Lung perfusion imaging

Lung perfusion imaging agents are 99mTc-labeled large aggregated human serum protein particles (99mTc-MAA) or 99mTc-labeled microspheres, which have a diameter of about 10-30 μm, and a single dose of 0.5-1.5 mg, about 100,000-300,000 particles. When the reagent is injected into the vein, it enters the right heart with the blood, and is fully mixed with the blood in the right heart, and then perfused into the vascular bed of the lung with the blood stream through the pulmonary artery. The embolism of pulmonary capillaries. (99mTc-MAA) The amount of embolized vascular beds in various parts of the lung is proportional to the amount of blood perfusion in the local area. Therefore, the (99mTc-MAA) radioactivity distribution image in the lung taken by the scanner or gamma camera That is, the image of blood flow perfusion in the lung. The higher radioactivity indicates that the local blood flow is better, and the lower position indicates that the blood flow is poor. If radioactivity is absent in a certain area, it indicates that there is no blood perfusion in the area, indicating that the blood vessels infused there have been blocked or occluded. The distribution of radioactivity in the lungs of normal people is basically uniform. Due to the influence of blood flow and (99mTc-MAA) on gravity, the radioactivity of the lung tip is slightly lower when injected in the sitting position, and the radioactivity in the dorsal lung is slightly higher when injected in the supine position. In one imaging, the number of blocked blood vessels only accounts for a few tenths of a million and a few millionths of the total number of anterior pulmonary blood vessels and capillaries, so it does not cause significant hemodynamic changes and changes in lung function.