Abstract
Since the early 2000’s, evaluation of pulmonary embolism (PE) has shifted from 99mTc macroaggregated albumin (MAA) perfusion lung scans to CT angiography (CTA). 99mTc MAA continues to be used in patients with contraindications to CTA and for other uses. A reduced number of MAA particles is used in patients with pulmonary hypertension (PH) or other risk factors. This study assessed the changing use patterns for 99mTc MAA by comparing snap-shots of procedures in 2000 and in 2015 in one institution. Methods: Records for all patients receiving 99mTc MAA in the year 2000 and in 2015 were reviewed, making note of the imaging procedure, any contraindication to CTA, and if a reduced number of MAA particles was used. Results: In 2000, 99mTc MAA was used for 489 lung scans for PE, 2 peritoneovenous shunts, and 1 cardiac shunt. Of the lung scan patients, 46 (9%) had PH. A reduced number of particles was used for PH and cardiac shunt patients, 47/492 = 9%. In 2015, 99mTc MAA was used for 263 lung scans for PE, 33 pre-surgical planning scans, 33 lung transplants, 16 pulmonary artery stenosis, 5 hepatic artery microspheres eligibility, and 1 peritoneovenous shunt. Of the lung scans for PE, 256/263 (97%) had a contraindication to CTA or a non-diagnostic CTA, including 99 (38%) with PH. A reduced number of particles was used for PH, pre-surgical, and lung transplant patients, 165/351 = 47%. Conclusion: Comparing 2015 to 2000, lung scans for PE decreased 46% from 489 to 263, apparently due to CTA, while other uses rose from 3 to 88. Use of 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 PE and other uses.