Objectives
Acoustic noise in magnetic resonance imaging (MRI) negatively impacts patients. We assessed a silent gradient coil switched at 20 kHz combined with a T
1
-weighted magnetisation prepared ...rapid gradient-echo (MPRAGE) sequence at 7 T.
Methods
Five healthy subjects (21–29 years; three females) without previous 7-T MRI experience underwent both a quiet MPRAGE (Q-MPRAGE) and conventional MPRAGE (C-MPRAGE) sequence twice. Image quality was assessed quantitatively, and qualitatively by two neuroradiologists. Sound level was measured objectively and rated subjectively on a 0 to 10 scale by all subjects immediately following each sequence and after the whole examination (delayed). All subjects also reported comfort level, overall experience and willingness to undergo the sequence again.
Results
Compared to C-MPRAGE, Q-MPRAGE showed higher signal-to-noise ratio (10%;
p
= 0.012) and lower contrast-to-noise ratio (20%;
p
< 0.001) as well as acceptable to good image quality. Q-MPRAGE produced 27 dB lower sound level (76
versus
103 dB). Subjects reported lower sound level for Q-MPRAGE both immediate (4.4 ± 1.4
versus
6.4 ± 1.3;
p
= 0.007) and delayed (4.6 ± 1.4
versus
6.3 ± 1.3;
p
= 0.005), while they rated comfort level (7.4 ± 1.0
versus
6.1 ± 1.7;
p
= 0.016) and overall experience (7.6 ± 1.0
versus
6.0 ± 0.9;
p
= 0.005) higher. Willingness to undergo the sequence again was also higher, however not significantly (8.1 ± 1.0
versus
7.2 ± 1.3;
p
= 0.066).
Conclusion
Q-MPRAGE using a silent gradient coil reduced sound level by 27 dB compared to C-MPRAGE at 7 T while featuring acceptable-to-good image quality and a quieter and more pleasant subject experience.
In this retrospective case series study, we used 7.0 tesla MRI to describe patterns of intracranial vessel wall abnormalities in relation to ischemic infarcts in 9 patients with different ...intracranial vessel wall pathologies.
A patient-specific clinical imaging protocol was obtained after regular clinical workup, including a fluid-attenuated inversion recovery and an intracranial vessel wall sequence before and after contrast administration using 7.0 tesla MRI. An attempt was made to describe patterns by grouping the patients by intracranial vessel wall abnormalities (eccentric or concentric; enhancing or nonenhancing), then on the presence of macroinfarcts and cortical microinfarcts (CMIs), and lastly on type of macroinfarct (lacunar, small macroinfarct, or large macroinfarct).
Intracranial vessel wall abnormalities were identified in all patients, totaling 45 lesions, 12 of which enhanced after contrast administration. CMIs were found in 5 patients. Two patients had eccentric, enhancing wall thickening but differed based on presence or absence of CMIs. Four patients also had eccentric but nonenhancing wall thickening, 2 of whom showed CMIs. The 2 patients lacking CMIs could be subdivided based on the type of macroinfarct. Concentric, enhanced wall thickening was observed in 2 patients with CMIs who differed regarding macroinfarct types. One patient with previous vasculitis showed concentric, nonenhancing wall thickening.
Our results suggest that the combination of intracranial vessel wall abnormalities and infarct type is related to different stroke etiologies.
Abstract
Background
Survival outcomes for glioblastoma (GBM) patients remain unfavorable, and tumor recurrence is often observed. Understanding the radiological growth patterns of GBM could aid in ...improving outcomes. This study aimed to examine the relationship between contrast-enhancing tumor growth direction and white matter, using an image registration and deformation strategy.
Methods
In GBM patients 2 pretreatment scans (diagnostic and neuronavigation) were gathered retrospectively, and coregistered to a template and diffusion tensor imaging (DTI) atlas. The GBM lesions were segmented and coregistered to the same space. Growth vectors were derived and divided into vector populations parallel (Φ = 0–20°) and perpendicular (Φ = 70–90°) to white matter. To test for statistical significance between parallel and perpendicular groups, a paired samples Student’s t-test was performed. O6-methylguanine-DNA methyltransferase (MGMT) methylation status and its correlation to growth rate were also tested using a one-way ANOVA test.
Results
For 78 GBM patients (mean age 61 years ± 13 SD, 32 men), the included GBM lesions showed a predominant preference for perineural satellitosis (P < .001), with a mean percentile growth of 30.8% (95% CI: 29.6–32.0%) parallel (0° < |Φ| < 20°) to white matter. Perpendicular tumor growth with respect to white matter microstructure (70° < |Φ| < 90°) showed to be 22.7% (95% CI: 21.3–24.1%) of total tumor growth direction.
Conclusions
The presented strategy showed that tumor growth direction in pretreatment GBM patients correlated with white matter architecture. Future studies with patient-specific DTI data are required to verify the accuracy of this method prospectively to identify its usefulness as a clinical metric in pre and posttreatment settings.
Background and Purpose:
Shear stress (WSS) is involved in the pathophysiology of atherosclerotic disease and might affect plaque ulceration. In this case-control study, we compared carotid plaques ...that developed a
new
ulcer during follow-up and plaques that remained silent for their exposure to time-dependent oscillatory shear stress parameters at baseline.
Materials and Methods:
Eighteen patients who underwent CTA and MRI of their carotid arteries at baseline and 2 years follow-up were included. These 18 patients consisted of six patients who demonstrated a new ulcer and 12 control patients selected from a larger cohort with similar MRI-based plaque characteristics as the ulcer group. (Oscillatory) WSS parameters time average WSS, oscillatory shear index (OSI), and relative residence time (RRT) were calculated using computational fluid dynamics applying the MRI-based geometry of the carotid arteries and compared among plaques (wall thickness>2 mm) with and without ulceration (Mann–Whitney
U
test) and ulcer-site vs. non-ulcer-site within the plaque (Wilcoxon signed rank test). More detailed analysis on ulcer cases was performed and the predictive value of oscillatory WSS parameters was calculated using linear and logistic mixed-effect regression models.
