Physical Performance and Clinical Workflow of a new LSO HI-REZ PET/CT Scanner

A new combined LSO PET/CT scanner with an extended axial field-of-view of 21.6 cm has been developed (Biograph TruePoint TrueV PET/CT, Siemens Molecular Imaging) and introduced into clinical practice. The scanner incorporates four rings of 48 detector blocks, 5.4 cm times 5.4 cm in cross-section; each block comprises a 13 times 13 matrix of 4 times 4 times 20 mm₃ elements. The scanner is operated with a coincidence time window of 4.5 ns and an energy window of 425-650 keV. The physical performance of the new scanner has been evaluated according to the NEMA NU 2-2001 protocol and the results have been compared with a previous design that incorporated three rings of detectors with an axial coverage of 16.2 cm (Biograph TruePoint PET/CT, Siemens Molecular Imaging). The spatial resolution is the same for both scanners: 4.4 mm and 5 mm at 1 cm and 10 cm respectively from the center of the transverse field-of-view. The scatter fraction is 34%, similar to that of the three ring design. However, compared to the three ring scanner, the system sensitivity and peak noise equivalent count rate (NECR) increase by 82% and 73% respectively. In addition to the phantom measurements, patient NECRs have been estimated for a range of patients with different body sizes. The increase in sensitivity and extended axial coverage facilitates a decrease in either scan time or injected dose without compromising diagnostic image quality.