Feasibility study of image reconstruction for a forceps-type positron emission counter: a simulation-based algorithm comparison.

Objective.The forceps-type positron emission counter (PEC) was developed for intraoperative quantification ofF-fluorodeoxyglucose uptake in individual lymph nodes. It employs coincidence detection between two opposingbismuth germanate crystal arrays, yielding only 16 lines of response (LOR). This study investigates the feasibility of image reconstruction from these 16 LORs to enable repositioning guidance and sensitivity-corrected quantification.Approach.Seven reconstruction algorithms-spanning different data-fidelity models (least-squares (LS) and Poisson likelihood), regularization priors (none,Tikhonov, and total variation), and optimization frameworks-were compared using Geant4-based Monte Carlo simulations. Phantom experiments assessed reconstruction quality and count-rate dependence, localization accuracy across the field of view, hot-background robustness, and dual-source separation.Main results.Among the tested design axes, regularization has the largest impact on reconstruction quality, and the optimal algorithm depends on the task: MAP-EM-TV (Poisson-likelihood with TV regularization) achieves the highest structural similarity while PLS-TV (LS with TV) achieves the best quantitative accuracy (FoV-sum CV reduced by 21.5 percentage points) and a mean localization error of 1.27 mm. Near-optimal image quality is reached at3000 counts, with spatial information retained down to100 counts; image quality degrades substantially below source-to-background ratio 12:1.Significance.The results demonstrate that the 16-LOR PEC can provide spatial information beyond count-rate or center-of-gravity estimation, enabling repositioning guidance and sensitivity-corrected quantification for intraoperative use. As the study relies on a shared forward model, validation with a physical prototype is the key next step.