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DOI:10.2214/AJR.07.2428
AJR 2007; 189:966-972
© American Roentgen Ray Society

Original Research

Dark-Blood MRI of the Thoracic Aorta with 3D Diffusion-Prepared Steady-State Free Precession: Initial Clinical Evaluation

Ioannis Koktzoglou1,2,3, Anish Kirpalani1,4, Timothy J. Carroll1,2, Debiao Li1,2 and James C. Carr1

1 Department of Radiology, Northwestern University Feinberg School of Medicine, 448 E Ontario St., Suite 700, Chicago, IL 60611.
2 Department of Biomedical Engineering, Northwestern University McCormick School of Engineering, Chicago, IL.
3 Present address: Department of Radiology, Evanston Northwestern Healthcare, Walgreen Jr. Bldg., 2650 Ridge Ave., Suite G507, Evanston, IL 60201.
4 Present address: Texas Radiology Associates, Plano, TX.

Received January 30, 2007; revised April 25, 2007;

 
Address correspondence to J. C. Carr (jcarr{at}northwestern.edu).

Address correspondence to I. Koktzoglou (i-koktzoglou{at}northwestern.edu).


Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
OBJECTIVE. The purpose of this study was to compare the performance of 3D diffusion-prepared balanced steady-state free precession (SSFP) imaging with that of 3D contrast-enhanced MR angiography in evaluation of the thoracic aorta.

MATERIALS AND METHODS. Twenty-one patients with indications for contrast-enhanced MR angiography and diffusion-prepared SSFP of the thoracic aorta were involved in this retrospective chart review study conducted with 1.5-T MRI. Two observers scored the quality of the contrast-enhanced MR angiographic and diffusion-prepared SSFP images on the basis of depicting the thoracic aorta. Image quality scores and diametric measurements of the aorta from both image sets were compared.

RESULTS. Diametric measurements of the thoracic aorta showed a strong linear association (r = 0.971, p < 0.0001; regression line indifferent from line of equality, p < 0.05). The aortic root was better visualized with contrast-enhanced MR angiography (image quality score, 3.6 ± 0.9 vs 3.0 ± 0.8 of 5; p < 0.05); however, the aortic wall was better visualized with diffusion-prepared SSFP (image quality score, 4.4 ± 0.6 vs 1.9 ± 0.3 of 5; p < 0.0001).

CONCLUSION. Three-dimensional diffusion-prepared SSFP yields better image quality than 3D contrast-enhanced MR angiography in evaluation of the thoracic aortic wall and appears to be a useful adjunct to 3D contrast-enhanced MR angiography for assessing aortic abnormalities before administration of a contrast agent.

Keywords: 3D imaging • dark-blood imaging • MR angiography • thoracic aorta • vascular wall imaging


Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Blood-suppressed (dark-blood) MRI is a useful technique for depicting the morphologic features of the heart and great vessels [1]. Dark-blood MRI of the aorta has shown value in the assessment of vasculitis [2, 3], dissection [3–5], coarctation [6], aneurysmal disease [3, 7], and atherosclerosis [8, 9]. In the early 1980s, dark-blood MRI contrast was encountered on spin-echo methods with long echo times due to outflow of blood from the imaging section excited by the sequence [10, 11]. Since then, substantial technical advancements include the introduction of blood-suppressing magnetization preparations [12, 13] and time-efficient multiple spin-echo methods [14–16]. However, most sequences used for dark-blood MRI of the aorta are 2D [17], which renders them susceptible to partial volume artifacts over the thickness of the section (5-mm-thick sections are common during aortic imaging) and compromises aortic coverage when sections are positioned perpendicular to the direction of aortic blood flow.

Three-dimensional dark-blood MRI may allow for improved slice resolution and more intuitive display of the thoracic aorta relative to 2D methods. Three-dimensional arterial wall MRI techniques using conventional inflow-dependent dark-blood preparations are limited by suboptimal blood signal suppression. Diffusion-prepared segmented balanced steady-state free precession (SSFP) has been proposed [18] as an MRI technique that allows 3D dark-blood imaging. Because it relies on blood motion rather than inflow to suppress MRI signal intensity from blood, the 3D diffusion-prepared SSFP technique may be useful for time-efficient blood-suppressed MRI of the entire thoracic aorta in a sagittal oblique plane. From a clinical perspective, the 3D diffusion-prepared SSFP technique may be used to assess disease of the thoracic aortic wall and may be a useful adjunct to 3D contrast-enhanced MR angiography of the aorta. In this article, we compared 3D diffusion-prepared SSFP dark-blood angiography with 3D contrast-enhanced MR angiography in evaluation of the thoracic aorta.


