7 Tesla MPRAGE Imaging of the Intracranial Arterial Vasculature: Nonenhanced versus Contrast-Enhanced

doi:10.1016/j.acra.2012.12.012

Academic Radiology

Volume 20, Issue 5, May 2013, Pages 628-634

https://doi.org/10.1016/j.acra.2012.12.012 Get rights and content

Purpose

To intraindividually compare the delineation of intracranial arterial vasculature in nonenhanced versus contrast-enhanced magnetization prepared rapid gradient echo (MPRAGE) imaging at 7 Tesla (T).

Materials and Methods

Sixteen subjects were examined on a 7 T whole-body magnetic resonance system (Magnetom 7T) equipped with a 32-channel transmit/receive head coil. MPRAGE imaging was performed pre- and postcontrast after the application of 0.1 mmol/kg bodyweight gadobutrol. For qualitative analysis, the delineation of the intracranial arteries, overall image quality, and image impairment were assessed in the nonenhanced and contrast-enhanced datasets using a 5-point scale (5 = excellent to 1 = nondiagnostic). Additionally, contrast ratios (CR) of the middle cerebral artery in correlation to surrounding gray matter in nonenhanced and postcontrast images were obtained. For statistical analysis a Wilcoxon signed-rank test was applied.

Results

Nonenhanced MPRAGE imaging offered an excellent delineation of the central vessel segments of the anterior circulation (mean anterior circulation 4.6) and a moderate- to high-quality assessment of the vessels of the posterior circulation (mean posterior circulation 3.9). Vessel delineation was improved in all assessed segments in the contrast-enhanced datasets, except for the cavernous segment of the internal carotid artery. Quantitative analysis revealed a mild, nonsignificant increase in CR mean values of the M1 segment (CR_nonenhanced 0.67; CR_{contrast-enhanced} 0.69).

Conclusion

Our results demonstrate the high diagnostic value of nonenhanced 7 T MPRAGE imaging for the assessment of the intracranial arterial vasculature, with improved assessment of the peripheral segments because of the application of a contrast agent.

Section snippets

Material and methods

The study was approved by the institutional review board. Written informed consent was obtained according to the institutional guidelines.

Fifteen healthy subjects (nine male, six female; mean age 43.2; age range 34–47) and one patient (53 years) with known giant aneurysm of the right internal carotid artery were examined on a 7 T whole-body MR system (Magnetom 7T, Siemens Healthcare, Erlangen, Germany) using a 32-channel transmit/receive head coil (Nova Medical, Wilmington, MA).

The study

Results

All MRI examinations were successfully performed and were well tolerated without any relevant side effects, except for minor dizziness in two cases.

The following normal variants were detected: two subjects with hypo-/aplastic unilateral A1 segments, three subjects with hypo-/aplastic A2 segment, and two subjects with hypo-/aplastic posterior communicating artery.

Discussion

The increase of the magnetic field strength to 7 T and the associated increase in signal-to-noise ratio has been demonstrated to yield a significant diagnostic benefit in neuroimaging in terms of improved assessment of anatomic structures as well as parenchymatous and vessel pathologies 4, 5, 6, 7, 8, 9, 10, 13.

Despite the increase in spatiotemporal resolution, initial 7 T neurologic and abdominal MRI studies have revealed an additional incidental finding, by means of a homogeneous hyperintense

Conclusion

Our results demonstrate the high diagnostic potential of nonenhanced ultra-high-field MPRAGE imaging in terms of an excellent delineation of the nonenhanced intracranial arterial vasculature with improvement after the application of contrast agent, particularly for assessment of the posterior circulation and peripheral vessel segments as well as vessel pathologies. The focus of future studies may lie in the comparison of the diagnostic potential of 7 T nonenhanced and contrast-enhanced MPRAGE

