3T Magnetic Resonance Angiography Research Articles

Comparison of computational fluid dynamics with transcranial Doppler ultrasound in response to physiological stimuli.

Cerebrovascular haemodynamics are sensitive to multiple physiological stimuli that require synergistic response to maintain adequate perfusion. Understanding haemodynamic changes within cerebral arteries is important to inform how the brain regulates perfusion; however, methods for direct measurement of cerebral haemodynamics in these environments are challenging. The aim of this study was to assess velocity waveform metrics obtained using transcranial Doppler (TCD) with flow-conserving subject-specific three-dimensional (3D) simulations using computational fluid dynamics (CFD). Twelve healthy participants underwent head and neck imaging with 3T magnetic resonance angiography. Velocity waveforms in the middle cerebral artery were measured with TCD ultrasound, while diameter and velocity were measured using duplex ultrasound in the internal carotid and vertebral arteries to calculate incoming cerebral flow at rest, during hypercapnia and exercise. CFD simulations were developed for each condition, with velocity waveform metrics extracted in the same insonation region as TCD. Exposure to stimuli induced significant changes in cardiorespiratory measures across all participants. Measured absolute TCD velocities were significantly higher than those calculated from CFD (P range < 0.001-0.004), and these data were not correlated across conditions (r range 0.030-0.377, P range 0.227-0.925). However, relative changes in systolic and time-averaged velocity from resting levels exhibited significant positive correlations when the distinct techniques were compared (r range 0.577-0.770, P range 0.003-0.049). Our data indicate that while absolute measures of cerebral velocity differ between TCD and 3D CFD simulation, physiological changes from resting levels in systolic and time-averaged velocity are significantly correlated between techniques.

Comparison of 1.5T and 3T magnetic resonance angiography for detecting cerebral aneurysms using deep learning-based computer-assisted detection software.

To compare the diagnostic performance of 1.5T versus 3T magnetic resonance angiography (MRA) for detecting cerebral aneurysms with clinically available deep learning-based computer-assisted detection software (EIRL aneurysm® [EIRL_an]), which has been approved by the Japanese Pharmaceuticals and Medical Devices Agency. We also sought to analyze the causes of potential false positives. In this single-center, retrospective study, we evaluated the MRA scans of 90 patients who underwent head MRA (1.5T and 3T in 45 patients each) in clinical practice. Overall, 51 patients had 70 aneurysms. We used MRI from a vendor not included in the dataset used to create the EIRL_an algorithm. Two radiologists determined the ground truth, the accuracy of the candidates noted by EIRL_an, and the causes of false positives. The sensitivity, number of false positives per case (FPs/case), and the causes of false positives were compared between 1.5T and 3T MRA. Pearson's χ2 test, Fisher's exact test, and the Mann‒Whitney U test were used for the statistical analyses as appropriate. The sensitivity was high for 1.5T and 3T MRA (0.875‒1), but the number of FPs/case was significantly higher with 3T MRA (1.511 vs. 2.578, p < 0.001). The most common causes of false positives (descending order) were the origin/bifurcation of vessels/branches, flow-related artifacts, and atherosclerosis and were similar between 1.5T and 3T MRA. EIRL_an detected significantly more false-positive lesions with 3T than with 1.5T MRA in this external validation study. Our data may help physicians with limited experience with MRA to correctly diagnose aneurysms using EIRL_an.

Prevalence of Unruptured Intracranial Aneurysms: A Single Center Experience Using 3T Brain MR Angiography.