Figure 1
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  		Fig. 1 —Sequence diagram for 3D diffusionprepared steady-state free precession (SSFP) sequence. Prospective ECG gating is used with data acquisition during diastole. Diffusion and fat-saturation preparations are applied before segmented 3D SSFP acquisition. Center-out phase encoding is used to achieve dark appearance of blood and fat.

 


Figure 2
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  		Fig. 2A —82-year-old man with suspected aortic dissection. Axial localizer MR image shows left anterior oblique slab orientation through thoracic aorta acquired with 3D diffusion-prepared steady-state free precession and 3D contrast-enhanced MR angiography sequences.

 


Figure 3
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  		Fig. 2B —82-year-old man with suspected aortic dissection. MR angiogram shows locations of orthogonal dimension measurements. 1 = sinotubular junction, 2 = mid ascending aorta, 3 = proximal aortic arch, 4 = distal aortic arch.

 

Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Patient Population
After institutional review board approval, we performed a retrospective review of the charts of patients with indications for MR angiography of the thoracic aorta at our medical center between October 2005 and January 2006. A total of 21 patients (13 men, eight women; age range, 28–84 years) were included in the study. Each patient underwent both 3D diffusion-prepared SSFP angiography before gadolinium administration and conventional 3D contrast-enhanced MR angiography. The cohort consisted of outpatients with suspected or known aortic lesions and patients with acute aortic disease and contraindications to CT, such as renal dysfunction. Indications for MRI examinations included suspected or known aortic aneurysm (n = 15), postoperative follow-up of repaired aneurysm (n = 1), suspected aortic dissection (n = 2), suspected vasculitis (n = 2), and assessment of aortic involvement of vascular tumor (n =1).

MRI Techniques
All patients underwent imaging with a 1.5-T whole-body MRI system (Avanto, Siemens Medical Solutions). Signal reception was performed with a four-channel phased-array coil placed over the patient's chest and with an eight-channel phased-array spinal coil. Prospective ECG gating was used for the 3D diffusion-prepared SSFP sequence, and retrospective ECG gating [19] was used for the 3D contrast-enhanced MR angiographic sequence. All patients underwent a conventional cardiac MRI examination in addition to diffusion-prepared SSFP and contrast-enhanced MR angiographic sequences.

Before administration of the contrast agent, the ECG-gated 3D diffusion-prepared SSFP examination was performed under free-breathing conditions. This sequence consisted of a segmented 3D SSFP data acquisition period preceded by a chemically selective fat-saturation pulse to suppress the signal intensity of perivascular fat and by a driven equilibrium Fourier transform preparation coupled with diffusion gradients [20–22] to suppress the signal intensity of the moving blood (Fig. 1). Imaging parameters for the 3D diffusion-prepared SSFP sequence were as follows: left anterior oblique orientation (Fig. 2A); prospective ECG gating with imaging performed 450 milliseconds after the ECG R-wave; TR/TE, 3.7/1.9; flip angle, 45°; field of view (read x phase x slice), 281 x 202 x 40 mm; imaging matrix size, 256 x 184 x 20; voxel size, 1.1 x 1.1 x 2.0 mm; slice oversampling, 20%; diffusion coefficient b value, 1.91 s/mm2; receiver bandwidth, 980 Hz/pixel; number of echoes per heartbeat, 71; generalized autocalibrating partially parallel acquisition [23] acceleration factor of 2 with 70 autocalibration k-space lines; number of signals averaged, 2; acquisition time, 96 heartbeats.

