New software for raw data mask processing increases diagnostic ability of myocardial SPECT imaging

Objective Increased activity of myocardial perfusion tracer technetium-99m in liver and hepatobiliary system causes streak artifacts, which may affect clinical diagnosis. We developed a mask-processing tool for raw data generated using technetium-99m as a myocardial perfusion tracer. Here, we describe improvements in image quality under the influence of artifacts caused by high accumulation in other organs. Methods A heart phantom (RH-2) containing 15 MBq of pertechnetate was defined as model A. Model B was designed in the same phantom containing ten times of cardiac radioactivity overlapping with other organs. Variance in the vertical profile count in the lower part of the myocardial inferior wall and in the myocardial circumferential profile curve were investigated in a phantom and clinical cases using our raw data masking (RDM) software. Results The profile variances at lower parts of myocardial inferior walls were 965.43 in model A, 1390.11 in model B and 815.85 in B-RDM. The mean ± SD of myocardial circumferential profile curves were 83.91 ± 7.39 in model A, 69.61 ± 11.45 in model B and 82.68 ± 9.71 in model B-RDM. For 11 clinical images with streak artifacts, the average of the variance significantly differed between with and without RDM (3.95 vs. 21.05; P\0.05). For 50 clinical images with hepatic accumulation artifacts, the average of the variance on vertical profiles on images with and without RDM significantly differed (5.99 vs. 15.59; P\0.01). Furthermore, when a segment with \60% uptake in polar maps was defined as abnormal, the average extent score of 1 h (Tc-1h), 5 min of RDM (Tc-0h-RDM) and 5 min of non-RDM (Tc-0h-non-RDM) were 2.25 ± 3.12, 2.35 ± 3.16, and 1.37 ± 2.41, respectively. Differences were significant between Tc-1h and Tc-0hnon- RDM (P\0.005) but not between Tc-1h and Tc-0h- RDM. Conclusion Batch processing was enabled in all frames by shifting the myocardium to the center of rotation using this software. The waiting time between infusion and image acquisition should be decreased, thus reducing patient burden and improving the diagnostic ability of the procedure.