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Ventilation imaging is most often performed in conjunction with lung perfusion to characterize perfusion defects as a matched, mismatched or reverse mismatched.
The optimal tracer for ventilation studies is Technegas, an ultra fine dispersion of 99mTc-labeled carbon. Despite that Technegas is not approved for use in the United States, it is used in 79% of ventilation imaging studies performed in Canada and is also commonly used in Europe. Its main advantage is greater percentage deposition in the alveolar spaces and less undesirable adherence to the central airways, compared with droplet radioaerosols.
Using 99mTc-Technegas has minimized the problem of hotspots in patients with obstructive lung disease and is according to clinical experience better than the best liquid aerosols
V/Q SPECT, using Technegas as the ventilation imaging agent, could diagnose and grade severity of COPD and also estimate preserved lung function in 94 patients. Moreover, V/Q SPECT appears to be a unique tool to reveal the heterogeneity of COPD caused by pulmonary comorbidities such as pulmonary embolism, left heart failure, lung tumor and pneumonia. The characteristics of these comorbidities suggest their significant impact in symptoms, their influence on prognosis and their response to treatment.
V/Q scintigraphy has affirmed its critical place in the evaluation of patients with lung cancer preparing for lung resection.
Enhanced by the advancements in hybrid imaging and computer processing, the V/Q scan examination continues to be reinvented and updated to keep pace with the needs of modern medicine.
Among the traditional imaging modalities for diagnosing pulmonary embolism (PE), the choice has narrowed to V/Q scan and CTPA. However, V/Q scan is preferred over CTPA for follow-up of PE particularly in young women in order to avoid the excessive breast radiation exposure associated with CTPA.
In recent years, the technology around V/Q scintigraphy has rapidly evolved allowing the introduction of SPECT, a new method of scintigraphic acquisition. SPECT V/Q has been reported to improve the diagnostic performances of the test and significantly decrease the proportion of non-diagnostic studies. [...] SPECT V/Q imaging has many proponents within the nuclear medicine community and has already largely replaced planar V/Q scintigraphy in daily practice for the diagnosis of pulmonary embolism (PE).
Pre-existing lung disease should not be a relative contraindication to the use of V/Q SPECT-CT. This modality has a sensitivity of 100% and specificity of 94% with lower radiation doses compared to CTPA.
We recommend nuclear V/Q lung scanning instead of CTPA as a screening test to rule out the possibility of CTEPH in patients diagnosed with PH. A normal V/Q scan effectively rules out the possibility of CTEPH.
99mTc-Technegas ventilation scintigraphy is an established and well-studied tool for imaging of lung ventilation and combined SPECT/CT has been shown to improve overall diagnostic accuracy in many areas of pulmonary nuclear medicine.