| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Original Research |
1 Department of Radiology, University Hospitals of Cleveland, 11100 Euclid Ave.,
Cleveland, OH 44106.
2 Department of Radiology, University Hospital of Ulm, Ulm, Germany.
Received March 31, 2005;
accepted after revision August 22, 2005.
Address correspondence to D. T. Boll
(boll{at}uhrad.com).
Abstract
 Top Abstract IntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
SUBJECTS AND METHODS. One hundred patients underwent contrast-enhanced MDCT of the thoracolumbar junction with collimation of 40 x 0.625 mm. The adapted brain algorithm reconstructed the spinal canal with a field of view of 90 mm at 0.6-mm slice thickness. Curved multiplanar reformations identified the artery of Adamkiewicz as a continuous vascular tract extending from the aortic orifices of the intercostal or lumbar arteries via the anterior radiculomedullary artery to the anterior spinal artery. Segment of origin and length were noted. Diameter and contrast-to-noise ratio (CNR) were evaluated along the posterior branch, the radiculomedullary artery, the artery of Adamkiewicz, and the anterior spinal artery. Univariate general linear model analysis with Bonferroni post hoc corrections evaluated whether laterality, segment of origin, and length of the artery of Adamkiewicz showed a sex-specific propensity. Multivariate general linear model analysis assessed whether spinal vascular diameters and intraluminal CNR showed correlations with sex, laterality, and segment of origin. Finally, the luminal diameters of the feeding posterior branches were statistically compared with those of the ipsilateral and contralateral adjacent posterior branches.
RESULTS. Successful depiction of the artery of Adamkiewicz was achieved in all patients; longitudinally the artery measured 40.1 ± 13.51 mm. In 63% of patients it originated from the left side of the body, and in 74% it originated from the level of the 10th-12th thoracic vertebrae. Duplications were found in 5% of patients. Segmental distribution, laterality, and length did not show significant sex-specific differences (p > 0.05). The vascular diameter and luminal contrast did not show significant differences caused by sex, laterality, or segment of origin (p > 0.05). The diameter of the posterior branches (2.8 ± 0.71 mm) arising in the segments of origin showed a significantly wider lumen than any of the other posterior branches (contralateral, 1.9 ± 0.32 mm; upper ipsilateral, 2.0 ± 0.47 mm; lower ipsilateral, 1.9 ± 0.39 mm) (p < 0.0001).
CONCLUSION. Contrast-enhanced 40-MDCT technology, in combination with an adapted brain reconstruction algorithm, can depict the artery of Adamkiewicz and its anatomic variants.
Keywords: angiography • artery of Adamkiewicz • cardiovascular imaging • MDCT • neuroradiology • spine • vasculature
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
|
|
The spinal vasculature and the cord located in the spinal canal are surrounded by high-density skeletal formations. In addition to the vertebral column, this anatomic arrangement can be found only in the skull, with either the flattened and jointed bones of the cranium surrounding the brain and intracerebral vasculature at varying distances, or in the petrous bones, which closely encase the internal carotid arteries. Reconstruction algorithms for cerebral MDCT visualization were modified to suit this anatomic arrangement. In particular, filtering procedures, an inherent part of raw data reconstruction, on the one hand must eliminate beam hardening artifacts originating from high-density osseous formations and thereby obscuring the sharp delineation of brain tissue and cerebral vascular adjacent to the osseous skull. On the other hand, filtering procedures rely on autocalibrated filtering parameters to realize an equal level of inevitable image noise throughout the reconstructed axial image data set.
In this prospective study we sought to use 40-MDCT technology in combination with adapted brain reconstruction algorithms to visualize the spinal canal, in particular the spinal vasculature. This study was performed to test the hypothesis that contrast-enhanced MDCT angiography can depict the artery of Adamkiewicz if high-resolution image acquisition and adapted brain reconstruction techniques are used.
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
|
|
An MDCT study was planned covering a longitudinal imaging volume from the liver dome at the level of the eighth thoracic vertebra to the tip of the liver at the level of the third lumbar vertebra. The scanning parameters were 120 kV, 200 mA adjusted by adaptive dose modulation techniques, 40 x 0.625 mm collimation, a table speed of 41.2 mm/sec (pitch, 0.824) at a 0.5-second gantry rotation period, and a matrix of 1,024 x 1,024 pixels. For automatic bolus tracking, axial slices were acquired just above the level of the celiac trunk orifice at the level of the 11th-12th thoracic vertebrae, which leads to early arterial contrast enhancement of the celiac trunk and the intercostal and lumbar arteries at this level. A region of interest (ROI) was positioned in the aorta, and Hounsfield (H) enhancement was plotted against time. Uniformly, 80 mL of the low-osmolar iodinated contrast agent iomeprol (Imeron 400 MCT, Bracco International) was administered via an 18-gauge IV line placed in an antecubital vein at a flow rate of 3.5 mL/sec followed by a saline chaser bolus of 40 mL administered at 3.5 mL/sec. Scanning was automatically initiated according to the peak enhancement derived from the ROI above a threshold level of 150 H. The duration of the entire examination was 6.2-7.4 seconds.
