DOI: 10.1148/rg.26si065506
RadioGraphics 2006;26:S63-S73
© RSNA, 2006
MR Angiography and CT Angiography of the Artery of Adamkiewicz: State of the Art1
Kunihiro Yoshioka, MD,
Hiroyuki Niinuma, MD,
Shigeru Ehara, MD,
Takayuki Nakajima, MD,
Motoyuki Nakamura, MD and
Kohei Kawazoe, MD
1 From the Department of Radiology (K.Y., S.E.), Second Department of Medicine (H.N., M.N.), and Department of Cardiovascular Surgery (T.N., K.K.), Iwate Medical University, 19-1 Uchimaru, Morioka, Iwate 020-8505, Japan. Presented as an education exhibit at the 2005 RSNA Annual Meeting. Received February 7, 2006; revision requested March 14 and received April 17; accepted May 12. All authors have no financial relationships to disclose.
Address correspondence to K.Y. (e-mail: kyoshi{at}iwate-med.ac.jp).
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Abstract
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It is very important to assess the artery of Adamkiewicz before repair of the thoracoabdominal or descending thoracic aorta. Several studies have demonstrated the feasibility and advantages of noninvasive assessment of the artery of Adamkiewicz with magnetic resonance (MR) angiography and multi–detector row computed tomographic (CT) angiography. Recent advances in MR angiography and CT angiography have led to changes in the detectability of this artery. In the present study, both MR angiography and CT angiography were performed without complications for preoperative evaluation of 30 patients who underwent repair of the thoracoabdominal or descending thoracic aorta. MR angiography provided detection rates as high as 93% and 80% with the morphologic "hairpin turn" criterion and the anatomic "continuity" criterion, respectively. Sixteen–detector row CT angiography provided detection rates as high as 83% and 60%, respectively. Use of both MR angiography and CT angiography provided higher detection rates of 97% and 90%, respectively. The collateral pathways were depicted in seven cases (23%). MR angiography is superior for depiction of the artery of Adamkiewicz, especially when it arises from the false lumen of a dissecting aneurysm. CT angiography has a wide field of view and allows depiction of significant collateral pathways associated with the internal thoracic artery and intercostal arteries.
© RSNA, 2006
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Introduction
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It is very important to identify the artery of Adamkiewicz in patients with thoracoabdominal or descending thoracic aortic aneurysms in order to minimize the risk of postoperative spinal cord ischemia and paraplegia. Owing to advances in anesthetic and surgical techniques, the frequency of severe neurologic complications has declined, but the rate of postoperative paraplegia or paraparesis remains high, in the range of 5%–10% (1–3), the so-called "Russian roulette for the vascular surgeon" (4). These critical complications are due to ischemia related to the anterior spinal artery. In the thoracolumbar region, blood is supplied to the anterior spinal artery by the great anterior radiculomedullary artery, which is also known as the artery of Adamkiewicz. However, it might be difficult to evaluate this vessel with conventional selective intercostal or lumbar angiography due to the variation in the branching levels of the artery, its small size, and the complications that may occur during the procedure (5).
Noninvasive assessment methods involving use of magnetic resonance (MR) angiography (6–8) and multi–detector row computed tomographic (CT) angiography have recently been employed (8,9). In the several years since both MR angiography and CT angiography were first used to depict the artery of Adamkiewicz, these modalities have undergone substantial development, with the shift from four- to 16-row CT angiography of particular note.
In this article, we discuss the feasibility, advantages, and limitations of both MR angiography and CT angiography, at their current level of development, for assessment of the artery of Adamkiewicz in patients with thoracoabdominal or thoracic descending aortic aneurysms. We describe the patient population that we studied, the normal anatomy, identification of the artery of Adamkiewicz, our imaging technique, and the results of imaging. We also discuss differentiation of the artery of Adamkiewicz from a vein, limitations of MR angiography and CT angiography, detection rates for the artery of Adamkiewicz, and surgical outcomes.
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Patients and Procedures
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Between January 2004 and April 2005, 30 consecutive patients (23 men and seven women; age range, 33–81 years; mean age, 63.8 years) with thoracoabdominal aortic aneurysms or descending thoracic aortic aneurysms underwent gadolinium-enhanced MR angiography and CT angiography to visualize the artery of Adamkiewicz for preoperative evaluation of the blood supply of the spinal cord. The underlying aortic disease was a dissecting thoracic aortic aneurysm in 12 patients and a true thoracic aortic aneurysm in 18 patients (descending thoracic aortic aneurysm in 12 patients and thoracoabdominal aortic aneurysm in six patients). Informed consent was obtained from all patients before MR angiography and CT angiography were performed. Approval by the institutional review board of our hospital was not required because both MR angiography and CT angiography were performed in accordance with routine diagnostic protocols.
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Normal Anatomy
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The most important feeding artery of the thoracolumbar spinal cord is the great anterior radiculomedullary artery, also called the artery of Adamkiewicz (Fig 1a).
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Figure 1a. Anatomy of the artery of Adamkiewicz. Anterior (a) and left anterosuperior (b) three-dimensional volume-rendered CT images, displayed with a semitransparent skeletal system, show the normal anatomy of the artery of Adamkiewicz. The thoracolumbar segment of the spinal cord is vascularized by branches of the thoracoabdominal aorta via the intercostal and lumbar arteries. The intercostal and lumbar arteries divide into anterior and posterior branches. The posterior branch subdivides into the radiculomedullary artery and the muscular branch. The radiculomedullary artery further subdivides into the anterior and posterior radiculomedullary arteries (not shown). The artery of Adamkiewicz is the largest radiculomedullary artery supplying the spinal cord and is usually found in the lower thoracic region. This artery demonstrates a characteristic "hairpin turn " at its junction with the anterior spinal artery.
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Figure 1b. Anatomy of the artery of Adamkiewicz. Anterior (a) and left anterosuperior (b) three-dimensional volume-rendered CT images, displayed with a semitransparent skeletal system, show the normal anatomy of the artery of Adamkiewicz. The thoracolumbar segment of the spinal cord is vascularized by branches of the thoracoabdominal aorta via the intercostal and lumbar arteries. The intercostal and lumbar arteries divide into anterior and posterior branches. The posterior branch subdivides into the radiculomedullary artery and the muscular branch. The radiculomedullary artery further subdivides into the anterior and posterior radiculomedullary arteries (not shown). The artery of Adamkiewicz is the largest radiculomedullary artery supplying the spinal cord and is usually found in the lower thoracic region. This artery demonstrates a characteristic "hairpin turn " at its junction with the anterior spinal artery.
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This artery supplies the lower one-third of the spinal cord, originating from a left intercostal or lumbar artery in 68%–73% of cases and at the level of the ninth to 12th intercostal artery in 62%–75%.
