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A Novel Technique for Scleredema Treatment Using Electron Therapy

N Neba1*, S Howard2 , J Coster3 , A Brito Delgado4 , H Saleh5 , K Guida6 , (1) ,,,(2) University of Kansas Health System, Overland Park, KS, (3) University of Kansas Health System, Overland Park, KS, (4) University of Kansas Hospital, Shawnee, KS, (5) University of Kansas Medical Center, Kansas City, Kansas, (6) University of Kansas Hospital, Kansas City, MO

Presentations

(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

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 “stationary� 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 “Rotational� 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.

Keywords

Electron Therapy, Total Skin Irradiation, MOSFET Detector

Taxonomy

TH- External beam- electrons: General (most aspects)

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