Minimum detectable defect thickness in SPECT myocardial perfusion test: phantom study with (99m)Tc and (201)Tl.

OBJECTIVE: The purpose of this study was to determine experimentally the minimum thickness (D(min)) of a defect inserted on the myocardial wall of a cardiac phantom at different locations that could be clearly detected in a SPECT perfusion study using (99m)Tc and (201)Tl. METHODS: Rectangular (or cylindrical) defects with the same thickness were inserted on the inner surface of a myocardial phantom at 5 different locations: anterior (ANT), septal (SEP), inferoposterior (IP), lateral (LAT), and apical (AP). For different defect thickness (from 1 to 7 mm, in increments of 1 mm) the myocardial SPECT perfusion study was performed with (99m)Tc and (201)Tl using the same protocol that we use for patients. Baseline studies (with no defect inserted) were also performed. The SPECT images of the myocardial phantom with defects were compared with baseline SPECT images to determine whether the defect could be clearly identified. RESULTS: The uniformity of the baseline SPECT images was analyzed very carefully where an IP artifact was detected. The D(min) was determined for (99m)Tc and (201)Tl at 3 radii of rotation: 21.0, 25.0, and 29.2 cm. CONCLUSION: To be detected on SPECT images, a defect must be of a thickness > or =D(min). A simple method for performing a quality control test for SPECT nuclear cardiology can be developed based on these findings.

Intrinsic uniformity and relative sensitivity quality control tests for single-head gamma cameras.

OBJECTIVE: We sought to determine the best parameters for rapid performance of daily quality control testing of intrinsic uniformity and relative sensitivity for the single-head gamma-camera system in our nuclear medicine department. METHODS: The effects of the following parameters on intrinsic uniformity were studied: gamma source activity, number of acquired counts for the flood image, source-to-camera distance, image matrix size, and source volume. The dead time of the system was determined experimentally using the two-source method for accurate calculation of relative sensitivity. RESULTS: A set of parameters for rapid performance of daily gamma-camera intrinsic uniformity and relative sensitivity was determined. The dead time of our gamma-camera system was found to be 4.5 +/- 0.2 micros. CONCLUSION: With our recommended parameters, the intrinsic uniformity and relative sensitivity quality control testing can be performed in 5-6 min. The dead time of each gamma-camera system must be determined experimentally in each nuclear medicine department.