The anatomic course of the artery of Adamkiewicz is as follows: The intercostal or lumbar arteries that arise from the descending aorta divide into an anterior branch and a posterior branch. The posterior branch subdivides into the radiculomedullary artery, the muscular branch, and the dorsal somatic branch. The radiculomedullary artery further subdivides into the anterior and posterior radiculomedullary arteries.
The artery of Adamkiewicz and anterior spinal artery form a hairpin turn. This is because the spinal cord initially occupied the full length of the vertebral canal including the embryonic tail derived from eight to 10 coccygeal sclerotomes. In the full term, except for the first cervical roots, ascent of all of the remaining segments has an additive effect from above downward, with the effect of producing an increasing disparity between spinal segmental levels and vertebral levels (10).
The artery of Adamkiewicz is the most dominant anterior radiculomedullary artery, with a diameter of 0.8–1.3 mm. The distal portion of this artery and the anterior spinal artery show a characteristic hairpin turn connection (Fig 1b).
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Identification of the Artery of Adamkiewicz
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The artery of Adamkiewicz was evaluated by an experienced radiologist and an experienced cardiologist, each of whom worked independently and used processed images. The diagnostic criteria for the artery of Adamkiewicz were as follows: (a) The morphologic diagnosis was based on the presence of a branching artery from the radiculomedullary artery running obliquely along the anterior surface of the spinal cord with a hairpin turn connection to the anterior spinal artery on oblique coronal multiplanar reformation (MPR) images (Fig 2a, 2c). (b) The definitive diagnosis of "continuity" was based on the depiction of a continuous vascular route for the anterior spinal artery, the artery of Adamkiewicz, the radiculomedullary artery, the posterior branch of the intercostal artery, the intercostal artery, and the aorta traced retrogradely on CPR images (Fig 2b, 2d).
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Figure 2a. Identification of the artery of Adamkiewicz in a 62-year-old man with a dissecting aortic aneurysm. T10 = 10th thoracic vertebra. (a, c) Oblique coronal MPR images from MR angiography (a) and CT angiography (c) show the artery of Adamkiewicz (arrow). This artery has a characteristic hairpin turn connection with the anterior spinal artery (arrowhead). (b, d) Images from MR angiography (b) and CT angiography (d), produced with curved planar reformation (CPR), show continuity of the aorta, right 10th intercostal artery (large black arrow), radiculomedullary artery (small black arrow), artery of Adamkiewicz (white arrow), and anterior spinal artery (arrowhead). DAA = dissecting aortic aneurysm.
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Figure 2b. Identification of the artery of Adamkiewicz in a 62-year-old man with a dissecting aortic aneurysm. T10 = 10th thoracic vertebra. (a, c) Oblique coronal MPR images from MR angiography (a) and CT angiography (c) show the artery of Adamkiewicz (arrow). This artery has a characteristic hairpin turn connection with the anterior spinal artery (arrowhead). (b, d) Images from MR angiography (b) and CT angiography (d), produced with curved planar reformation (CPR), show continuity of the aorta, right 10th intercostal artery (large black arrow), radiculomedullary artery (small black arrow), artery of Adamkiewicz (white arrow), and anterior spinal artery (arrowhead). DAA = dissecting aortic aneurysm.
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Figure 2c. Identification of the artery of Adamkiewicz in a 62-year-old man with a dissecting aortic aneurysm. T10 = 10th thoracic vertebra. (a, c) Oblique coronal MPR images from MR angiography (a) and CT angiography (c) show the artery of Adamkiewicz (arrow). This artery has a characteristic hairpin turn connection with the anterior spinal artery (arrowhead). (b, d) Images from MR angiography (b) and CT angiography (d), produced with curved planar reformation (CPR), show continuity of the aorta, right 10th intercostal artery (large black arrow), radiculomedullary artery (small black arrow), artery of Adamkiewicz (white arrow), and anterior spinal artery (arrowhead). DAA = dissecting aortic aneurysm.
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Figure 2d. Identification of the artery of Adamkiewicz in a 62-year-old man with a dissecting aortic aneurysm. T10 = 10th thoracic vertebra. (a, c) Oblique coronal MPR images from MR angiography (a) and CT angiography (c) show the artery of Adamkiewicz (arrow). This artery has a characteristic hairpin turn connection with the anterior spinal artery (arrowhead). (b, d) Images from MR angiography (b) and CT angiography (d), produced with curved planar reformation (CPR), show continuity of the aorta, right 10th intercostal artery (large black arrow), radiculomedullary artery (small black arrow), artery of Adamkiewicz (white arrow), and anterior spinal artery (arrowhead). DAA = dissecting aortic aneurysm.
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The branching level of the artery of Adamkiewicz was determined on the basis of the anatomic level of the intercostal or lumbar artery that was seen branching from the artery of Adamkiewicz. The anatomic level of the intercostal artery was defined as the level of the rib below which the intercostal artery ran.
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Imaging Technique
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MR Angiography
The imaging technique for MR angiography has been reported previously (8). MR angiography was performed with a 1.5-T superconducting MR imaging system (Signa EXCITE X1; GE Medical Systems, Milwaukee, Wis) and 11.0 system software, along with a four-channel phased-array coil for the spine to optimize signal detection.
First, localization imaging with a wide field of view (480 x 480 mm) was performed in coronal, sagittal, and transverse orientations. Next, a gadolinium-enhanced MR angiographic sequence was performed. We used a three-dimensional fast spoiled gradient-echo sequence with a chemical shift–selective fat-suppression technique. Imaging parameters were as follows: 50–60-mm section thickness with 50–60 partitions (1-mm partition thickness), 0.5-mm reconstruction interval with the zero-filling interpolation technique, 18-msec repetition time, 2.1-msec echo time, 40° flip angle, 32-Hz acquisition bandwidth, 168 x 240-mm field of view, and a 384 x 512 matrix. The resulting pixel size was 0.47 x 0.44 mm. The section orientation was sagittal, allowing coverage of the area from the seventh thoracic vertebra to the second lumber vertebra. Acquisition time was 4–6 minutes. With this pulse sequence, k-space was acquired in the standard sequential linear fashion. We selected sequential order for sampling the k-space so that half-acquisition time could become a center of k-space.
A 22-gauge plastic intravenous catheter was placed in an antecubital vein. A total of 0.2 mmol/kg of body weight of gadopentetate dime-glumine (Magnevist; Schering, Berlin, Germany) was administered at a rate of 0.2 mL/sec with a power injector (Sonicshot 50; Nemotokyorindou, Tokyo, Japan), which was then flushed with 20 mL of normal saline solution, also at 0.2 mL/sec. Injection was initiated 60–70 seconds before half-acquisition time so that contrast material reached the target site (descending aorta) within this time delay.
