(Radiographics. 2000;20:107-120.)
© RSNA, 2000
MR Angiography of the Thoracic Aorta with an Electrocardiographically Triggered Breath-Hold Contrast-enhanced Sequence1
Paul J. Arpasi, MD,
Kostaki G. Bis, MD,
Anil N. Shetty, PhD ,
Richard D. White, MD and
Orlando P. Simonetti, PhD
1 From the Department of Radiology, William Beaumont Hospital, 3601 W 13 Mile Rd, Royal Oak, MI 48073 (P.J.A., K.G.B., A.N.S.); the Department of Radiology, Cleveland Clinic, Cleveland, Ohio (R.D.W.); and Siemens Medical Systems, Iselin, NJ (O.P.S.). Presented as a scientific exhibit at the 1997 RSNA scientific assembly. Received February 16, 1999; revision requested April 5; final revision received June 10; accepted June 14. Address reprint requests to K.G.B.
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Abstract
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An electrocardiographically (ECG) triggered breath-hold contrast material–enhanced magnetic resonance (MR) angiography sequence has been developed for imaging the thoracic aorta. A three-dimensional (3D) gradient-echo sequence is used with a contrast material bolus. Forty-nine patients with various aortic abnormalities and five healthy volunteers underwent imaging with the sequence. All studies were performed in a single breath hold. ECG-triggered breath-hold contrast-enhanced MR angiography was tolerated in 48 of the 49 patients. The images demonstrated no respiratory motion artifacts and diminished pulsation artifacts. The cardiac chambers, aortic root, ascending and descending aorta, aortic arch, proximal arch vessels, and proximal coronary arteries were clearly demonstrated and not obscured by ghost artifacts. The 3D data set allowed excellent multiplanar reformation, permitting orthogonal or oblique views of the vascular anatomy. A variety of congenital and acquired abnormalities were clearly identified. When this sequence is used, it is important to evaluate both the maximum-intensity projection and source images. Delayed imaging should be performed to detect late filling. In conjunction with cine MR and T1-weighted spin-echo imaging, ECG-triggered breath-hold contrast-enhanced MR angiography should be considered the technique of choice for imaging the thoracic aorta.
Index Terms: Aorta, MR, 56.12142, 94.12942 • Magnetic resonance (MR), pulse sequences • Magnetic resonance (MR), vascular studies, 56.12142, 94.12942
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Introduction
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Several investigations have demonstrated the usefulness of contrast material–enhanced three-dimensional (3D) magnetic resonance (MR) angiography of the thoracic vasculature (1–7). It is well known that this technique is able to demonstrate the thoracic aorta in great detail and is complementary to T1-weighted spin-echo and cine MR imaging. Recently, an electrocardiographically (ECG) triggered breath-hold contrast-enhanced 3D MR angiography sequence was described (8). This sequence can eliminate respiratory motion artifacts and diminishes artifacts related to cardiac motion and pulsatile flow.
In this article, the technique of ECG-triggered breath-hold contrast-enhanced MR angiography is described and our clinical experience with imaging the thoracic and upper abdominal aorta with this sequence is presented.
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Technique
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We perform ECG-triggered breath-hold contrast-enhanced MR angiography on a 1.5-T imager (Magnetom Vision; Siemens Medical Systems, Iselin, NJ) with 25-mT/m, 600-msec rise time gradients and a body phased-array coil. The basic sequence is a 3D fast low-angle shot sequence with the following parameters: 5.0/2.0 (repetition time msec/echo time msec), 14° flip angle, 96–130 x 256 matrix, 70–110-mm slab thickness, 20–34 partitions, 2–3.5-mm partition thickness, and 50–250-msec trigger delay (Fig 1). A trigger delay after the R wave is used to drive the acquisition window into diastole, thus decreasing the artifacts related to rapid flow changes. Linear ordering of phase-encoding tables is used with the central partitions acquired halfway through the acquisition.
