Scintigraphic imaging of the lungs is a sensitive diagnostic imaging tool to detect certain kinds of pulmonary abnormalities in correlation with clinical data and chest radiographs. Pulmonary scintigraphy is particularly useful in diagnosing medical conditions such as pulmonary embolism, bronchial carcinoma and chronic obstructive pulmonary disease.
Lung scintigraphy can be performed with radioaerosols, gaseous radiopharmaceuticals and technetium-99m-labeled perfusion agents that are localized by temporary capillary blockade.

Different types of lung scintigraphy include:
The choice of the radioactive tracer varies and depends on the pulmonary function to be imaged. The radioactive tracer distribution within the lungs can be displayed on a computer screen via a gamma camera, a scanner or some other similarly suitable detector that records the radioactive disintegrations emitted by the patient. The images obtained present chromatic variations proportional to the regional radioactivity.

An aerosol ventilation scintigraphy is a nuclear medical imaging procedure that records the distribution of an inhaled radioactive aerosol within the bronchopulmonary system.
Aerosol ventilation in the gamma camera section does not constitute a significant radiation hazard to personnel. Patient compliance is an important factor to minimizing the dose. Clear instructions and practice are a vital part of the diagnostic imaging procedure.

See also Lung Scintigraphy, Aerosol Method, Gas Ventilation Scintigraphy and Inhalation Scintigraphy.

The pulmonary perfusion scintigraphy records the distribution of pulmonary arterial blood flow. The most common indication for lung scintigraphy is the detection of pulmonary embolism. The most widely used radiopharmaceuticals are technetium-99m MAA (macroaggregates of albumin) or 99mTc-HAM. Other radiopharmaceuticals include sulphur colloid macroaggregated albumin, radioactive albumin microspheres and albumin labeled with I-131, or I-113m.
Perfusion imaging of the bronchopulmonary system is based on the principle of capillary blockade. The perfusion study is accomplished by injecting 40 to 160 MBq (1-4 mCi) of the radiopharmaceutical and during repeated deep inhalation. The aggregates are extracted during their first pass through the lung, thus imaging can begin immediately. Pulmonary perfusion scintigraphy is particularly useful in combination with gas ventilation scintigraphy and aerosol ventilation scintigraphy.

See also Inhalation Scintigraphy.

The basis of pulmonary scintigraphy is the detection of gamma rays emitted from the lung after administration of a radioactive tracer.
See Lung Scintigraphy.

See also Aerosol Ventilation Scintigraphy, Gas Ventilation Scintigraphy, Pulmonary Perfusion Scintigraphy, Computed Tomography Pulmonary Angiography and Lung Imaging.

A gas ventilation scintigraphy is a diagnostic imaging test of lung ventilation with radioactive noble gases during breathing maneuvers, e.g. with krypton (81mKr) or xenon (133Xe).
The radioactive gas is administered by a mask and requires a special delivery and trapping system (gas trap). The radioactivity in the lungs is measured with a gamma camera and is subsequently evaluated.
The use of krypton or xenon gases involves problems like the relatively short half-lives (about 15-30 seconds) and relatively high costs of xenon and krypton. The short half-life requires that the scan is performed directly after administration of the gas. In addition, the gaseous radiopharmaceutical is expelled from the body almost quantitatively within a few minutes of completing the study.
A ventilation scintigraphy combined with a pulmonary perfusion scintigraphy is highly sensitive for the detection of pulmonary embolism.
Radioactive noble gases are widely used as a ventilation agent to diagnose pulmonary embolism. However, 81mKr and 133Xe are rare and expensive, which limits their continuous availability. Tc99m-Technegas can be an alternative ventilation agent with the advantage of being less expensive and available daily.

See also Inhalation Scintigraphy.