PurposeThe purpose of this study was to evaluate the prevalence and risk factors of unruptured intracranial aneurysms (UIAs), which can help establish guidelines of treatment for asymptomatic Korean adults using 3T magnetic resonance angiography (MRA).Materials and MethodsOur Institutional Review Board approved this retrospective study, and informed consent was waived. All patients consisted of healthy individuals who underwent brain MRA using 3T magnetic resonance imaging between January 2011 and December 2012 as part of a routine health examination. Patient data and follow-up results were obtained from medical records.ResultsA total of 2,118 individuals (mean age=53.9±9.6 years, male:female=1,188:930) who had undergone brain MRA were enrolled in the study. UIAs were found in 80 patients with 105 UIAs (3.77%). Female predominance (55% in UIA vs. 43.47% in non-UIA, P=0.0416) and hypertension were more common in the UIA group (43.75% vs. 28.8%, P=0.004, respectively). The mean size of the aneurysms was 3.10±1.62 mm, and they were all saccular in shape and asymptomatic. The UIAs were most common in the internal carotid artery (59.1%), internal carotid-posterior communicating artery (15.2%), middle cerebral artery (9.5%), anterior communicating artery (8.6%), anterior cerebral artery (4.8%), and vertebral artery (2.9%). Twenty-eight of 80 patients (35%) had multiple aneurysms. The incidence of UIAs increased significantly with age (P=0.014).ConclusionIn single center experience, we demonstrated the characteristics and prevalence of UIAs in asymptomatic adults, which may help establish guidelines or therapeutic standards for UIAs.

Feasibility and Robustness of 3T Magnetic Resonance Angiography Using Modified Dixon Fat Suppression in Patients With Known or Suspected Peripheral Artery Disease.

Objective: Contrast-enhanced magnetic resonance angiography (CE-MRA) is a well-established non-invasive imaging technique for the assessment of peripheral artery disease (PAD). A subtractionless method using modified Dixon (mDixon) fat suppression showed superior image quality at 1.5T over the common subtraction method, using a three-positions stepping table approach with a single dose of contrast agent. The aim of this study was to investigate the feasibility of subtractionless first-pass peripheral MRA at 3T in patients with known or suspected PAD and to compare the performance in terms of vessel-to-background contrast (VBC), signal-to-noise ratio (SNR), and subjective image quality to conventional subtraction MRA.Methods: Ten patients [mean age 69 years ± 12 standard deviation (SD)] with known or suspected PAD were examined on a clinical 3T scanner (Ingenia, Philips Healthcare, Best, Netherlands) at three table positions using subtractionless and subtraction first-pass peripheral MRA. Two readers rated image quality on a four- point scale. Interobserver agreement was expressed in quadratic weighted κ values. VBC was assessed with a semi-automated process and SNR was compared in a healthy volunteer.Results: Subjective image quality was significantly better with the subtractionless method overall (mean image quality for mDixon imaging: 2.88 ± 0.32 SD vs. for subtraction imaging: 2.57 ± 0.48 SD; P < 0.001) and per table position (abdominal position: 2.88 ± 0.32 vs. 2.57 ± 0.48 SD; P < 0.001); upper leg position: (2.97 ± 0.15 SD vs. 2.68 ± 0.37 SD; P < 0.001; lower leg position: 2.60 ± 0.50 SD vs. 2.13 ± 0.60 SD; P < 0.001). Vessel-to-background contrast increased by 22% with the subtractionless method overall (mean VBC for mDixon imaging: 23.16 ± 8.4 SD vs. for subtraction imaging: 19.00 ± 8.1 SD; factor 1.22, P < 0.001). SNR was 82% higher with the subtractionless method (overall SNR gain 1.82; P < 0.001).Conclusion: This study demonstrated the feasibility and robustness of subtractionless first-pass peripheral MRA at 3T in patients with known or suspected PAD using a three- positions stepping table approach with a single dose of contrast agent. It showed increased image quality compared to the conventional subtraction method and superior performance in terms of SNR and vessel-to-background contrast.

7T versus 3T MR Angiography to Assess Unruptured Intracranial Aneurysms.