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Figure 1. ECG-triggered contrast-enhanced 3D fast low-angle shot sequence. During each R-R interval, the phase-encoding steps for a given partition are all collected during a 500-msec acquisition window after a predetermined trigger delay, which is used to drive acquisition of the partitions during the diastolic phase of the cardiac cycle. Therefore, every heartbeat yields a single 3D partition.
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A 0.2-mmol/kg dose of gadoteridol (ProHance; Bracco Diagnostics, Princeton, NJ) is injected intravenously at a rate of 2 mL/sec, and acquisition of the first 3D slab is initiated 10–15 seconds after the start of contrast material injection. An oblique sagittal plane is used, which is prescribed from a transverse localizing image. An additional 3D slab is obtained with an 8-second interacquisition delay, which allows the patient to breathe out and then breath hold for the second acquisition. The second acquisition is performed in the oblique sagittal or coronal plane.
The imaging protocol is supplemented with half-Fourier single-shot turbo spin-echo imaging (repetition time = R-R interval to 100 msec, echo time = 43 msec, 150° flip angle, 8-mm section thickness, 20% gap), as well as with breath-hold cine MR imaging (40/4.8, 20° flip angle, 6–8-mm section thickness) and velocity-encoded cine MR imaging when deemed appropriate.
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Clinical Experience
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Forty-nine patients with a variety of aortic disease and five healthy volunteers were studied. ECG-triggered breath-hold contrast-enhanced 3D MR angiography of the thoracic aorta was tolerated in 48 of the 49 patients; unlike MR angiograms obtained with nontriggered acquisition (Fig 2), the resulting images demonstrated no respiratory motion artifacts and diminished pulsation artifacts, especially at the level of the heart and ascending aorta. One patient with congestive heart failure was unable to tolerate the breath-hold portion of the examination, and the resulting images were degraded by artifact. Data acquisition required less than 1 minute and processing time was 15–20 minutes in each case. The cardiac chambers, aortic root, ascending and descending aorta, aortic arch, proximal arch vessels, and proximal coronary arteries were clearly demonstrated and not obscured by ghost artifacts. In addition, the 3D data set allows excellent multiplanar reformation, which permits orthogonal or oblique views of the vascular anatomy. Such views are particularly useful in demonstrating the course of a dissection, which may not be seen if the aorta is imaged parallel to the dissection.
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Figure 2. Nontriggered acquisition limited by artifact. Oblique sagittal maximum-intensity projection (MIP) image obtained without ECG triggering shows a moderate amount of artifact in the phase-encoding direction (arrows). This artifact obscures the ascending aorta and a moderate portion of the descending thoracic aorta. Images obtained with ECG-triggered acquisition do not demonstrate this degree of artifact.
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Normal Anatomy
ECG-triggered breath-hold contrast-enhanced MR angiography demonstrated the normal anatomy and a normal variant (ductus bump [n = 1]) in five healthy subjects and provided a high-resolution 3D perspective of the entire thoracic aorta and its branches (Fig 3).
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Figure 3a. Normal thoracic aorta. Coronal (a) and oblique sagittal (b) MIP images show the thoracic aorta in a healthy subject. The coronal image (a) shows overlap between the aorta and the pulmonary vasculature. However, the ascending aorta is not obscured by the pulmonary vasculature on the oblique sagittal image (b). Note the small ductus bump (arrow). The arch vessels are well demonstrated on both images.
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Figure 3b. Normal thoracic aorta. Coronal (a) and oblique sagittal (b) MIP images show the thoracic aorta in a healthy subject. The coronal image (a) shows overlap between the aorta and the pulmonary vasculature. However, the ascending aorta is not obscured by the pulmonary vasculature on the oblique sagittal image (b). Note the small ductus bump (arrow). The arch vessels are well demonstrated on both images.
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Congenital Abnormalities
Congenital anomalies such as aberrant right subclavian artery (n = 2, one with a diverticulum of Kommerell) (Figs 4, 5); aortic coarctation (n = 2) (Fig 6); right aortic arch (n = 1); transposition of the great vessels (n = 1); and aortic sinus aneurysm (n = 1) (Fig 7) were clearly identified.
