The aims of this study were to evaluate the effectiveness of low-dose, contrast-enhanced (CE), time-resolved, three-dimensional magnetic resonance angiography (MRA) in the assessment of the abdominal ...aorta and its major branches at 3 T and to compare the results with those of high-spatial resolution CE MRA.
Twenty-two consecutive patients (eight men, 14 women; mean age, 43.9 +/- 17.9 years) underwent CE time-resolved three-dimensional MRA and high-spatial resolution three-dimensional MRA. Studies were performed using a 3-T magnetic resonance system; gadolinium-based contrast medium was administered at a dose of 3 to 5 mL for time-resolved MRA, followed by 0.1 mmol/kg gadopentetate dimeglumine for single-phase CE MRA. For analysis purposes, the abdominal arterial system was divided into 11 arterial segments, and image quality as well as the presence and degree of vascular pathology were evaluated by two independent magnetic resonance radiologists.
A total of 242 arterial segments were visualized with good image quality. Time-resolved MRA was able to visualize the majority of arterial segments with good definition in the diagnostic range. Vascular pathologies (stenosis, occlusion) or abnormal vascular anatomy was detected in 19 arterial segments, with good interobserver agreement (kappa = 0.78). All image findings were detected with time-resolved CE MRA by both observers and were confirmed by correlative imaging.
Low-dose, time-resolved MRA at 3 T yields rapid and important anatomic and functional information in the evaluation of the abdominal vasculature. Because of its limited spatial resolution, time-resolved MRA is inferior to CE MRA in demonstrating fine vascular details.
Objectives
The purpose of this study was to determine the image quality and diagnostic accuracy of three-dimensional (3D) unenhanced steady state free precession (SSFP) magnetic resonance angiography ...(MRA) for the evaluation of thoracic aortic diseases.
Methods
Fifty consecutive patients with known or suspected thoracic aortic disease underwent free-breathing ECG-gated unenhanced SSFP MRA with non-selective radiofrequency excitation and contrast-enhanced (CE) MRA of the thorax at 1.5 T. Two readers independently evaluated the two datasets for image quality in the aortic root, ascending aorta, aortic arch, descending aorta, and origins of supra-aortic arteries, and for abnormal findings. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were determined for both datasets. Sensitivity, specificity, and diagnostic accuracy of unenhanced SSFP MRA for the diagnosis of aortic abnormalities were determined.
Results
Abnormal aortic findings, including aneurysm (
n
= 47), coarctation (
n
= 14), dissection (
n
= 12), aortic graft (
n
= 6), intramural hematoma (
n
= 11), mural thrombus in the aortic arch (
n
= 1), and penetrating aortic ulcer (
n
= 9), were confidently detected on both datasets. Sensitivity, specificity, and diagnostic accuracy of SSFP MRA for the detection of aortic disease were 100% with CE-MRA serving as a reference standard. Image quality of the aortic root was significantly higher on SSFP MRA (
P
< 0.001) with no significant difference for other aortic segments (
P
> 0.05). SNR and CNR values were higher for all segments on SSFP MRA (
P
< 0.01).
Conclusion
Our results suggest that free-breathing navigator-gated 3D SSFP MRA with non-selective radiofrequency excitation is a promising technique that provides high image quality and diagnostic accuracy for the assessment of thoracic aortic disease without the need for intravenous contrast material.
Objectives
High resolution MRI of the intracranial vessel wall provides important insights in the assessment of intracranial vascular disease. This study aims to refine high resolution 3D MRI ...techniques for intracranial vessel wall imaging at both 3 and 7 T using customized flip angle train design, and to explore their comparative abilities.
Materials and methods
11 patients with intracranial artery disease (four atherosclerotic plaques, six aneurysms and one reversible cerebral vasoconstriction syndrome) were imaged at 3 and 7 T with a 3D
T
1
-weighted fast-spin-echo sequence (SPACE) both pre and post Gd contrast injection. Wall to lumen contrast ratio (CR
wall-lumen
), contrast enhancement ratio (ER) and the sharpness of the vessel wall were quantified. Two experienced radiologists evaluated the image quality on a 0–5 scale.
