Nuclear medicine lung scan
Special information on this examination
The lung scintigraphy is applied both for analysing the pulmonary perfusion (perfusion scintigraphy) and pulmonary ventilation (ventilation scintigraphy). With both examinations, the radiation of the administered dose will be recorded from different angles by means of a gamma camera and the images will be made. In order to achieve particularly high resolution, cross-sectional images are made. The patient lies on the examination table and the head of the gamma camera rotates around his chest (SPECT).
It serves to examine the lung perfusion that can be particularly impaired in case of pulmonary embolism. A protein molecule marked with technetium 99m (Tc 99m MAA) is used here as a tracer. The protein causes a temporary blockage of the separate pulmonary vessels (microembolism) so that the marked particles can produce an image by means of the radiation they emit. The additional ventilation scintigraphy and often additional X-rays will be necessary in order to be able to differentiate between pulmonary embolism and other causes of circulatory disorders.
Ventilation scintigraphy (inhalation scintigraphy)
This examination is normally carried out prior to the perfusion scintigraphy, in case if both examinations are to be performed. For that purpose, the patient inhales an air mixture (aerosol), which is also marked by Tc 99m. During this inhalation, the patient must breathe through a mouthpiece adjusted to a pulveriser that produces the aerosol. Directly after inhaling of the aerosol, the images of the lungs are taken in a similar way to the perfusion scintigraphy.
In a typical case, pulmonary embolism is characterised by interruptions of blood circulation in separate parts of the lungs causing image defects on the perfusion scintigraphy recordings, whereas a normal pattern of distribution is revealed when performing ventilation scintigraphy (mismatch).