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Figure 4a. Aberrant right subclavian artery. Oblique (a) and coronal (b) MIP images show an aberrant right subclavian artery (straight arrows). This finding is seen as the terminal tributary from the arch. Loss of signal near the pulmonary apex (curved arrow) is due to the vessel passing out of the plane of acquisition.
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Figure 4b. Aberrant right subclavian artery. Oblique (a) and coronal (b) MIP images show an aberrant right subclavian artery (straight arrows). This finding is seen as the terminal tributary from the arch. Loss of signal near the pulmonary apex (curved arrow) is due to the vessel passing out of the plane of acquisition.
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Figure 5a. Aberrant right subclavian artery. (a) Sagittal 3D partition obtained in another patient shows an aberrant right subclavian artery (arrow) passing posterior to the trachea and esophagus. (b) Oblique sagittal MIP image shows the aberrant right subclavian artery (straight arrow), which is associated with a diverticulum of Kommerell. In addition, there is a small ductus bump (curved arrow).
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Figure 5b. Aberrant right subclavian artery. (a) Sagittal 3D partition obtained in another patient shows an aberrant right subclavian artery (arrow) passing posterior to the trachea and esophagus. (b) Oblique sagittal MIP image shows the aberrant right subclavian artery (straight arrow), which is associated with a diverticulum of Kommerell. In addition, there is a small ductus bump (curved arrow).
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Figure 6a. Aortic coarctation. (a) Oblique sagittal MIP image shows a discrete postductal coarctation (straight arrow), which is associated with dilatation of the left subclavian artery (curved arrow). (b) Left anterior oblique digital subtraction angiogram shows similar findings.
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Figure 6b. Aortic coarctation. (a) Oblique sagittal MIP image shows a discrete postductal coarctation (straight arrow), which is associated with dilatation of the left subclavian artery (curved arrow). (b) Left anterior oblique digital subtraction angiogram shows similar findings.
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Figure 7a. Aortic sinus aneurysm. (a) Sagittal contrast-enhanced 3D partition shows dilatation of the right coronary cusp (arrow). (b-d) Angled vertical long-axis turbo spin-echo breath-hold MR image (b), oblique axial turbo spin-echo breath-hold MR image (c), and oblique axial breath-hold cine MR image (d) show the dilatation more clearly (arrow).
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Figure 7b. Aortic sinus aneurysm. (a) Sagittal contrast-enhanced 3D partition shows dilatation of the right coronary cusp (arrow). (b-d) Angled vertical long-axis turbo spin-echo breath-hold MR image (b), oblique axial turbo spin-echo breath-hold MR image (c), and oblique axial breath-hold cine MR image (d) show the dilatation more clearly (arrow).
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Figure 7c. Aortic sinus aneurysm. (a) Sagittal contrast-enhanced 3D partition shows dilatation of the right coronary cusp (arrow). (b-d) Angled vertical long-axis turbo spin-echo breath-hold MR image (b), oblique axial turbo spin-echo breath-hold MR image (c), and oblique axial breath-hold cine MR image (d) show the dilatation more clearly (arrow).
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Figure 7d. Aortic sinus aneurysm. (a) Sagittal contrast-enhanced 3D partition shows dilatation of the right coronary cusp (arrow). (b-d) Angled vertical long-axis turbo spin-echo breath-hold MR image (b), oblique axial turbo spin-echo breath-hold MR image (c), and oblique axial breath-hold cine MR image (d) show the dilatation more clearly (arrow).
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Acquired Abnormalities
Rapid evaluation of aortoannular ectasia (n = 6) was feasible with precise measurements of the aortic annular diameters from the initial data and subsequent multiplanar reconstructions (Fig 8). Aortic insufficiency manifesting as flow void was detected in eight of 10 patients with aortic root abnormalities on the contrast-enhanced 3D partitions (Fig 9). Rapid evaluation was also feasible in patients with atherosclerotic disease such as aortic aneurysm (n = 6) (Fig 10), atherosclerotic stenosis (n = 1) (Fig 11), and penetrating ulcer (n = 1) (Fig 12). Aortic dissection, both type A (n = 6) (Figs 13, 14) and type B (n = 4) (Fig 15), was also well evaluated. Additional entities that were imaged included poststenotic aneurysm from aortic stenosis (n = 3) (Fig 16); aortic grafts (n = 5) (Figs 17, 18); periaortic abscess (n = 1); subclavian artery stenosis (n = 2); and postoperative coarctation (n = 2).
