A pulmonary perfusion scan looks at the blood flow to the lung tissue. It is used most often to diagnose a blood clot in the lung, known as a pulmonary embolus.
The healthcare provider may order a pulmonary perfusion scan in the following circumstances:
For the scan, a person is often asked to sit upright. If a person is unable to sit, he or she can lie flat on a table. A radioactive substance known as Tc-99m macroaggregated albumin will be injected into a vein in the arm. The substance gives off gamma rays from within the body. These rays are detected by a "gamma camera" that is positioned over the chest.
A computer then generates pictures that can be interpreted by a radiologist. The lungs will be scanned in multiple positions (usually six). The exam takes approximately 45 minutes. Usually, a second test called a pulmonary ventilation scan will follow the perfusion scan.