Effect of patient positioning on the evaluation of myocardial perfusion SPECT

Ecg-gated spect myocardial perfusion imaging is usually acquired in supine position. however, some patients are not comfortable in this position for a variety of personal or medical reasons. our aim was to investigate the effect of patient positioning on quantitative spect imaging results using normal supine database. 55 patients (mean age 58.5 ± 8.3 years) were enrolled in this prospective study. each patient had a pair of ecg-gated stress spect myocardial perfusion images acquired on two gamma cameras: one in supine position and the other in upright sitting position. left ventricular (lv) ejection fraction (ef), end-diastolic (ed), and end-systolic (es) left ventricular volumes (v), lv mass, summed stress perfusion defect score (sss), and total severity score (tss) were calculated automatically relative to a supine normal reference database. there were no significant differences in lvef using the two cameras (0.65 ± 0.08 vs. 0.66 ± 0.10; p > 0.1). however, edv, esv, and lv mass were significantly smaller in sitting position than in supine position (89 vs. 80 ml; 33 vs. 29 ml and 115 vs. 109 ml, respectively, all p < 0.0001). on the other hand, sss and tss were significantly higher in sitting position than in supine position (5.16 vs. 8.73 and 166.82 vs. 288.27, both p < 0.0001). overall, more studies in sitting position were interpreted as abnormal than in supine position (p < 0.05). patient positioning has a significant impact on quantitative gated spect imaging results. using a supine normal reference database, sss and tss were larger in sitting position than in supine position. thus, for imaging in sitting position, separate normal limits are required.