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MP2RAGE has been used for T1 structural imaging and morphometry22,23 as well as whole-brain segmentation.24 In addition, MPRAGE imaging at 7 T has shown the ability to delineate intracranial vasculature.25 The white matter–nulled MPRAGE (WMnMPRAGE) generates additional contrast by suppressing signal from white matter, with inversion times chosen such that fluid is bright, and gray-white contrast is even better than with MPRAGE.
Moyamoya vessel pathology imaged by ultra-high-field magnetic resonance imaging at 7.0 T
2016, Journal of Stroke and Cerebrovascular Diseases
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Only 7.0 T MPRAGE-MRA and 7.0 T TOF-MRA were able to depict MMV-specific small-vessel pathologies comparable with DSA. Considering previous MR studies of MMV, higher magnetic field strength seems to correlate with more precise results of MRA.11,12,16,18-20 Isotropic spatial resolution of conventional angiography has been described to be 0.4 mm, which is theoretically comparable to the 0.4 mm isotropic resolution of our 7.0 T TOF-MRA images.
Prompt diagnosis of vessel pathology and appropriate treatment of moyamoya vasculopathy (MMV) are essential to improve long-term prognosis. The aims of our study were to explore the diagnostic value of ultra–high-field (UHF) magnetic resonance imaging at 7.0 T in MMV patients and to compare the applicability of two different 7.0 T vessel imaging modalities to 3.0 T magnetic resonance angiography (MRA) and digital subtraction angiography (DSA).
In a World Health Organization-registered and prospective imaging trial, patients were investigated at 7.0 T magnetization-prepared rapid-acquisition gradient echo (MPRAGE)-MRA and time-of-flight (TOF)-MRA, 3.0 T TOF-MRA, and by DSA.
Six patients were included in our study and evaluated for MMV. 3.0 T TOF-MRA and 7.0 T MPRAGE-MRA were able to depict the complete major vascular tree and confirmed MMV-specific steno-occlusions of major intracranial arteries, as previously identified by DSA. 7.0 T TOF-MRA was limited to visualization of the circle of Willis as well as the internal carotid artery only. Donor vessels for bypass surgery (i.e., branches of superficial temporal artery) could be sufficiently visualized with all magnetic resonance modalities.
Our results indicate that a specific 7.0 T vascular imaging protocol yields diagnostic information about vessel pathology in MMV that approximates conventional DSA. 7.0 T MPRAGE was superior to 7.0 T TOF-MRA due to shorter scanning times and better brain coverage. To date, however, limited availability of 7.0 T technology in medical facilities as well as technical and procedural constraints excludes a fair amount of patients from the clinical 7.0 T imaging process.
Ultrahigh-field MPRAGE Magnetic Resonance Angiography at 7.0 T in patients with cerebrovascular disease
2015, European Journal of Radiology
Citation Excerpt :
Then, a multi-scale vesselness filter was applied to the masked images (lower sigma = 0.5 mm, upper sigma = 1.5, number of scales = 4) for the enhancement of the vessel contrast [10]. Visual analysis was performed using a standardized qualitative evaluation procedure modified from Umutlu et al. [11]. Two radiologists (JW, board-certified, 13 years experience in neuroimaging; PvG, 4 years experience in neuroimaging) analyzed angiographic source image data (2D, slice by slice) independently from each other and blinded to any clinical information.
Time-of-flight (TOF) magnetic-resonance-angiography (MRA) identifies vessel pathology in cerebrovascular disease. At 7.0 T, the clinical performance of TOF-MRA is constrained owing to radio frequency power deposition. We studied the diagnostic value of whole-brain MPRAGE-based MRA as an alternative imaging technique in comparison to the clinical standard 3.0 T TOF-MRA.
Patients with stroke and/or moya-moya disease were included. TOF-MRA was performed at 3.0 T and MPRAGE-MRA at 7.0 T. Two radiologists rated the MRAs independently for overall quality and local arterial segment visualization. The identification of steno-occlusive pathology was reported for each protocol.
In 18 patients (9 females; 6 patients with moya-moya) 7.0 T MPRAGE-MRA provided better overall image quality and better distinction of small structures compared to 3.0 T TOF-MRA. These findings were pronounced in the proximal segments of the anterior cerebral artery (A1), middle cerebral artery (M1, M2), posterior cerebral artery (P1) and the posterior communicating artery. Seven steno-occlusive findings were identified by both imaging protocols.
For clinical studies using ultrahigh field MRI, 7.0 T MPRAGE-MRA provides a suitable alternative to TOF-MRA imaging to identify brain vessel pathology and yields simultaneous structural brain imaging within clinically feasible acquisition times.
Synthesized 7T MPRAGE From 3T MPRAGE Using Generative Adversarial Network and Validation in Clinical Brain Imaging: A Feasibility Study
2024, Journal of Magnetic Resonance Imaging
Visualisation of lenticulostriate arteries using contrast-enhanced time-of-flight magnetic resonance angiography at 7 Tesla
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Technical report7 Tesla MPRAGE Imaging of the Intracranial Arterial Vasculature: Nonenhanced versus Contrast-Enhanced

Purpose

Materials and Methods

Results

Conclusion

Section snippets

Material and methods

Results

Discussion

Conclusion

First clinical study on ultra-high-field MR imaging in patients with multiple sclerosis: comparison of 1.5T and 7T

AJNR Am J Neuroradiol

Whole-body high-field-strength (3.0-T) MR imaging in clinical practice part II. Technical considerations and clinical applications

Radiology

Whole-body high-field-strength (3.0-T) MR imaging in clinical practice part I. Technical considerations and clinical applications

Radiology

Evaluation of intracranial aneurysms with 7 T versus 1.5 t time-of-flight MR angiography: initial experience

Rofo

Imaging of adult astrocytic brain tumours with 7 T MRI: preliminary results

Eur Radiol

Imaging of brain metastases of bronchial carcinomas with 7 T MRI: initial results

Rofo

Pre-interventional assessment of a vertebrobasilar aneurysm with 7 Tesla time-of-flight MR angiography

Rofo

7 tesla MRI of microbleeds and white matter lesions as seen in vascular dementia

J Magn Reson Imaging

To TOF or not to TOF: strategies for non-contrast-enhanced intracranial MRA at 7 T

Magn Reson Materials Phys Biol Med

MR angiography of the cerebral perforating arteries with magnetization prepared anatomical reference at 7T: comparison with time-of-flight

J Magn Reson Imaging

First-pass contrast-enhanced renal MRA at 7 Tesla: initial results

Eur Radiol

Technical report
7 Tesla MPRAGE Imaging of the Intracranial Arterial Vasculature: Nonenhanced versus Contrast-Enhanced