Evaluation of High-Sensitivity Organ-Specific Positron Emission Tomography (PET) System

Positron Emission Tomography (PET) has been proven to be a very promising functional imaging technique for cancer detection, prognosis, staging, treatment planning, and treatment monitoring due to its high specificity for malignancy. Detection of small size tumors and effective tumor treatment follow-up requires both, ultra-high sensitivity, and high spatial resolution of PET detectors. This can be achieved by using organ-specific PET where detectors are positioned close to the object to subtend more solid angle around the organ. This significantly improves gamma-ray detection and reduces signal from elsewhere in the body providing a high sensitivity in the organ and permitting a lower dosage of the radiotracer. On the other hand, organ-specific PET detectors may have greater segmentation of the scintillators than whole-body PET cameras typically use which leads to improved spatial resolution and increases detectability of small lesions. Here we report on evaluation of a breast-dedicated PET system designed specifically to fit the requirement of high spatial resolution and high-sensitivity imaging. The system utilizes silicon based high quantum efficiency solid state photosensor - the so-called Silicon Photomultipliers (SiPM) - in conjunction with highyield scintillation crystals for enhanced gamma-ray detection efficiency. Breast phantom imaging, performed with the radioisotope F-18 saline solution, show the resolution of a hot sphere with a lesion to background ratio of less than 2.5:1. Phantom acquisitions show clear resolvability of a NEMA image quality phantom down to the 2.0 mm source rods. High spatial resolution, with average values of 1.8-2.0 mm across the field-of-view were also measured.