a measuring devices for absolute dose, B‐Factor, stationary and rotational percent depth dose and beam uniformity. To reduce inter‐film dosimetric variation we introduced a new specific correction method to analyze beam uniformity. This correction method uses some image processing techniques combining film value before and after radiation dose to compensate the inter‐variation dose response differences among films.Results:Stationary and rotational depth of dose demonstrated that the Rp is 2 cm for rotational and the maximum dose is shifted toward the surface (3mm). The dosimetry for the phantom showed that dose uniformity reduced to 3.01% for the vertical flatness and 2.35% for horizontal flatness after correction thus achieving better flatness and uniformity. The absolute dose readings of calibrated films after our correction matched with the readings from OSLD.Conclusion:The proposed correction method for Gafchromic films will be a useful tool to correct inter‐film dosimetric variation for the future clinical film dosimetry verification in very large fields, allowing the optimizations of other parameters.

CD30+ Cutaneous T Cell Lymphoma: Response to Rotational Total Skin Electron Irradiation.

IntroductionRotational total skin electron irradiation (RTSEI) is an effective therapy for cutaneous T cell lymphoma (CTCL). CD30 expression has been identified as a prognostic factor in CTCL. Therefore, we investigated CD30 status, treatment response, and survival in our cohort of patients with CTCL treated with RTSEI.MethodsPatients with CTCL treated with RTSEI (≥30 Gy) between 2000 and 2013 at our institution were identified, and clinical and pathologic data were retrospectively reviewed. Primary outcomes were complete clinical response (CCR; >90% reduction of skin disease burden), relapse-free survival (RFS), and overall survival (OS).ResultsSixty-eight patients with CTCL treated with RTSEI were identified. Median age at diagnosis was 51 years with median follow-up of 61 months. Median OS was 76 months and median RFS was 11 months. Thirteen patients (19%) had CD30+ lymphocytes on initial pathology. In the CD30+ cohort, there were no T2, eight T3, and five T4 cases. In comparison, in the CD30− cohort, there were 18 T2, 29 T3, and 8 T4 cases (P = 0.01). Six weeks post-RTSEI, CCR was 85% in CD30+ and 81% in CD30− cases (P = 1). Six months post-RTSEI, CCR was 23% in CD30+ and 50% in CD30− cases (P = 0.083).ConclusionRTSEI resulted in excellent CCR at 6 weeks in our cohort of patients with CTCL, with a median RFS of 11 months. We found CD30+ patients presented with significantly higher T stage at time of RTSEI and trended towards decreased CCR at 6 months post-RTSEI compared with the CD30− group.

Cutaneous CD30+ Mycosis Fungoides: Response to Rotational Total Skin Electron Irradiation

Cutaneous CD30+ Mycosis Fungoides: Response to Rotational Total Skin Electron Irradiation

Total Skin Electron Therapy for Cutaneous T-Cell Lymphoma Using a Modern Dual-Field Rotational Technique

To report our experience with rotational total skin electron irradiation (RTSEI) in cutaneous T-cell lymphoma (CTCL), and to examine response by disease stage and race. We reviewed our outcomes for 68 CTCL patients who received RTSEI (≥ 30 Gy) from 2000 to 2013. Primary outcomes were complete clinical response (CCR), recurrence-free survival (RFS), and overall survival (OS). Using log-rank tests and Cox proportional hazards, OS and RFS were compared across tumor stages at time of RTSEI with further racial subgroup analysis. Median age at diagnosis and at time of radiation was 52 and 56 years, respectively. Median follow-up was 5.1 years, 49% were African American, and 49% were female. At time of treatment, 18, 37, and 13 patients were T stage 2, 3, and 4, respectively. At 6 weeks after RTSEI, overall CCR was 82% (88%, 83%, and 69% for T2, T3, and T4, respectively). Median RFS was 11 months for all patients and 14, 10, and 12 months for stage T2, T3, and T4, respectively. Tumor stage was not associated with RFS or CCR. Maintenance therapy after RTSEI was associated with improved RFS in both crude and multivariable analysis, controlling for T stage. Median OS was 76 months (91 and 59 months for T3 and T4, respectively). With the exception of improved OS in African Americans compared with whites at stage T2, race was not associated with CCR, RFS, or OS. These results represent the largest RTSEI clinical outcomes study in the modern era using a dual-field rotational technique. Our observed response rates match or improve upon the standard set by previous outcome studies using conventional TSEI techniques, despite a large percentage of advanced CTCL lesions in our cohort. We found that clinical response after RTSEI did not seem to be affected by T stage or race.

