Practical and Diagnostic Considerations for Gated Myocardial Perfusion Tomography Using Sestamibi

Abstract

Technetium-99m (^99mTc) sestamibi makes gated single-photon emission computed tomography (SPECT) perfusion imaging possible because of ^99mTc’s energy and counting statistics. The aim of this study was to analyze the practical and diagnostic value of gated SPECT imaging while considering the extra investment in time and effort. We studied 73 subjects (20 normals, 53 patients) using a 1-day rest/stress protocol (6 mCi at rest/24 mCi at peak stress). Camera time was ~50% longer than a standard nongated SPECT study; filtering and reconstruction took 2.5 times longer. Processing of diastolic studies took ~8 min. Acquisition data, reconstructed studies, and formatted diastolic and dynamic studies occupied 5.6 times more storage space. High quality dynamic and perfusion studies were obtained in 70/73 patients. The right ventricle (RV) appeared more distinct on diastolic studies than in nongated studies (p < 0.01). The left ventricle (LV) cavity was larger in diastolic studies than in nongated studies (p < 0.001), leading to more useful coronal slices with cavity (p < 0.001). A significant inverse relation between LV size and increase in number of useful coronal slices with ventricular cavity in diastolic studies was found (r = –0.71. p < 0.001). The extra effort, time, and storage space required by gated SPECT was balanced by the additional diagnostic information gained from dynamic and diastolic images and by clearer RV and LV cavity visualization. Gated SPECT is particularly useful in patients with small hearts or in patients with LV hypertrophy.