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Figure 8a. Aortoannular ectasia in a patient with Marfan disease. (a) Oblique MIP image clearly shows aortoannular ectasia (arrow). The entire thoracic aorta was imaged in a single breath hold, thus eliminating the need for acquisition of multiple breath-hold cine or spin-echo sections. (b) Coronal 3D partition shows a focal area of signal void due to aortic insufficiency (arrow).
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Figure 8b. Aortoannular ectasia in a patient with Marfan disease. (a) Oblique MIP image clearly shows aortoannular ectasia (arrow). The entire thoracic aorta was imaged in a single breath hold, thus eliminating the need for acquisition of multiple breath-hold cine or spin-echo sections. (b) Coronal 3D partition shows a focal area of signal void due to aortic insufficiency (arrow).
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Figure 9a. Aortic aneurysm with aortic insufficiency. Coronal (a) and oblique sagittal (b) MIP images show a 10-cm-wide ascending aortic aneurysm (arrow). (c) Coronal 3D partition shows signal void due to aortic insufficiency (arrow). The image provides a 3D perspective on the
relationship of the aneurysm to the aortic arch.
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Figure 9b. Aortic aneurysm with aortic insufficiency. Coronal (a) and oblique sagittal (b) MIP images show a 10-cm-wide ascending aortic aneurysm (arrow). (c) Coronal 3D partition shows signal void due to aortic insufficiency (arrow). The image provides a 3D perspective on the
relationship of the aneurysm to the aortic arch.
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Figure 9c. Aortic aneurysm with aortic insufficiency. Coronal (a) and oblique sagittal (b) MIP images show a 10-cm-wide ascending aortic aneurysm (arrow). (c) Coronal 3D partition shows signal void due to aortic insufficiency (arrow). The image provides a 3D perspective on the
relationship of the aneurysm to the aortic arch.
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Figure 10a. Aortic aneurysm. (a) Coronal MIP image shows a large thoracoabdominal aortic aneurysm. However, only the lumen of the aneurysm is shown. (b) Coronal 3D partition shows enhancement of the lumen. The wall of the aneurysm, which is lined with subintimal thrombus, is better seen on this image (arrows). Therefore, the size and extent of aneurysms are best determined by reviewing the source images.
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Figure 10b. Aortic aneurysm. (a) Coronal MIP image shows a large thoracoabdominal aortic aneurysm. However, only the lumen of the aneurysm is shown. (b) Coronal 3D partition shows enhancement of the lumen. The wall of the aneurysm, which is lined with subintimal thrombus, is better seen on this image (arrows). Therefore, the size and extent of aneurysms are best determined by reviewing the source images.
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Figure 12a. Penetrating ulcer. (a) Lateral digital subtraction angiogram obtained with a pigtail catheter in the proximal descending aorta shows a large penetrating ulcer involving the ventral aspect of the descending aorta (arrow). (b, c) Sagittal contrast-enhanced 3D partition (b) and sagittal MIP image (c) also show this finding (arrow). The subintimal penetration is best seen on the 3D partition (b). The diagnosis of penetrating ulcer was confirmed at surgery.
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Figure 12b. Penetrating ulcer. (a) Lateral digital subtraction angiogram obtained with a pigtail catheter in the proximal descending aorta shows a large penetrating ulcer involving the ventral aspect of the descending aorta (arrow). (b, c) Sagittal contrast-enhanced 3D partition (b) and sagittal MIP image (c) also show this finding (arrow). The subintimal penetration is best seen on the 3D partition (b). The diagnosis of penetrating ulcer was confirmed at surgery.