CT Angiography
The imaging technique for CT angiography has been reported previously (8). We performed CT angiography with a 16-channel multi–detector row helical CT scanner (Aquilion 16; Toshiba, Tokyo, Japan). Scanning parameters were as follows: 120 kV, 400 mA, 0.5-mm section thickness, 11.0 helical pitch (0.6875 beam pitch), and 0.5-second rotation speed. Scanning was performed from the seventh thoracic vertebra to the second lumber vertebra (location was determined with use of a scout digital radiograph).
A 20-gauge plastic intravenous catheter was placed in an antecubital vein. The line was then connected to a power injector (Autoenhance A-250, Nemotokyorindou). A total of 2.0 mL/kg of body weight of high-osmolarity iopamidol (Iopamiron, Schering; iodine, 370 mg/mL) was administered at a rate of 3.5 mL/sec with a power injector, which was then flushed with 35 mL of normal saline solution, also at 3.5 mL/sec. The scan delay was set with an automatic triggering system (Surestart, Toshiba). Continuous low-dose fluoroscopy (120 kV, 50 mA) performed at the level of the descending aorta was initiated 10 seconds after the start of contrast material injection. The attenuation of the round, 1-cm-diameter region of interest in the descending aorta at the level of the seventh thoracic vertebra was measured three times per second. When this value reached a preset threshold (an absolute attenuation value of 200 HU) three consecutive times, helical CT began automatically.
Image Analysis
All MR angiographic and CT angiographic data were transferred to the workstation (Zio M900 Quadra; Ziosoft, Tokyo, Japan) and displayed as MPR, CPR, maximum intensity projection (MIP), and three-dimensional display (volume-rendered) images. The 0.5-mm-thick MPR images were obtained at 0.5-mm intervals. Section thickness for the MIP images was 2–28 mm to ensure the longest possible time for vessel visualization.
Some oblique MPR images with nearly coronal orientations were obtained to compensate for the curvature of the spinal cord. If a vessel was determined or suspected to run from the dorsal branch of the intercostal or lumber artery to the anterior surface of the spinal cord, some oblique axial and coronal MPR images were obtained to track the continuity between the aorta and anterior spinal artery. In all cases, CPR images were obtained along the vessels of interest (aorta, intercostal or lumber artery, radiculomedullary artery, artery of Adamkiewicz, anterior spinal artery); partial MIP images were created from a small volume of MR and CT images to show the longest possible continuity in a single plane and to avoid "contaminating" the other arteries.
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Results of Imaging
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All of the patients gave informed consent for MR angiography and CT angiography, and all examinations were completed without incident. The obtained data could be analyzed in all cases.
According to the morphologic "hairpin turn" diagnostic criteria, the artery of Adamkiewicz was successfully visualized in 28 of 30 cases (93%) with MR angiography and in 25 of 30 cases (83%) with CT angiography on MPR images. According to the "continuity" diagnostic criteria, the artery of Adamkiewicz was depicted in 24 of 30 cases (80%) with MR angiography and in 18 of 30 cases (60%) with CT angiography on CPR images.
There was only one case in which the hairpin turn could not be depicted with either MR angiography or CT angiography. The artery of Adamkiewicz was visualized in 29 of 30 cases (97%) at MR angiography or CT angiography. In another two cases, both MR angiography and CT angiography were able to depict the hairpin turn but not continuity on CPR images. The artery of Adamkiewicz was successfully depicted with the continuity criteria in the remaining 27 of 30 cases (90%) at MR angiography or CT angiography on CPR images.
With regard to true aneurysms, the artery of Adamkiewicz was depicted in 17 of 18 cases (94%) at MR angiography and in 15 of 18 cases (83%) at CT angiography on MPR images. Continuity was observed in 13 of 18 cases (72%) at MR angiography and in 11 of 18 cases (61%) at CT angiography on CPR images.
With regard to dissecting aneurysms, the artery of Adamkiewicz was visualized in 11 of 12 cases (92%) at MR angiography and in 10 of 12 cases (83%) at CT angiography on MPR images. Continuity was observed in 11 of 12 cases (92%) at MR angiography and in seven of 12 cases (58%) at CT angiography on CPR images (Figs 3, 4).
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Figure 3a. Dissecting aortic aneurysm in a 59-year-old man. (a) Three-dimensional volume-rendered image from MR angiography (left anterior oblique view) shows a dissecting aneurysm of the thoracoabdominal aorta. (b, c) CPR images from MR angiography (b) and CT angiography (c) show continuity of the aorta, left 10th intercostal artery (large black arrow), radiculomedullary artery (small black arrow), artery of Adamkiewicz (white arrow), and anterior spinal artery (arrowhead). The 10th intercostal artery originates from the true lumen (T) of the aorta. F = false lumen, T10 = 10th thoracic vertebra.
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Figure 3b. Dissecting aortic aneurysm in a 59-year-old man. (a) Three-dimensional volume-rendered image from MR angiography (left anterior oblique view) shows a dissecting aneurysm of the thoracoabdominal aorta. (b, c) CPR images from MR angiography (b) and CT angiography (c) show continuity of the aorta, left 10th intercostal artery (large black arrow), radiculomedullary artery (small black arrow), artery of Adamkiewicz (white arrow), and anterior spinal artery (arrowhead). The 10th intercostal artery originates from the true lumen (T) of the aorta. F = false lumen, T10 = 10th thoracic vertebra.
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Figure 3c. Dissecting aortic aneurysm in a 59-year-old man. (a) Three-dimensional volume-rendered image from MR angiography (left anterior oblique view) shows a dissecting aneurysm of the thoracoabdominal aorta. (b, c) CPR images from MR angiography (b) and CT angiography (c) show continuity of the aorta, left 10th intercostal artery (large black arrow), radiculomedullary artery (small black arrow), artery of Adamkiewicz (white arrow), and anterior spinal artery (arrowhead). The 10th intercostal artery originates from the true lumen (T) of the aorta. F = false lumen, T10 = 10th thoracic vertebra.
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Figure 4a. Dissecting aortic aneurysm in a 60-year-old man who previously underwent repair of the ascending aorta and aortic arch for acute aortic dissection. (a) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view) shows a dissecting aneurysm of the thoracoabdominal aorta. (b) Axial CT image obtained at the level of the 10th thoracic vertebra (Th10) shows a small true lumen and a large false lumen. (c, d) CPR images from MR angiography (c) and CT angiography (d) show continuity of the aorta; left 10th intercostal artery (large black arrow); radiculomedullary artery (black arrowhead); artery of Adamkiewicz (white arrow in c, small black arrow in d); and anterior spinal artery (white arrowhead). The 10th intercostal artery originates from the false lumen (F). The image from CT angiography shows poor opacification of the artery of Adamkiewicz (small black arrow in d). T = true lumen, T10 = 10th thoracic vertebra.