The contrast-enhanced MR angiographic portion of the study was performed in a manner similar to that described previously [24]. Gadopentetate dimeglumine (Magnevist, Berlex) was administered in an antecubital vein with an MRI-compatible power injector (Spectris, Medrad). Before acquisition of the MR angiogram, a timing run was performed with a 2-mL bolus of gadopentetate dimeglumine (flow rate, 2 mL/s). During this run, a sagittal oblique slice positioned along the long axis of the thoracic aorta was acquired repetitively with a 2D fast low-angle shot (FLASH) sequence. The transit time for the contrast agent to the reach the aortic root was recorded. After the timing run, contrast-enhanced MR angiography with a 3D FLASH sequence was performed under an end-inspiratory breath-hold at injection of contrast agent at a dose of 0.2 mmol/kg (flow rate, 2 mL/s). Before arrival of contrast agent to the aorta, an unenhanced 3D FLASH image set was acquired and subtracted from the contrast-enhanced 3D FLASH image set to eliminate background signal intensity. Parameters for the 3D contrast-enhanced MR angiographic sequence were as follows: left anterior oblique projection through the thoracic aorta; 2.8/1.4; flip angle, 20°; field of view (read x phase x slice), 380 x 285 x 90 mm; imaging matrix size, 256 x 155 x 56 (interpolated to 512 x 310 x 56); acquired voxel size, 1.5 x 1.8 x 1.6 mm; 6/8th partial Fourier; generalized autocalibrating partially parallel acquisition acceleration factor of 2 with 24 autocalibration k-space lines; retrospective reconstruction of images acquired in diastole [24]; acquisition time, 20 seconds.

Quantitative Measurements
On a 3D postprocessing workstation (Leonardo, Siemens Medical Solutions), multiplanar reformations of the thoracic aorta were constructed for both the contrast-enhanced MR angiographic and diffusion-prepared SSFP examinations. For each examination of every patient, the orthogonal pairs of aortic luminal diameter were measured at four distinct locations (Fig. 2B) by an observer with 2 years of cardiovascular MRI experience. The locations were the sinotubular junction, mid ascending aorta (at the level of the main pulmonary artery), proximal aortic arch (at the level of the innominate artery), and distal aortic arch (distal to the left subclavian artery). To minimize recall bias, aortic diameter measurements were first obtained from the contrast-enhanced MR angiographic image sets for all 21 patients. Only afterward were diameter measurements obtained from the diffusion-prepared SSFP image sets. In total, 168 individual measurements of aortic diameter were obtained from the 21 patients who underwent imaging with each technique (four measurement pairs per patient).

Qualitative Measurements
The contrast-enhanced MR angiograms and diffusion-prepared SSFP images for each of the 21 patients were reviewed by two blinded independent observers with 2 and 8 years of cardiovascular MRI experience. After all image sets (contrast-enhanced MR angiography and diffusion-prepared SSFP) were randomized, the two observers scored the image quality of each set on the basis for assessing the aortic root, ascending aorta, aortic arch, aortic lumen, aortic wall, and pathologic findings. Qualitative assessments were scored on the following five-point scale: 1, image quality inadequate for diagnosis; 2, poor image quality; 3, fair image quality; 4, good image quality; 5, excellent image quality. At review of each image set, a diagnosis was made by each reviewer independently. The presence or absence of pathologic findings was recorded for each imaging technique and observer. A final diagnosis was made by consensus between reviewers.

Statistical Analysis
Statistical analysis was performed with two statistical software programs (Systat, version 10.2, Systat Software; SPSS version 11.0, SPSS). The quantitative measurements of aortic diameter made from the 3D contrast-enhanced MR angiographic and 3D diffusion-prepared SSFP images were compared by calculation of the intraclass correlation coefficient, linear regression analysis, and the method of Bland and Altman [25]. After qualitative scores for both observers were averaged, scores achieved with 3D contrast-enhanced MR angiography and 3D diffusion-prepared SSFP MRI were compared by use of Wilcoxon's signed ranked test. For all tests, statistical significance was defined at the p < 0.05 level. In all linear regression analyses, power analysis at the 5% level of significance was performed to verify the acceptability of the statistical results. Any power 0.8 or greater was considered acceptable.


Results
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 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Imaging Findings
Six of the 21 patients in the study had normal findings (Table 1). The diagnoses in the remaining patients were ascending aortic aneurysm (n = 9) (Fig. 3A, 3B), aortic ectasia (n =2), ulcerative atherosclerotic plaque (n =1) (Fig. 4A, 4B), aortic sarcoma (n = 1) (Fig. 5A, 5B), and giant cell arteritis (n = 1) (Fig. 6A, 6B, 6C). The fifteenth patient was being observed after repair of an aortic aneurysm.


