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Total Skin Electron Therapy Using Rotational Vs Static Fields Irradiation Techniques with and Without a Scatter Plate

G Ding*, M Price , Vanderbilt University, Nashville, TN


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

Room: Exhibit Hall

Purpose: To evaluate the dose distributions of total skin electron (TSE) therapy between using rotational dual fields and 6 static dual fields with and without scatter plate.

Methods: We studied a 6 MeV optional high-dose total skin electron (HDTSe) beam at a dose rate of 2500 monitor units per minute from Varian TrueBeam Linac which is housed in a conventional radiation therapy treatment room. The EGSnrc Monte Carlo simulation codes are used to model the realistic beams and to calculate the dose distributions. The simulated beams are benchmarked with experiments. The angle between the two dual beams is 43 degrees. The jaws are set to the opening to give 36 x 36 cm² field at SSD=100 cm. An acrylic scattering plate (1 cm thick) is 50 cm x 200 cm. When the plate is used it is placed 179 cm from the Linac isocenter, the electron beam passes through the scatter plate before it impinges on the patient. The patient stands at a distance of 225 cm from Linac isocenter on a rotating platform.

Results: There is no significant difference in dose distributions between using rotational dual-fields and 6 static dual fields. Both irradiation techniques provide uniform dose distribution to patient skin with maximum dose at the surface. The depth that dose falls to 50% of dose at the skin surface is approximately 0.6 cm and 1.3 cm for with and without acrylic scatter plate respectively.

Conclusion: The results of the comparison show that both rotational dual fields and 6 static dual fields provide equally uniform dose distributions to patient skin. The therapeutic treatment depth can be increased by 0.7 cm by removing the 1 cm thick acrylic scattering plate while still maintaining the maximum dose at the skin surface.


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