Limited-Angle TOF-PET for Intraoperative Surgical Application

Accurate identification of sentinel lymph nodes (SNL) and complete tumor removal in cancer patients is of critical importance and leads to improved patient recovery and survival. Gamma probes along with near infrared (NIR) probes are the gold standard in SNL identification but have failed to reduce false negative rates (FNR) to the desirable 5% value. By developing a high-resolution Positron Emission Tomography (PET) detector atop the patient in coincidence with a partially populated detector ring placed underneath the patient bed with <; 250 ps coincidence timing resolution, we are aiming to reduce the FNR compared to what is achievable today.In this regard, we modeled variations of the intraoperative system as well as a reference whole-body PET using the MonteCarlo code GATE. Detector blocks are 13×13 arrays of 3.6×3.6×20 mm3 LYSO:Ce pixels with 3.8 mm pitch. Models varied by the number of detector blocks underneath the patient bed and location of both top and bottom detectors with respect to the patient body. Unlike conventional PET with image slices along the body axis (transverse view), here the slices are defined horizontally and parallel with body axis (coronal view).A torso phantom with background activity concentration of 1/10th of that of hot spheres with 2,4,6,8, and 10 mm diameter and 10 mm spacing was also modeled. Reconstructed images show that 6, 8, and 10 mm lesions can be identified with 40 sec image acquisition. As expected, lesion detectability is reduced when coincidence time resolution (CTR) was changed from 150 ps to 250 ps which can be compensated by increasing acquisition time.