Technetium[99mTc]Sestamibi

General Description

Technetium (^99mTc) sestamibi is a lipophiliccation complex represented as ^99mTc-(MIBI)6⁺, whereMIBI is 2-methoxyisobutyl isonitrile.It is clinically indicatedas a myocardial perfusion agent for detecting coronaryartery disease and evaluation of myocardial function(accomplished by imaging during rest and during cardiovascularstress with either exercise or pharmacologic stress)as well as a second line diagnostic drug after mammographyto assist in the evaluation of breast lesions in patientswith an abnormal mammogram or a palpable breast mass.An additional clinical use is the evaluation of hyperparathyroidism.
Preparation of 99mTc sestamibi begins with the additionof sodium pertechnetate (^99mTc) to shielded reaction vialcontaining tetrakis (2methoxyisobutyl isonitrile) copper (I)tetrafluoroborate, sodium citrate, L-cysteine hydrochloride,mannitol, and stannous chloride. Initially, the reducedtechnetium-99m forms a weak complex with citrate, whichundergoes a ligand exchange with the isonitrile during a10-minute heating period in a boiling water bath. The reactionvial requires cooling for 15 minutes before use. Therecommended shelf life is 6 hours.
The recommended dose for ^99mTc sestamibi when usedfor breast imaging is 20 to 30 mCi (740–1,110 MBq). Whenused for parathyroid imaging, the recommended dose is 25to 30 mCi (925–1,110 MBq).