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  		TABLE 1: Identification of Lesions and Normal Findings with Contrast-Enhanced MR Angiographic and Diffusion-Prepared Steady-State Free Precession (SSFP) Techniques

 

Figure 4
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  		Fig. 3A —54-year-old man with suspected aortic aneurysm. Left anterior oblique diffusion-prepared steady-state free precession (SSFP) MR image shows fusiform ascending aortic aneurysm (arrow). Given that diffusion-prepared SSFP imaging was performed under free-breathing conditions, faint striplike artifact present near arrowhead is likely ghost arising from anterior chest wall. Mean image quality score for aortic wall is 5 (lumen, 3).

 

Figure 5
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  		Fig. 3B —54-year-old man with suspected aortic aneurysm. Contrast-enhanced MR angiogram shows fusiform ascending aortic aneurysm. Mean image quality score for aortic wall is 1 (lumen, 4).

 

Figure 6
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  		Fig. 4A —84-year-man with suspected aortic dissection. (Reprinted with permission from Kirpalani A, Koktzoglou I, Dill K, Carroll T, Li D, Carr J. Diffusion-weighted 3D dark blood SSFP imaging of the thoracic aorta: initial clinical evaluation. Proceedings of the International Society of Magnetic Resonance in Medicine. Seattle, WA: ISMRM, 2006:651 [26]) Left anterior oblique diffusion-prepared steady-state free precession MR image shows irregular and ulcerative atherosclerotic plaque (arrow) in descending thoracic aorta. Morphologic features of plaque are better appreciated than in B. Inset shows 3D axial image through plaque (arrow). Mean image quality score for aortic wall is 5 (lumen, 4).

 

Figure 7
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  		Fig. 4B —84-year-man with suspected aortic dissection. (Reprinted with permission from Kirpalani A, Koktzoglou I, Dill K, Carroll T, Li D, Carr J. Diffusion-weighted 3D dark blood SSFP imaging of the thoracic aorta: initial clinical evaluation. Proceedings of the International Society of Magnetic Resonance in Medicine. Seattle, WA: ISMRM, 2006:651 [26]) Contrast-enhanced MR angiogram shows irregular and ulcerative atherosclerotic plaque in descending thoracic aorta. Mean image quality score for aortic wall is 2.5 (lumen, 4.5).

 

Figure 8
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  		Fig. 5A —46-year-old woman with suspected aortic involvement of vascular tumor. Left anterior oblique diffusion-prepared steady-state free precession MR image shows invasive mass (arrows) eroding through anterior wall of descending thoracic aorta. Insets correspond to adjacent slices within 3D slab. Extent of vessel wall involvement is better appreciated than in B. Mean image quality score for aortic wall is 5 (lumen, 4).

 

Figure 9
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  		Fig. 5B —46-year-old woman with suspected aortic involvement of vascular tumor. Contrast-enhanced MR angiogram shows invasive mass eroding through anterior wall of descending thoracic aorta. Mean image quality score for aortic wall is 1.5 (lumen, 4.5).

 

Figure 10
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  		Fig. 6A —59-year-old woman with suspected vasculitis. Left anterior oblique diffusion-prepared steady-state free precession MR image shows diffuse thickening of aortic wall, which led to diagnosis of giant cell arteritis. Biopsy of temporal artery confirmed diagnosis. Mean image quality score for aortic wall is 5 (lumen, 4.5).

 

Figure 11
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  		Fig. 6B —59-year-old woman with suspected vasculitis. Contrast-enhanced MR angiogram shows normal appearance. Mean image quality score for aortic wall is 2 (lumen, 2.5).

 

Figure 12
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  		Fig. 6C —59-year-old woman with suspected vasculitis. Coronal maximum intensity projection of time-resolved MR angiogram shows bilateral subclavian stenosis and further implicates vasculitic involvement.

