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(Sunday, 7/14/2019) 5:00 PM - 6:00 PM
Room: 302
Purpose: To significantly advance the breast radiotherapy dosimetry, immobilization repeatability, and patient comfort, we invented and evaluated a soft pneumatic breast shaping and immobilization device on its role in producing superior breast geometry for supine patients without interfering with radiation delivery. We then then created 4π treatment plans by utilizing automatic beam angle selection methods to maximally exploit this geometry.
Methods: A pneumatically-driven soft robot was developed and tested on a breast phantom. The soft robot consists of 18 chambers in three rows and 6 columns. When the chambers are inflated sequentially, the robot securely lifts and supports the breast for radiotherapy in the supine position. The set-up reproducibility was tested by repeated application and CT imaging. Benefits of using the soft robot for breast set-up were compared with standard breast positioning by using a prone patient scan to simulate supine set-up with the soft robot. 4π plans solving an integrated beam orientation and fluence map optimization problem were created for each using the fast-iterative shrinkage-thresholding algorithm (FISTA). Twenty optimal beams were selected for each case. Dose metrics for organs-at-risk and breast targets for each case were compared.
Results: The application of the soft robot set-up device on the breast phantom is shown to be repeatable. In the simulated soft robot assisted set-up position, average reduction in the mean and maximum doses delivered to the left lung are 53.6% and 50%, respectively, compared to the natural position. Automatically selected beam angles also show that the soft robot-assisted OAR sparing is superior to that achieved in the natural position.
Conclusion: The feasibility of supine breast set-up using a novel soft robot was demonstrated on a phantom. In the simulated patient planning study using the non-coplanar 4π technique, the improved breast geometry leads to significantly improved OAR sparing and breast dose homogeneity.
Funding Support, Disclosures, and Conflict of Interest: NIH R01CA230278 NIH R44CA183390 NIH R01CA188300
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