Two approaches to implementing projector–backprojector pairs for 3D reconstruction from Compton scattered data

Iterative image reconstruction for the Compton camera is computationally challenging since the projection and backprojection operations are performed on conical surfaces rather than along straight lines and there are many possible combinations of positions and energy measurements. Here, we note that implementing a computationally efficient projector–backprojector pair with good accuracy is an important factor to be considered in image reconstruction. In this study, two different approaches to conical surface integration were investigated for rapid calculations of projection and backprojection in 3D reconstruction; the ellipse-stacking method (ESM) and the ray-tracing method (RTM). Our experimental results indicated that while both methods produced equivalent reconstruction accuracies, RTM performed better than ESM in both computation time per iteration and total number of iterations for convergence.