Abstract
Total skin electron therapy (TSET) is used for the treatment of Mycosis Fungoides. Several tech-niques have been developed, in order to achieve homogeneous dose distribution over the complete body surface. To implement a TSET technique, one has to optimize a variety of parameters. Monte Carlo simulation of TSET can facilitate this optimization. The aim of this study was to commission and optimize a TSET technique using the 4 and 6 MeV electron and the high dose rate facility on the Elekta Precise accelerator. The EGS4nrc/BEAMnrc Monte Carlo code was used. The beam data were calculated and measured at two different scoring planes for a single beam. The Model was validated by comparing the simulation with measurements. Two different vertical angles were used to obtain a uniform dose. The angle was optimized for best dose uniformity. The Rando phantom is placed on a rotating platform and rotates 60 degrees apart to facilitate the six patient position orientations. The doses delivered in a phantom by complete treatment were measured with Kodak EDR2 films and TLDs. The dose distribution varied among various scanning directions by 2 - 3 mm and 3 - 4 mm for 4 and 6 MeV respectively. The composite percentage depth dose of all six dual fields for the 4 and 6 MeV yielded an R80 of ~4 mm and ~6 mm, respectively. Dose uniformity was ±6% for 4 MeV and ±5% for 6 MeV. The bremsstrahlung contamination was 0.9% - 1.3%. Good agreements were found with published literature and inline with international protocols.
Highlights
Skin tumors, such as mycosis fungoides and cutaneous lymphomas, are often treated with nitrogen mustard and Photo Ultra Violet type-A (PUVA) [1], but the most effective treatment is Total Skin Electron Therapy (TSET) [2]-[4]
Monte Carlo (MC) simulation has been successfully used for TSET beam design and optimization, most of the above studies were limited to a single electron energy that produced by Siemens or Varian Linear accelerates
It can be clearly seen from the results that the dose rate at treatment plane in High Dose Rate Electron (HDRE) mode is comparable with the dose rate at isocentre in normal mode
Summary
Skin tumors, such as mycosis fungoides and cutaneous lymphomas, are often treated with nitrogen mustard and Photo Ultra Violet type-A (PUVA) [1], but the most effective treatment is Total Skin Electron Therapy (TSET) [2]-[4]. The technique aims to deliver a relatively uniform dose distributions over the entire surface of standing body at an extended distances (e.g. 350 cm), while maintain minimum X-ray contaminations and limited doses to Organ-At-Risks (OAR). This will remain a challenge to achieve, because of the irregular shape of the body, which will result in non-uniform dose distributions on the skin surface [5] [7] [8] [10]. The dosimetric procedure intends to obtain adequate dose uniformity over the entire surface of the patient, and to reduce the patient treatment time using a high dose rate facility on the Elekta Precise accelerator
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