Procedure
The ventilation and perfusion phases of a V/Q lung scan are performed together and may include a chest x-ray for comparison or to look for other causes of lung disease. A defect in the perfusion images requires a mismatched ventilation defect to be indicative of pulmonary embolism.
In the ventilation phase of the test, a gaseous radionuclide such as xenon or technetium DTPA in an aerosol form is inhaled by the patient through a mouthpiece or mask that covers the nose and mouth. Ventilation imaging can also be performed using a Technegas machine which produces technetium labelled carbon nanoparticles, called Technegas. The perfusion phase of the test involves the intravenous injection of radioactive technetium macro aggregated albumin (Tc99m-MAA). A gamma camera acquires the images for both phases of the study.
It is also possible to perform the scan with positron emission tomography (PET) rather than conventional gamma camera scintigraphy. This has been performed with Gallium-68 labelled carbon nanoparticles (Galligas) using a conventional Techngas machine for ventilation images, and with Gallium-68 labelled MAA (Ga68-MAA) for perfusion images. PET has multiple potential advantages including superior resolution, speed and quantification.
Read more about this topic: Ventilation/perfusion Scan