Spectral Computed Tomography for the Detection and Characterization of Communications Between the True and the False Lumen in Aortic Dissections.

Objectives: To compare the performance of conventional CT (conv-CT) and spectral CT (spectral-CT) for the detection and characterization of communications between the true (TL) and false lumen (FL) in aortic dissections, using 4D flow MRI as the reference.

Materials and methods: Eighteen patients with type A and type B aortic dissection who underwent 4D flow MRI, conv-CT and spectral-CT were retrospectively analyzed. For each patient, the examinations closest in time, without any intervention in-between, were retrieved and subjectively analyzed by 2 observers, independently for conv-CT and in consensus for MRI and spectral-CT. Communications between the two lumina were identified as: focal alterations in velocities corresponding to jet flows on 4D flow; both intimal tears and/or focal changes of contrast concentration corresponding to jet flows on conv-CT and spectral-CT. The number and location of communications were noted. The direction of the flow was assessed whenever the jet flow was visible. The performance of conventional and spectral-CT was calculated.

Results: Of the 176 communications detected with 4D flow, spectral-CT allowed visualization of 122(69%) compared with 58 (33%) for observer-1 and 38 (22%) for observer-2 for conv-CT, yielding an accuracy twice as high (63% vs 29% to 30%).Only jet flows, without visible intimal tears, were detected in 0 and 77 (63%) cases for conv-CT and spectral-CT, respectively.The flow was unidirectional FL-TL in 2 cases for MRI and spectral-CT and 1 case for conv-CT, bidirectional in 5 and 3 cases for MRI and spectral-CT, respectively. In all other cases, the direction was TL-FL.

Conclusion: Spectral-CT outperformed conv-CT for the detection of communications between TL and FL in aortic dissections. Spectral-CT allowed for direct visualization of flow jets, and their direction, through intimal tears.