Abstract
PurposePositron emission tomography (PET) range verification is an important method that can help improve the confidence in proton therapy for clinical applications. Two kinds of verification methods are implemented and compared based on clinical cases in this study.MethodThe study is conducted on 14 breast cancer patients following proton irradiation treatment. Verification is done by calculating the depth error between the numerically predicted values with the measured PET image along the beam direction. Point-based and segment-based methods are applied and compared. The verification results are presented as depth error means and standard deviations in a region of interest (ROI).ResultsThe mean value of the depth error of all 14 cases is within the range of [−3, 3] mm for both point-based and segment-based methods, and only one case result calculated by the point-based method is slightly beyond −3 mm. When comparing the mean depth error from the two methods, the paired t-test result shows that the p-value is 0.541, and the standard deviation of the segment-based method is smaller than that of the point-based method.ConclusionIn breast cancer case verification application, point-based and segment-based methods show no significant difference in the mean value of results. Both methods can quantify the accuracy of proton radiotherapy to the millimeter level.
Highlights
A proton beam demonstrates a good dose distribution with a clear edge because of the presence of the Bragg peak on the dose depth deposition curve
Uniformly distributed in the clinical target volume (CTV) region in each fraction; Boost: dose is delivered to the tumor bed region in one fraction; SIB: uniform and boost dose are simultaneously delivered in one fraction
The mean value of the depth error in all these 14 cases is within the range of [−3, 3] mm for both R50 and Rshift methods, except case 9 CTV region with the R50 method
Summary
A proton beam demonstrates a good dose distribution with a clear edge because of the presence of the Bragg peak on the dose depth deposition curve. Proton therapy is widely utilized to treat solid tumors close to critical organs, as the clear dose edge is good at sparing normal tissue while destroying tumor tissue. The range verification methods, which are necessary to check the PET Verification Methods irradiation accuracy, are applied to patients during or/and after proton therapy to ensure the proton beam delivered the dose to tumor tissue precisely. Many in vivo non-invasive verification methods are developed [1]; positron emission tomography (PET) is one of the most widely used verification techniques following proton irradiation. Positron emitter isotopes are generated by proton beam decay and release a positron. Using a suitable reconstruction algorithm, the positron distribution image can be reconstructed to reveal quantified information about beam irradiation
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