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Session: Radiobiology and Preclinical Systems [Return to Session]

Improving the Efficiency of Small Animal IMRT with Submillimeter Dose Deposition Kernels and Total Variation Regularization

X Liu*, A Van Slyke, K Shoniyozov, R Wiersma, University of Pennsylvania, Philadelphia, PA


TU-D-TRACK 6-7 (Tuesday, 7/27/2021) 2:00 PM - 3:00 PM [Eastern Time (GMT-4)]

Purpose: There is growing interest in the use of modern 3D printing technology to implement intensity-modulated radiation therapy (IMRT) on the preclinical scale which is analogous to clinical IMRT. However, current 3D-printed IMRT methods suffer from long delivery times, excess filament usage, and complex modulation patterns. In this work, a comprehensive practical implementation of IMRT using 3D-printed beam compensators on the Xstrahl Small Animal Radiation Research Platform (SARRP) is presented, with an emphasis on accurate submillimeter dose calculation and the use of total variation regularization (TVR) to facilitate 3D printing.

Methods: Custom micrometer-scale dose deposition kernels were developed based on actual beam commissioning data. TVR-IMRT, a technique designed to minimize the intensity difference between neighboring beamlets, was used to optimize the beamlet intensity map, which was then converted to corresponding compensator thicknesses in copper-doped PLA filament. IMRT and TVR-IMRT plans using five beams were generated to treat a mouse heart while sparing lung tissue. The individual field doses and composite dose were delivered to film and compared to the corresponding planned doses using gamma analysis.

Results: The use of micrometer-scale dose kernels led to better agreement between the planned and measured doses, especially in low-dose regions. TVR-IMRT reduced the total variation of both the beamlet intensities and compensator thicknesses by 45-55%. The total mass of compensator material consumed and radiation beam-on time were both reduced by 15-25%, while DVH curves remained comparable. Gamma analysis passing rate with 3%/0.5mm criterion was 93.6% for IMRT and 97.3% for TVR-IMRT.

Conclusion: TVR can be applied to small animal IMRT in order to produce fluence maps and subsequent 3D-printed compensator patterns with less total variation, facilitating 3D printing and reducing the amount of filament required. The TVR-IMRT plan required less beam-on time while maintaining the dose conformity when compared to a traditional IMRT plan.



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