ABSTRACTBACKGROUND AND PURPOSEAneurysm size and neck measurements are important for treatment decisions. The introduction of 7T magnetic resonance angiography (MRA) led to new possibilities assessing aneurysm morphology and flow due to the higher signal‐to‐noise ratio. However, it is unknown if the size measurements on 7T MRA are similar to those on the standard 3T MRA. This study aimed to compare aneurysm size measurements between 7T and 3T MRA.METHODSWe included 18 patients with 22 aneurysms who underwent both 3T and 7T MRA. Three acquisition protocols were compared: 3T time of flight (TOF), 7T TOF, and 7T contrast‐enhanced MRA. Each aneurysm on each protocol was measured by at least two experienced neuroradiologists. Subsequently, the differences were evaluated using scatterplots and the intraclass correlation coefficients (ICC) of agreement.RESULTSThere was a good agreement among the neuroradiologists for the height and width measurements (mean ICC: .78‐.93); the neck measurements showed a moderate agreement with a mean ICC of .57‐.72. Between the MR acquisition protocols, there was a high agreement for all measurements with a mean ICC of .81‐.96. Measurement differences between acquisition protocols (0‐2.9 mm) were in the range of the differences between the neuroradiologists (0‐3.6 mm).CONCLUSIONOur study showed that 7T MRA, both nonenhanced and contrast‐enhanced, has a high agreement in aneurysm size measurements compared to 3T. This suggests that 7T is useful for reliable aneurysm size assessment.

Validity of Magnetic Resonance Imaging Measurement of Hip Labral Width Compared With Intraoperative Assessment

To determine if magnetic resonance angiography (MRA) and/or magnetic resonance imaging (MRI) could accurately determine the width of the labrum. Consecutively enrolled patients between the ages of 18 and 65 indicated for hip arthroscopy for femoroacetabular impingement were included between December 2017 and June 2018. Inclusion criteria for preoperative MRIs included: MRI availability in picture archiving and communication system; performance on a 1.5T or 3T MRI or 3T MRA; and adequate quality and lack of labrum ossification. Intraoperative labral width measurements were taken at standardized locations using an established acetabular "clockface" paradigm. Measurement was performed using a calibrated probe. The labral width was defined as the distance from the labrum extended laterally from the acetabular rim. MRI measurements were taken by 2 blinded musculoskeletal fellowship-trained radiologists at the same positions. Measurements were made at the 11:30 o'clock position (indirect rectus) on coronal proton density (PD) sequence, at 3 o'clock position (psoas-U) on axial oblique PD sequence, and at 1:30 (a point halfway between the 2) on sagittal fat-suppressed PD. The surgeons were blinded to the radiologists' measurements and vice versa. Intraoperative and radiographic labral width measurements were compared using an intraclass correlation coefficients (ICC), absolute agreement, and 2-way random effects model. The 2 radiologists' measurements were compared for interrater reliability using the same ICC model. Fifty-one patients were included (30 females, 26 right hips). Average labrum width at the 3:00, 11:30, and 1:30 o'clock positions by arthroscopic measurement were 5.8 mm (range; standard deviation, 2-8; ±1.4), 6.3 mm (2-10; ±1.5) and 6.0 mm (2-9; ±1.5), and by MRI were 6.3 mm (2-10; ±1.5), 6.7 mm (3-10; ±1.4), and 6.1 mm (2-9; ±1.6), respectively. When including all MRI modalities, ICC agreement between intraoperative assessment, and radiologist assessment at the 3:00 o'clock, 11:30, and point halfway between was 0.82 (P<.001), 0.78 (P < .001), 0.84 (P < .001), respectively. Radiologist interrater ICC agreement at the same points was 0.88 (P < .001), 0.93 (P < .001), and 0.88 (P < .001). Strong agreement was found between radiologic and arthroscopic measurement of labrum width when using MRI, suggesting MRI is an accurate way to measure labral width. There was not a significant difference between different MRI modalities. Accurately measuring labral width preoperatively with MRI may aid in surgical decision making. Level II, diagnostic study.

Mid-term 3T MRA follow-up of intracranial aneurysms treated with the Woven EndoBridge.

