Room: Exhibit Hall
Purpose: We present a unique method for treatment of scleredema using circumferential partial body electron therapy. This rotational technique delivers a uniform dose to a depth of 1cm for optimal clinical management of this condition.
Methods: The system consisted of a custom rotating platform fitted with Styrofoam to reduce scatter radiation. The platform was set to a rotating speed of 2RPM and a treatment distance (SSD) of 330cm. A degrader located at 75.5cm from isocenter leads to a â€œstationaryâ€? dmax of 1cm for 9 MeV electrons. Best dose uniformity was achieved at gantry angles of 67 degrees and 113 degrees.Absolute dose calibration was done as per TG-51. The â€œRotationalâ€? PDD had dmax at 0.6cm. Mosfet measurements at this depth gave the dose per monitor unit for the rotational case. A Rotational factor, R, was determined using equation 1.The total number of MUs per fraction was calculated using equation 2. Final End-to-End tests were done by placing MOSFETs at depths of 1cm around the phantom encompassing the entire treatment length.
Results: Plots of the stationary and rotational PDDs, vertical profiles are shown in figures 1 and 2 respectively. TG-51 calibration gave a Dmax of 0.046cGy/MU. Rotational Dmax was 0.0085cGy/MU, resulting in an R factor of 5.4. For 100cGy prescription dose to 1cm depth, the total number of MUs was 11739 (5870 per field). Results of end-to-end test for this prescription are shown in figure 2.
Conclusion: The results validated that our partial TSET can effectively deliver the prescribed dose to the required skin depth for scleredema treatment. However, a disadvantage is longer treatment times due to increased treatment depth compared to standard TSET.