Methodology and Clinical Implementation of Ventilation/Perfusion Tomography for Diagnosis and Follow-up of Pulmonary Embolism and Other Pulmonary Diseases

Ventilation/perfusion single-photon emission computed tomography (V/P SPECT) is recommended as the first-choice imaging technique for the diagnosis of acute pulmonary embolism (PE) and is the gold standard for the diagnosis of chronic PE. Furthermore, interpreting ventilation and corresponding perfusion images enables pattern recognition of many other cardiopulmonary disorders. An optimal combination of nuclide activities and acquisition times for ventilation and perfusion, collimators, and imaging matrix yields an adequate V/P SPECT study in approximately 20 minutes of imaging time. V/P SPECT uses a holistic interpretation strategy on the basis of all relevant information about the patient and all ventilation/perfusion patterns. PE is diagnosed when there is more than one subsegment showing a V/P mismatch representing an anatomic lung unit. Using Technegas for the ventilation study over radiolabelled liquid aerosols enable grading of airway obstruction in COPD patients as well as simultaneously allowing diagnostics of other pulmonary comorbidities. The method allows quantification of lung function and measurement of the extent of functional deteriorations that have impact on the therapy. Apart from PE, other pathologies should be identified and reported, such as obstructive disease, heart failure, and pneumonia, according to the European Association of Nuclear Medicine guidelines. Hybrid V/P SPECT-CT has added value in patients with COPD.