Applications of Tc-99m Sestamibi: Cardiac Imaging and Beyond

Educational objectives: 1. Learn the mechanism of Tc-99m sestamibi localization in tissue. 2. Learn the major indications of Tc-99m sestamibi imaging. 3. Be aware and recognize patterns of various incidental findings on Tc-99m sestamibi scintigraphy. Technetium-99m sestamibi myocardial perfusion imaging (most often employing the 1-day rest/stress protocol) is a commonly used non-invasive test for evaluation and risk stratification of patients with known or suspected coronary artery disease. Another well-established indication for Tc-99m sestamibi is parathyroid imaging for pre-operative localization of parathyroid adenomas or ectopic parathyroid tissue in patients with hyperparathyroidism. Breast specific gamma imaging (BSGI) / scintimammography is yet another indication where Tc-99m sestamibi (under the brand name Miraluma™) may be helpful in certain patients as supplemental breast imaging (for example in patients with dense breasts, with a lump at previous surgical site, with breast implants, indeterminate mammograms, or when multiple tumors are suspected). Often, unsuspected or incidental findings on these images may be seen and can be important in the clinical course and management of the patients. We will present multiple case examples of sestamibi scintigraphy along with correlative images from other modalities, as well as histopathology. We will discuss the subcellular mechanism of sestamibi uptake that may explain its localization in some of the pathologic conditions. These will include myocardial perfusion imaging, parathyroid imaging, BSGI, thyroid cancer (especially Hurthle cell) and a variety of incidental extracardiac findings (e.g., breast ca, hibernoma, hiatal hernia). Some of these diagnoses were unexpected and had an impact on patient management, therefore, timely communication of even some incidental findings to the referring physician is essential.