Angiography is the standard follow-up modality for treated aneurysms with the Woven EndoBridge (WEB), and magnetic resonance angiography (MRA) is useful for extended follow-up. We present the results of WEB-treated aneurysms with angiographic follow-up at three months and at least 18months' 3TMRA follow-up. Included were 52 patients with 53 aneurysms treated with the WEB between February2015 and July 2016. There were 29 women and 23 men with a mean age of 60 years (median 62, range 23-76). Mean aneurysm size was 6.2 mm (median 6, range 3-16 mm). 3T MRA follow-up was mean 19.6 months (median 18, range 18-36 months). One patient had an aneurysm remnant at three-month angiography that was additionally coiled and with stable complete occlusion at 18 months' 3T MRA follow-up. At three-month follow-up angiography, 44 aneurysms were completely occluded and eight had a neck remnant. At latest 3T MRA, stable complete occlusion was present in 43aneurysms and stable neck remnant in eight. One posterior cerebral artery (PCA) dissection aneurysm was stable at three and six months but was enlarged and reopened at 18 months, confirmed with angiography. Focal signal loss by the proximal marker of the WEB was apparent in four patients without compromising diagnostic evaluation. WEB-treated aneurysms with adequate occlusion at three-month angiography remained stable during serial 3T MRA follow-up of 18-36 months. One PCA aneurysm reopened during the 6- to 18-month interval. Once the WEB-treated aneurysm is adequately occluded in the short term, later reopening is uncommon.

Assessing Vascular Changes Associated with Healthy Aging using 7T Magnetic Resonance Angiography

Aging is known to produce changes in the cerebral vasculature and circulation. We aimed to quantitatively assess age-related changes in the morphology of small perforating vessels, lenticulostriate arteries (LSAs). LSA images were acquired using ultra-high field 7-Tesla magnetic resonance imaging (7T MRI) from 24 young healthy volunteers (young group: YG) and 25 old healthy volunteers (old group: OG). Vessel-related factors such as curvature and tortuosity were analyzed using two-dimensional images. Our quantitative results demonstrated a fewer in their branches and a significantly more pronounced curvature in the OG compared to the YG. These findings were further confirmed qualitatively using image analysis. Our study findings show that MR angiography utilizing ultra-high field MRI can provide high-resolution images that can identify morphological characteristics of small perforating vessels. Based on these features, it is possible to document ageinduced changes in cerebral small vessels.

Cognitive impairment and intracranial atherosclerotic stenosis in general population.

To investigate the association between asymptomatic intracranial atherosclerosis and cognitive impairment in the Atherosclerosis Risk in Communities (ARIC) cohort. ARIC participants underwent high-resolution 3T magnetic resonance angiography and a neuropsychology battery and neurologic examination adjudicated by an expert panel to detect mild cognitive impairment (MCI) and dementia. We adjusted for demographic and vascular risk factors in weighted logistic regression analysis, accounting for stratified sampling design and attrition, to determine the association of intracranial atherosclerotic stenosis (ICAS) with cognitive impairment. In 1,701 participants (mean age 76 ± 5.3, 41% men, 71% whites, 29% blacks) with adequate imaging quality and no history of stroke, MCI was identified in 578 (34%) and dementia in 79 (4.6%). In white participants, after adjustment for demographic and vascular risk factors, ICAS ≥50% (vs no ICAS) was strongly associated with dementia (odds ratio [OR] 4.1, 95% confidence interval [CI] 1.7-10.0) and with any cognitive impairment (OR 1.7, 95% CI 1.1-2.8). In contrast, no association was found between ICAS ≥50% and MCI or dementia in blacks, although the sample size was limited and estimates were imprecise. Our results suggest that asymptomatic ICAS is independently associated with cognitive impairment and dementia in whites.