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Figure 4b. Dissecting aortic aneurysm in a 60-year-old man who previously underwent repair of the ascending aorta and aortic arch for acute aortic dissection. (a) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view) shows a dissecting aneurysm of the thoracoabdominal aorta. (b) Axial CT image obtained at the level of the 10th thoracic vertebra (Th10) shows a small true lumen and a large false lumen. (c, d) CPR images from MR angiography (c) and CT angiography (d) show continuity of the aorta; left 10th intercostal artery (large black arrow); radiculomedullary artery (black arrowhead); artery of Adamkiewicz (white arrow in c, small black arrow in d); and anterior spinal artery (white arrowhead). The 10th intercostal artery originates from the false lumen (F). The image from CT angiography shows poor opacification of the artery of Adamkiewicz (small black arrow in d). T = true lumen, T10 = 10th thoracic vertebra.
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Figure 4c. Dissecting aortic aneurysm in a 60-year-old man who previously underwent repair of the ascending aorta and aortic arch for acute aortic dissection. (a) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view) shows a dissecting aneurysm of the thoracoabdominal aorta. (b) Axial CT image obtained at the level of the 10th thoracic vertebra (Th10) shows a small true lumen and a large false lumen. (c, d) CPR images from MR angiography (c) and CT angiography (d) show continuity of the aorta; left 10th intercostal artery (large black arrow); radiculomedullary artery (black arrowhead); artery of Adamkiewicz (white arrow in c, small black arrow in d); and anterior spinal artery (white arrowhead). The 10th intercostal artery originates from the false lumen (F). The image from CT angiography shows poor opacification of the artery of Adamkiewicz (small black arrow in d). T = true lumen, T10 = 10th thoracic vertebra.
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Figure 4d. Dissecting aortic aneurysm in a 60-year-old man who previously underwent repair of the ascending aorta and aortic arch for acute aortic dissection. (a) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view) shows a dissecting aneurysm of the thoracoabdominal aorta. (b) Axial CT image obtained at the level of the 10th thoracic vertebra (Th10) shows a small true lumen and a large false lumen. (c, d) CPR images from MR angiography (c) and CT angiography (d) show continuity of the aorta; left 10th intercostal artery (large black arrow); radiculomedullary artery (black arrowhead); artery of Adamkiewicz (white arrow in c, small black arrow in d); and anterior spinal artery (white arrowhead). The 10th intercostal artery originates from the false lumen (F). The image from CT angiography shows poor opacification of the artery of Adamkiewicz (small black arrow in d). T = true lumen, T10 = 10th thoracic vertebra.
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The presence of collateral circulation due to occlusion of the intercostal or lumbar arteries was depicted in seven of 30 cases (23%) at MR angiography. Five of these seven cases had true aneurysms. The most common source of collaterals was the muscular branch in five cases: of the lumbar artery in two cases, of the intercostal artery in two cases, and of both arteries in one case (Fig 5).
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Figure 5a. Demonstration of collateral circulation to the artery of Adamkiewicz in a 78-year-old man with a true thoracoabdominal aortic aneurysm. TAAA = thoracoabdominal aortic aneurysm, T10 = 10th thoracic vertebra, T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from MR angiography shows the artery of Adamkiewicz (white arrowhead) branching from the left 10th intercostal artery and anterior spinal artery (black arrowhead). (b) On an axial partial MIP image from MR angiography, the proximal portion (large arrow) of the left 10th intercostal artery (small arrow) cannot be visualized. (c) Oblique sagittal partial MIP image from MR angiography shows two collateral arteries: a small ventral artery (small white arrow) and a large dorsal artery (large white arrow). They extend from the left 11th intercostal artery (large black arrow) to the left 10th intercostal artery (small black arrow) via muscular branches. (d, e) CPR images from MR angiography (d) and CT angiography (e) show continuity of the aorta, left 11th intercostal artery (large black arrow), small ventral collateral artery (long white arrow), left 10th intercostal artery (small black arrow), anterior radiculomedullary artery (short white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (f, g) CPR images from MR angiography (f ) and CT angiography (g) show continuity of the aorta, left 11th intercostal artery (large black arrow), large dorsal collateral artery (large white arrow), left 10th intercostal artery (small black arrow), radiculomedullary artery (small white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (h) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view), displayed with a semitransparent skeletal system and aorta, shows the entire collateral circulation via the two muscular branches: the small ventral artery (small arrow) and the large dorsal artery (large arrow). Thus, there is continuity from the aorta to the artery of Adamkiewicz (white arrowhead) and anterior spinal artery (black arrowhead).
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Figure 5b. Demonstration of collateral circulation to the artery of Adamkiewicz in a 78-year-old man with a true thoracoabdominal aortic aneurysm. TAAA = thoracoabdominal aortic aneurysm, T10 = 10th thoracic vertebra, T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from MR angiography shows the artery of Adamkiewicz (white arrowhead) branching from the left 10th intercostal artery and anterior spinal artery (black arrowhead). (b) On an axial partial MIP image from MR angiography, the proximal portion (large arrow) of the left 10th intercostal artery (small arrow) cannot be visualized. (c) Oblique sagittal partial MIP image from MR angiography shows two collateral arteries: a small ventral artery (small white arrow) and a large dorsal artery (large white arrow). They extend from the left 11th intercostal artery (large black arrow) to the left 10th intercostal artery (small black arrow) via muscular branches. (d, e) CPR images from MR angiography (d) and CT angiography (e) show continuity of the aorta, left 11th intercostal artery (large black arrow), small ventral collateral artery (long white arrow), left 10th intercostal artery (small black arrow), anterior radiculomedullary artery (short white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (f, g) CPR images from MR angiography (f ) and CT angiography (g) show continuity of the aorta, left 11th intercostal artery (large black arrow), large dorsal collateral artery (large white arrow), left 10th intercostal artery (small black arrow), radiculomedullary artery (small white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (h) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view), displayed with a semitransparent skeletal system and aorta, shows the entire collateral circulation via the two muscular branches: the small ventral artery (small arrow) and the large dorsal artery (large arrow). Thus, there is continuity from the aorta to the artery of Adamkiewicz (white arrowhead) and anterior spinal artery (black arrowhead).
