PT - JOURNAL ARTICLE AU - Kalluri, Kesava AU - Auer, Benjamin AU - Zeraatkar, Navid AU - Doty, Kimberly AU - Momsen, Neil AU - Kuo, Phillip AU - Furenlid, Lars AU - King, Michael TI - Comparison of System Designs for AdaptiSPECT-C using Curved Detectors: Initial Findings DP - 2020 May 01 TA - Journal of Nuclear Medicine PG - 1511--1511 VI - 61 IP - supplement 1 4099 - http://jnm.snmjournals.org/content/61/supplement_1/1511.short 4100 - http://jnm.snmjournals.org/content/61/supplement_1/1511.full SO - J Nucl Med2020 May 01; 61 AB - 1511Introduction: Clinical brain imaging is currently performed using 2 or 3 headed SPECT cameras employing parallel or fan-beam collimators. AdaptiSPECT-C (ASC), an adaptive multi-detector multi-pinhole (MPH) dedicated-brain imaging system is being designed for usage with both clinical and novel drug discovery applications [1]. Initial designs employed flat detectors [2]; however, curved detectors (CD) may improve combined spatial resolution / sensitivity for dedicated brain SPECT imaging. Through simulated imaging of select phantoms we compared the imaging performance of multiple ASC system designs using detectors that are curved about the axial axis. Methods: We investigated ASC designs using 6” and 8” NaI(Tl) CDs, each with a 2-cm-thick MPH-collimator plate with 5 apertures that could be adaptably shuttered [3]. When fabricated, curved-to-flat fiber-optics transfer plates would be employed between the crystal and light sensors [4]. In the systems, CDs are arranged in 3 rings (caudal, middle and quasi-vertex) tangent to a truncated sphericalsurface. Each detector is adaptively irradiated using distinct-temporal acquisition frames involving either a central pinhole or 4 oblique pinholes. Simulated acquisition and image reconstruction were performed for the designs using a Monte Carlo GATE based system matrix that modeled the system response of the ASC [5,6]. Projections acquired using oblique apertures were both multiplexed and truncated to varying extents in different designs. In each case, aperture diameters which provided a tomographic resolution of 8 mm at the center of the 21-cm spherical volume-of-interest (VOI) were employed as calculated from the collimator equations [7,8]. The ASC imaging performance was evaluated using a uniform 21 cm-diameter sphere phantom (for uniformity in reconstruction), a Defrise phantom (for axial sampling), a Derenzo phantom (for resolution), and the standard XCAT brain phantom [9] modeling a 123I IMP distribution (clinical case emulation). The normalized relative mean squared error (NRMSE) was used as IQ metric to asses imaging fidelity of the ASC for the XCAT phantom. Results: The brain reach for the current 6” and 8” CD-ASC designs was ~ 4 cm and ~8 cm, respectively. Volumetric sensitivity at the center of the VOI of the 6” with the 4 oblique pinholes was 4.6 times that of a dual-headed LEHR SPECT, and with all the pinholes was 5.6. Similarly, for 8” CDs the sensitivities were 3 and 3.8, respectively. The reconstructed images for the sphere phantom for the single central aperture showed good uniformity; however, when all oblique apertures were used streak artifacts were noted due to multiplexing. The reconstruction of a noise free Derenzo phantom resolved the 6.4 mm rods and spatial resolution improvement was noted along caudo-cranial direction in the VOI. When brain perfusion imaging was simulated with the XCAT phantom for a duration equal to that used clinically with either the central pinholes or the 4 oblique pinhole combination, the resulting counts were 5.2 M and 17.6 M, respectively. The XCAT reconstructed images with noise acquired with the 4 oblique pinholes were of higher image quality, showed no sign of artifacts due to the minimal overlap of the brain in the projections, and resulted in lower NRMSE (0.31) compared to using the central pinholes only (NRMSE 0.35). Conclusion: We have determined that CDs can be employed as an alternative to flat detectors in ASC. Future investigations will include further exploration of system design alternatives, various combinations of temporal shuttering of apertures, levels of multiplexing and truncation of projections, and using XCAT phantoms modeling clinical imaging of different sized patients [10], and imaging agents. Research Support: NIH-NIBIB, Grant No R01 EB022521.