 

Quantitative Measurements
Figure 7A shows the orthogonal measurements of aortic diameter made with 3D diffusion-prepared SSFP and 3D contrast-enhanced MR angiography. A strong linear relation (r = 0.971; p < 0.0001) and correlation (intraclass correlation coefficient, 0.969; p < 0.0001) between measurements were observed. The linear regression equation was y =1.018x – 0.09, where y and x denote measurements of aortic diameter made from the diffusion-prepared SSFP and contrast-enhanced MR angiographic image sets. Ninety-five percent CIs for the slope and y-intercept were 0.980–1.056 and –0.208–0.029, indicating the equation did not significantly differ from the line of equality (slope = 1, y-intercept = 0) (p < 0.05). Bland-Altman analysis (Fig. 7B) revealed the mean difference in aortic diameter (diffusion-prepared SSFP minus contrast-enhanced MR angiography) between techniques was –0.344 mm, with a slight but insignificant positive bias (r = 0.195; p = 0.09 at a statistical power of 0.8).


Figure 13
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  		Fig. 7A —Aortic diameter measurements with 3D diffusion-prepared steady-state free precession (SSFP) MRI and contrast-enhanced MR angiography. Scatterplot shows linear relation (r = 0.971, power > 0.99, p < 0.05) between 3D diffusion-prepared SSFP and contrast-enhanced MR angiographic measurements. Regression line slope, 1.018; intercept, –0.089. Intraclass correlation coefficient, 0.969 (p < 0.0001).

 

Figure 14
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  		Fig. 7B —Aortic diameter measurements with 3D diffusion-prepared steady-state free precession (SSFP) MRI and contrast-enhanced MR angiography. Bland-Altman plot shows limits of agreement. For difference (diffusion-prepared SSFP minus contrast-enhanced MR angiography) in aortic diameter measured with both techniques, 95% CI is –0.349 to 0.280 cm. At statistical power of 0.8, no significant bias is detected. Bias line slope, 0.048; intercept, –0.180; r = 0.195; p = 0.09.

 

Qualitative Measurements
Results for the qualitative measurements are shown in Table 2. Comparison of the two techniques by the two observers showed no significant difference between the techniques in assessment of the aortic lumen (p > 0.05); average observer scores were 3.81 of 5 for diffusion-prepared SSFP and 4.12 of 5 for contrast-enhanced MR angiography. There was, however, a significant difference between the techniques in assessment of the aortic wall (p < 0.001); average observer scores were 4.36 of 5 for diffusion-prepared SSFP and 1.86 of 5 for contrast-enhanced MR angiography. At the aortic root, the mean image quality score of contrast-enhanced MR angiography was better than that of diffusion-prepared SSFP MRI (3.56 vs 3.0, p < 0.05). In the ascending aorta and aortic arch, however, no significant differences in image quality between techniques were present (p >0.05 for both locations).


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  		TABLE 2: Mean Qualitative Image Quality Scores

 

Detection of Abnormalities
Contrast-enhanced MR angiography was considered the reference standard for assessment of aortic lesions in this analysis. Solely on the basis of contrast-enhanced MR angiographic findings, 14 of the 21 patients were deemed to have aortic abnormalities, and seven patients were deemed healthy. Diffusion-prepared SSFP images depicted abnormalities in the same 14 patients deemed to have abnormal findings on contrast-enhanced MR angiography. In one of the seven patients with normal findings on contrast-enhanced MR angiography, diffuse thickening of the aortic wall was found on the diffusion-prepared SSFP images (Fig. 6A, 6B, 6C). In this patient, giant cell arteritis was diagnosed and confirmed with biopsy of the temporal artery.


Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
Blood-suppressed MRI appears to be a useful approach to locating pathologic changes in the aortic wall. We evaluated a 3D dark-blood SSFP-based imaging sequence (diffusion-prepared SSFP) for assessment of the thoracic aorta in a cohort of patients referred for contrast-enhanced MR angiography. Measurements of aortic diameter obtained from the contrast-enhanced MR angiographic and diffusion-prepared SSFP image sets were strongly correlated and differed, on average, by approximately one third of a millimeter. In particular, good agreement between sequences was observed for aortic diameters greater than 4 cm. These findings suggest that 3D diffusion-prepared SSFP may be an alternative to 3D contrast-enhanced MR angiography for measuring normal and aneurysmal aortic diameters. However, relative to contrast-enhanced MR angiography, the diffusion-prepared SSFP image sets had lower image quality scores for depicting the aortic root.