Comparison between multi-shot gradient echo EPI and balanced SSFP in unenhanced 3T MRA of thoracic aorta in healthy volunteers

PurposeThe purpose of this study was to compare scan time and image quality between magnetic resonance angiography (MRA) of the thoracic aorta using a multi-shot gradient echo planar imaging (MSG-EPI) and MRA using balanced steady-state free precession (b-SSFP). Materials and methodsHealthy volunteers (n=17) underwent unenhanced thoracic aorta MRA using balanced steady-state free precession (b-SSFP) and MSG-EPI sequences on a 3T MRI. The acquisition time, total scan time, signal-to-noise ratio (SNR) of the thoracic aorta, and the coefficient of variation (CV) of thoracic aorta were compared with paired t-tests. Two radiologists independently recorded the images’ contrast, noise, sharpness, artifacts, and overall quality on a 4-point scale. ResultsThe acquisition time was 36.2% shorter for MSG-EPI than b-SSFP (115.5±14.4 vs 181.0±14.9s, p<0.01). The total scan time was 40.4% shorter for MSG-EPI than b-SSFP (272±78 vs 456±144s, p<0.01). There was no significant difference in mean SNR between MSG-EPI and b-SSFP scans (17.3±3.6 vs 15.2±4.3, p=0.08). The CV was significantly lower for MSG-EPI than b-SSFP (0.2±0.1 vs. 0.5±0.2, p<0.01). All qualitative scores except for image noise were significantly higher in MSG-EPI than b-SSFP scans (p<0.05). ConclusionThe MSG-EPI sequence is a promising technique for shortening scan time and yielding more homogenous image quality in MRA of thoracic aorta on 3T scanners compared with the b-SSFP.

Abstract WP450: Cognitive Impairment and Asymptomatic Intracranial Atherosclerotic Stenosis in General Population

Background: There is growing evidence suggesting that intracranial atherosclerosis is associated with cognitive impairment. We investigated the association between asymptomatic intracranial atherosclerosis and cognitive impairment in the bi-racial Atherosclerosis Risk in Communities (ARIC) cohort. Methods: ARIC participants who underwent high-resolution 3T magnetic resonance angiography, and a neuropsychology battery and neurological examination adjudicated by an expert panel, to detect mild cognitive impairment (MCI) and dementia. We adjusted for demographic and vascular risk factors in weighted logistic regression analysis, accounting for stratified sampling design and attrition, to determine the association of intracranial atherosclerotic stenosis (ICAS) with cognitive impairment. Results: In 1705 participants (mean age 76 ± 5.3, 41% men, 71% Whites and 29% African-Americans) with adequate imaging quality and no previous history of stroke, MCI was identified in 578 (34%) and dementia in 79 (4.6%). In white participants, after adjustment for demographic and vascular risk factors, ICAS ≥50% (vs no ICAS) was strongly associated with dementia (odds ratio [OR] 4.1, 95% confidence interval [CI] 1.7-10) and with any-cognitive impairment (OR 1.7, 95% CI 1.06 - 2.8). In contrast, no association was found between ICAS ≥50% and MCI or dementia in African-Americans, though sample size was limited and estimates were imprecise. Conclusion: Our results suggest asymptomatic ICAS is independently associated with cognitive impairment and dementia in Whites

Advances in MR angiography with 7T MRI: From microvascular imaging to functional angiography

Over the past few decades, vascular flow-dependent imaging techniques have proven to be effective for the visualization of large vessel diseases. However, these approaches are unlikely to be efficacious for small vessels because the affected small vessels cannot always be visualized directly, owing to a lack of detection sensitivity. Recently, many researchers have introduced state-of-the-art imaging techniques to visualize cerebral microvessels using ultra-high-field (UHF) magnetic resonance angiography (MRA). They have demonstrated the superiority of UHF MRA, especially for visualization of the microvasculature compared with clinical MRA images using 1.5T or 3T magnetic resonance imaging (MRI). Thus, UHF MRA may become an important investigative tool for research, facilitating examinations of vascular mechanisms for small vessel diseases and contributing to the early detection of cerebrovascular diseases in clinics. Furthermore, new imaging methods for visualizing vascular dynamics or flow effects may help investigate brain functions, especially in conjunction with blood oxygenation level-dependent contrast functional MRI modalities, as well as situations in which small vessel abnormalities are clinically important. The present article reviews recent technological advances in UHF MRA, especially 7T MRA, and discusses the potential benefits and future directions of UHF MRA.

