Which tracer is primarily excreted via the hepatobiliary system?

99mTc-sestamibi is a radiopharmaceutical that is predominantly excreted through the hepatobiliary system. This tracer is commonly used in myocardial perfusion imaging and studies involving breast cancer detection due to its ability to accumulate in myocardial tissue and cancer cells. The hepatobiliary system's involvement in the excretion of 99mTc-sestamibi is primarily due to the compound being lipophilic, which allows it to be cleared from the bloodstream via bile secretion into the biliary tract.

In contrast, the other tracers mentioned have different mechanisms of excretion. For instance, 99mTc-exametazime generally undergoes renal excretion, making it less relevant for studies requiring hepatobiliary tracking. Similarly, 99mTc-medronate is predominantly used for bone imaging and is eliminated via renal pathways. On the other hand, 201Tl-thallous chloride, a thallium-based tracer, is not known for significant biliary excretion but rather is primarily retained in myocardial and other tissues with blood flow.

Thus, the unique pharmacokinetics of 99mTc-sestamibi, particularly its clearance through the liver and biliary system, is what makes it the correct choice for