We suspect the degradation of the aortic root on the diffusion-prepared SSFP images may have been caused by increased motion of the aortic root in relation to other portions of the aorta due to use of a motion-sensitizing diffusion preparation. Nevertheless, diffusion-prepared SSFP MRI had significantly higher scores than contrast-enhanced MR angiography for depicting the aortic wall. Better delineation of the aortic wall with diffusion-prepared SSFP relative to contrast-enhanced MR angiography was not unexpected because the latter MRI technique is luminographic. An important finding was that diffusion-prepared SSFP images depicted the pathologic changes in all 14 patients deemed to have abnormalities on the basis of the contrast-enhanced MR angiographic findings.

Although it is increasingly considered the reference standard MRI technique for assessing diseases involving the aortic lumen, contrast-enhanced MR angiography is less efficient at depicting the vessel wall. Diffusion-prepared SSFP, on the other hand, is superior for depicting the vessel wall. This quality is of particular importance for diagnosis of conditions confined to the aortic wall, such as vasculitis, intramural hematoma, and atherosclerotic ulceration. In our study, the only case of vasculitis, which was missed on contrast-enhanced MR angiography, was detected with the diffusion-prepared SSFP technique. Because the diffusion-prepared SSFP method provides information regarding the arterial wall that may be complementary to that provided by contrast-enhanced MR angiography, we believe it to be a useful adjunct to contrast-enhanced MR angiography for evaluating and characterizing diseases of the thoracic aorta. Although 2D rather than 3D wall imaging can complement contrast-enhanced MR angiography, the contrast-to-noise ratio between aortic wall and lumen of 3D diffusion-prepared SSFP for a given voxel volume and acquisition time reportedly is better than that of 2D methods [18]. Furthermore, 3D image sets permit retrospective reformatting of the image data for depicting pathology along arbitrary planes.

This study had limitations. First, the number of patients was rather small. Further assessment of the diffusion-prepared SSFP technique in comparison with contrast-enhanced MR angiography in a larger cohort of patients is warranted. Second, the diffusion-prepared SSFP imaging sequence was performed under free-breathing conditions without use of breathhold or respiratory-compensation techniques. To improve image quality, future implementations of the diffusion-prepared SSFP technique may incorporate motion-tracking methods (e.g., a navigator) to reduce or compensate for respiratory motion. An alternative approach may be to eliminate respiratory motion altogether by shortening the acquisition time to the duration of a breath-hold with use of higher parallel imaging acceleration factors or other fast imaging strategies. Third, the diffusion b value used for diffusion-prepared SSFP imaging was fixed throughout the study to allow routine use of the sequence with little or no setup. Although the b value used was observed sufficient to suppress intraluminal blood signal intensity and delineate the arterial wall, optimization of this value on a patient-to-patient basis may improve image quality with diffusion-prepared SSFP.

In conclusion, the dark-blood method of 3D diffusion-prepared SSFP depicts the thoracic aortic wall better than 3D contrast-enhanced MR angiography and appears to be a useful adjunct to contrast-enhanced MR angiography for assessing the thoracic aorta.


