Program Information
Methods for Improving Accuracy in Interaction Vertex Imaging
D Hymers*, D Muecher , V Bildstein , University of Guelph, Guelph, ON, Canada
Presentations
SU-E-FS4-7 (Sunday, July 30, 2017) 1:00 PM - 1:55 PM Room: Four Seasons 4
Purpose: Interaction vertex imaging is a medical imaging method relying on detections of secondary particles created by beam interactions in the target. This project investigated the impact of two key image reconstruction algorithms in interaction vertex imaging on the accuracy of the final image. The first method investigated is a single-particle-and-beam method proposed by previous work, and the second is a new triangulation approach believed to achieve greater accuracy than previously-examined techniques, as well as allowing determination of the 3D position of interaction in the patient.
Methods: Using Geant4, we simulated fragmentation and secondary particle production by a 145 MeV/u ¹²C beam with Gaussian distribution (FWHM = 5mm) in a cylindrical water target. Data was collected on the incoming position of the beam, as well as particles exiting the target in a forward direction, using thin silicon detectors. A software filtration reconstruction algorithm was applied to this data to refine the image of the beam path.
Results: The best vertex accuracy was observed using triangulation reconstruction with the incoming beam and two coincident secondary particles. Accuracy is improved by considering only secondary particles detected more than 45 degrees from the beam axis, and with incident energy above 40 MeV for use in the reconstruction algorithm. Under these criteria, close to 90% of vertices directly correspond to beam interactions in the target, and reconstructed vertices display a mean distance of just over 2mm from actual sites of interaction as reported by Geant4.
Conclusion: The triangulation method is considered to be a significant improvement over previous methods of interaction vertex imaging, halving the average distance between the reconstructed vertex and the actual site of reaction in the target. This algorithm will be further refined in future investigations, including ongoing tests using phantoms derived from CT scans of human patients.
Funding Support, Disclosures, and Conflict of Interest: NSERC SAPIN-2016-00030
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