Two image data sets were subsequently reconstructed at 0.6-mm slice thickness and a 0.3-mm slice increment. One data set measured a cross-sectional field of view of 350 mm and encompassed the entire circumference of the thoracoabdominal junction using an abdominal soft-tissue reconstruction algorithm. The resulting voxels measured 0.34 x 0.34 x 0.6 mm, corresponding to 0.07 mm3. In the second data set, the cross-sectional field of view was uniformly set to 90 mm and centered on the spinal canal at the 11th thoracic vertebra. A brain reconstruction algorithm with filtering procedures to eliminate beam hardening artifacts originating from high-density osseous formations and autocalibrating filtering parameters to realize an equal level of inevitable image noise throughout the axial reconstructed image data set were used. The resulting voxels measured 0.09 x 0.09 x 0.6 mm, corresponding to 0.005 mm3.
Image Analysis
Originating from the descending aorta, the intercostal or lumbar arteries
subdivide into anterior and posterior branches. The anterior branch continues
as the intercostal artery in the costal groove. The posterior branch courses
to the spine and subdivides into three distal vessels—the muscular
branch, the somatic branch, and the radiculomedullary artery. The artery of
Adamkiewicz is the most dominant anterior branch of the radiculomedullary
arteries and originates unilaterally at the level of the 9th-12th intercostal
arteries in 75% of all patients studied
[16]. The distal portion of
the artery of Adamkiewicz, together with the anterior spinal artery, forms a
characteristic hairpin turn (Fig.
1A). Because CT angiography lacks both selective vascular contrast
enhancement at individual vertebral segments and a steady-state technique to
allow temporal differentiation between arterial and venous contrast
enhancement, the artery of Adamkiewicz was defined as a continuous vascular
tract extending from an intercostal or lumbar artery via the anterior
radiculomedullary artery to the anterior spinal artery by ascending to the
midsagittal surface of the spinal cord and making the characteristic hairpin
turn [14].
Primary identification of the artery of Adamkiewicz was performed on the high-resolution image data set. To identify the hairpin turn at the junction of the anterior spinal artery and the great anterior radiculomedullary artery, double oblique multiplanar reformations were performed in an oblique coronal plane parallel to the spinal cord and tilted parallel to the transverse processes of the 11th vertebra. Subsequently, curved multiplanar reformations defined the vessel centerline, connecting the anterior spinal artery via the hairpin turn with an intercostal or lumbar artery along a continuous contrast-enhanced vessel tract (Fig. 1B). Anomalies such as duplications were assessed individually.
|
The ROI estimating background opacification and SD of image noise was 20
mm2 in surface size and was located in the spinal cord at the level
of the various measurement segments; subsequent calculation of the
contrast-to-noise ratios (CNRs) was performed according to the following
formula:
 |
ROI placement and measurements along the diameter were performed by an experienced radiologist with 7 years of experience in vascular imaging who was blinded to the underlying vessel segment. Measurements were repeated three times for each segment, and the measurement results were then averaged. The defined vessel centerline was thereafter applied to the 350-mm cross-sectional field of view and the vascular continuity was assessed.
Statistical Analysis
Univariate general linear model analysis with Bonferroni post hoc
corrections evaluated whether laterality, segment of the origin, and length of
the artery of Adamkiewicz showed a sex-specific propensity, defining sex as
the dependent factor and laterality and the originating segment and length as
independent factors. Multivariate general linear model analysis with
Bonferroni post hoc corrections was performed to assess vascular segmental CNR
and the diameter of the feeding posterior branch, the radiculomedullary
artery, the artery of Adamkiewicz, and the draining spinal anterior artery,
with sex, laterality, and segment of origin as independent factors. Finally,
multivariate general linear model analysis evaluated whether the vascular
diameter of the feeding posterior branch differed in magnitude from the
contralateral and the cranial and caudal adjacent posterior branches.
All statistical analysis was performed using SPSS software, version 11.5; a p value of 0.05 was considered to be statistically significant.
