EANM guidelines for ventilation/perfusion scintigraphy

Pulmonary embolism (PE) can only be diagnosed with imaging techniques, which in practice is performed using ventilation/perfusion scintigraphy (V/P-SCAN) or multidetector computed tomography of the pulmonary arteries (MDCT). The epidemiology, natural history, pathophysiology and clinical presentation of PE are briefly reviewed. The primary objective of Part 1 of the Task Group's report was to develop a methodological approach to and interpretation criteria for PE. The basic principle for the diagnosis of PE based upon V/P-SCAN is to recognize lung segments or subsegments without perfusion but preserved ventilation, i.e. mismatch. Ventilation studies are in general performed after inhalation of Krypton or technetium-labelled aerosol of diethylene triamine pentaacetic acid (DTPA) or Technegas. Perfusion studies are performed after intravenous injection of macroaggregated human albumin. Radiation exposure using documented isotope doses is 1.2-2 mSv. Planar and tomographic techniques (V/P-PLANAR and V/P-SPECT) are analysed. V/P-SPECT has higher sensitivity and specificity than V/P-PLANAR. The interpretation of either V/P-PLANAR or V/P-SPECT should follow holistic principles rather than obsolete probabilistic rules. PE should be reported when mismatch of more than one subsegment is found. For the diagnosis of chronic PE, V/P-SCAN is of value. The additional diagnostic yield from V/P-SCAN includes chronic obstructive lung disease (COPD), heart failure and pneumonia. Pitfalls in V/P-SCAN interpretation are considered. V/P-SPECT is strongly preferred to V/P-PLANAR as the former permits the accurate diagnosis of PE even in the presence of comorbid diseases such as COPD and pneumonia. Technegas is preferred to DTPA in patients with COPD.