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Session: Treatment Planning and Delivery in Particle Therapy [Return to Session]

Biological Optimization of Peak-To-Valley Dose Ratio and Normal-Tissue Survival Fraction for Proton Minibeam Radiation Therapy

W Zhang, W Li*, Y Lin, F Wang, R Chen, H Gao, University of Kansas Medical Center, Kansas City, KS


SU-J-206-2 (Sunday, 7/10/2022) 4:00 PM - 5:00 PM [Eastern Time (GMT-4)]

Room 206

Purpose: Proton minibeam radiation therapy (pMBRT) is a novel proton modality that delivers homogeneous dose to tumor targets and spatially fractionated dose to normal tissues, which can be characterized by the peak-to-valley dose ratio (PVDR). pMBRT can reduce the radiation damage to normal tissues via biological dose sparing of high PVDR. Currently, PVDR is optimized by changing machine configuration (e.g., spot size, thickness and center-to-center distances for the collimator). The contribution of this work is to develop a biological optimization method for pMBRT that can optimize PVDR and also normal-tissue survival fraction (SF), which can be combined with the hardware approach for maximizing PVDR.

Methods: The new optimization method so-called “TVL1” simultaneously maximizes the normal-tissue PVDR and optimizes the dose distribution at tumor targets and organs-at-risk (OAR). TVL1 does not require the pre-specification of locations of peak or valley dose before treatment planning, and rather maximizes the total variation (TV) of the dose (i.e., the dose difference between peak and valley), which automatically sets peak and valley locations in normal tissues per the joint optimization of plan quality and PVDR. That is, at beam-eye-view projected dose slices of several depths for each beam angle, the TV of dose is maximized, corresponding to the PVDR maximization, while the L1 of dose is minimized, corresponding to the minimization of the OAR dose and maximization of survival fraction (SF).

Results: TVL1 was validated in comparison with conventional IMPT treatment planning method (CONV) for pMBRT on several clinical cases. The results show that TVL1 provided larger PVDR and SF than CONV for biological sparing of normal tissues, with preserved plan quality in terms of physical dose distribution.

Conclusion: A new biological optimization method is developed for pMBRT that can optimize normal-tissue PVDR and SF.

Funding Support, Disclosures, and Conflict of Interest: This research is partially supported by the NIH Grant No. R37CA250921 and a KUCC physicist-scientist recruiting grant.


Protons, Treatment Planning, Inverse Planning


TH- External Beam- Particle/high LET therapy: Proton therapy – Development (new technology and techniques)

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