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Comparison of Proton Stopping Power Measurements of Animal Tissues From Proton CT and X-Ray CT Systems

D DeJongh1*, E DeJongh1, V Rykalin1, M Pankuch2, B Kreydick2, J Welsh3, R Schulte4, N Karonis5, C Ordonez5, K Duffin5, J Winans5, G Coutrakon6, C Sarosiek6, (1) ProtonVDA LLC, Naperville, IL, (2) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (3) Edward Hines Jr VA Hospital, Hines, IL, (4) Loma Linda University, Loma Linda, CA, (5) Northern Illinois University, Computer Science, Dekalb, IL, (6) Northern Illinois University, Physics, Dekalb, IL


(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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