Pulmonary perfusion imaging is a method of intravenous injection of an imaging agent containing large polymerized human serum protein particles and radionuclide-labeled microspheres with a diameter larger than the capillaries of the lungs. The imaging agent enters the human vein, passes through the right ventricle with the body’s blood circulation, and is then perfused through the heart into the vascular bed of the lungs, where an obstructive stay occurs when there is an embolism in the capillaries of the lungs. When there is an embolic condition in the capillaries of the lung, there will be obstructive retention. Then, with medical imaging equipment to image the internal tissues of the lung, lung perfusion planes or tomographic images are obtained, and the emissive distribution of the imaging agent in the lung is observed using the relationship between the distribution of radioactive particles and the blood flow in the pulmonary artery in direct proportion. Currently, pulmonary perfusion imaging is clinically useful for diagnosing conditions such as pulmonary embolism, pneumoconiosis, pulmonary artery hypoplasia, and pulmonary artery orifice stenosis.