High resolution insert for clinical whole body PET scanners: Design and optimization

We are developing an insert device that will improve image resolution within a smaller FOV for clinical whole-body PET scanners. To optimize its design, we modified simSET to simulate the insert and a PET scanner. The system consists of two detector rings. The inner ring represents an insert (r = 153 mm) with high-resolution detectors using 10 mm thick LSO. The outer ring represents a PET scanner (R = 413 mm) with 25 mm thick LSO. Events were binned into 3 sets of sinograms assuming a 2.4 and 6.75 mm crystal-pitch for the insert and the PET scanner, respectively. The detectors in the insert are modeled as 1, 2, 3, or 4 layers with different offset configurations to evaluate the impact of DOL Results show that image resolution at 1 cm radial offset is improved from 5.0 mm FWHM of the original PET scanner to 1.8 mm with the insert. At 12 cm offset, the resolution of the original system is 5.4 and 6.5 mm for radial and tangential directions, respectively. With the insert, the radial resolution is 5.0 mm FWHM for a single-layer detector design, but improves to 2.7, 2.4, and 2.1 mm for 2, 3, and 4 layer DOI detectors, respectively. Different offsets for multi-layer detectors have negligible effect on resolution. Sensitivity of the device is, assuming the insert has a 2 cm axial extend, estimated to be 3.3%, including coincidence events from the insert-alone and insert-to-scanner sinograms. In contrast, if the insert is used as a stand-alone microPET scanner, its sensitivity is 1.3%.