Findings: Following the intravenous administration of Persantine, 30 mCi of Technetium-99M Sestamibi (MIBI) was administered intravenously and tomographic images of the myocardium were obtained. The following day, the intravenous 30 mCi of MIBI was administered at rest and repeat tomographic images of the myocardium were obtained.

Moderately diminished perfusion involving the distal third of the anterior wall and apex was observed following stress and this area was noted to improve at rest. No other perfusion abnormalities were demonstrated. The left ventricular ejection fraction measured 75%.

Diagnosis: Moderate ischemia of the distal third of the anterior wall and apex. Normal left ventricular ejection fraction.

Discussion: MIBI is used with exercise and pharmacologic testing to assess the presence of coronary artery disease. It is accumulated within the myocardium in proportion to regional myocardial blood flow. A fixed defect on the scanning indicates myocardial infarction or severe ischemia at the site; whereas a defect that reperfuses suggests myocardial ischemia.

MIBI is a newer myocardial perfusion agent that has a higher photo-peak of 140 keV than 201T1 of 80 keV and much shorter half life. These characteristics allow ue of larger doses of MIBI than 201T1, less soft tissue attenuation, better counting statistics, and improved image quality with single-photon emission CT.

An increasing body of literature indicates that MIBI can also be used to assess the risk of future cardiac events such as myocardial infarction or death.

References:
Mandalpu BP, Amoto M, Stratmann HG. Technetium Tc 99M
Sestamibi myocardial peerfusion imaging: Current Role for
Evaluation of Prognosis. Chest. 1999;115(6):1684-1694.

Putman CF, Ravin, CE. Textbook of Diagnostic Imaging, 2nd Edition.
W.B. Saunders, Philadelphia; 1994:1669.

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