Abstract 15175: Differentiation Between Intramural Hematoma and Thrombosed False Lumen in Aortic Dissection Using Latest Spectral Computed Tomography With Dual-Layer Detector

Abstract

Introduction: Differentiating intramural hematoma (IH) from a thrombosed false lumen (FL) in aortic dissection (AD) is difficult by CT since both are regarded as AD without a tear. IH may be caused by vasa vasorum rupture, and therefore differentiation should be by histology. Spectral CT with a dual layer detector can generate CT images at any keV after ordinary acquisition using virtual monoenergetic settings (VMS). Hypothesis: Using spectral CT (range 40-200 keV), and a spectral distribution of CT values for aortic true lumen (TL) and FL, we can differentiate IH from thrombosed FL in AD in early and late-phase enhanced CT values. Methods: We performed enhanced 128-slice spectral CT 7500 (Philips) scans with a dual-layer detector in 8 patients (5 males, 71±14 years), with suspected IH or thrombosed FL in AD in the ascending aorta (Group 1), and 6 patients (4 males, 67±12 years) with thrombosed FL in AD in the descending aorta (Group 2). VMS images at various keV values were created from spectral-based images. We measured TL, FL or IH lumens in axial images at each keV in early and late phases using contrast. Results: On spectral profile analysis, in Group 1, lower keV values were associated with almost no and slightly increased mean CT values for FL or IH, in early and late phases using contrast. In Group 2, lower keV values were associated with slightly and moderately increased mean CT values for FL, in early and late phases using contrast. The degree of increments in CT values in lower keV images in late phase with contrast was significantly smaller for FL or IH in ascending aortas (n=8) than for FL in descending aortas (n=6) (P<0.05). Conclusions: On CT, TL, FL, and IH lumens, in early and late phases using contrast are unique. IH may be caused by vasa vasorum rupture and thrombosed FL in AD spreading contrast in late phase. This may cause a difference in the degree of increments in CT values in lower keV images in late phase using contrast for FL or IH in the ascending aorta and for FL in the descending aorta.