Purpose The circulation of cerebrospinal fluid (CSF) is closely associated with many aspects of brain physiology. When gadolinium(Gd)‐based contrast is administered intravenously, pre‐ and post‐contrast MR signal changes can often be observed in the CSF at certain locations within the intra‐cranial space, mainly due to the lack of a blood‐brain barrier in the dural blood vessels. This study aims to develop and systemically optimize MRI sequences that can detect dynamic signal changes in the CSF after Gd administration with a sub‐millimeter spatial resolution, a temporal resolution of <10 s, and whole brain coverage. Methods Bloch simulations were performed to determine optimal imaging parameters for maximum CSF contrast before and after Gd injection. Simulations were validated with phantom scans. An optimized turbo‐spin‐echo (TSE) sequence was performed on healthy volunteers on 3T and 7T. Results Simulation results agreed well with phantom scans. In human scans, dynamic signal changes after Gd injection in the CSF were detected at several locations where cerebral lymphatic vessels were identified in previous studies. The concentration of Gd in CSF in these regions was estimated to be approximately 0.2 mmol/L. Conclusion Dynamic signal changes induced by the distribution of Gd in the CSF can be detected in healthy human subjects with an optimized TSE sequence. The proposed methodology does not rely on any particular theory on CSF circulation. We expect it to be useful for studies on CSF circulation and cerebral lymphatic vessels in the brain.
Purpose Digital subtraction angiography (DSA) remains the gold standard to diagnose intracranial arteriovenous malformations (AVMs) but is invasive. Existing magnetic resonance angiography (MRA) is suboptimal for assessing the hemodynamics of AVMs. The objective of this study was to evaluate the clinical utility of a novel noncontrast four-dimensional (4D) dynamic MRA (dMRA) in the evaluation of intracranial AVMs through comparison with DSA and time-of-flight (TOF) MRA. Materials and methods Nineteen patients (12 women, mean age 26.2±10.7 years) with intracranial AVMs were examined with 4D dMRA, TOF and DSA. Spetzler–Martin grading scale was evaluated using each of the above three methods independently by two raters. Diagnostic confidence scores for three components of AVMs (feeding artery, nidus and draining vein) were also rated. Kendall's coefficient of concordance was calculated to evaluate the reliability between two raters within each modality (dMRA, TOF, TOF plus dMRA). The Wilcoxon signed-rank test was applied to compare the diagnostic confidence scores between each pair of the three modalities Results dMRA was able to detect 16 out of 19 AVMs, and the ratings of AVM size and location matched those of DSA. The diagnostic confidence scores by dMRA were adequate for nidus (3.5/5), moderate for feeding arteries (2.5/5) and poor for draining veins (1.5/5). The hemodynamic information provided by dMRA improved diagnostic confidence scores by TOF MRA. Conclusion As a completely noninvasive method, 4D dMRA offers hemodynamic information with a temporal resolution of 50–100 ms for the evaluation of AVMs and can complement existing methods such as DSA and TOF MRA.
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