Image Quality of Computed Tomographic Pulmonary Angiography for Suspected Pulmonary Embolus in Patients With Diffuse Interstitial Lung Disease

Purpose: To investigate the effect of diffuse interstitial lung disease (DILD) on the image quality of computed tomographic pulmonary angiography (CTPA). Materials and Methods: The study group comprised 130 patients with DILD who underwent CTPA between April 2005 and April 2009. One hundred and thirty patients without significant parenchymal lung disease were used as a control group. Contrast enhancement of pulmonary arteries in the left upper lobe and right lower lobe was evaluated to the sub-subsegmental level both subjectively and objectively. The global and lobar extents of interstitial lung disease were also estimated in the study group. Subjective assessment was performed by 2 observers, initially independently and subsequently by consensus in cases of discordance. Results: At the sub-subsegmental level, the number of patients with adequately opacified arteries was significantly lower in the DILD group (29.2% left upper lobe, 36.2% right lower lobe) compared with the control group (78.5% left upper lobe, 89.2% right lower lobe) (P<0.001). Subjective image quality scores of the sub-subsegmental arteries were strongly correlated with mean vascular attenuation values at this level (P<0.001) but not to the global or lobar extent of lung parenchymal disease. There was no clinically significant difference in image quality (either subjectively or objectively) between the DILD and control groups in the subsegmental and more proximal arterial branches. Conclusions: In the majority of patients with DILD, CTPA image quality is sufficient only to the subsegmental level. Emboli at the sub-subsegmental level, which may have greater clinical significance in patients with DILD than in those without, are unlikely to be excluded using CTPA.