Ventilation/perfusion scan

[6] Decreased uptake of the inhaled radioisotope may indicate an impaired ability to breathe, airway obstruction, or possible pneumonia.

A CT pulmonary angiogram (CTPA) with radiocontrast can alternatively be performed, although this can result in a greater radiation dose to the patient.

[8] In the ventilation phase of the test, a gaseous radionuclides such as xenon-133, krypton-81m, or technetium-99m DTPA in an aerosol form is inhaled by the patient through a mouthpiece or mask that covers the nose and mouth.

[11] The perfusion phase of the test involves the intravenous injection of radioactive technetium macro aggregated albumin (Tc99m-MAA).

It is also possible to perform the scan with positron emission tomography (PET) rather than conventional gamma camera scintigraphy.

Ventilation-perfusion scintigraphy in a woman taking oral contraceptives and valdecoxib with a pulmonary embolism. (A) After inhalation of 20 mCi of Xenon-133 gas, scintigraphic images were obtained in the posterior projection, showing uniform ventilation to lungs.. (B) After intravenous injection of 4.1 mCi of Technetium-99m-labeled macroaggregated albumin, scintigraphic images were obtained, shown here in the posterior projection. This and other views showed decreased activity in the following regions: apical segment of right upper lobe, anterior segment of right upper lobe, superior segment of right lower lobe, posterior basal segment of right lower lobe, anteromedial basal segment of left lower lobe, and lateral basal segment of left lower lobe.