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Figure 5c. Demonstration of collateral circulation to the artery of Adamkiewicz in a 78-year-old man with a true thoracoabdominal aortic aneurysm. TAAA = thoracoabdominal aortic aneurysm, T10 = 10th thoracic vertebra, T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from MR angiography shows the artery of Adamkiewicz (white arrowhead) branching from the left 10th intercostal artery and anterior spinal artery (black arrowhead). (b) On an axial partial MIP image from MR angiography, the proximal portion (large arrow) of the left 10th intercostal artery (small arrow) cannot be visualized. (c) Oblique sagittal partial MIP image from MR angiography shows two collateral arteries: a small ventral artery (small white arrow) and a large dorsal artery (large white arrow). They extend from the left 11th intercostal artery (large black arrow) to the left 10th intercostal artery (small black arrow) via muscular branches. (d, e) CPR images from MR angiography (d) and CT angiography (e) show continuity of the aorta, left 11th intercostal artery (large black arrow), small ventral collateral artery (long white arrow), left 10th intercostal artery (small black arrow), anterior radiculomedullary artery (short white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (f, g) CPR images from MR angiography (f ) and CT angiography (g) show continuity of the aorta, left 11th intercostal artery (large black arrow), large dorsal collateral artery (large white arrow), left 10th intercostal artery (small black arrow), radiculomedullary artery (small white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (h) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view), displayed with a semitransparent skeletal system and aorta, shows the entire collateral circulation via the two muscular branches: the small ventral artery (small arrow) and the large dorsal artery (large arrow). Thus, there is continuity from the aorta to the artery of Adamkiewicz (white arrowhead) and anterior spinal artery (black arrowhead).
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Figure 5d. Demonstration of collateral circulation to the artery of Adamkiewicz in a 78-year-old man with a true thoracoabdominal aortic aneurysm. TAAA = thoracoabdominal aortic aneurysm, T10 = 10th thoracic vertebra, T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from MR angiography shows the artery of Adamkiewicz (white arrowhead) branching from the left 10th intercostal artery and anterior spinal artery (black arrowhead). (b) On an axial partial MIP image from MR angiography, the proximal portion (large arrow) of the left 10th intercostal artery (small arrow) cannot be visualized. (c) Oblique sagittal partial MIP image from MR angiography shows two collateral arteries: a small ventral artery (small white arrow) and a large dorsal artery (large white arrow). They extend from the left 11th intercostal artery (large black arrow) to the left 10th intercostal artery (small black arrow) via muscular branches. (d, e) CPR images from MR angiography (d) and CT angiography (e) show continuity of the aorta, left 11th intercostal artery (large black arrow), small ventral collateral artery (long white arrow), left 10th intercostal artery (small black arrow), anterior radiculomedullary artery (short white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (f, g) CPR images from MR angiography (f ) and CT angiography (g) show continuity of the aorta, left 11th intercostal artery (large black arrow), large dorsal collateral artery (large white arrow), left 10th intercostal artery (small black arrow), radiculomedullary artery (small white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (h) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view), displayed with a semitransparent skeletal system and aorta, shows the entire collateral circulation via the two muscular branches: the small ventral artery (small arrow) and the large dorsal artery (large arrow). Thus, there is continuity from the aorta to the artery of Adamkiewicz (white arrowhead) and anterior spinal artery (black arrowhead).
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Figure 5e. Demonstration of collateral circulation to the artery of Adamkiewicz in a 78-year-old man with a true thoracoabdominal aortic aneurysm. TAAA = thoracoabdominal aortic aneurysm, T10 = 10th thoracic vertebra, T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from MR angiography shows the artery of Adamkiewicz (white arrowhead) branching from the left 10th intercostal artery and anterior spinal artery (black arrowhead). (b) On an axial partial MIP image from MR angiography, the proximal portion (large arrow) of the left 10th intercostal artery (small arrow) cannot be visualized. (c) Oblique sagittal partial MIP image from MR angiography shows two collateral arteries: a small ventral artery (small white arrow) and a large dorsal artery (large white arrow). They extend from the left 11th intercostal artery (large black arrow) to the left 10th intercostal artery (small black arrow) via muscular branches. (d, e) CPR images from MR angiography (d) and CT angiography (e) show continuity of the aorta, left 11th intercostal artery (large black arrow), small ventral collateral artery (long white arrow), left 10th intercostal artery (small black arrow), anterior radiculomedullary artery (short white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (f, g) CPR images from MR angiography (f ) and CT angiography (g) show continuity of the aorta, left 11th intercostal artery (large black arrow), large dorsal collateral artery (large white arrow), left 10th intercostal artery (small black arrow), radiculomedullary artery (small white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (h) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view), displayed with a semitransparent skeletal system and aorta, shows the entire collateral circulation via the two muscular branches: the small ventral artery (small arrow) and the large dorsal artery (large arrow). Thus, there is continuity from the aorta to the artery of Adamkiewicz (white arrowhead) and anterior spinal artery (black arrowhead).
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Figure 5f. Demonstration of collateral circulation to the artery of Adamkiewicz in a 78-year-old man with a true thoracoabdominal aortic aneurysm. TAAA = thoracoabdominal aortic aneurysm, T10 = 10th thoracic vertebra, T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from MR angiography shows the artery of Adamkiewicz (white arrowhead) branching from the left 10th intercostal artery and anterior spinal artery (black arrowhead). (b) On an axial partial MIP image from MR angiography, the proximal portion (large arrow) of the left 10th intercostal artery (small arrow) cannot be visualized. (c) Oblique sagittal partial MIP image from MR angiography shows two collateral arteries: a small ventral artery (small white arrow) and a large dorsal artery (large white arrow). They extend from the left 11th intercostal artery (large black arrow) to the left 10th intercostal artery (small black arrow) via muscular branches. (d, e) CPR images from MR angiography (d) and CT angiography (e) show continuity of the aorta, left 11th intercostal artery (large black arrow), small ventral collateral artery (long white arrow), left 10th intercostal artery (small black arrow), anterior radiculomedullary artery (short white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (f, g) CPR images from MR angiography (f ) and CT angiography (g) show continuity of the aorta, left 11th intercostal artery (large black arrow), large dorsal collateral artery (large white arrow), left 10th intercostal artery (small black arrow), radiculomedullary artery (small white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (h) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view), displayed with a semitransparent skeletal system and aorta, shows the entire collateral circulation via the two muscular branches: the small ventral artery (small arrow) and the large dorsal artery (large arrow). Thus, there is continuity from the aorta to the artery of Adamkiewicz (white arrowhead) and anterior spinal artery (black arrowhead).
