Comparison of V/Q SPECT and CT Angiography for the Diagnosis of Chronic Thromboembolic Pulmonary Hypertension

Background Accurate methods for identifying obstructions in both large and small vessels are crucial for diagnosis and treatment of chronic thromboembolic pulmonary hypertension (CTEPH). Purpose To compare the performance of ventilation-perfusion (V/Q) scanning, V/Q SPECT, and CT pulmonary angiography (PA) in CTEPH by using digital subtraction PA as the reference standard. Materials and Methods This prospective study was conducted from January 2016 to January 2018. A total of 229 participants suspected of having CTEPH were evaluated with V/Q SPECT, V/Q planar scintigraphy, CT PA, and digital subtraction PA. Participants underwent all four procedures within 1 week. Differences in the diagnostic performance of V/Q SPECT, V/Q planar scintigraphy, and CT PA were evaluated with areas under the curve receiver operator curve, the McNemar test, and generalized estimating equations analysis. Results A total of 150 participants (mean age, 42 years ± 15 [standard deviation]; 99 women) were enrolled. Digital subtraction PA assessments confirmed CTEPH in 51 participants and indicated that 602 of 1020 lung segments (20 segments per participant) were obstructed. The three imaging methods showed high sensitivity (V/Q SPECT, 98%; V/Q planar scintigraphy, 98%; CT PA, 94%) and specificity (V/Q SPECT, 89%; V/Q planar scintigraphy, 91%; CT PA, 96%) (all > .05). However, both V/Q scanning techniques were more sensitive (V/Q SPECT: 85%, < .001 vs CT PA: 67%; V/Q planar scintigraphy: 83%, < .001 vs CT PA: 67%), and less specific (V/Q planar scintigraphy: 51%, = .03 vs CT PA: 60%; V/Q SPECT: 42%, < .01 vs CT PA: 60%) than was CT PA for segmental analysis. Areas under the curve for CT PA, V/Q planar scintigraphy, and V/Q SPECT were 0.95, 0.95, and 0.94, respectively (all > .05), for individual analysis, and 0.64, 0.67, and 0.64, respectively, by segment (V/Q planar scintigraphy vs V/Q SPECT, = .02; V/Q planar scintigraphy vs CT PA, = .08; V/Q SPECT vs CT PA, = .94). Conclusion Ventilation-perfusion scanning was more sensitive and less specific than was CT pulmonary angiography for detecting vascular obstructions at the segmental pulmonary arterial level. © RSNA, 2020 See also the editorial by Swift and Rajaram in this issue.