(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: Characterize proton CT (pCT) images from a prototype clinical proton imaging system that is simple, lightweight, easily scaled to large field sizes, operates at high speed to maximize throughput, and uses the minimum possible radiation dose for a given resolution. The system fully exploits individual proton path information and utilizes pencil beam scanning systems delivering low fluence beams.
Methods: Acquire pCT images with the system operating with a scanning pencil beam at the Northwestern Medicine Chicago Proton Center. Compare with relative stopping power (RSP) maps derived from x-ray CT images using stoichiometric calibration.
Results: Figure 1 shows a 1 mm thick pCT slice of a sample of pork shoulder and ribs along with a slice, at the same location, of an RSP map derived from x-ray CT. Figure 2 shows a difference map and a photograph of the setup. The average agreement is better than 1% in uniform regions of muscle, fat and bone. Local discrepancies occur in regions with high density variation. Noise in the pCT slice could be improved by using more protons.
Conclusion: We have characterized the first pCT images of complex animal tissue samples mimicking human patients in size and composition. In comparison, x-ray CT images using stoichiometric calibration produce good agreement in these samples. Further comparisons with complex samples are in progress.
Funding Support, Disclosures, and Conflict of Interest: Supported by NCI SBIR grant R44CA203499 ProtonVDA LLC has intellectual property rights to certain innovations described in this presentation. DD and VR are co-owners of ProtonVDA LLC
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