Lung scintigraphy

Special information about this examination

Lung scintigraphy can be carried out to analyse pulmonary circulation (perfusion scintigraphy) or pulmonary ventilation (ventilation scintigraphy).

With both examinations, the radiation of the emitted activity is recorded from different perspectives using a gamma camera, thus producing images. Slice images can also be created to achieve particularly high resolution. For this the patient lies on the examination couch and the gamma camera's head rotates around the thorax (SPECT).

Perfusion scintigraphy:

This is used to examine pulmonary circulation, which can be impaired in particular in case of pulmonary embolism. The examination substance is a protein molecule which is labelled with Technetium 99m (Tc 99m MAA). Using the protein a temporary blockage (microembolism) is produced in the individual pulmonary vessels so that the labelled particles can be produced as an image using radiation. To be able to distinguish between a pulmonary embolism and other causes of circulatory disorders, an additional x-ray, ventilation scintigraphy or computed tomography may be necessary under certain circumstances.

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Ventilation scintigraphy (inhalation scintigraphy):

This examination is usually carried out before perfusion scintigraphy, if both examinations are required. For this, the patient inhales a mixture of air (aerosol), which is also labelled radioactive with Tc 99m. For this inhalation, the patient must inhale through a mouthpiece, which is connected to a nebuliser that the aerosol produces. Images of the lungs are produced in the same way as with perfusion scintigraphy immediately after inhaling this aerosol.

Evaluation:

In a typical case of pulmonary embolism, circulatory disorders are found in individual sections of the lung that produce image defects on the perfusion scintigraphy images, whilst a normal distribution pattern results in the ventilation scintigraphy (mismatch).