H (Parenica) Paschal*, C Kabat, S Stathakis, M Bonnen, N Papanikolaou, N Kirby, UT Health San Antonio, San Antonio, TX

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PO-GePV-T-72 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

ePoster Forums

Purpose: We aim to improve the conformality of electron radiotherapy treatments with a surface conforming collimation system.

Methods: We have created a proof-of-principle surface collimating device for electron radiotherapy. The device consists of a set of cables that run parallel to each other with a variable compression system around them. With no compression, the cables can slide relative to each other. This enables the collection of cables to be flexible and morphed into the desired collimator shape. When compression is applied, the increase in frictional forces does not allow the cables to slide relative to each other, thus causing the shape to be fixed. A 10x10 cm applicator was further blocked on one side with the cable collimator placed on solid water. The cable collimator was tested for the lowest and highest electron energies available in our clinic (6 MeV and 15 MeV). Radiochromic film was placed at the surface and at 12 mm and 27 mm depths (dmax) for 6 MeV and 15 MeV, respectively.

Results: The cable collimator provided the greatest improvement for 6 MeV at the surface. The penumbra at the surface for the conventional collimator was 11.8 mm, while the cable collimator penumbra was 0.9 mm. At 12 mm depth, the penumbra was 16.9 mm and 7.9 mm for the conventional and cable collimators, respectively. Penumbra also improved for 15 MeV with the cable collimator. At the surface, the penumbra decreased from 16.9 mm (conventional) to 7.9 mm (cable), and at 27 mm penumbra decreased from 12.1 mm to 9.0 mm.

Conclusion: The initial prototype shows significant improvement in dose falloff from conventional collimation. This system can serve as a replacement for conventional Cerrobend applicators. Additionally, it could be used as an add-on to hand-block an area of concern during treatment.

Keywords

Electron Therapy, Beam Shaping

Taxonomy

TH- External Beam- Electrons: Development (new technology and techniques)

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