Enhancing Lung Scintigraphy With Single-Photon Emission Computed Tomography
Section snippets
How to Optimally Perform V/Q SPECT
SPECT can be used to image both ventilation and perfusion, however, this requires the use of appropriate imaging agents.
How Does V/Q SPECT Compare With Planar Imaging?
The advantages of SPECT over planar lung imaging have been demonstrated repeatedly over many years. In a study performed 25 years ago in which subsegmental and segmental clots were induced in dogs, SPECT was shown to be more sensitive than planar imaging.36 Similar results were described by Bajc and coworkers,37 who compared SPECT and planar imaging using 99mTc-DTPA aerosols and 99mTc-MAA in a porcine model. They induced artificial emboli labeled with 201Tl and demonstrated SPECT to have an
How Does V/Q SPECT Compare With CTPA?
Multidetector CTPA has evolved to the point in which it is frequently used as an initial investigation of patients with potential PE. Recent literature suggests that although it is highly specific, its sensitivity is somewhat less than desirable. With the multidetector CT scanners used in the large PIOPED II study, CTPA had a reported sensitivity of 83%, indicating that emboli were not detected in 1 in 6 patients.40 Although the accuracy of CTPA appears to be high in cases in which the scan
How Should V/Q SPECT Results Be Reported?
The optimal way to report V/Q SPECT has yet to be clearly defined, and the supporting literature is sparse. Although the traditional way to report planar scintigraphy has revolved around the use of PIOPED probability categories, the adoption of these criteria to SPECT reporting seems inappropriate. This is particularly so, given that these criteria were derived using planar perfusion imaging and single view 133Xe ventilation, a very different imaging technique to V/Q SPECT.
Reinartz and
Generation of Planar Images From SPECT
For reporting specialists, viewing scintigraphic data in tomographic planes represents a significant change compared with traditional planar reporting. A good ability to relate image data to the underlying segmental lung anatomy is required, something that is helped by having access to an accurate lung atlas. During the transition phase to SPECT imaging, there may be a need for reporting clinicians to view both planar and SPECT data on each patient. Although the acquisition of both data sets
Conclusion
Although it has been used in the diagnosis of PE for many years, it is evident that planar V/Q scintigraphy has some limitations. If the V/Q scan is to remain relevant as an imaging tool, it is important that it be optimized so that the diagnostic information it provides is maximized. V/Q SPECT can be readily performed in most nuclear medicine centers today with no increase in patient imaging time. It has been shown to have superior sensitivity, specificity, reduced interobserver variability,
Acknowledgments
The authors acknowledge the assistance of Elizabeth Bailey who helped to generate the images for this article.
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2016, Seminars in Nuclear MedicineCitation Excerpt :With the latest developments in integrated multimodality hybrid SPECT/CT cameras, it is now possible to acquire V/Q SPECT scans along with a low-dose CT scan to provide a comprehensive assessment of the pulmonary function and morphology in the patient suspected of PE. Numerous articles have demonstrated the high sensitivity and specificity for the detection of pulmonary emboli using SPECT and SPECT/CT.3-7 Also, the radiation dose from the V/Q scan is acceptably low, making it often the diagnostic imaging test of choice for many patients, in particularly young women and in pregnancy because of the high breast dose from CT pulmonary angiography (CTPA) as well as the reduced accuracy of CTPA in pregnancy.8-12 SPECT V/Q imaging has a role in both clinical medicine and research.