SU-E-T-68: Clinical Implementation of Total Skin Electron Beam Therapy: A New- York Presbyterian Hospital Experience

Authors


Abstract

Purpose:

Total skin electron beam therapy (TSET) is used in the treatment of rare skin diseases such as mycosis fungoides, the most common type of cutaneous T-cell lymphoma. We report our experience with clinical implementation of TSET.

Methods:

A modified six-dual-field irradiation technique was chosen to deliver TSET. A Varian Trilogy linear accelerator with a nominal 6 MeV beam using high dose rate total skin electron mode (HDTSe) was employed. The recommendations of AAPM task group report 23 were followed for the commissioning. An acrylic plate (energy degrader) of 3.2 mm depth was mounted on the HDTSe applicator. The nominal source to skin distance was set at 450 cm. The optimum tilt angle of the gantry was determined using NACP-02 ionization chamber embedded in certified therapy grade solid water. Percent depth dose measurements were performed using ionization chamber and radiochromic films embedded in solid water and anthropomorphic phantom. For absolute dose measurements, TG-51 formalism was employed. The dose distribution on the entire skin was measured by irradiating the anthropomorphic phantom, with TLDs attached, mimicking the real treatment.

Results:

The 3.2 mm acrylic plate mounted on the HDTSe applicator degraded the energy of the electron beam to 4.1 MeV in the treatment plane, located at an SSD of 450 cm. The optimum tilt angle was found to be ±20°. A single-dual field had a longitudinal uniformity, measured at a depth of dose maximum, of ±7% over a length of about 200 cm. For the entire treatment the multiplication factor was found to be 2.86. On the surface of the phantom, the dose varied from 108% to 93% of the prescription dose.

Conclusion:

We have successfully commissioned TSET meeting the guidelines of the TG report 23, and treated our first patient on February 25, 2014.

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