RT Journal Article SR Electronic T1 A Study of Narrow Energy Window on the Siemens Vision 600 PET/CT Scanner JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 390 OP 390 VO 61 IS supplement 1 A1 Mehmet Aykac A1 Harshali Bal A1 Vladimir Panin A1 Maurizio Conti YR 2020 UL http://jnm.snmjournals.org/content/61/supplement_1/390.abstract AB 390Introduction: Recent developments in detector technologies made possible to build SiPM-based PET scanner with nearly 200ps time resolution and high spatial resolution. PET detector module consists of 2x4 mini-block configuration and each mini-block has 5x5 LSO array by using 3.2x3.2x20mm3 crystals. Due to the high packing ratio in the detector, efficient light collection mechanism provides excellent energy resolution and timing performance. Even though system energy resolution is below 10%, the energy window of the PET scanner for the clinical imaging protocols is set between 435keV and 585keV in order to maximize the scanner sensitivity. In this work, the energy window was narrowed between 460keV and 560keV and some of the scanner performance parameters were measured. In addition, contrast recovery coefficients by using NEMA image quality (IQ) phantom were measured and compared to the clinical imaging energy window. Methods: The scanner provides listmode data format with energy information included for both photons of a coincidence event. In order to compare the two energy window settings, both normalization and scatter parameters were optimized separately. Starting with the normalization, the listmode data from a low activity Ge-68 rotating line source was histogrammed for two energy windows and two sets of normalization components were generated. Deadtime was excluded because only low count rate measurements were performed during this investigation. Scatter correction is based on single scatter simulation by using tail-fitting approach. Two sets of parameters were generated for scatter correction. Scatter fractions were measured by using NEMA scatter phantom and simulated as well by Monte Carlo method for two energy windows. Monte Carlo approach was a useful tool to understand the fractions of no scatter, single scatter and multiple scatter events from a given phantom for both energy windows. Decaying line source in NEMA scatter phantom was measured only one time for both energy windows and NEC performances were obtained for comparison. Scanner time performances for two energy windows were also compared by placing a Ge-68 rod source at the center. Finally, NEMA IQ phantom was used to see whether there is any improvement in spatial resolution. 30-minute acquisition were performed from ~2mCi total activity of F-18 in the NEMA IQ phantom. After the sinograms were corrected for normalization, attenuation and scatter, the images were reconstructed by using TOF-OSEM 4i5s with no PSF for both energy windows. Contrast recovery coefficients were estimated for hot phantom spheres in the NEMA IQ phantom to assess the image quality. Results: Preliminary Monte Carlo simulations for NEMA scatter phantom showed that scatter fraction values for the clinical and narrow energy windows were 34.3% and 28.0%, respectively. Simulations also showed that the fractions of singles scattered events to all scattered events for the clinical and narrow energy windows were estimated to be ~83% and ~86%, respectively. Experimental scatter fractions for the clinical and narrow energy windows were 37.0% and 29.3%, respectively. Patient bed was not included in the simulation model. NEC performance for narrow energy window was measured to be 313kcps at 25kBq/cc, that is ~6.5% higher up to peak NEC value compared to the clinical energy window. Time resolution measurements from a Ge-68 rod source in the center of the scanner provided similar values around 206ps for both energy windows. When the energy window was reduced, contrast recovery coefficients for the NEMA IQ phantom were improved by 11.7%, 6.5%, 6.7%, 3.4%, 1.4% and 1.5% for 10mm, 13mm, 17mm, 22mm, 28mm and 37mm diameter hot phantom spheres, respectively. Conclusions: In this study, both NEC rates and scatter fraction value were improved due to reduced scatter and randoms for the narrow energy window compared to the clinical energy window. when narrow energy window was used, image contrast also showed an improvement for the hot spheres in the NEMA IQ phantom. View this table:Measured and Simulated Scatter Fraction Values between Two Energy Windows(Patient bed NOT simulated)