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.
Magnetization prepared rapid acquisition gradient echo sequence (MPRAGE) imaging is a commonly applied pulse sequence for T1-weighted anatomical imaging of the brain. The increase of the magnetic field strength >1.5 T has been proven beneficial in neuro imaging , allowing for a successful transformation of the associated increase in signal-to-noise ratio into imaging at higher spatiotemporal resolution.
Furthermore, initial 7T neuro and abdominal magnetic resonance imaging (MRI) studies have revealed an additional incidental finding by means of a homogeneous hyperintense delineation of nonenhanced arterial vasculature in T1-weighted MRI, offering the diagnostic potential for nonenhanced MR angiographic applications. Maderwald et al and Zwanenburg et al demonstrated the strong diagnostic ability of nonenhanced 7T MPRAGE MRI in the assessment of intracranial arterial vasculature and their related anatomical structures . Although the feasibility of first-pass contrast-enhanced MR angiography of the renal arteries at 7 T has been successfully demonstrated, the administration of gadolinium for 7 T brain imaging has mainly focused on the assessment of parenchymatous features up to current status .
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Material and methods
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Results
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Qualitative Analysis: Anterior Circulation
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Qualitative Analysis: Posterior Circulation
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Overall Image Quality and Overall Image Impairment
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Quantitative Analysis
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Patient Analysis
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Discussion
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Conclusion
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