Criteria for the addition of prone imaging to myocardial perfusion single-photon emission computed tomography for inferior wall
Myocardial perfusion single-photon emission computed tomography (SPECT) is occasionally suspected to generate images that represent either ischemia or infarction for the inferior wall [right coronary artery (RCA) disease] or attenuation artifacts because of the diaphragm. We often encounter this. The application of prone imaging is advantageous in the differentiation of RCA disease because of attenuation artifacts. If decreased accumulation of radioisotopes is observed at the site with either RCA disease or attenuation artifacts, then a criterion that enables the addition of prone imaging should be implemented. Then, we evaluated sites where RCA disease and attenuation artifacts would likely appear and investigated the threshold of decreased accumulation that enables utilization of prone imaging.Patients and methods
The patients in this study were divided into two groups: group A (20 patients) suspected to have attenuation artifacts because of the diaphragm and group B (14 patients) with RCA disease. Additional evaluation by prone imaging was performed in all patients. We utilized a 20-segment quantitative perfusion SPECT polar map in the supine and prone positions to compare the percentage increase in 201Thallium chloride (201Tl) in both groups. We then investigated the percent uptake (%uptake) value of decreased accumulation in the inferior wall for the addition of prone imaging.Results
The highest %uptake was present in segments 3, 4, 5, and 10 in group A after the prone imaging. Detection of attenuation artifacts from the diaphragm was easy in segments 3, 4, 5, and 10, and we set the %uptake threshold at 62, 61, 71, and 76%, respectively, in the supine position for the addition of prone imaging.Conclusion
A decrease of the %uptake in segments 3, 4, 5, and 10 after supine imaging is presumed to result from attenuation artifact or RCA disease. We established evaluation criteria for the addition of prone imaging in patients with decreased accumulation in the inferior wall during supine imaging.