CTA Lung perfusion

Spiral dual energy CT angiography offers new opportunities for the assessing the relevance of pulmonary emboli. In an initial study at the University of Munich, we examined 24 patients with suspected pulmonary embolism.

Exams were performed with a single acquisition, spiral dual energy CT angiography protocol on a SOMATOM Definition. Voxels containing iodine and air were color-coded by the dual-energy evaluation software. Lung perfusion was assessed by two blinded radiologists. Perfusion defects were classified as being consistent or non-consistent with pulmonary embolism (e.g. caused by artifacts). Subjective image quality of the perfusion maps and CT angiography were rated using a 5-point score. The peak attenuation of the pulmonary arteries, normal lung parenchyma and perfusion defects was assessed. Finally, the CT angiography data alone was assessed for pulmonary embolism by an independent third reader.

Perfusion defects consistent with pulmonary embolism were identified in four patients. In all these cases, pulmonary emboli were visible in the segmental arteries and were also confirmed by the third independent reader. Perfusion defects rated as non-consistent with pulmonary embolism were most frequently caused by streak artifacts from very dense contrast material in the great mediastinal vessels or heart. Other reasons included atelctasis or pulmonary edema.

Ten pulmonary emboli were regarded as non-occlusive in CT angiography, and there were no perfusion defects detected for these emboli. The median score for the image quality of both the perfusion maps and CT angiography was two. The median quantified iodine-related attenuation of pulmonary ateries, normal lung parenchyma, and perfusion defects was 453 HU, 56 HU, and 18 HU, respectively.

In conclusion, spiral dual energy CT angiography of pulmonary embolism is feasible and simultaneously provides a high-resolution angiography of the pulmonary arteries and the possibility to assess perfusion defects caused by pulmonary embolism. Thus, spiral dual energy CT of pulmonary perfusion offers the possibility to assess the functional relevance of pulmonary emboli without additional dose, contrast application or examination time.

See corresponding protocol CTA lung perfusion
See corresponding case: Pulmonary hypertension due to chronic recurrent pulmonary embolism
See corresponding case: Acute Pulmonary Embolism
See corresponding news: Detecting small pulmonary emboli with Dual Energy