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Figure 5g. Demonstration of collateral circulation to the artery of Adamkiewicz in a 78-year-old man with a true thoracoabdominal aortic aneurysm. TAAA = thoracoabdominal aortic aneurysm, T10 = 10th thoracic vertebra, T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from MR angiography shows the artery of Adamkiewicz (white arrowhead) branching from the left 10th intercostal artery and anterior spinal artery (black arrowhead). (b) On an axial partial MIP image from MR angiography, the proximal portion (large arrow) of the left 10th intercostal artery (small arrow) cannot be visualized. (c) Oblique sagittal partial MIP image from MR angiography shows two collateral arteries: a small ventral artery (small white arrow) and a large dorsal artery (large white arrow). They extend from the left 11th intercostal artery (large black arrow) to the left 10th intercostal artery (small black arrow) via muscular branches. (d, e) CPR images from MR angiography (d) and CT angiography (e) show continuity of the aorta, left 11th intercostal artery (large black arrow), small ventral collateral artery (long white arrow), left 10th intercostal artery (small black arrow), anterior radiculomedullary artery (short white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (f, g) CPR images from MR angiography (f ) and CT angiography (g) show continuity of the aorta, left 11th intercostal artery (large black arrow), large dorsal collateral artery (large white arrow), left 10th intercostal artery (small black arrow), radiculomedullary artery (small white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (h) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view), displayed with a semitransparent skeletal system and aorta, shows the entire collateral circulation via the two muscular branches: the small ventral artery (small arrow) and the large dorsal artery (large arrow). Thus, there is continuity from the aorta to the artery of Adamkiewicz (white arrowhead) and anterior spinal artery (black arrowhead).
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Figure 5h. Demonstration of collateral circulation to the artery of Adamkiewicz in a 78-year-old man with a true thoracoabdominal aortic aneurysm. TAAA = thoracoabdominal aortic aneurysm, T10 = 10th thoracic vertebra, T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from MR angiography shows the artery of Adamkiewicz (white arrowhead) branching from the left 10th intercostal artery and anterior spinal artery (black arrowhead). (b) On an axial partial MIP image from MR angiography, the proximal portion (large arrow) of the left 10th intercostal artery (small arrow) cannot be visualized. (c) Oblique sagittal partial MIP image from MR angiography shows two collateral arteries: a small ventral artery (small white arrow) and a large dorsal artery (large white arrow). They extend from the left 11th intercostal artery (large black arrow) to the left 10th intercostal artery (small black arrow) via muscular branches. (d, e) CPR images from MR angiography (d) and CT angiography (e) show continuity of the aorta, left 11th intercostal artery (large black arrow), small ventral collateral artery (long white arrow), left 10th intercostal artery (small black arrow), anterior radiculomedullary artery (short white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (f, g) CPR images from MR angiography (f ) and CT angiography (g) show continuity of the aorta, left 11th intercostal artery (large black arrow), large dorsal collateral artery (large white arrow), left 10th intercostal artery (small black arrow), radiculomedullary artery (small white arrow), artery of Adamkiewicz (white arrowhead), and anterior spinal artery (black arrowhead). (h) Three-dimensional volume-rendered image from CT angiography (left anterior oblique view), displayed with a semitransparent skeletal system and aorta, shows the entire collateral circulation via the two muscular branches: the small ventral artery (small arrow) and the large dorsal artery (large arrow). Thus, there is continuity from the aorta to the artery of Adamkiewicz (white arrowhead) and anterior spinal artery (black arrowhead).
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The artery of Adamkiewicz was seen to originate at the following levels: the left eighth intercostal artery in two cases, the left ninth intercostal artery in four cases, the left 10th intercostal artery in seven cases, the left 11th intercostal artery in three cases, the left subcostal artery in two cases, and the left first lumbar artery in three cases. It was seen to originate at the level of the right ninth intercostal artery in one case, the right 10th intercostal artery in two cases, the right 11th intercostal artery in two cases, the right subcostal artery in two cases, and the right first lumbar artery in one case.
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Discussion
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Differentiation of the Artery of Adamkiewicz from a Vein
In the identification of the artery of Adamkiewicz with MR angiography and CT angiography, it is very important to distinguish the artery of Adamkiewicz from the anterior radiculomedullary vein because this vein is very similar in shape to the artery of Adamkiewicz and may follow a course very close to that of the artery of Adamkiewicz. The anterior radiculomedullary vein is larger than the artery of Adamkiewicz. The angle of the anterior radiculomedullary vein and the anterior spinal vein, which is called a "coat hook" shape, is wider than that of the artery of Adamkiewicz and the anterior spinal artery, which is called a "hairpin turn." However, it is very difficult to distinguish between these two vessels on the basis of their characteristic shapes in the clinical setting (Fig 6).
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Figure 6a. Differentiation of the artery of Adamkiewicz from the anterior radiculomedullary vein. These vessels have similar morphologic characteristics, making it difficult to distinguish between them. It is essential to demonstrate the continuity between the aorta and the anterior spinal artery. T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from arterial phase CT angiography shows a vessel with a hairpin turn configuration (arrow) at the level of the 11th thoracic vertebra. (b) Oblique coronal MPR image from venous phase CT angiography shows a vessel with a hairpin turn configuration (arrowhead) at the level of the 12th thoracic vertebra. (c) Oblique coronal MPR image from late arterial phase CT angiography shows the two vessels with hairpin turn configurations (arrow, arrowhead). (d) CPR image from CT angiography clearly shows continuity of the aorta (Ao), left 11th intercostal artery (large black arrow), anterior radiculomedullary artery (white arrow), artery of Adamkiewicz (small black arrow), and anterior spinal artery (arrowhead). (e) Image from selective digital subtraction angiography of the left 11th intercostal artery (large arrow) shows the artery of Adamkiewicz (small arrow) and anterior spinal artery (arrowhead). Selective digital subtraction angiography of the left 12th intercostal artery showed no connection with the artery of Adamkiewicz.
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Figure 6b. Differentiation of the artery of Adamkiewicz from the anterior radiculomedullary vein. These vessels have similar morphologic characteristics, making it difficult to distinguish between them. It is essential to demonstrate the continuity between the aorta and the anterior spinal artery. T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from arterial phase CT angiography shows a vessel with a hairpin turn configuration (arrow) at the level of the 11th thoracic vertebra. (b) Oblique coronal MPR image from venous phase CT angiography shows a vessel with a hairpin turn configuration (arrowhead) at the level of the 12th thoracic vertebra. (c) Oblique coronal MPR image from late arterial phase CT angiography shows the two vessels with hairpin turn configurations (arrow, arrowhead). (d) CPR image from CT angiography clearly shows continuity of the aorta (Ao), left 11th intercostal artery (large black arrow), anterior radiculomedullary artery (white arrow), artery of Adamkiewicz (small black arrow), and anterior spinal artery (arrowhead). (e) Image from selective digital subtraction angiography of the left 11th intercostal artery (large arrow) shows the artery of Adamkiewicz (small arrow) and anterior spinal artery (arrowhead). Selective digital subtraction angiography of the left 12th intercostal artery showed no connection with the artery of Adamkiewicz.
