(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: Anesthesia is commonly used to immobilize young children during radiation therapy, however it can create a negative patient experience. A pediatric video projection system, intended as an alternative to anesthesia, was tested to quantify the dosimetric effects of materials in the path of the treatment beam.
Methods: Output measurements for four sample screen materials, 2cm of carbon fiber, 0.3cm of polycarbonate, and a Calypso detector panel, were measured on a Varian Truebeam. A farmer chamber at 10cm depth in solid water was used to measure the attenuation of each material placed 15cm from the surface of the solid water. A Markus parallel plate chamber was also used to measure surface dose.
Results: For a 6MV, 10x10cm2 field, at 10cm depth the attenuation caused by 2cm carbon fiber was 2.31% (STDEV 0.03%), for 0.3cm polycarbonate it was 1.56% (STDEV 0.04%), for Calypso detector 1.34% (STDEV 0.03%), and for the screen samples an average 0.28% (STDEV 0.08%). For the same beam parameters, the surface dose enhancement was 13.16% (STDEV 2.27%) for 2cm carbon fiber, 12.66% (STEDEV 0.99%) for 0.3cm polycarbonate, 16.70% (STDEV 2.00%) for Calypso detector, and an average 3.57% (STDEV 2.39%) for the samples. For a 10MV beam, with all other parameters constant, the materials demonstrated a decrease in percent difference from open for both attenuation at a depth and surface dose compared to the 6MV.
Conclusion: Attenuation and surface dose effects were quantified for the potential materials in the pediatric system. The four samples had a negligible effect on attenuation at large depth. They showed a small, but measureable effect on surface dose increase. All screen materials tested could be suitable for the pediatric video projector system, however the surface dose effects should be considered in moving forward with the system development.
Keywords
Immobilization, Patient Movement, Radiation Therapy
Taxonomy
TH- External beam- photons: General (most aspects)
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