Results
Both 3 and 7 T achieved good image quality with high resolution (nominal 0.5 mm isotropic) and whole brain coverage. The CR
wall-lumen
and the ER measurements were comparable (
p
> 0.05). The 7 T images were significantly sharper (sharpness: 2.69 ± 0.50 vs. 1.88 ± 0.53 mm
−1
,
p
< 0.001) with higher image quality (reader 1 score: 3.5 ± 1.1 vs. 2.4 ± 1.1,
p
= 0.002) compared to 3 T.
Conclusions
3D
T
1
-weighted SPACE can be used for intracranial vessel wall evaluation at both 3 and 7 T. 7 T provides significantly better image quality and improves the confidence of diagnosis.
Objective
Develop and optimize an accelerated, high-resolution (0.5 mm isotropic) 3D black blood MRI technique to reduce scan time for whole-brain intracranial vessel wall imaging.
Materials and ...methods
A 3D accelerated T
1
-weighted fast-spin-echo prototype sequence using compressed sensing (CS-SPACE) was developed at 3T. Both the acquisition echo train length (ETL), under-sampling factor and reconstruction parameters (regularization parameter, number of iterations) were first optimized in 5 healthy volunteers. Ten patients with a variety of intracranial vascular disease presentations (aneurysm, atherosclerosis, dissection, vasculitis) were imaged with SPACE and optimized CS-SPACE, pre and post Gd contrast. Lumen/wall area, wall-to-lumen contrast ratio (CR), enhancement ratio (ER), sharpness, and qualitative scores (1–4) by two radiologists were recorded.
Results
The optimized CS-SPACE protocol has ETL 60, 20%
k
-space under-sampling, 0.002 regularization factor with 20 iterations. In patient studies, CS-SPACE and conventional SPACE had comparable image scores both pre- (3.35 ± 0.85 vs. 3.54 ± 0.65,
p
= 0.13) and post-contrast (3.72 ± 0.58 vs. 3.53 ± 0.57,
p
= 0.15), but the CS-SPACE acquisition was 37% faster (6:48 vs. 10:50). CS-SPACE agreed with SPACE for lumen/wall area, ER measurements and sharpness, but marginally reduced the CR.
Conclusion
In the evaluation of intracranial vascular disease, CS-SPACE provides a substantial reduction in scan time compared to conventional T
1
-weighted SPACE while maintaining good image quality.
The purpose of this study was to evaluate the effect of breathing on image quality of the aortic arch and carotid vessels during contrast-enhanced MR angiography and to show that high-resolution ...breath-hold contrast-enhanced MR angiography combined with a timing-bolus technique can produce high-quality images of the entire carotid circulation.
Forty patients underwent high-resolution contrast-enhanced MR angiography on a 1.5-T Magnetom Symphony. A coronal three-dimensional (3D) gradient-echo sequence (TR/TE, 4.36/1.64; flip angle, 25 degrees) with asymmetric k-space acquisition was used. The 136 x 512 matrix yielded voxel sizes of 1.33 x 0.64 x 1.0 mm. A timing-bolus acquisition, orientated in the coronal plane to include the aortic arch, was obtained initially during free-breathing. Twenty milliliters of gadopenetate dimeglumine was injected at 2 mL/sec. Unenhanced and enhanced 3D volumes were recorded. A subtracted 3D set was calculated and subjected to a maximum-intensity-projection algorithm. Half of the patients held their breath during angiography and the other half did not. Aortic arch motion was measured on the timing-bolus acquisition as the distance moved by a single pixel in both the x and y directions. Maximum-intensity-projection MR images were assessed independently by two observers, and vessel sharpness was scored on a scale of 1-5. Sharpness was also assessed quantitatively by generating a signal intensity profile across the aortic arch vessel wall and calculating the average of the upslope and downslope at full-width half maximum. Visualization of carotid branch vessels was scored on a scale of 0-5, and venous contamination was scored on a scale of 0-3.
Average in-plane aortic arch movement was 10.3 mm in the x direction and 8.7 mm in the y direction. Quantitative and qualitative sharpness of the aortic arch and great vessel origins was better (p < 0.05) during breath-holding than during non-breath-holding. No difference in the sharpness of the carotid vessels was noted between the two groups. Carotid branch vessels were well visualized from the aortic arch to the intracerebral circulation. The average venous contamination score was 0.56.
Breath-holding greatly improves the sharpness of the aortic arch and great vessel origins but has no effect on visualization of the carotid vessels. High-resolution breath-hold contrast-enhanced MR angiography can produce high-quality, artifact-free images of the entire carotid circulation from the aortic arch to the intracerebral circulation.
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