Results:
The ulcer group demonstrated no difference in maximum WSS 9.9 (6.6–18.5) vs. 13.6 (9.7–17.7) Pa,
p
= 0.349, a lower maximum OSI 0.04 (0.01–0.10) vs. 0.12 (0.06–0.20)
p
= 0.019 and lower maximum RRT 1.25 (0.78–2.03) Pa
−1
vs. 2.93 (2.03–5.28) Pa
−1
,
p
= 0.011 compared to controls. The location of the ulcer (ulcer-site) within the plaque was not always at the maximal WSS, but demonstrated higher average WSS, lower average RRT and OSI at the ulcer-site compared to the non-ulcer-sites. High WSS (WSS>4.3 Pa) and low RRT (RRT < 0.25 Pa) were associated with ulceration with an odds ratio of 3.6 CI 2.1–6.3 and 2.6 CI 1.54–4.44 respectively, which remained significant after adjustment for wall thickness.
Conclusion:
In this explorative study, ulcers were not exclusively located at plaque regions exposed to the highest WSS, OSI, or RRT, but high WSS and low RRT regions had a significantly higher odds to present ulceration within the plaque even after adjustment for wall thickness.
In this article, we report data on vessel wall thickness parameters derived from different arterial segments of the circle of Willis and its primary branches in patients with and without ...cerebrovascular disease. Also data on inter-rater reliability and agreement of the derived vessel wall parameters are reported. For further interpretation and discussion please refer to the research article “ex vivo vessel wall thickness measurements of the human circle of Willis using 7T MRI” (Harteveld et al., in press) 1.
Magnetic resonance imaging (MRI) plays a key role in the investigation of cerebrovascular diseases. Compared with computed tomography (CT) and digital subtraction angiography (DSA), its advantages in ...diagnosing cerebrovascular pathology include its superior tissue contrast, its ability to visualize blood vessels without the use of a contrast agent, and its use of magnetic fields and radiofrequency pulses instead of ionizing radiation. In recent years, ultrahigh field MRI at 7 tesla (7 T) has shown promise in the diagnosis of many cerebrovascular diseases. The increased signal-to-noise ratio (SNR; 2.3x and 4.7x increase compared with 3 and 1.5 T, respectively) and contrast-to-noise ratio (CNR) at this higher field strength can be exploited to obtain a higher spatial resolution and higher lesion conspicuousness, enabling assessment of smaller brain structures and lesions. Cerebrovascular diseases can be assessed at different tissue levels; for instance, changes of the arteries feeding the brain can be visualized to determine the cause of ischemic stroke, regional changes in brain perfusion can be mapped to predict outcome after revascularization, and tissue damage, including old and recent ischemic infarcts, can be evaluated as a marker of ischemic burden. For the purpose of this review, we will discriminate 3 levels of assessment of cerebrovascular diseases using MRI: Pipes, Perfusion, and Parenchyma (3 Ps). The term Pipes refers to the brain-feeding arteries from the heart and aortic arch, upwards to the carotid arteries, vertebral arteries, circle of Willis, and smaller intracranial arterial branches. Perfusion is the amount of blood arriving at the brain tissue level, and includes the vascular reserve and perfusion territories. Parenchyma refers to the acute and chronic burden of brain tissue damage, which includes larger infarcts, smaller microinfarcts, and small vessel disease manifestations such as white matter lesions, lacunar infarcts, and microbleeds. In this review, we will describe the key developments in the last decade of 7-T MRI of cerebrovascular diseases, subdivided for these 3 levels of assessment.
In this review, current (clinical) applications and possible future directions of ultrahigh-field (≥7 T) magnetic resonance (MR) imaging in the brain are discussed. Ultrahigh-field MR imaging can ...provide contrast-rich images of diverse pathologies and can be used for early diagnosis and treatment monitoring of brain disease. These images may provide increased sensitivity and specificity. Several limitations need to be overcome before worldwide clinical implementation can be commenced. Current literature regarding clinically based ultrahigh-field MR imaging is reviewed, and limitations and promises of this technique are discussed, as well as some practical considerations for the implementation in clinical practice.
Carotid plaque composition is a major determinant of cerebrovascular events. In the present analysis, we evaluated the relationship between intraplaque hemorrhage (IPH) and a thin/ruptured fibrous ...cap (TRFC) in moderately stenosed carotid arteries and cerebral infarcts on MRI in the ipsilateral hemisphere.
A total of 101 patients with a symptomatic 30% to 69% carotid artery stenosis underwent MRI of the carotid arteries and the brain, within a median time of 45 days from onset of symptoms. The presence of ipsilateral infarcts in patients with and without IPH and TRFC was evaluated.
IPH was seen in 40 of 101 plaques. TRFC was seen in 49 of 86 plaques (postcontrast series were not obtained in 15 patients). In total, 51 infarcts in the flow territory of the symptomatic carotid artery were found in 47 patients. Twenty nine of these infarcts, found in 24 patients, were cortical infarcts. No significant relationship was found between IPH or TRFC and the presence of ipsilateral infarcts.
MRI detected IPH and TRFC are not related to the presence of old and recent cortical and subcortical infarcts ipsilateral to a symptomatic carotid artery stenosis of 30% to 69%.
http://www.clinicaltrials.gov. Unique identifier: NCT01208025.
PDF
