Abstract
1133
Introduction: We propose a novel point-of-care (POC) PET imaging system that can be brought to patient bedside to deliver molecular imaging capability on-demand with near real-time feedback. This system can measure localized tracer uptake quantitatively in user-selected organ(s) using FDG or disease-targeting novel PET tracers. In this feasibility study, we evaluated the interactive and quantitative imaging capability of the proposed system for lung imaging where nonuniform tissue attenuation is a challenge.Methods: The proposed prototype POC-PET imager consists of a hand-maneuverable PET detector probe attached to a robotic arm, a large PET detector panel, a transmission source, data acquisition electronics, and a multi-GPU workstation. All detectors are made of LYSO crystal arrays coupled to SiPM arrays with 200 ps coincidence timing resolution. The imaging probe can be moved around a patient to collect coincidence events from a region-of-interest by working in conjunction with the PET detector panel slid under a patient’s body. These events are used for list-mode image reconstruction in near real-time to provide visual feedback to an operator who can interactively control the probe to collect additional counts to optimize image quality. We performed a Monte-Carlo (MC) simulation study to image a torso phantom using the system. The transmission sheet source was attached to the imaging probe to collect both emission and transmission scans simultaneously. Emission events are used for list-mode image reconstruction implemented in GPU to facilitate near real-time reconstruction. Attenuation correction was estimated from the transmission events. The quantitative accuracy was assessed by measuring the contrast recovery coefficient of lesions with respect to lungs from PET images with (1) no attenuation correction, (2) measured correction using transmission scan, (3) analytic correction by known attenuation-coefficient map.Results: We report sensitivity and reconstructed images as well as demonstrate an interactive scanning strategy. The quantitative accuracy (measured in terms of contrast recovery) is 82% for a lesion of 3cm in diameter with an activity ratio of 3:1 with respect to lung. The difference between the simultaneously measured attenuation correction and the analytic method is within 5.6% measured across the imaging field-of-view.Conclusion: The proposed POC-PET imager can resolve elevated radiotracer uptake in a torso within the targeted imaging FOV, with a quantitative accuracy of 82.01% using simultaneously measured attenuation correction. This technology can be easily integrated with other POC imaging modalities such as an ultrasound or a portable chest x-ray unit to provide anatomic, functional and molecular imaging information for imaging pulmonary diseases.