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
In 63% of patients, the great anterior radiculomedullary artery originated from the left side of the body, and in 37%, from the right side, with a segmental range from the eighth thoracic to the second lumbar intervertebral space (Fig. 3). The artery of Adamkiewicz measured 13.1-98.2 mm in length (mean, 40.1 ± 13.51 mm) and spanned one to three vertebral segments (Fig. 4). Segmental distribution, as shown in Table 1, laterality, and length did not show statistically significant sex-specific differences (p > 0.05).
|
Because the feeding posterior branch of the intercostal or lumbar artery measured 2.8 ± 0.71 mm (range, 1.4-5.6 mm) in diameter, intravascular CNR was determined at 49.3 ± 22.1 H (range, 16.1-130.3 H). The radiculomedullary artery was visualized as having a mean diameter of 1.8 ± 0.37 mm (range, 1.0-2.8 mm) and a foramen enhancement of 26.2 ± 11.1 H (range, 10.1-52.6 H). The base segment and the hairpin turn of the artery of Adamkiewicz measured 1.7 ± 0.35 mm (range, 1.0-2.5 mm) and 1.3 ± 0.31 mm (range, 0.7-1.9 mm), respectively. During its course, the great anterior radiculomedullary artery showed an intraluminal contrast of 19.3 ± 7.9 H (range, 3.9-44.4 H). The draining anterior spinal artery was 1.9 ± 0.54 mm in luminal diameter (range, 1.4-2.9 mm) and had an intraluminal contrast of 26.6 ± 10.9 H (range, 6.3-47.4 H). The multivariate statistical analysis of luminal diameter and contrast did not present significant differences according to sex, laterality, or segment of origin (p > 0.05).
Multivariate analysis evaluated the diameters of the posterior branches of the intercostal or lumbar arteries at the segment of origin of the artery of Adamkiewicz compared with the contralateral side and cranially and caudally located adjacent segments. No statistical differences in lumen diameter were apparent when comparing the contralateral segment with the upper and lower ipsilateral segments (p > 0.05), resulting in an average of 1.9 ± 0.32 mm (range, 1.1-3.1 mm), 2.0 ± 0.47 mm (1.0-3.3 mm), and 1.9 ± 0.39 mm (1.0-3.0 mm) in diameter, respectively. In contrast, the diameter of the posterior branch arising in the segment of origin of the great anterior radiculomedullary artery, with a diameter of 2.8 ± 0.71 mm (1.4-5.6 mm), showed a statistically significantly wider lumen compared with any other of the evaluated posterior branches (p < 0.0001) (Fig. 5).
|
|
|
|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
Within this interconnected longitudinal anastomosing system, the blood flow is not unidirectional but can be observed to be directed cranially and caudally. Usually, radiculomedullary arteries supply a limited territory related to the nerve roots; however, not all intercostal and lumbar arteries have radiculomedullary feeders. In contrast, the great anterior radiculomedullary artery is characterized functionally by a significantly extended supplied territory and morphologically by a specific course of the ascending branch and the hairpin turn [17, 18].
The venous drainage of the spinal cord does not parallel the arterial supply and relies on radially symmetric intrinsic spinal cord veins, which in turn drain into the longitudinal median spinal cord vein before reaching the epidural plexus via the radicular veins [19]. Of importance is the extent of interconnections in this venous system and the fact that the median spinal cord vein, transforming into a radicular vein, shows the same hairpin shape as the artery of Adamkiewicz [17].
Three unique morphologic and functional vascular characteristics of the intrinsic spinal vasculature directly affect the method of visualization: the location of the spinal vasculature in the spinal canal surrounded by high-density skeletal formations; the bidirectional flow along its longitudinal course; and the extensive venous anastomoses, resembling spinal arteries in contrast enhancement and morphology. A similar anatomic arrangement and functionally small imaging window for solitary arterial vascular visualization without venous contamination can be found in the brain. Optimized interactions of selected image acquisition parameters, timing of contrast bolus application, and choice of image reconstruction algorithms allow successful visualization of the cerebral vasculature [20, 21].
The hypothesis that contrast-enhanced MDCT angiography can depict the artery of Adamkiewicz if high-resolution image acquisition and brain reconstruction techniques are used can be accepted because in all 100 patients examined the great anterior radiculomedullary artery was identified as a continuous vascular tract extending from an intercostal or lumbar artery via the radiculomedullary artery to the anterior spinal artery by its ascent to the midsagittal surface of the spinal cord and its characteristic hairpin turn.
