Enhancing lung scintigraphy with single-photon emission computed tomography.

Although widely used for many years in the assessment of pulmonary embolism, planar ventilation-perfusion (V/Q) scintigraphy has well-recognized limitations. Single-photon emission computed tomography (SPECT) imaging, which can be readily performed in most modern nuclear medicine centers equipped with multihead gamma cameras, overcomes many of these limitations through its ability to generate 3-dimensional imaging data. V/Q SPECT has been shown to have a greater sensitivity and specificity than planar imaging and has a lower nondiagnostic rate. For reporting clinicians who may be reluctant to abandon conventional planar V/Q images, planar-like images can also be readily obtained from V/Q SPECT with the use of postacquisition techniques. The use of SPECT can also facilitate advances in V/Q imaging, including the generation of parametric V:Q ratio images, coregistration with computed tomography, respiratory gating, and more accurate quantification of regional lung function. Although direct comparisons in the literature are limited in number, V/Q SPECT appears to have comparable, or greater, sensitivity than multidetector computed tomography pulmonary angiography and is not associated with contrast-related complications such as allergy and nephropathy. It also involves significantly less radiation dose to breast tissue, an important consideration, particularly in young women. For the V/Q scan to remain relevant in the evaluation of patients with suspected pulmonary embolism, it is essential that image data are obtained so as to maximize their accuracy and diagnostic usefulness. V/Q SPECT can achieve this and, furthermore, may have a role in conditions other than pulmonary embolism, including both clinical and research fields.