Very large and giant microsurgical bifurcation aneurysms in rabbits: Proof of feasibility and comparability using computational fluid dynamics and biomechanical testing

BackgroundGiant aneurysms are challenging lesions with unacceptable high rates of aneurysm recanalization and rerupture following embolization. Reliable in vivo models are urgently needed to test the performance of new more efficient endovascular devices. Materials and methodsAneurysms were created in 11 New Zealand white rabbits (4.5–5.5kg): A long venous pouch (length 25–30mm) mimicking the aneurysm sac was derived from the external jugular vein and sutured into a microsurgically created bifurcation between both common carotid arteries. After 4 weeks the rabbits underwent 3T Magnetic resonance angiography (3T-MRA). Exemplary computational fluid dynamics (CFD) simulations were performed to compare the flow conditions of giant rabbit and human aneurysms. We used species-related boundary conditions, in particular, we measured blood viscosity values. Biaxial mechanical tests were performed for the mechanical characterization and comparison. Comparison with exisiting method(s)None. ResultsNo peri- or postoperative mortality was observed. 3T-MRA showed aneurysm patency in 10 out of 11 aneurysms (90.9%). Aneurysm lengths ranged from 21.5–25.6mm and aneurysm necks from 7.3–9.8mm. CFD showed complex flow profiles with multiple vortices in both, rabbit and human aneurysms. Lower blood viscosity values of the rabbit (3.92mPas vs. human 5.34mPas) resulted in considerable lower wall shear stress rates (rabbit 0.38Pa vs. human 1.66Pa). Mechanical tests showed lower stiffness of rabbit aneurysms compared to unruptured human aneurysms. ConclusionsThe proposed model showed favorable aneurysm patency rates, low morbidity and good hemodynamic comparability with complex flow patterns. Biomechanical testing suggests that experimental aneurysms might be even more fragile compared to human aneurysms.

Prevalence of Intracranial Atherosclerotic Stenosis Using High-Resolution Magnetic Resonance Angiography in the General Population: The Atherosclerosis Risk in Communities Study.

Intracranial atherosclerotic stenosis (ICAS) is a common cause of stroke, but little is known about its epidemiology. We studied the prevalence of ICAS and its association with vascular risk factors using high-resolution magnetic resonance angiography in a US cardiovascular cohort. The Atherosclerosis Risk in Communities (ARIC) study recruited participants from 4 US communities from 1987 to 1989. Using stratified sampling, we selected 1980 participants from visit 5 (2011-2013) for high-resolution 3T-magnetic resonance angiography. All images were analyzed in a centralized laboratory, and ICAS was graded as: no stenosis, <50% stenosis, 50% to 69% stenosis, 70% to 99% stenosis, and complete occlusion. We calculated per-vessel and per-person prevalence of ICAS (weighted for n=6538 visit 5 participants) and also estimated the US prevalence. We used multivariable logistic regression to identify variables independently associated with ICAS. Subjects who had an adequate magnetic resonance angiography (n=1765) were aged 67 to 90 years, 41% were men, 70% were white, and 29% were black. ICAS was prevalent in 31% of participants and 9% had ICAS ≥50%. Estimated US prevalence of ICAS ≥50% for 65 to 90 years old was 8% for whites and 12% for blacks. Older age, black race, higher systolic blood pressure, and higher low-density lipoprotein cholesterol levels were associated with increased odds of ICAS, whereas higher levels of high-density lipoprotein cholesterol and use of cholesterol-lowering medications were associated with decreased odds of ICAS. Body mass index and smoking were not associated with ICAS. The prevalence of ICAS in older adults is high, and it could be a target for primary prevention of stroke and dementia in this population.

