Diagnostic Performance of Quantitative Lung Perfusion SPECT/CT for Chronic Thromboembolic Pulmonary Hypertension: A Pilot Study

Background: Lung perfusion SPECT/CT is central to the diagnostic evaluation of chronic thromboembolic pulmonary hypertension (CTEPH), yet current assessments remain qualitative. This pilot study aimed to explore a standardized quantitative method for lung perfusion SPECT/CT to differentiate CTEPH from non-CTEPH patients. Methods: We retrospectively analyzed lung perfusion SPECT/CT studies obtained over a three-year period in patients assessed for suspected CTEPH. Perfusion counts were divided into ten equal intervals from zero to the maximum perfusion counts, and each decile was used as a threshold to define perfusion defects. Perfusion defect fraction was quantified, and group differences, diagnostic performance, and correlations with mean pulmonary arterial pressure (mPAP) were evaluated. Results: CTEPH patients showed significantly higher perfusion defect fraction than non-CTEPH controls. The 10% threshold demonstrated the best diagnostic performance, with an optimal cutoff of 20.6%, yielding a sensitivity of 75% and specificity of 100% for identifying CTEPH. Patients with distal-type disease or small, localized perfusion defects exhibited perfusion defect fraction overlapping with controls. Perfusion defect fraction correlated significantly and positively with mPAP. Conclusions: In this pilot study, quantitative analysis of lung perfusion SPECT/CT demonstrated feasibility as a complementary method to visual interpretation. While promising, these findings are preliminary and require validation in larger populations to establish their clinical utility for CTEPH diagnosis.