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Figure 12c. Penetrating ulcer. (a) Lateral digital subtraction angiogram obtained with a pigtail catheter in the proximal descending aorta shows a large penetrating ulcer involving the ventral aspect of the descending aorta (arrow). (b, c) Sagittal contrast-enhanced 3D partition (b) and sagittal MIP image (c) also show this finding (arrow). The subintimal penetration is best seen on the 3D partition (b). The diagnosis of penetrating ulcer was confirmed at surgery.
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Figure 13a. Type A thoracic aortic dissection. (a, b) Immediate (a) and delayed (b) oblique sagittal 3D partitions show a dissection flap in the ascending aorta (arrow). On the immediate image (obtained 10 seconds after the start of contrast material injection) (a), low signal intensity within the false channel produces a false impression of thrombosis. On the delayed image (b), the false channel demonstrates enhancement, with delayed washout manifesting as higher signal intensity than in the true channel. (c, d) Coronal (c) and axial (d) 3D partitions show the morphology of the dissection flap.
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Figure 13b. Type A thoracic aortic dissection. (a, b) Immediate (a) and delayed (b) oblique sagittal 3D partitions show a dissection flap in the ascending aorta (arrow). On the immediate image (obtained 10 seconds after the start of contrast material injection) (a), low signal intensity within the false channel produces a false impression of thrombosis. On the delayed image (b), the false channel demonstrates enhancement, with delayed washout manifesting as higher signal intensity than in the true channel. (c, d) Coronal (c) and axial (d) 3D partitions show the morphology of the dissection flap.
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Figure 13c. Type A thoracic aortic dissection. (a, b) Immediate (a) and delayed (b) oblique sagittal 3D partitions show a dissection flap in the ascending aorta (arrow). On the immediate image (obtained 10 seconds after the start of contrast material injection) (a), low signal intensity within the false channel produces a false impression of thrombosis. On the delayed image (b), the false channel demonstrates enhancement, with delayed washout manifesting as higher signal intensity than in the true channel. (c, d) Coronal (c) and axial (d) 3D partitions show the morphology of the dissection flap.
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Figure 13d. Type A thoracic aortic dissection. (a, b) Immediate (a) and delayed (b) oblique sagittal 3D partitions show a dissection flap in the ascending aorta (arrow). On the immediate image (obtained 10 seconds after the start of contrast material injection) (a), low signal intensity within the false channel produces a false impression of thrombosis. On the delayed image (b), the false channel demonstrates enhancement, with delayed washout manifesting as higher signal intensity than in the true channel. (c, d) Coronal (c) and axial (d) 3D partitions show the morphology of the dissection flap.
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Figure 14a. Thrombosed type A thoracic aortic dissection. (a) Coronal 3D partition shows a dissection flap in the ascending aorta (arrow). The false channel enhances proximally; however, there is evidence of thrombosis distally, which manifests as a lack of enhancement. (b) Oblique sagittal 3D partition shows the extent of the dissection, which extends to the diaphragm. The false channel does not enhance (arrows). (c, d) Oblique sagittal MIP images show components of the dissection.
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Figure 14b. Thrombosed type A thoracic aortic dissection. (a) Coronal 3D partition shows a dissection flap in the ascending aorta (arrow). The false channel enhances proximally; however, there is evidence of thrombosis distally, which manifests as a lack of enhancement. (b) Oblique sagittal 3D partition shows the extent of the dissection, which extends to the diaphragm. The false channel does not enhance (arrows). (c, d) Oblique sagittal MIP images show components of the dissection.
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Figure 14c. Thrombosed type A thoracic aortic dissection. (a) Coronal 3D partition shows a dissection flap in the ascending aorta (arrow). The false channel enhances proximally; however, there is evidence of thrombosis distally, which manifests as a lack of enhancement. (b) Oblique sagittal 3D partition shows the extent of the dissection, which extends to the diaphragm. The false channel does not enhance (arrows). (c, d) Oblique sagittal MIP images show components of the dissection.
