Pulmonary vascular optical coherence tomography in fibrosing mediastinitis: Imaging manifestations and findings

Fibrosing mediastinitis (FM) causes extrinsic pulmonary vascular compression that mimics intraluminal lesions. Optical coherence tomography (OCT) provides high-resolution vessel wall imaging that enables differentiation.

We analyzed consecutive FM patients with pulmonary vascular involvement who underwent OCT between December 2021 and June 2025. Quantitative OCT measurements (lumen diameter, area, and maximal eccentricity index [E_max]) were compared between compressed and distal reference segments, and qualitative signs of lumen, intima, and perivascular abnormalities were evaluated. Optical density (OD) on OCT and corresponding perivascular CT density were assessed, and pre- to post-intervention changes were analyzed.

24 patients were included (age: 58.67 ± 8.25 years; 17 males). 16 had pre-stenting OCT images, and 8 had only post-stenting images. In the former, compressed vs. reference segments differed significantly in minimal area (1.55 [1.08, 2.05] vs 4.33 [2.27, 8.72] mm², p < 0.001), mean area (2.43 [1.91, 3.60] vs 4.65 [2.58, 10.60] mm², p = 0.017), and E_max (0.44 [0.35, 0.51] vs 0.16 [0.13, 0.21], p < 0.001). 95.00% of compressed segments showed a large-small-large pattern. Perivascular signal attenuation, chronic thrombus, and intimal thickening were present in 85.00%, 25.00% and 15.00%, respectively. Both mean OD and OD range correlated negatively with CT density (r = -0.657, p = 0.004; r = -0.484, p = 0.049). Minimal luminal area differed significantly across pre-stenting, follow-up (median 78 days between the first and latest stent OCT), and post-dilation (all p < 0.05).

Pulmonary vascular OCT reveals FM vascular features, including the large-small-large pattern, distinguishes external compression from intraluminal lesions, and assists in evaluating treatment response.