Transesophageal magnetic resonance imaging of the aortic arch and descending thoracic aorta in patients with aortic atherosclerosis
Kendrick A. Shunk, MD, PhD*,
J.érôme Garot, MD*,
Ergin Atalar, PhD and
João A. C. Lima, MD, FACC*
* Division of Cardiology of the Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
View larger version (121K):
[in a new window]
|
Figure 1 The transesophogeal magnetic resonance imaging (TEMRI) device. The probe consists of a 1.2 mm-diameter loopless radiofrequency receiver and a modified Levin tube housing. A standard transesophageal echocardiography probe and a U.S. 5-cent coin are shown for size comparison. The TEMRI probe is connected via a BALUN circuit and a tuning, matching and decoupling circuit (TMD) to the scanner as described in the Methods section.
|
|
View larger version (95K):
[in a new window]
|
Figure 2 (A–F) Transesophageal magnetic resonance images in humans. (A,B) Descending thoracic aortae. (A) normal 33-year-old man and (B) 57-year-old woman with recent transient ischemic attack demonstrating diffuse and homogeneous thickening. (C,D) Distal aortic arch, 77-year-old man with remote stroke, showing heterogeneous (arrows) atherosclerotic thickening consistent with intraplaque calcification or hemorrhage. (C) Transesophageal magnetic resonance imaging (TEMRI) (repetition time/echo delay time [TR/TE] 1690/15 ms) and (D) corresponding transesophageal echocardiography (TEE). (E) Normal 33-year-old man. 10-mm-thick sagittal slice through the arch and descending thoracic aorta illustrating the longitudinal imaging range of the device (scout images, fast gradient echo [FGRE] sequence). (F) Bland-Altman plot of difference between circumferential extent of abnormal wall thickening assessed by TEE (a) and TEMRI (b). Each point represents an individual study patient. The underestimation by TEE is significant by paired t test (p = 0.001). Ao = aorta; De = device.
|
|
View larger version (18K):
[in a new window]
|
Figure 3 Distribution of multiple measurements of aortic wall thickness in normal subjects by transesophageal magnetic resonance imaging. Aortic wall thickness (excluding adventitia) was measured in 82 locations in multiple transesophageal magnetic resonance images from normal subjects using National Institutes of Health Image 1.62 and allowing multiple measurements per individual. The distribution appears Gaussian, with mean = 1.03 mm; standard deviation (SD) = 0.32 mm; mean + 2 SD = 1.67 mm; mean + 3 SD = 1.99 mm. In subsequent subjects, abnormal thickness was arbitrarily defined as mean + 3 SD (i.e.,  2.0 mm). The circumferential extent of disease was defined as the number of degrees (of 360) over which the wall thickness was abnormal.
|
|
View larger version (77K):
[in a new window]
|
Figure 4 Descending thoracic aorta in a male cadaver with diffuse aortic atherosclerosis. (A) transesophageal echocardiography (TEE) (7 MHz) and (B) transesophageal magnetic resonance imaging (12-cm field of view, TR 1600 ms, TE 25 ms, 3-mm-slice thickness, 1 NEX, ETL 24) and (C) histopathology. The TEE fails to image the entire aortic cross section as demonstrated by the arrows in the three panels. Small arrows indicate the same blood vessel as well as other morphologic landmarks, confirming accuracy of the cross-registration protocol. Es = esophagus, T = tip of vitamin E-filled balloon for registration purposes.
|
|
|