Total Skin Electron Irradiation (TSEI) Using Rotational Technique for Cutaneous T-Cell Lymphoma

To review the clinical outcomes for a single institutional experience of using rotational total skin electron irradiation (R-TSEI) technique of 30 Gy or greater in patients with primary cutaneous t-cell lymphoma (CTCL).

SU‐C‐BRA‐05: Commissioning of Rotational Total Skin Electron Irradiation on Trilogy Machine

Purpose: To commission 6MEV beam in HDTSe mode on a Varian Trilogy machine for rotational total skin treatment. Methods: HDTSe 6MEV beam with field size 40cm × 40cm at 380cm SSD was planned for total skin irradiation treatment. A custom designed flattening filter was added to improve beam uniformity. Rotational speed during treatment was to set at 3–5 revolution/minute. Beam calibration was at 100cm SSD following TG51 protocol. Beam parameters at extended distance were measured using GafChromic EBT2 films placed in solid water phantom. 30cm × 30cm square phantom and 33cm diameter round phantom were for stationary and rotational target respectively. Dose distribution during rotational treatment was verified by GafChromic films sandwiched inside a Rando phantom. Beam uniformity was verified using Kodak EDR2 ready pack films on a ½” thick, 4′×8′ plexiglas hanging perpendicular to the beam at distance. Results: At SSD of 380cm, with filter in place, stationary beam output was 89.6cGy/1000mu; dmax is at 0.9 cm; R50 is 1.82 cm and Rp is2.4cm. With rotational target, dmax is shifted to surface with R50 at 1.54 cm and output at surface was 38.8cGy/1000mu. Measured rotational factor was 0.433. X‐ray contamination is of the order of 3% for rotational target. Dose uniformity along the vertical axis from −90 cm to about 80cm is within +/− 5%, and within +/−10% from ‐95cm to 95cm. For the horizontal axis, the entire range is covered with the dose of better than 95%. Dose distribution using the rotational technique was shown to be uniform at different levels of a Rando phantom Conclusions: Dosimetric properties of the modified HDTSe 6MEV beam on a Varian Trilogy machine are verified to be optimal for rotational total skin irradiation treatment.

Rotational total skin electron irradiation with a linear accelerator

The rotational total skin electron irradiation (RTSEI) technique at our institution has undergone several developments over the past few years. Replacement of the formerly used linear accelerator has prompted many modifications to the previous technique. With the current technique, the patient is treated with a single large field while standing on a rotating platform, at a source‐to‐surface distance of 380 cm. The electron field is produced by a Varian 21EX linear accelerator using the commercially available 6 MeV high dose rate total skin electron mode, along with a custom‐built flattening filter. Ionization chambers, radiochromic film, and MOSFET (metal oxide semiconductor field effect transistor) detectors have been used to determine the dosimetric properties of this technique. Measurements investigating the stationary beam properties, the effects of full rotation, and the dose distributions to a humanoid phantom are reported. The current treatment technique and dose regimen are also described.PACS numbers: 87.55.ne, 87.53.Hv, 87.53.Mr

Sci‐Sat AM (2) Therapy‐01: A rotational total skin electron irradiation technique using a linear accelerator with a commercially available high dose rate total body electron mode

We have transferred and modernized our 25‐year‐old rotational total skin electron irradiation (RTSEI) technique 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. 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. 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. 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. Patients are treated on a rotating platform with a high dose rate 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. Treatment times 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.

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.

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.

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.

Physical aspects of a rotational total skin electron irradiation.

A technique for rotational total skin electron irradiation is presented in which the patient stands on a slowly rotating platform (SSD = 285 cm) in a large uniform linear accelerator electron field (Eo = 3.5 MeV). The beam is scattered by the transmission ionization chamber and by a special lead/aluminum scattering filter, and then degraded by a sheet of Lucite. A Farmer chamber is used as a patient dose monitor and a method for absolute dose calibration is presented. The field is uniform to within +/- 5% for dimensions of 180 X 40 cm2. The surface dose for rotational therapy is equal to 45% of the maximum dose in a stationary beam. The rotating beam exhibits a dose maximum on the surface, falls to 80% at 0.5 cm and has an x-ray contamination of approximately 4%. The surface dose rate is about 25 cGy/min for the rotating beam. The rotational beam percentage depth dose distributions, calculated using stationary beam information, agree well with measured data. The stationary beam exhibits a dose maximum at 4 mm in tissue, a surface dose of 93%, 80% dose at a depth of 1 cm, a practical range of 1.75 cm, and an x-ray contamination of 2.5%. The rotational total skin electron irradiation significantly reduces the patient treatment and setup time and solves the problem of beam matching, when compared to standard multiple-beam techniques.