Clinical results of a novel wide beam reconstruction method for shortening scan time of Tc-99m cardiac SPECT perfusion studies
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Newly developed reconstruction algorithms enable the acquisition of images at half of the scan time while maintaining image quality. The purpose of this investigation was to evaluate a novel wide beam reconstruction (WBR) method developed by UltraSPECT for decreasing scan times and to compare it with filtered backprojection (FBP), which is the technique routinely used.
Methods and Results
Phantom and clinical studies were performed. Hot and cold sphere and cardiac phantom acquisitions were reconstructed via WBR, FBP, and ordered-subsets expectation maximization. Fifty patients were prospectively studied by use of both a standard and a short protocol. The short protocol was performed first on 29 of 50 patients via 8-frame gated technetium 99m stress single photon emission computed tomography and low-energy high-resolution collimators. Stress Tc-99m studies (30–45 mCi) were scanned for 20 seconds per frame. For the short protocol, all parameters remained constant except for the time per frame, which was reduced by 50% on Tc-99m studies. All resting Tc-99m scans (36/50 patients) were processed with FBP for the standard full-scan time studies and with WBR for the short scan studies. The images were interpreted by use of a 17-segment model and 5-degree severity score, and the perfusion and functional variables were determined. Distributions including mean, median, and interquartile ranges were examined for all variables. The differences (FBP-WBR) were computed for all variables and were examined by use of nonparametric signed rank tests to determine whether the median difference was 0. The absolute value of the difference was also examined, Spearman rank-order correlation, a nonparametric measure of association, was used for the 2 methods to determine significant correlations between variables. The hot and cold sphere phantom studies demonstrated that WBR had improved contrast recovery and slightly better background uniformity than did the ordered-subsets expectation maximization. The cardiac phantom studies performed with attenuating medium and background activity showed that the half-scan time images processed with WBR had better contrast recovery and background uniformity than did the full-scan time FBP reconstruction. In the clinical studies, highly significant correlations were observed between WBR and FBP for functional as well as perfusion variables (P<.0001). The summed stress score, summed rest scores, and summed difference score were not statistically different for FBP and WBR (P<.05). Left ventricular volumes had a high correlation coefficient but were significantly larger with FBP than with WBR.
Our study results suggest that cardiac single photon emission computed tomography perfusion studies may be performed with the WBR algorithm using half of the scan time without compromising qualitative or quantitative imaging results.
Key WordsSingle photon emission computed tomography wide beam reconstruction filtored backprojection
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