RT Journal Article SR Electronic T1 Dedicated cardiac SPECT imaging with multi-pinhole collimators on a clinical scanner JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1951 OP 1951 VO 57 IS supplement 2 A1 Hui Liu A1 Tianyu Ma A1 Jing Wu A1 Si Chen A1 Shi Wang A1 Zhaoxia Wu A1 Yan Xia A1 Yaqiang Liu YR 2016 UL http://jnm.snmjournals.org/content/57/supplement_2/1951.abstract AB 1951Objectives Cardiac imaging with parallel-hole SPECT has suffered from low resolution and sensitivity. This work aimed to develop dedicated cardiac imaging functionality on a clinical scanner with high resolution and sensitivity.Methods Our dedicated cardiac SPECT imaging was based on a clinical dual-head SPECT scanner. Two NaI(Tl) SPECT detector heads were placed in 90 degree setup. Conventional parallel-hole collimators were replaced with well-designed multi-pinhole collimators. All the pinholes focused on the heart region without projection overlap. Collimator parameters were optimized with an exhaustive searching method to maximize sensitivity at fixed resolution. The pinhole numbers were 16 and 20 respectively for top detector and side detector heads. The optimized pinhole diameter was 4.1 mm and 3.4 mm respectively. SPECT projection data were acquired in stationary imaging mode. Accurate geometry calibration was performed by scanning a point source at 108 positions with known relative distance. Maximum likelihood expectation maximization (MLEM) iterative algorithm with a pre-stored system matrix was developed for SPECT image reconstruction. The image voxel size was 4.0 x 4.0 x 4.0 mm3. To improve image quality, the system matrix was calculated using a finer voxel grid (0.5 x 0.5 x 0.5 mm3 step). Pinhole geometric model was calculated through ray-tracing. Three experiments were conducted to evaluate imaging performance. 1) A 4.6 mCi 99mTc point source was scanned across the field of view (FOV) to calculate average sensitivity. 2) Two point sources at 1 cm distance was imaged to evaluate system spatial resolution. 3) A heart phantom with myocardium defect (2 cm in length), injected by 10 mCi 99mTc, was scanned for 5 s, 15 s and 5 min and were reconstructed with 200 iterations. For comparison, the same phantom was also scanned for 30 min by mounting low-energy high-resolution (LEHR) parallel-hole collimator on SPECT heads. Sixty projections were acquired and data were reconstructed with ordered subset expectation maximization (OSEM) iterative algorithm using 6 subsets and 4 iterations.Results The average sensitivity across the ~14 cm FOV was 0.03%, higher than dual-head LEHR SPECT (typically 0.015%). Two point sources with 1 cm distance were distinguishable in reconstructed image. Full width at half maximum (FWHM) of the point source was 6.4 x 7.5 x 7.0 mm3, which also showed the spatial resolution was much better than LEHR SPECT system (~8 mm). The total counts of 5 s, 15 s and 5 min scan were about 3e5, 1e6 and 2e7 respectively. Reasonable myocardium phantom images without prominent artifact could be acquired with 5 min scan. Compared with the LEHR SPECT image, dedicated cardiac SPECT showed superior spatial resolution and defect identification capability. In low count studies, the 15 s scan and 5 s scan images showed increased noise and reduced boundary visualization, but were still better than LEHR SPECT image in terms of defect identification.Conclusions Our dedicated cardiac SPECT imaging method was demonstrated to be feasible for cardiac imaging with high resolution and sensitivity compared with conventional parallel-hole SPECT. We will evaluate the system performance with anthropomorphic phantom and patient studies in future. Research Support: This study was supported by China Postdoctoral Science Foundation (2015M581113).