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Figure 14d. Thrombosed type A thoracic aortic dissection. (a) Coronal 3D partition shows a dissection flap in the ascending aorta (arrow). The false channel enhances proximally; however, there is evidence of thrombosis distally, which manifests as a lack of enhancement. (b) Oblique sagittal 3D partition shows the extent of the dissection, which extends to the diaphragm. The false channel does not enhance (arrows). (c, d) Oblique sagittal MIP images show components of the dissection.
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Figure 15a. Type B thoracic aortic dissection. (a, b) Oblique sagittal (a) and coronal (b) 3D partitions show a dissection flap with entry (arrow in b) and reentry (arrow in a) points. (c-e) Targeted coronal (c, d) and targeted oblique sagittal (e) MIP images show the proximal and distal aspects of the dissection and its relationship to the abdominal aortic tributaries. The flap extends to the celiac artery (arrow).
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Figure 15b. Type B thoracic aortic dissection. (a, b) Oblique sagittal (a) and coronal (b) 3D partitions show a dissection flap with entry (arrow in b) and reentry (arrow in a) points. (c-e) Targeted coronal (c, d) and targeted oblique sagittal (e) MIP images show the proximal and distal aspects of the dissection and its relationship to the abdominal aortic tributaries. The flap extends to the celiac artery (arrow).
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Figure 15c. Type B thoracic aortic dissection. (a, b) Oblique sagittal (a) and coronal (b) 3D partitions show a dissection flap with entry (arrow in b) and reentry (arrow in a) points. (c-e) Targeted coronal (c, d) and targeted oblique sagittal (e) MIP images show the proximal and distal aspects of the dissection and its relationship to the abdominal aortic tributaries. The flap extends to the celiac artery (arrow).
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Figure 15d. Type B thoracic aortic dissection. (a, b) Oblique sagittal (a) and coronal (b) 3D partitions show a dissection flap with entry (arrow in b) and reentry (arrow in a) points. (c-e) Targeted coronal (c, d) and targeted oblique sagittal (e) MIP images show the proximal and distal aspects of the dissection and its relationship to the abdominal aortic tributaries. The flap extends to the celiac artery (arrow).
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Figure 15e. Type B thoracic aortic dissection. (a, b) Oblique sagittal (a) and coronal (b) 3D partitions show a dissection flap with entry (arrow in b) and reentry (arrow in a) points. (c-e) Targeted coronal (c, d) and targeted oblique sagittal (e) MIP images show the proximal and distal aspects of the dissection and its relationship to the abdominal aortic tributaries. The flap extends to the celiac artery (arrow).
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Figure 16a. Bicuspid aortic valve stenosis with poststenotic dilatation. (a) Early-phase oblique sagittal MIP image shows an aneurysm of the ascending aorta. The presence of underlying valvular disease cannot be determined with contrast-enhanced MR angiography. (b) Oblique coronal cine MR image shows the bicuspid nature of the aortic valve in this patient (arrowhead). (c) Coronal systolic cine MR image shows an area of signal void due to underlying aortic stenosis (arrow). (d, e) In-plane (d) and through-plane (e) velocity-encoded cine MR images allow calculation of the gradient through the valve. Gadolinium-enhanced MR angiography should be used in conjunction with traditional spin-echo and cine MR angiography to optimize evaluation of the thoracic aorta.
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Figure 16b. Bicuspid aortic valve stenosis with poststenotic dilatation. (a) Early-phase oblique sagittal MIP image shows an aneurysm of the ascending aorta. The presence of underlying valvular disease cannot be determined with contrast-enhanced MR angiography. (b) Oblique coronal cine MR image shows the bicuspid nature of the aortic valve in this patient (arrowhead). (c) Coronal systolic cine MR image shows an area of signal void due to underlying aortic stenosis (arrow). (d, e) In-plane (d) and through-plane (e) velocity-encoded cine MR images allow calculation of the gradient through the valve. Gadolinium-enhanced MR angiography should be used in conjunction with traditional spin-echo and cine MR angiography to optimize evaluation of the thoracic aorta.
