Utility of technetium-t-butyl isonitrile (99mTc-TBI) myocardial imaging in coronary artery disease.

: 99mTc-t-butyl isonitrile is a useful agent for myocardial perfusion imaging. The superior physical advantages of technetium over 201thallium make larger doses possible for imaging. Accumulation in the myocardium is unidirectional in that once attached it does not leave the myocardium and hence two separate injections are needed for rest and stress imaging. High liver uptake frequently conceals the inferior wall and high early uptakes make immediate post-injection imaging almost impossible at least up to 45-60 min. This agent, however, was seen to accurately identify under-perfused areas and distinguish between ischaemia and infarct in our patients. Agreement with 201Tl and with GBP study of regional wall motion was excellent. While its individual sensitivity and specificity are quite high at 82.6 and 90.9%, in combined GBP studies the sensitivity rose to 93.4%. It is concluded that Tc-TBI is a valuable agent for myocardial perfusion scintigraphy, especially in a developing country like India where Tc-MIBI cannot be routinely used, since it is expensive, and where regular supplies of 201Tl are also not always feasible due to the high cost of importing. 99mTc-TBI can be made cheaply here and in a select population, notably in those with left anterior descending and circumflex coronary artery disease, it can provide valuable information.