Several types of patients should receive a reduced number of particles for perfusion imaging.
① Patients with severe pulmonary hypertension and right-to-left shunts should be given only half the conventional dosage.
Pulmonary segments with decreased or absent blood flow show diminished radioactivity.
2.2 Methods
2.2.1 Radiopharmaceuticals
99mTc-labeled macroaggregated albumin (99mTcMAA) is the most frequently used radiopharmaceutical to imaging lung perfusion. The MAA has a mean size of 40 um with a range of 10 to 90 um.
Typically, 100,000 to 700,000 particles are injected to ensure reliable count statistics and image pulmonary arterial trees are temporarily and safely occluded.
2. Lung Perfusion Imaging
2.1 Principle
Pulmonary perfusion imaging is based on the principle of capillary blockade.