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Figure 6c. Differentiation of the artery of Adamkiewicz from the anterior radiculomedullary vein. These vessels have similar morphologic characteristics, making it difficult to distinguish between them. It is essential to demonstrate the continuity between the aorta and the anterior spinal artery. T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from arterial phase CT angiography shows a vessel with a hairpin turn configuration (arrow) at the level of the 11th thoracic vertebra. (b) Oblique coronal MPR image from venous phase CT angiography shows a vessel with a hairpin turn configuration (arrowhead) at the level of the 12th thoracic vertebra. (c) Oblique coronal MPR image from late arterial phase CT angiography shows the two vessels with hairpin turn configurations (arrow, arrowhead). (d) CPR image from CT angiography clearly shows continuity of the aorta (Ao), left 11th intercostal artery (large black arrow), anterior radiculomedullary artery (white arrow), artery of Adamkiewicz (small black arrow), and anterior spinal artery (arrowhead). (e) Image from selective digital subtraction angiography of the left 11th intercostal artery (large arrow) shows the artery of Adamkiewicz (small arrow) and anterior spinal artery (arrowhead). Selective digital subtraction angiography of the left 12th intercostal artery showed no connection with the artery of Adamkiewicz.
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Figure 6d. Differentiation of the artery of Adamkiewicz from the anterior radiculomedullary vein. These vessels have similar morphologic characteristics, making it difficult to distinguish between them. It is essential to demonstrate the continuity between the aorta and the anterior spinal artery. T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from arterial phase CT angiography shows a vessel with a hairpin turn configuration (arrow) at the level of the 11th thoracic vertebra. (b) Oblique coronal MPR image from venous phase CT angiography shows a vessel with a hairpin turn configuration (arrowhead) at the level of the 12th thoracic vertebra. (c) Oblique coronal MPR image from late arterial phase CT angiography shows the two vessels with hairpin turn configurations (arrow, arrowhead). (d) CPR image from CT angiography clearly shows continuity of the aorta (Ao), left 11th intercostal artery (large black arrow), anterior radiculomedullary artery (white arrow), artery of Adamkiewicz (small black arrow), and anterior spinal artery (arrowhead). (e) Image from selective digital subtraction angiography of the left 11th intercostal artery (large arrow) shows the artery of Adamkiewicz (small arrow) and anterior spinal artery (arrowhead). Selective digital subtraction angiography of the left 12th intercostal artery showed no connection with the artery of Adamkiewicz.
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Figure 6e. Differentiation of the artery of Adamkiewicz from the anterior radiculomedullary vein. These vessels have similar morphologic characteristics, making it difficult to distinguish between them. It is essential to demonstrate the continuity between the aorta and the anterior spinal artery. T11 = 11th thoracic vertebra. (a) Oblique coronal MPR image from arterial phase CT angiography shows a vessel with a hairpin turn configuration (arrow) at the level of the 11th thoracic vertebra. (b) Oblique coronal MPR image from venous phase CT angiography shows a vessel with a hairpin turn configuration (arrowhead) at the level of the 12th thoracic vertebra. (c) Oblique coronal MPR image from late arterial phase CT angiography shows the two vessels with hairpin turn configurations (arrow, arrowhead). (d) CPR image from CT angiography clearly shows continuity of the aorta (Ao), left 11th intercostal artery (large black arrow), anterior radiculomedullary artery (white arrow), artery of Adamkiewicz (small black arrow), and anterior spinal artery (arrowhead). (e) Image from selective digital subtraction angiography of the left 11th intercostal artery (large arrow) shows the artery of Adamkiewicz (small arrow) and anterior spinal artery (arrowhead). Selective digital subtraction angiography of the left 12th intercostal artery showed no connection with the artery of Adamkiewicz.
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Because of these problems, it is important to recognize the possibility of mistakenly identifying the anterior radiculomedullary vein as the artery of Adamkiewicz if determination is based on the characteristic hairpin turn. Accordingly, it is better to identify the artery of Adamkiewicz by visualizing the continuity of the aorta, the artery of Adamkiewicz, and the anterior spinal artery.
This method has another advantage in that it may also depict the collateral blood supply due to occlusion of feeding arteries such as the intercostal and lumbar arteries (Fig 5).
On the other hand, two studies have reported another method for identifying the artery of Adamkiewicz by obtaining images during several phases in dynamic MR studies, which provide superior temporal resolution (6,7). However, this method is limited by a number of important problems. First, it is impossible to confirm continuity by generating CPR images due to the poor spatial resolution. Second, it is impossible to demonstrate the ostia of the intercostal and lumbar arteries due to the limited lateral coverage needed to maintain high temporal resolution in sagittal imaging. These problems mean that this method cannot provide surgeons with critical information needed for reconstruction of the intercostal and lumbar arteries and is therefore unsuitable as a preoperative study for patients with thoracic aortic aneurysms.
In addition, the intercostal and lumbar arteries, from which collaterals may arise when an intercostal or lumbar artery is connected to the artery of Adamkiewicz, may be misidentified if they are occluded at the branching level. In the present study, the collaterals were supplied from arteries at different levels in seven of 30 cases (23%), which indicates that this is not an uncommon finding. This is another problem with the dynamic study method in MR angiography. However, a recent study has reported that MR angiography is able to show continuity on MIP and CPR images when a high dose of gadopentetate dime-glumine is employed (11). Such methods may overcome this problem.
Although CPR images are suitable for evaluation of continuity between the aorta and the artery of Adamkiewicz, it is difficult to visualize the anatomic relationships between the aneurysm and the artery of Adamkiewicz. To overcome this problem, volume-rendered images permit such anatomic information to be clearly visualized at both MR angiography and CT angiography (12,13).
Limitations of MR Angiography and CT Angiography
It is well known that osseous structures sometimes interfere with visualization of arteries. Even when the osseous structures are normal, it may be difficult to visualize an artery that runs into an intervertebral foramen because not only is the artery very thin but it also runs close to the osseous structures (Fig 7a). Scoliosis, osteophytes, and narrowing of the intervertebral foramen due to spondylosis deformans may also interfere with visualization of a nearby artery. In MR angiography, on the other hand, bony structures show no signal and fatty tissues show low signal intensity with fat suppression, permitting arteries close to osseous structures to be depicted very clearly (Fig 7b).