References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Higgins CB. Overview of MR of the heart: 1986. AJR 1986; 146:907 –918[Abstract/Free Full Text]
  2. Atalay MK, Bluemke DA. Magnetic resonance imaging of large vessel vasculitis. Curr Opin Rheumatol 2001;13 : 41–47[CrossRef][Medline]
  3. Amparo EG, Higgins CB, Hoddick W, et al. Magnetic resonance imaging of aortic disease: preliminary results. AJR1984; 143:1203 –1209[Abstract/Free Full Text]
  4. Amparo EG, Higgins CB, Hricak H, Sollitto R. Aortic dissection: magnetic resonance imaging. Radiology1985; 155:399 –406[Abstract/Free Full Text]
  5. Geisinger MA, Risius B, O'Donnell JA, et al. Thoracic aortic dissections: magnetic resonance imaging. Radiology1985; 155:407 –412[Abstract/Free Full Text]
  6. Amparo EG, Higgins CB, Shafton EP. Demonstration of coarctation of the aorta by magnetic resonance imaging. AJR1984; 143:1192 –1194[Free Full Text]
  7. Lee JK, Ling D, Heiken JP, et al. Magnetic resonance imaging of abdominal aortic aneurysms. AJR 1984;143 :1197 –1202[Abstract/Free Full Text]
  8. Kaufman L, Crooks L, Sheldon P, Hricak H, Herfkens R, Bank W. The potential impact of nuclear magnetic resonance imaging on cardiovascular diagnosis. Circulation 1983;67 : 251–257[Abstract/Free Full Text]
  9. Herfkens RJ, Higgins CB, Hricak H, et al. Nuclear magnetic resonance imaging of atherosclerotic disease. Radiology 1983;148 : 161–166[Abstract/Free Full Text]
  10. Axel L. Blood flow effects in magnetic resonance imaging. AJR 1984; 143:1157 –1166[Free Full Text]
  11. Bradley WG Jr, Waluch V, Lai KS, Fernandez EJ, Spalter C. The appearance of rapidly flowing blood on magnetic resonance images. AJR 1984; 143:1167 –1174[Abstract/Free Full Text]
  12. Felmlee JP, Ehman RL. Spatial presaturation: a method for suppressing flow artifacts and improving depiction of vascular anatomy in MR imaging. Radiology 1987;164 : 559–564[Abstract/Free Full Text]
  13. Edelman RR, Chien D, Kim D. Fast selective black blood MR imaging. Radiology 1991;181 : 655–660[Abstract/Free Full Text]
  14. Hennig J, Nauerth A, Friedburg H. RARE imaging: a fast imaging method for clinical MR. Magn Reson Med1986; 3:823 –833[Medline]
  15. Simonetti OP, Finn JP, White RD, Laub G, Henry DA. "Black blood" T2-weighted inversion-recovery MR imaging of the heart. Radiology 1996;199 : 49–57[Abstract/Free Full Text]
  16. Gaa J, Fischer H, Laub G, Georgi M. Breath-hold MR imaging of focal liver lesions: comparison of fast and ultrasound techniques. Eur Radiol 1996; 6:838 –843[Medline]
  17. Fayad ZA, Nahar T, Fallon JT, et al. In vivo magnetic resonance evaluation of atherosclerotic plaques in the human thoracic aorta: a comparison with transesophageal echocardiography. Circulation 2000;101 :2503 –2509[Abstract/Free Full Text]
  18. Koktzoglou I, Li D. Diffusion-prepared segmented steady-state free precession: application to 3D black-blood cardiovascular magnetic resonance of the thoracic aorta and carotid artery walls. J Cardiovasc Magn Reson 2007; 9:33 –42[CrossRef][Medline]
  19. Lenz GW, Haacke EM, White RD. Retrospective cardiac gating: a review of technical aspects and future directions. Magn Reson Imaging 1989; 7:445 –455[CrossRef][Medline]
  20. Okada Y, Ohtomo K, Kiryu S, Sasaki Y. Breathhold T2-weighted MRI of hepatic tumors: value of echo planar imaging with diffusion-sensitizing gradient. J Comput Assist Tomogr 1998;22 : 364–371[CrossRef][Medline]
  21. Sirol M, Itskovich VV, Mani V, et al. Lipid-rich atherosclerotic plaques detected by gadofluorine-enhanced in vivo magnetic resonance imaging. Circulation 2004;109 :2890 –2896[Abstract/Free Full Text]
  22. Koktzoglou I, Harris KR, Tang R, et al. Gadofluorine-enhanced magnetic resonance imaging of carotid atherosclerosis in Yucatan miniswine. Invest Radiol 2006;41 : 299–304[CrossRef][Medline]
  23. Griswold MA, Jakob PM, Heidemann RM, et al. Generalized autocalibrating partially parallel acquisitions (GRAPPA). Magn Reson Med 2002; 47:1202 –1210[CrossRef][Medline]
  24. Groves EM, Bireley W, Dill K, Carroll TJ, Carr JC. Quantitative analysis of ECG-gated high-resolution contrast-enhanced MR angiography of the thoracic aorta. AJR 2007;188 : 522–528[Abstract/Free Full Text]
  25. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet1986; 1:307 –310[CrossRef][Medline]
  26. Kirpalani A, Koktzoglou I, Dill K, Carroll T, Li D, Carr J. Diffusion-weighted 3D dark blood SSFP imaging of the thoracic aorta: initial clinical evaluation. Proceedings of the International Society of Magnetic Resonance in Medicine. Seattle, WA: ISMRM,2006 : 651

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