(Sunday, 7/14/2019) 3:30 PM - 4:00 PM
Room: Exhibit Hall | Forum 6
Purpose: Proton therapy has an important source of uncertainty: Range uncertainties arising from the use of x-ray images rather than proton images for treatment planning. The conversion from x-ray absorption power to proton stopping power can be patient and tissue specific. Current practice typically assigns a range uncertainty of 3% + 3 mm during treatment planning, causing unwanted toxicities. Proton imaging is a method of directly measuring proton stopping power, which can drastically reduce the magnitude of these additional deep margins. Proton CT will reduce the uncertainties of treatment planning by directly measuring stopping power with much lower dose to the patient than comparable x-ray images. Proton radiography will provide the capability to verity the range of individual proton beams before treatment. A clinical proton imaging system should be simple, lightweight, easily scaled to large field sizes, operate at high speed to maximize patient throughput, and expose the patient to the minimum possible radiation dose for a given resolution.
Methods: We have developed a system to produce images of proton stopping power by tracking individual protons before and after the patient and measuring the proton residual range after the patient, as illustrated in Fig. 1. Our fully functional prototype fully exploits proton path information and is optimized for pencil beam scanning systems.
Results: Our system setup and a resulting radiograph are shown in Fig. 2. A first test of our system for tomography using a continuously rotating platform and repeating scanning pencil beam pattern is shown in Fig. 3. The image demonstrates a further advantage of proton imaging: The lack of artifacts from high-Z inserts.
Conclusion: A proton imaging system optimizing image sharpness and dose to the patient will individually track protons before and after the patient. An iterative algorithm produces images with spatial resolution given by the tracking accuracy.
Funding Support, Disclosures, and Conflict of Interest: ProtonVDA Inc has intellectual property rights to certain innovations described in this presentation. DD and VR are co-owners of ProtonVDA Inc.
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