Program Information
A Monte Carlo Study of the Relative Stopping Power Reconstruction Accuracy for Helium CT
P Piersimoni1*, V Bashkirov2 , B Faddegon3 , J Ramos-Mendez3 , R Schulte2 , J Seco1 , (1) DKFZ - German Cancer Research Center, Heidelberg, Germany, (2) Loma Linda University, Loma Linda, CA, USA (3) University of California San Francisco, San Francisco, CA, USA
Presentations
SU-E-708-3 (Sunday, July 30, 2017) 1:00 PM - 1:55 PM Room: 708
Purpose: To evaluate the accuracy of relative stopping power measured with helium CT in comparison to proton CT.
Methods: A prototype particle computerize tomography (pCT) scanner that tracks individual particles and measures their water equivalent path length (WEPL), originally developed for proton CT, was installed on the beam line at the Heidelberg Ion-Beam Therapy (HIT) facility, Germany. We present a Monte Carlo (MC) simulation study performed using the TOPAS tool to compare the accuracy of the pCT reconstructed relative stopping power (RSP) values obtained with a low fluence (200 MeV/u) of protons and, for the first time, helium ions. An ideal setup was implemented, consisting of a flat beam source and an ideally totally absorbing energy-range detector, to estimate the theoretically best achievable RSP accuracy. A set of different phantoms was used: a cylindrical water phantom with inserts of different materials, sizes, and positions; a Catphan phantom with high resolution (CTP528) and sensitometry (CTP404) modules; and a voxelized 10-year-old female phantom.
Results: For the simulation in the ideal configuration, an average error better than 0.8% was obtained for the water phantoms with all of the different inserts. The CTP404 module was reconstructed and an average RSP accuracy of ~1% was obtained. The digitized phantom was reconstructed with helium CT, and all structures were well recognizable in the reconstructed image (brain, bones, air cavities, etc.) and no artifacts were visible. The three main tissue materials (soft tissue, brain, and cranium) were well identifiable in the reconstructed RSP-volume distribution. Results were in close agreement with those obtained for proton CT.
Conclusion: For the first time, MC simulation was used to demonstrate accurate image reconstruction using helium beams. The prototype scanner itself has tested for the first time at the HIT facility with proton and helium beams.
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