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Patient-specific stopping power calibration for proton therapy planning based on single-detector proton radiography

P J Doolan, M Testa, G Sharp, E H Bentefour, G Royle, H-M Lu
2015 Physics in Medicine and Biology  
A simple robust optimizer has been developed that can produce patientspecific calibration curves to convert x-ray computed tomography (CT) numbers to relative stopping powers (HU-RSPs) for proton therapy treatment planning. The difference between a digitally reconstructed radiograph waterequivalent path length (DRR WEPL ) map through the x-ray CT dataset and a proton radiograph (set as the ground truth) is minimized by optimizing the HU-RSP calibration curve. The function of the optimizer is
more » ... the optimizer is validated with synthetic datasets that contain no noise and its robustness is shown against CT noise. Application of the procedure is then demonstrated on a plastic and a real tissue phantom, with proton radiographs produced using a single detector. The mean errors using generic/optimized calibration curves between the DRR WEPL map and the proton radiograph were 1.8/0.4% for a plastic phantom and −2.1/ − 0.2% for a real tissue phantom. It was then demonstrated that these optimized calibration curves offer a better prediction of the water equivalent path length at a therapeutic depth. We believe that these promising results are suggestive that a single proton radiograph could be used to generate a patientspecific calibration curve as part of the current proton treatment planning workflow.
doi:10.1088/0031-9155/60/5/1901 pmid:25668437 fatcat:eidzpsqfdzd53j7zuuypfvjxgi