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Feasibility of Soft Robot Assisted 4pi Supine Breast Radiotherapy

D Shang*, Q Lyu , R Neph , W Gu , K Sheng , UCLA School of Medicine, Los Angeles, CA


(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 4Ï€ 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. 4Ï€ 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 4Ï€ 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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