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Figure 7a. Limitation of CT angiography in a 70-year-old woman with a true aortic aneurysm. CPR images from CT angiography (a) and MR angiography (b) show normal osseous structures, an osteophyte, and scoliosis, which may obscure the artery of Adamkiewicz (large arrow) at CT angiography. Ao = aorta, L1 = first lumbar vertebra, arrowhead = anterior spinal artery, small arrow = left first lumbar artery.
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Figure 7b. Limitation of CT angiography in a 70-year-old woman with a true aortic aneurysm. CPR images from CT angiography (a) and MR angiography (b) show normal osseous structures, an osteophyte, and scoliosis, which may obscure the artery of Adamkiewicz (large arrow) at CT angiography. Ao = aorta, L1 = first lumbar vertebra, arrowhead = anterior spinal artery, small arrow = left first lumbar artery.
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In patients with dissecting aneurysms, it is difficult to depict the artery of Adamkiewicz with CT angiography when the intercostal artery arises from the false lumen (Fig 4). This is due to the large difference in blood flow velocity between the true and false lumina. We were not able to determine which lumen supplied the intercostal or lumbar artery as the source of the artery of Adamkiewicz before CT angiography. Even when such determination is possible, it is very difficult to start scanning at the optimal timing to obtain a good image even if we know that the artery arises from the false lumen, in which blood flow is very slow.
On the other hand, MR angiography requires a long acquisition time of 5 minutes and k-space is acquired in a standard linear fashion. MR angiography may show such slow flow in the false lumen because contrast enhancement may occur between 2 and 3 minutes after the infusion of contrast material. MR angiography has the disadvantage of a more limited field of view as compared with CT angiography (Fig 8). This is related to the imaging protocol for MR angiography that is employed for sagittal imaging. It is very difficult to visualize the collaterals when they run out of the field of view. For the same reason, if the internal thoracic artery supplies the collaterals, MR angiography may fail to depict it (14).
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Figure 8. Limitation of MR angiography in a 74-year-old man with a true aortic aneurysm. Anterior three-dimensional volume-rendered image from CT angiography, displayed with the aorta digitally eliminated, shows a collateral vessel (arrow) from the left ninth intercostal artery to the left 10th intercostal artery. The box indicates the field of view in MR angiography. Because the field of view of MR angiography is limited in sagittal imaging, some collateral vessels are not visualized at MR angiography. T9 = ninth thoracic vertebra, T10 = 10th thoracic vertebra.
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Comparison of Detection Rates for the Artery of Adamkiewicz
In this study, the detection rate (93%) for the artery of Adamkiewicz with morphologic evaluation at MR angiography based on the presence of a hairpin turn was higher than that reported in previous studies (67%–84%) (Table). In addition, the depiction of continuity was increased from 57% to 80%. This increase in the detection rate can be attributed mainly to improvements in the gradient amplifier of MR systems, leading to shorter repetition times and echo times, as well as the use of new four-channel phased-array coils with higher signal-to-noise ratios.
With regard to CT angiography, although the number of detector rows has been increased to 16 and the section thickness has been reduced to 0.5 mm, no improvement in the detection rate based on morphologic criteria was observed. The reason is that reducing the section thickness to less than 1 mm does not directly improve the detectability of the artery of Adamkiewicz, which is 1 mm in diameter. However, there was some improvement in identification based on the continuity criteria because thinner sections improve the spatial resolution in the z axis, which improves the traceability of thin and complicated vessels even in elderly patients, who may have a large number of osteophytes or spondylosis deformans.
In general, conventional selective angiography has been employed for preoperative assessment of the artery of Adamkiewicz (5,15–17). The highest detection rate for the artery of Adamkiewicz has been achieved by Kieffer et al (5), who reported a detection rate of 86% in 480 cases. In their study, critical complications developed in six patients, including two patients with paraplegia. Compared with these results, MR angiography, which is a noninvasive diagnostic method, was able to provide a high detection rate of 80% without any complications. Furthermore, the use of both MR angiography and CT angiography can provide a very high detection rate of 90% based on the continuity criteria, which is superior to that of conventional selective angiography. These important findings suggest that MR angiography and CT angiography will replace the invasive method of conventional selective angiography.
Surgical Outcomes
Recent studies have reported the usefulness of preoperative evaluation of the artery of Adamkiewicz by comparing the occurrence of postoperative spinal cord ischemia between an identified artery of Adamkiewicz group and a nonidentified artery of Adamkiewicz group in patients undergoing thoracoabdominal aortic or descending thoracic aortic repair. The results showed that the rate of spinal cord ischemia was significantly lower in the identified artery of Adamkiewicz group than in the nonidentified artery of Adamkiewicz group (7,18). Although these single-center studies have the limitation of small sample sizes, studies involving larger numbers of patients may provide good reproducibility if noninvasive diagnostic methods such as MR angiography and CT angiography gain widespread acceptance.
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Conclusions
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MR angiography and CT angiography are useful, noninvasive, and safe methods for evaluating the artery of Adamkiewicz on the basis of continuity from the aorta to the anterior spinal artery in patients with thoracoabdominal and thoracic descending aortic aneurysms. It is expected that these noninvasive methods will play an important role in minimizing the risk of spinal cord ischemia in surgical patients. When such noninvasive methods for preoperative identification of the artery of Adamkiewicz become widespread, they will be considered essential whenever surgery is considered.
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Footnotes
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Abbreviations: CPR = curved planar reformation, MIP = maximum intensity projection, MPR = multiplanar reformation
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References
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M. H. Rodallec, A. Feydy, F. Larousserie, P. Anract, R. Campagna, A. Babinet, M. Zins, and J.-L. Drape
Diagnostic Imaging of Solitary Tumors of the Spine: What to Do and Say
RadioGraphics,
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[Abstract]
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W.H. Backes and R.J. Nijenhuis
Advances in Spinal Cord MR Angiography
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April 1, 2008;
29(4):
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[Abstract]
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Y. Miyamoto, T. Ohata, M. Mitsuno, M. Yamamura, H. Tanaka, Y. Kobayashi, M. Ryomoto, and S. Fukui
Long-term outcomes after entry closure and aneurysmal wall plication for type B aortic dissection
Eur. J. Cardiothorac. Surg.,
February 1, 2008;
33(2):
152 - 156.
[Abstract]
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K. Uotani, N. Yamada, A.K. Kono, T. Taniguchi, K. Sugimoto, M. Fujii, A. Kitagawa, Y. Okita, H. Naito, and K. Sugimura
Preoperative Visualization of the Artery of Adamkiewicz by Intra-Arterial CT Angiography
AJNR Am. J. Neuroradiol.,
February 1, 2008;
29(2):
314 - 318.
[Abstract]
[Full Text]
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D. T. Boll
Reply
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July 1, 2007;
189(1):
W46 - W46.
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Top
Abstract
Introduction
