Pulmonary perfusion imaging

The lung perfusion imaging agent is 99mTc-labeled macro-polymerized human serum protein particles (99mTc-MAA) or 99mTc-labeled microspheres having a diameter of about 10 to 30 μm, a single dose of 0.5 to 1.5 mg, and about 100,000 to 300,000 particles. When the reagent is injected into the vein, it enters the right heart with the blood, mixes well with the blood in the right heart, and then perfused through the pulmonary artery into the vascular bed of the lung with the blood flow. The larger particles can temporarily embolize the pulmonary anterior blood vessels, which is smaller. The patient embolizes the pulmonary capillaries. (99mTc-MAA) The amount of vascular bed at various sites in the lung is proportional to the local blood perfusion, so the radioactive distribution image (99mTc-MAA) captured by the scanner or gamma camera is embedded in the lung. That is, the image of blood perfusion in the lung, the higher radioactivity shows that the local blood perfusion is better, and the lower part shows that the blood perfusion is poor. If a part of the radioactive absence is absent, it indicates that there is no perfusion at this site, indicating that the blood vessel perfused there has been blocked or occluded. The radioactivity distribution in the lungs of normal people is basically uniform. Due to the blood flow and (99mTc-MAA), the lung tip radioactivity is slightly lower when the seat is injected, and the radioactivity in the dorsal lung is slightly higher when the supine position is injected. In one imaging, the number of blocked blood vessels accounts for only a few ten thousandths of parts of the total number of pulmonary capillaries and capillaries, and therefore does not cause significant hemodynamic changes and changes in lung function. Basic Information Specialist Category: Respiratory Examination Category: Radionuclide Applicable gender: whether men and women apply fasting: fasting Tips: Disable congenital heart disease, pulmonary arteriovenous fistula and severe lung impaired, severe neutropenia, thrombocytopenia, aplastic anemia in right-left shunt. Normal value In normal images, the lungs have a complete contour, a relatively uniform distribution of radioactivity, and a slightly lower radioactivity in the extrapulmonary zone and lung tip. The right lung of the AP is often in an upward arc shape, and the left lung has an aortic arch and a heart indentation, which is smaller than the right lung. The PA position is close to the size of the lungs. The middle blank area is the spine and mediastinum, and the heart shadow is covered by the left lower lung. The anterior lower edge of the LL position is a heart indentation. Clinical significance Abnormal results: 1. Abnormal lung perfusion imaging shows pulmonary or segmental (wedge, common in pulmonary embolism) or irregular radioactive defects, but defects in one position, especially oblique position, must be the same in other positions. Defects in the site can be judged abnormal. 2. Images of normal smokers may also have small perfusion defects. 3. Pleural lesions can affect normal patterns, such as pleural thickening or a small amount of pleural effusion in the lateral or oblique position can produce "leaf sign" (leaf interlobular widening, the formation of linear radioactive defects); medium amount of fluid can form Similar to lung segmental radioactive defects, but the change of body position imaging can disappear, a large amount of effusion can compress the whole lung to narrow the lung shadow. Need to check the crowd: There are abnormal diseases in the lungs and patients with lung examination are required. Low results may be diseases: acute right heart failure, purpura - clubbing - liver disease syndrome, pulmonary embolism, acute cardiac insufficiency results may be high disease: pulmonary arteriovenous disease considerations Note before inspection: 1. Ask about the history of allergies before the examination, but the patient needs to have a skin test first. After the skin test, the lung perfusion imaging can be performed after 15 minutes of no positive reaction, but it needs to be closely observed and provided with emergency medicine. Requirements for inspection: 1. Inhale oxygen for 10 minutes before intravenous injection to avoid false positives caused by pulmonary vasospasm. 2. The speed of intravenous injection of imaging agents should be slow, so that blood should be pumped back to avoid blood clotting and imaging agents condense into larger masses to block pulmonary arterioles. Otherwise, abnormal radioactive hot spots in lung imaging can be caused, affecting the test results, and Excessive obstruction of the pulmonary blood vessels can lead to adverse reactions such as hernia. For patients with allergies and patients whose pulmonary vascular bed has been significantly impaired, the injection should be stopped immediately when symptoms appear during the injection. 3. In patients with a deficiency of one lung, removal of the lobes, or significant impairment of the known pulmonary vascular bed, the injected granules should be reduced accordingly. The amount of injection in children when performing lung perfusion imaging should be calculated by reference to body weight, and is generally injected at 2 to 3 MBq per kilogram of body weight. 4. Inject radiation protection for patients and medical staff. Inspection process A skin test is performed first, then oxygen is taken for 10 minutes, then the reagent is injected, and finally the machine is developed. Not suitable for the crowd 1. Disable congenital heart disease, pulmonary arteriovenous fistula and severe lung impaired, severe neutropenia, thrombocytopenia, aplastic anemia in right-left shunt. 2. Those who have a history of severe allergies should not do this check in principle. Adverse reactions and risks May cause an infection.