Mit·]: iiI: til I: ttl 4 ·illlf·S i [,]: M An Optimized Protocol for Detection of Coronary Artery Disease Using Technetium-99m-Sestamibi Lynne Roy, Kenneth Van Train, James Bietendorf, Ernest Garcia, Russel Folks, Hosen Kiat Jamshid Maddahi, and DanielS. Berman ' Cedars-Sinai Medical Center, Los Angeles, California and Emory University Hospital, Atlanta, Georgia This is the second article in the four-part series on "New Radiopharmaceutica/s." Upon completion of this article the reader should be able to: (1) identify imaging characteristics of technetium-99m-sestamibi and (2) understand the recon- struction and processing protocol. Thallium-201 e 0 'Tl) has been the agent used in imaging myocardial perfusion. To circumvent the physical limitations of 201 Tl (low-energy photons, long half-life), technetium-99m- (99mTc) labeled myocardial perfusion agents have been sought. Technetium-99m-sestamibi* (Cardiolite, Du Pont de Nem- ours, N. Billerica, MA) was found to exhibit properties which offer several advantages over 201 TI for myocardial perfusion imaging. These include higher energy emission, shorter half- life: administrable activity red1stnbut10n several hours after injection ( 1 ). In addition tlieseJ>roPerties mak:e itJ,-ossibteto asses5not only myocardiai perfusion, but also function (including first-pass ejection frac- tion) with a single injection (2). The superior imaging characteristics of 99 mTc-sestamibi over 201 TI are only fully realized if the technical aspects associated with single-photon emission computed tomogra- phy (SPECT) of the myocardium are optimized. Our institu- tions have developed image processing parameters to fully utilize the improved imaging qualities of 99 mTc-sestamibi (Fig. 1). Acquisition parameters for single-detector camera systems were developed by using phantom studies. Reconstruction parameters were initially defined using phantom studies and then refined further by using clinical data. By employing first- pass acquisition (both at rest and during exercise), wall motion and ejection fraction information is obtained, improving the diagnostic interpretation of the patient's study. A same-day protocol as well as a two-day protocol are compared in this article. For reprints contact: Lynne Roy. CNMT. Cedars-Sinai Medical Center. Dept. of Nuclear Medicine. 8700 Beverly Blvd .. Los Angeles, CA 90048. VOLUME 19, NUMBER 2, JUNE 1991 Imaging sequence can be particularly flexible in that both same-day or two-day protocols can be used. The radiophar- maceutical dose depends upon which protocol is employed. Preparation and quality control of 99 mTc-sestamibi are shown in Table I. MATERIALS AND METHODS Optimization of the acquisition parameters for single-detec- tor camera systems was performed using phantom studies where the contrast of simulated perfusion defects and uni- formity of normal slices were used as parameters for evaluat- ing imaging characteristics. The optimal parameters deter- mined for the rest and exercise studies included the use of a 20% symmetric energy window centered on the 140 keV photopeak, a high-resolution collimator, and a circular 180" acquisition with 64 projections (from a 45" RAO to a 45" LPO) (3). In addition, preliminary studies, using actual pa- tient data, indicated that a 64 x 64 matrix is preferable to a 128 x 128 matrix ( 4). Both provide similar image uniformity, but the 64 x 64 matrix better conserves computer disc space and computer processing time. The above image acquisition parameters can be used for both the same-day and two-day protocols. To further optimize image quality, patients are instructed to drink 8 oz of whole milk (or a light fatty meal, (e.g., doughnuts in patients with intolerance to dairy products) immediately after both rest and stress injections. This proce- dure promotes tracer clearance from the gallbladder which otherwise may obscure the inferior wall of the left ventricle (5). The post-exercise image acquisition is ECG-gated using eight frames/cardiac cycle. This resting wall motion infor- mation provided by the gated display may be useful for evaluation of artifacts and assists in the assessment of myo- cardial viability. That is, segments with perfusion defects and normal wall motion represent viable myocardium, whereas segments with perfusion defects and akinesis represent scar (6). The subsequent quantitative analysis of myocardial per- fusion involves the comparison of regional myocardial counts 63