Changes in Patterns of ^99mTc-Macroaggregated Albumin Use Between 2000 and 2015

Since the early 2000s, the method of evaluating pulmonary embolism has shifted from ^99mTc-macroaggregated albumin (MAA) perfusion lung scans to CT angiography. ^99mTc-MAA continues to be applied for patients with contraindications to CT angiography and for other uses. A reduced number of ^99mTc-MAA particles is administered to patients with pulmonary hypertension or other risk factors. This study assessed the changing patterns of ^99mTc-MAA use between 2000 and 2015 at a single institution by comparing snapshots of the procedures performed in those two years. Methods: Records for all patients receiving ^99mTc-MAA in 2000 and 2015 were reviewed, making note of the type of imaging procedure, whether there was any contraindication to CT angiography, and whether a reduced number of ^99mTc-MAA particles was administered. Results: In 2000, ^99mTc-MAA was used for 489 lung scans for pulmonary embolism, 2 for peritoneovenous shunts, and 1 for a cardiac shunt. Of the lung scan patients, 46 (9%) had pulmonary hypertension. A reduced number of particles was administered to the pulmonary hypertension and cardiac shunt patients (47/492, or 9%). In 2015, ^99mTc-MAA was used for 263 lung scans for pulmonary embolism, 33 for presurgical planning, 33 for patients with a lung transplant, 16 for pulmonary artery stenosis, 5 to determine hepatic artery microsphere eligibility, and 1 for a peritoneovenous shunt. Of the lung scans for pulmonary embolism, 256 of the 263 patients (97%) had a contraindication to CT angiography or a nondiagnostic CT angiogram, including 99 (38%) with pulmonary hypertension. A reduced number of particles was administered to the pulmonary hypertension patients, presurgical patients, and lung-transplant patients (165/351, or 47%). Conclusion: Comparing 2015 with 2000, lung scans for pulmonary embolism decreased 46%, from 489 to 263, apparently because of a shift to CT angiography, whereas other uses rose from 3 to 88. Administration of a reduced number of particles rose significantly from 9% to 47% of ^99mTc-MAA doses. Although the total number of ^99mTc-MAA doses dropped 29%, from 492 to 351, ^99mTc-MAA remains an important radiopharmaceutical for both pulmonary embolism and other uses.