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Figure 16c. Bicuspid aortic valve stenosis with poststenotic dilatation. (a) Early-phase oblique sagittal MIP image shows an aneurysm of the ascending aorta. The presence of underlying valvular disease cannot be determined with contrast-enhanced MR angiography. (b) Oblique coronal cine MR image shows the bicuspid nature of the aortic valve in this patient (arrowhead). (c) Coronal systolic cine MR image shows an area of signal void due to underlying aortic stenosis (arrow). (d, e) In-plane (d) and through-plane (e) velocity-encoded cine MR images allow calculation of the gradient through the valve. Gadolinium-enhanced MR angiography should be used in conjunction with traditional spin-echo and cine MR angiography to optimize evaluation of the thoracic aorta.
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Figure 16d. Bicuspid aortic valve stenosis with poststenotic dilatation. (a) Early-phase oblique sagittal MIP image shows an aneurysm of the ascending aorta. The presence of underlying valvular disease cannot be determined with contrast-enhanced MR angiography. (b) Oblique coronal cine MR image shows the bicuspid nature of the aortic valve in this patient (arrowhead). (c) Coronal systolic cine MR image shows an area of signal void due to underlying aortic stenosis (arrow). (d, e) In-plane (d) and through-plane (e) velocity-encoded cine MR images allow calculation of the gradient through the valve. Gadolinium-enhanced MR angiography should be used in conjunction with traditional spin-echo and cine MR angiography to optimize evaluation of the thoracic aorta.
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Figure 16e. Bicuspid aortic valve stenosis with poststenotic dilatation. (a) Early-phase oblique sagittal MIP image shows an aneurysm of the ascending aorta. The presence of underlying valvular disease cannot be determined with contrast-enhanced MR angiography. (b) Oblique coronal cine MR image shows the bicuspid nature of the aortic valve in this patient (arrowhead). (c) Coronal systolic cine MR image shows an area of signal void due to underlying aortic stenosis (arrow). (d, e) In-plane (d) and through-plane (e) velocity-encoded cine MR images allow calculation of the gradient through the valve. Gadolinium-enhanced MR angiography should be used in conjunction with traditional spin-echo and cine MR angiography to optimize evaluation of the thoracic aorta.
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Figure 17a. Aortic graft. (a) Sagittal contrast-enhanced 3D partition shows atheromatous changes with postoperative deformity of the distal ascending aorta and portions of a graft that extends from the aortic arch to the mid-descending thoracic aorta (arrows). (b) Sagittal MIP image shows the graft more clearly (arrows).
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Figure 17b. Aortic graft. (a) Sagittal contrast-enhanced 3D partition shows atheromatous changes with postoperative deformity of the distal ascending aorta and portions of a graft that extends from the aortic arch to the mid-descending thoracic aorta (arrows). (b) Sagittal MIP image shows the graft more clearly (arrows).
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Figure 18a. Aortic graft in a patient who underwent resection of a large thoracoabdominal aortic aneurysm with graft placement and reimplementation of abdominal aortic visceral tributaries. Sagittal targeted MIP image (a) and sagittal contrast-enhanced 3D partition (b) show a large graft that extends from the proximal descending thoracic aorta to include the entire abdominal aorta (arrows).
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Figure 18b. Aortic graft in a patient who underwent resection of a large thoracoabdominal aortic aneurysm with graft placement and reimplementation of abdominal aortic visceral tributaries. Sagittal targeted MIP image (a) and sagittal contrast-enhanced 3D partition (b) show a large graft that extends from the proximal descending thoracic aorta to include the entire abdominal aorta (arrows).
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Pitfalls
When this sequence is used, it is important to evaluate both the MIP and source images. In cases of dissection, it is possible to overlook a dissection flap on an MIP image that is clearly evident on the individual partitions (Fig 19). This problem was also encountered when characterizing atherosclerotic aneurysms. In one patient, the extent of thrombus adherent to the wall was not evident on the MIP images but was clearly evident on the partitions (Fig 10). Slow flow can be mistaken for thrombus if images from only one data acquisition are evaluated. We routinely perform delayed imaging to detect late filling. Performing delayed imaging is especially important when imaging patients with dissection. Contrast-enhanced MR angiography performed with early and delayed imaging can help differentiate slow flow from thrombus in the false channel (Fig 13). Other pitfalls encountered were pseudodissection secondary to enhancing atelectasis (Fig 20) and pseudodissection secondary to an adjacent azygos vein in a patient with a right aortic arch (Fig 21).
