Program Information
Theoretical Prediction and Experimental Verification of the Spatial Resolution and Stopping Power Accuracy of Ion Radiography/tomography
C-A Collins-Fekete1,2,3*, L Volz3 , P Piersimoni3 , C Ordonez4 , V Bashkirov5 , G Coutrakon4, R Johnson6 , L Beaulieu1,2 , R Schulte5 , J Seco3 , (1) Universite Laval, Quebec, QC, (2) Centre hospitalier universitaire de Quebec, Quebec, QC,(3) DKFZ - German Cancer Research Center, Heidelberg, FS05, Baden-Wurttemberg, (4) Northern Illinois University, Dekalb, Illinois, (5) Loma Linda University, Loma Linda, Ca, (6) University of California, Santa Cruz, Santa Cruz, CA
Presentations
WE-G-605-5 (Wednesday, August 2, 2017) 4:30 PM - 6:00 PM Room: 605
Purpose: Multiple Coulomb scattering (MCS) is the largest contributor to blurring in proton CT (pCT), reducing its clinical applicability. Heavier particles suffer less from MCS due to their lower charge/mass ratio. This work will investigate theoretically and experimentally the spatial resolution and stopping power accuracy achievable using heavier ions compared to protons in particle imaging.
Methods: A theoretical framework was developed to predict the most-likely path (MLP) of ions crossing a medium. Every ion from proton to carbon was simulated through water at fixed initial velocity in the Monte Carlo (MC) algorithm. The maximal MLP root-mean square (RMSmax) error to the MC path is compared between ions. Helium (HeRad) and proton radiographies (pRad) (n=90) were acquired experimentally for 1) the Catphan-CTP600 to evaluate RSP accuracy and spatial resolution and 2) the CIRS paediatric head for achievable clinical quality. The radiographies were acquired using a prototype particle-CT detector that tracks individual particles position/energy loss. The Heidelberg Ion-Therapy facility produced the particle beam. An algebraic iterative reconstruction algorithm was used to reconstruct the pCT. The modulation transfer function (MTF) was evaluated using a sharp-edge method on the ion radiography/tomography.
Results: The MLP RMSmax dropped significantly between proton (0.29mm) and helium (0.09mm) but then increased again up to carbon (0.12mm). The HeRad resolution (MTF10%=6.07lp/cm) is above that of proton (MTF10%=3.35lp/cm). The number of projections acquired limits the tomographic resolution (MTF10%=2.5lp/cm) for both ions. RSP accuracy will be evaluated using the Catphan-CTP404 phantom.
Conclusion: Helium has the lowest path estimate uncertainty in simulations, which is hypothesized to lead to higher spatial resolution images. Accordingly, experimental HeRad showed an increased spatial resolution compared to pRad. This suggests clinical application for orthogonal registration or to be combined with X-ray imaging for stopping power validation. Further evaluation of the HeCT/pCT spatial resolution is required using more projections.
Contact Email: