Detectability of subsegmental lesions in patients with inoperable CTEPH: Comparison between ultra-high-resolution vs. conventional CT

Background: CT pulmonary angiography (CTPA) plays a critical role in guiding balloon pulmonary angioplasty (BPA) for patients with chronic thromboembolic pulmonary hypertension (CTEPH). However, conventional CT (cCT) has limited sensitivity in detecting peripheral lesions, which is critical for avoiding complications. This study compared ultra-high-resolution CT (UHRCT; 0.25 mm detector elements) and conventional CT (cCT; 0.6 mm detector elements) in identifying and classifying segmental and subsegmental lesions, using invasive selective angiography during BPA as the reference standard. Methods: This single-center retrospective study included 42 patients with newly diagnosed CTEPH who underwent CT pulmonary angiography (CTPA) with either cCT or UHRCT and subsequently completed BPA. The morphology and location of lesions were independently assessed using selective angiography and CTPA. Sensitivity, specificity, and lesion classification accuracy were assessed using selective angiography as the reference standard. Results: A total of 1687 branches in 42 patients (male/female 11/31, mean age 66 years) were analyzed. The sensitivity and specificity of cCT were 54.6% (95% CI: 48.2-60.8) and 85.2% (95% CI: 75.6-91.4), respectively. In contrast, UHRCT demonstrated significantly higher sensitivity (94.3%, 95% CI: 91.9-96.1) but lower specificity (60.2%, 95% CI: 46.7-72.2). The sensitivity difference was more prominent in subsegmental branches (p for interaction = 0.11). UHRCT more accurately classified lesion types in 83.7% of cases (95% CI: 76.7-88.9), versus 69.1% (95% CI: 58.3-78.1) with cCT. Web lesions remained the most difficult to detect. Conclusion: Higher-spatial-resolution CTPA provides a higher lesion detection sensitivity, particularly in subsegmental branches, and more accurately classified lesion type in patients with CTEPH treated with BPA, potentially aiding procedural planning and guidance.