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A new combined lutetium oxyorthosilicate (LSO) PET/CT scanner with an extended axial field-of-view (FOV) of 21.8 cm has been developed (Biograph TruePoint PET/CT with TrueV; Siemens Molecular Imaging) and introduced into clinical practice. The scanner includes the recently announced point spread function (PSF) reconstruction algorithm. The PET components incorporate four rings of 48 detector blocks, 5.4 cm × 5.4 cm in cross-section. Each block comprises a 13 × 13 matrix of 4 × 4 × 20 mm3 elements. Data are acquired with a 4.5 ns coincidence time window and an energy window of 425-650 keV. The physical performance of the new scanner has been evaluated according to the recently revised National Electrical Manufacturers Association (NEMA) NU 2-2007 standard and the results have been compared with a previous PET/CT design that incorporates three rings of block detectors with an axial coverage of 16.2 cm (Biograph TruePoint PET/CT; Siemens Molecular Imaging). In addition to the phantom measurements, patient Noise Equivalent Count Rates (NECRs) have been estimated for a range of patients with different body weights (42-154 kg). The average spatial resolution is the same for both scanners: 4.4 mm (FWHM) and 5.0 mm (FWHM) at 1 cm and 10 cm respectively from the center of the transverse FOV. The scatter fractions of the Biograph TruePoint and Biograph TruePoint TrueV are comparable at 32%. Compared to the three ring design, the system sensitivity and peak NECR with smoothed randoms correction (1R) increase by 82% and 73%, respectively. The increase in sensitivity from the extended axial coverage of the Biograph TruePoint PET/CT with TrueV should allow a decrease in either scan time or injected dose without compromising diagnostic image quality. The contrast improvement with the PSF reconstruction potentially offers enhanced detectability for small lesions. [ABSTRACT FROM AUTHOR]

The combination of PET and SPECT in one device may have clinical and economic advantages. The PET/SPECT camera developed as a joint venture between CPS Innovations, Knoxville, TN, and Siemens Medical Systems, Hoffmann Estates, IL, is a fully 3-D system with 511 keV transmission sources. The detector is based on a NaI-LSO phoswich scintillator. The individual LSO and NaI crystals have a size of 4.3 x 4.3 10 mm³. The 12 x 12 crystal blocks are read out by 2 x 2 in photomultiplier tubes, arranged in a low cost quadrant sharing system. The purpose of this paper is to illustrate phoswich detector setup and to evaluate the detector performance for both modes, PET, and SPECT. The quadrant sharing method and the two crystal layers require special algorithms to find the individual crystal regions and distinguish them from light cross talk caused by adjacent blocks. The base for this procedure is a position profile acquired with a flood source. The mean energy resolution for the NaI(TI) crystal layer was 13.1% (FWHM) at 140 kev and 15.7% (FWHM) at 511 keV for the LSO crystal layer. For the PET setup the average time resolution was 3.4 ns (FWHM). A daily quality check showed a very stable detector condition. Peak shifts due to room temperature changes were very little for both modes and both crystal layers. [ABSTRACT FROM AUTHOR]