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Sequential MR signal change of the thrombus in the false lumen of thrombosed aortic dissection
T Kaminaga1, N Yamada, M Takamiya
1Tracer kinetics, Biomedical Research Center, Osaka University Medical School, Japan.
Abstract:
The evolution of thrombus in the false lumen was investigated in 14 patients with thrombosed aortic dissection, by reviewing the findings acquired at a total of 21 magnetic resonance imaging (MRI) examinations performed between 2 and 146 days after the onset. On electrocardiographic gated 1.5-Tesla MRI, T1-(TR/TE = 860 +/- 190 ms/17-40 ms) and T2-(TR/TE = 1620 +/- 240 ms/70-80 ms) weighted spin echo and gradient echo images were obtained, and the signal intensity of the thrombus on these images was evaluated independently by two observers. The density of the thrombus was also evaluated using computed tomography (CT) images obtained at a total of 54 examinations. On both T1- and T2-weighted images, the thrombus showed signal iso- or hypointensity compared to that of skeletal muscle during the first several days after the onset and, thereafter, showed signal intensity similar to that of fat tissue. It is suggested that the low signal intensity of the thrombus observed during the initial period after the onset was caused by the presence of deoxyhemoglobin and the high intensity observed thereafter was caused by methemoglobin. Focal discrepancy of the signal intensities within two parts of the lumen on spin echo images was observed in 7 patients, and a low-intensity layer on the surface of the thrombus inside the false lumen was observed on gradient echo images in 5 of these 7 patients. This characteristic MR signal change of the thrombus in the false lumen of thrombosed aortic dissection provides useful information concerning the age of the thrombus and in the differential diagnosis of the thrombus from a mural thrombus of aortic aneurysm.
Insights
Magnetic resonance imaging (MRI) reveals thrombus signal changes in aortic dissection over time. These changes, related to deoxyhemoglobin and methemoglobin, help determine thrombus age and differentiate it from other conditions.
Area of Science:
- Cardiovascular Imaging
- Radiology
- Medical Diagnostics
Background:
- Thrombosed aortic dissection involves thrombus formation within the false lumen.
- Understanding thrombus evolution is crucial for diagnosis and management.
- Magnetic resonance imaging (MRI) offers detailed insights into tissue characteristics.
Purpose of the Study:
- To investigate the evolution of thrombus in thrombosed aortic dissection.
- To characterize the signal intensity changes of thrombus over time using MRI.
- To assess the utility of MRI in determining thrombus age and differential diagnosis.
Main Methods:
- Retrospective analysis of 21 MRI examinations in 14 patients with thrombosed aortic dissection.
- Evaluation of T1- and T2-weighted spin echo and gradient echo MRI sequences.
- Correlation of MRI findings with computed tomography (CT) density measurements.
- Independent assessment of thrombus signal intensity by two observers.
Main Results:
- Thrombus initially showed iso- or hypointensity compared to skeletal muscle on T1- and T2-weighted MRI.
- After several days, thrombus signal intensity became similar to fat tissue.
- Signal changes are attributed to deoxyhemoglobin (early) and methemoglobin (later).
- Gradient echo imaging revealed a low-intensity surface layer in some cases.
Conclusions:
- Characteristic MRI signal changes provide information on thrombus age in aortic dissection.
- MRI findings aid in differentiating dissection thrombus from mural thrombus in aortic aneurysms.
- This imaging approach enhances diagnostic accuracy for thrombosed aortic dissections.