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Figure 19a. Dissection flap missed on an MIP image. (a) Sagittal contrast-enhanced 3D partition shows a dissection flap in the ascending aorta (arrow). (b) MIP image from sagittal 3D partitions shows the aorta; however, the underlying dissection flap is obscured by the surrounding enhancing blood pool. Thus, it is imperative to review the source images in patients with dissection.
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Figure 19b. Dissection flap missed on an MIP image. (a) Sagittal contrast-enhanced 3D partition shows a dissection flap in the ascending aorta (arrow). (b) MIP image from sagittal 3D partitions shows the aorta; however, the underlying dissection flap is obscured by the surrounding enhancing blood pool. Thus, it is imperative to review the source images in patients with dissection.
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Figure 20. Pseudodissection from subjacent enhancing atelectasis. Sagittal contrast-enhanced 3D partitions show areas of enhancement subjacent to the descending aorta, which represent areas of enhancing atelectasis (arrows). This finding should not be confused with the false channel in a patient with dissection; careful evaluation of all images including multiplanar reformations is required to avoid this pitfall.
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Figure 21. Pseudodissection due to passage of the azygos vein along a right-sided aortic descent. Sagittal MIP image shows a subjacent enhancing azygos vein (arrows). This finding should not be confused with a dissection; review of the source images and multiplanar reformations is required to avoid this pitfall.
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Conclusions
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Rapid ECG-triggered breath-hold contrast-enhanced 3D MR angiography demonstrates the thoracic aorta and proximal arch vessels with high resolution, free from respiratory motion artifacts, and with diminished pulsation artifacts. In conjunction with cine MR and standard T1-weighted spin-echo imaging, ECG-triggered breath-hold contrast-enhanced MR angiography should be considered the technique of choice for imaging the thoracic aorta in cooperative patients in hemodynamically stable condition. This technique is easily implemented for evaluating congenital and acquired diseases of the thoracic aorta.
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Footnotes
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Abbreviations: ECG = electrocardiography
MIP = maximum-intensity projection
3D = three-dimensional
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References
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Link KM, Lesko NM. The role of MR imaging in the evaluation of acquired diseases of the thoracic aorta. AJR Am J Roentgenol 1992; 158:1115-1125.[Abstract/Free Full Text]
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Prince MR. Gadolinium-enhanced MR aortography. Radiology 1994; 191:155-164.[Abstract/Free Full Text]
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Hartnell GG, Finn JP, Zenni M, et al. MR imaging of the thoracic aorta: comparison of spin-echo, angiographic, and breath-hold techniques. Radiology 1994; 191:697-704.[Abstract/Free Full Text]
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Prince MR, Narasimham DL, Jacoby WT, et al. Three-dimensional gadolinium-enhanced MR angiography of the thoracic aorta. AJR Am J Roentgenol 1996; 166:1387-1397.[Abstract/Free Full Text]
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Krinsky GA, Rofsky NM, DeCorato DR, et al. Thoracic aorta: comparison of gadolinium-enhanced three-dimensional MR angiography with conventional MR imaging. Radiology 1997; 202:183-193.[Abstract/Free Full Text]
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Ho VB, Prince MR. Thoracic MR aortography: imaging techniques and strategies. RadioGraphics 1998; 18:287-309.[Abstract]
-
Shetty AN, Shirkhoda A, Bis KG, Alcantara A. Contrast-enhanced three-dimensional MR angiography in a single breath hold: a novel technique. AJR Am J Roentgenol 1995; 165:1290-1292.[Free Full Text]
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Vrachliotis T, Bis KG, Aliabadi D, et al. Contrast-enhanced breath-hold MR angiography for evaluating the patency of coronary artery bypass grafts. AJR Am J Roentgenol 1997; 168:1073-1080.[Abstract/Free Full Text]
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Abstract
Introduction
