Room: AAPM ePoster Library
Purpose: clinic routinely treats adult total skin electron irradiation (TSI) patients. Patients must stand, posing, for long periods of time during irradiation. The purpose of this study is to commission a recumbent TSI procedure on a Siemens Artiste accelerator accommodating the necessary sedation for treating a 3.5-year-old T-cell lymphoma patient with skin involvement.
Methods: and Antolak previously developed a recumbent TSI technique with a Varian Truebeam at the Mayo Clinic from which our approach was informed. The technique consists of 6 equally-weighted and spaced, low-energy, electron irradiations about the patient axis. Gantry angles were chosen to maximize flatness. A 25x25 electron cone was modified by removing the scrapers and bolting a 6 mm thick acrylic sheet across the opening in order to disperse and reduce the treatment beam energy. No additional spoilers were required. Patient was positioned both prone and supine on a foam mattress for treatments. Styrofoam blocks were used to elevate arms and legs to avoid self-shadowing. OSLD detectors were used to monitor the skin dose for each fraction, and patient position readjusted per the running average dose measurements.
Results: flatness was within 11% across all treatment dimensions for all beams. Dose uniformity across the Alderson-RANDO phantom was within +/- 15% (n=35) (excluding apex of head). We found a broad bremsstrahlung component (1.6% on axis, 5 cm deep). The final accumulated treatment dose distribution was within clinical expectations. Additional, anticipated, electron boost treatments were performed to patient’s axilla, perineum, and scalp.
Conclusion: treatment was highly successful, with no further evidence of skin disease. The patient’s fractional skin dose was very sensitive to daily positioning changes and needed to be monitored and patient position re-adjusted each fraction. Patients with height < 100 cm and chest diameter < 15 cm may be treated with this procedure.