The lung scan is used to determine the cause of shortness of breath or chest pain. It is used to evaluate possible blood clots (a pulmonary embolism) in the lungs. The lung scan is usually performed in two parts: first the ventilation image is acquired to determine the air supply to the lungs. After this a perfusion image is obtained which looks at the blood supply. The blood supply is then compared to the air supply to determine if they match. Any mismatch can indicate a pulmonary embolism.
There is no special preparation for the scan. You can eat as normal and take any medications as usual.
There are two parts to a lung scan, although it may only be necessary to have one. The first part of the test involves breathing in a slightly radioactive aerosol. This enables an image to be obtained of the air supply to the lungs. The aerosol is delivered through a mask over your nose and mouth and will take about 5 minutes. The radiographer will then ask you to lie still on the couch. The gamma camera will be positioned above and below your chest and images will be taken. The camera will then be moved around your chest and further images taken. The camera will be close to your body but will not touch you. This scan will last around 20 minutes.
If required, for part two of the scan, you will remain lying on the imaging couch. The radiographer will then give you an injection of a radioisotope into a vein on your arm. The radiographer will then reposition the cameras above and below your chest and repeat taking the images as in the first part of the study. This will take about 30 minutes. Occasionally some images may be taken with you sitting upright.