Abstract
In particle radiotherapy, range uncertainty is an important issue that needs to be overcome. Because high-dose conformality can be achieved using a particle beam, a small uncertainty can affect tumor control or cause normal-tissue complications. From this perspective, the treatment planning system (TPS) must be accurate. However, there is a well-known inaccuracy regarding dose computation in heterogeneous media. This means that verifying the uncertainty level is one of the prerequisites for TPS commissioning. We evaluated the range accuracy of the dose computation algorithm implemented in a commercial TPS, and Monte Carlo (MC) simulation against measurement using a CT calibration phantom. A treatment plan was produced for eight different materials plugged into a phantom, and two-dimensional doses were measured using a chamber array. The measurement setup and beam delivery were simulated by MC code. For an infinite solid water phantom, the gamma passing rate between the measurement and TPS was 97.7%, and that between the measurement and MC was 96.5%. However, gamma passing rates between the measurement and TPS were 49.4% for the lung and 67.8% for bone, and between the measurement and MC were 85.6% for the lung and 100.0% for bone tissue. For adipose, breast, brain, liver, and bone mineral, the gamma passing rates computed by TPS were 91.7%, 90.6%, 81.7%, 85.6%, and 85.6%, respectively. The gamma passing rates for MC for adipose, breast, brain, liver, and bone mineral were 100.0%, 97.2%, 95.0%, 98.9%, and 97.8%, respectively. In conclusion, the described procedure successfully evaluated the allowable range uncertainty for TPS commissioning. The TPS dose calculation is inefficient in heterogeneous media with large differences in density, such as lung or bone tissue. Therefore, the limitations of TPS in heterogeneous media should be understood and applied in clinical practice.
Highlights
Proton therapy is a recently developed state-of-the-art radiation therapy technique
We could successfully assessthe accuracy of range computation for the pencil beam (PB) algorithm in a treatment planning system (TPS) and Monte Carlo (MC) simulation compared with measurements using a computed tomography (CT) calibration phantom
There was a small difference in the proton range between measurement and calculation from TPS when infinitely homogeneous solid water is considered as the medium
Summary
Proton therapy is a recently developed state-of-the-art radiation therapy technique. It has the advantage of delivering a minimum dose to normal organs, while delivering a large dose to cancer cells, using a physical property known as the Bragg peak of the proton [1,2,3]. A dose to normal tissue proximal to the target can be greatly reduced by accurately positioning the Bragg peaks at the target. This is done by controlling the range of the proton beams. The Samsung Medical Center Proton Therapy Center (SMC-PTC) is the first private hospital-based proton therapy center in Korea [4]. SMC-PTC treated its first patient in December 2015, and currently treats cancer patients with both wobbling and line-scanning proton therapy modes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
