Comparison of 180 degrees and 360 degrees data collection in thallium-20 1 imaging using single-photon emission computerized tomography (SPECT): concise communication.

Thallium-201 imaging using SPECT is being done with 180 degrees (RAO to LPO) data collection in some centers with single-gamma camera systems. Using our SPECT system with two gamma cameras, we have compared the effects of 180 degrees data collection without attenuation correction against 360 degrees collection with attenuation correction, using phantoms and patients. With a heart phantom in a chest phantom, TI-201 activities simulating "normal myocardium," "ischemia," "infarction," and "background" were placed in object contrast ratios (with respect to background) of 5.0, 2.0, and -1.0, respectively. The 180 degrees data gave image contrast ratios of 1.6, 0.2, and -0.8, and the 260 degrees data gave ratios of 1.5, 0.8, and -0.3, respectively. Uniform activity throughout the heart gave similar image contrast with both data-collection methods, but there was more variability with the 180 degrees collection than with 360 degrees collection. Since attenuation correction is available with the 260 degrees collection, the effects of attenuation are seen only on the 180 degrees collection images. In eight patients the image contrasts from the 180 degrees and 260 degrees collections are similar. For our two-camera SPECT system, the 360 degrees collection permits attenuation correction, has less variability in counting statistics, and gives contrast ratios like those of 180 degrees collection.