The current and continuing important role of ventilation-perfusion scintigraphy in evaluating patients with suspected pulmonary embolism

Abstract

After the publication of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study in 1990, there was considerable controversy concerning the ventilation-perfusion (V/Q) study in regard to its low sensitivity and high number of nondiagnostic examinations when used in patients with suspected pulmonary embolism (PE). Many lessons have been learned from the PIOPED database that have greatly improved our interpretive skills in the 2 decades since the study was performed. One of the key problems negatively impacting interpretation was the predominantly inpatient population that was studied. Inpatients generally are sicker patients with abnormal chest x-rays. This factor significantly degrades V/Q interpretation. A normal chest x-ray greatly facilitates accurate interpretation of the lung scan. The emergence of computed tomography angiography (CTA) in the early to mid-1990s provided a superb new means of imaging patients with suspected PE. As this technology became more sophisticated with multidetector units, it became the procedure of choice in the great majority of medical centers. CT scanners located in or proximal to many emergency departments as well as its 24/7 availability supported this preference. Within the past 2 to 3 years, the publication of the PIOPED II study as well as some other prospective and retrospective studies have confirmed similar diagnostic accuracy for CTA and V/Q studies. Additionally, there have been several recent publications cautioning physicians about the large radiation dose associated with CTA, particularly to the female breast. Considering the great benefits of both techniques as well as their limitations, it is prudent for both clinicians and imaging physicians to develop an appropriate approach to studying patients with suspected PE. Considerations such as objective clinical assessment, D-dimer assay and the chest x-ray appearance all play significant roles in this decision-making process.