Compton-camera-based radiopharmaceutical imaging with an attenuation-corrected LM-MLEM reconstruction strategy

Abstract

Compton cameras have garnered attention in nuclear medicine due to their broad energy detection range and high efficiency, showing potential for imaging of various therapeutic and diagnostic isotopes and theranostics. However, a current limitation on the application of Compton cameras in nuclear medical imaging is the lack of a suitable method for correcting human tissue attenuation. This research aims to propose a precise system matrix probability model that explicitly considers the attenuation effect for correcting tissue attenuation in Compton imaging of radionuclides. The model calculates the probability of tissue attenuation between imaging space pixels and detector positions and is integrated into the calculation of the system matrix and sensitivity matrix within the list-mode maximum likelihood expectation maximization (LM-MLEM) algorithm. To validate this attenuation-corrected LM-MLEM (AC-LM-MLEM) algorithm, phantom studies were conducted using both GEANT4 simulations and experiments with [¹⁸F]FDG radiopharmaceutical and a 3D-CZT Compton camera, along with animal experiments on a Sprague Dawley rat. In the simulated imaging results on the phantom model, the AC-LM-MLEM algorithm closely match the prescribed spherical source activity distribution. In the imaging results of experiments, the highly radioactive areas reconstructed by the AC-LM-MLEM algorithm are largely consistent with the clinically used positron emission tomography/computed tomography (PET/CT) reconstruction results. Qualitative and quantitative analyses of the reconstruction results indicate that the proposed AC-LM-MLEM algorithm corrects effectively for tissue attenuation.