Numerous vascular conditions, in combination with inherent deficiencies in collateral blood supply to the spinal cord and the iatrogenic exclusion of critical intercostal or lumbar arteries, might culminate in ischemia of the spinal cord. Therefore, spinal cord ischemia might present as a de novo symptom [22] as well as after surgical aortic repair [23]. However, the thoracolumbar region of the spinal cord is at increased risk for ischemia or infarction during periods of hypoperfusion not only because of the vascular supply: The cross-sectional area of gray matter has been histopathologically proven to be greatest in the thoracolumbar segment of the spinal cord, which also results in higher metabolic demands [23]. Spinal cord ischemia is a complex multifactorial event. Therefore, vascular mapping of the artery of Adamkiewicz is important in reducing the risk of de novo or postinterventional spinal cord ischemia, which presents clinically as paraplegia or paraparesis, disturbances of urination and defecation, and impairment of pain and temperature sensations.
Spinal cord angiography, performed with selective catheterization of the intercostal and lumbar arteries, has been the gold standard for four decades. However, a success rate of not more than 75% in locating the origin and course of the great anterior radiculomedullary artery and a frequency of up to 4.6% for neurologic complications have characterized this procedure as technically difficult and risky [24]. In patients in whom the artery of Adamkiewicz was not identified angiographically, an adequate collateral circulation and subsequent hypoplasia of the great anterior radiculomedullary artery were assumed [24].
MR angiography was able to depict the artery of Adamkiewicz in only 67% of patients in a recent study [14]. Investigating the vascular continuity of the aorta, intercostal artery, radiculomedullary artery, artery of Adamkiewicz, and anterior spinal artery, a continuous vessel tract was depicted in 85% in these patients compared with only 62.5% if CTA without an optimized reconstruction algorithm was used [14]. However, MR angiography is not only able to depict the collateral pathways of the artery of Adamkiewicz in patients with thoracoabdominal aneurysm, it can also supply vital information about the integrity and morphology of the spinal cord and surrounding dura [14].
In contrast, 40-MDCT technology, using a spatial resolution of 0.005 mm3 voxel volume in combination with an adapted brain reconstruction algorithm, allowed the successful temporal visualization of a sharply demarcated contrast bolus in the arterial spinal vasculature without venous contamination in all examined patients. Our study showed that millimeter-sized vasculature located in the spinal canal can be successfully delineated when image acquisition and reconstruction parameters, in combination with contrast bolus timing, are adapted to the special requirements necessitated by location, bidirectional flow, and the extensive anastomoses.
The asymmetric origin of the artery of Adamkiewicz, with a propensity to be supplied by left-sided radiculomedullary arteries and to have variations in length and diameter, was in agreement with the results of an autopsy study [25]. Prior studies have proven that intercostal or lumbar arteries at the vertebral segment of origin did not present with a significantly wider luminal diameter [23]. However, our study has shown that the further distal feeding posterior branch of the intercostal or lumbar arteries indeed is characterized by a significantly wider diameter than its ipsilateral and contralateral neighbors. Therefore, identification of origin and hairpin using the described methods of multiplanar reformation and vascular assessment along the diameter could accelerate the identification of the artery of Adamkiewicz.
Duplications of the artery of Adamkiewicz presented with variations of ipsilateral and bilateral origins, thereby emphasizing the importance of extensive mapping of the entire spinal cord blood supply to further reduce the frequency of neurologic complications.
Our study had limitations that must be addressed. First, our study was not validated against any imaging gold standard. The currently accepted gold standard, spinal angiography, is known to be a technically difficult and risky procedure compared with CTA. Therefore, definitive validation of arterial versus venous contrast enhancement cannot be provided by MDCT angiography. Second, the visualized longitudinal scanning volume from the eighth thoracic to the third lumbar vertebrae prohibited visualization of the duplicated great anterior radiculomedullary arteries at levels above and below those segments [24, 26]. Third, MDCT cannot show the spinal cord and the surrounding dura to the extent that MRI can for depicting its integrity and morphology. Furthermore, MRI allows precise definition of the imaged anatomic compartments and their characteristic vasculature. Finally, significant radiation exposure due to high-resolution MDCT cannot be avoided, even though adaptive dose modulation techniques were used.
In conclusion, contrast-enhanced CTA can depict the artery of Adamkiewicz and its anatomic variants using 40-MDCT technology in combination with an adapted brain reconstruction algorithm.
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  R. J. Nijenhuis and W. H. Backes Inlet Arteries or Outlet Veins of the Spinal Cord? Am. J. Roentgenol., July 1, 2007; 189(1): W45 - W45. [Full Text] [PDF]
|
|
|
|
|
|
D. T. Boll Reply Am. J. Roentgenol., July 1, 2007; 189(1): W46 - W46. [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