Differential visceral blood flow in the hyperdynamic circulation of patients with liver cirrhosis

With advancing liver disease and the development of portal hypertension, there are major alterations in somatic and visceral blood flow. Using phase-contrast magnetic resonance angiography, we characterised alterations in blood flow within the hepatic, splanchnic and extra-splanchnic circulations of patients with established liver cirrhosis. To compare blood flow in splanchnic and extra-splanchnic circulations in patients with varying degrees of cirrhosis and healthy controls. In a single-centre prospective study, 21 healthy volunteers and 19 patients with established liver disease (Child's stage B and C) underwent electrocardiogram-gated phase-contrast-enhanced 3T magnetic resonance angiography of the aorta, hepatic artery, portal vein, superior mesenteric artery, and the renal and common carotid arteries. In comparison to healthy volunteers, resting blood flow in the descending thoracic aorta was increased by 43% in patients with liver disease (4.31 ± 1.47 vs. 3.31 ± 0.80 L/min, P = 0.011). While portal vein flow was similar (0.83 ± 0.38 vs. 0.77 ± 0.35 L/min, P = 0.649), hepatic artery flow doubled (0.50 ± 0.46 vs. 0.25 ± 0.15 L/min, P = 0.021) and consequently total liver blood flow increased by 30% (1.33 ± 0.84 vs. 1.027 ± 0.5 L/min, P = 0.043). In patients with liver disease, superior mesenteric artery flow was threefold higher (0.65 ± 0.35 vs. 0.22 ± 0.13 L/min, P < 0.001), while total renal blood flow was reduced by 40% (0.37 ± 0.14 vs. 0.62 ± 0.22 L/min, P < 0.001) and total carotid blood flow unchanged (0.62 ± 0.20 vs. 0.65 ± 0.13 L/min, P = 0.315). Rather than a generalised systemic hyperdynamic circulation, liver disease is associated with dysregulated splanchnic vasodilatation and portosystemic shunting that, while inducing a high cardiac output, causes compensatory extra-splanchnic vasoconstriction - the 'splanchnic steal' phenomenon. These circulatory disturbances may underlie many of the manifestations of advanced liver disease.

Abstract W P45: High Resolution Images of Perforating Arteries With 7T MRA in Acute Subcortical Infarction

Introduction: Patients with acute subcortical infarction show various clinical courses according to the pathology of perforating artery so that the noninvasive and precise neuroradiological evaluation of these arteries is very important for prevention of progression and recurrence of the disease. 7 Tesla (7T) - MRI (Magnetic Resonance Imaging) makes it possible to visualize perforating arteries in a way that would not otherwise be possible using conventional MRI. We attempted to assess perforating arteries and infarct lesions in the lenticulostriate artery (LSA) area using 7T- High resolution MRA (Magnetic Resonance Angiography), and to evaluate the association between image findings and clinical courses of treatment. Method: We included 13 patients (M:F = 7:6, mean age: 65 years old) with acute noncardioembolic stroke in LSA area detected by 1.5-T MRI. 7T MRI was acquired among these patients within 2 weeks after onset to visualize responsible LSA and to measure the volume of infarction by 7T-MRI- 3D-TOF MRA, 3D-FLAIR. We also evaluated the association between these results and the severity of stroke by National Institute of Health Stroke Scale (NIHSS). Results: Perforating arteries in the basal ganglia area were clearly visualized in all patients using 7T MRA. According to the location of occlusion and ischemic lesion, patients were categorized into 3 groups (A, B, and C): Group A - patients with proximal branch occlusion of LSA (2 cases), Group B - patients with occlusion of LSA adjacent to the ischemic lesion (7 cases), Group C - no occlusions (4 cases) in LSA associated with infarction. Significant association between overall infarct volume and NIHSS(r=0.636, p=0.020)was observed, whereas infarct volume of each group was not associated with NIHSS. Clinical outcome were not associated with volume of infarction in all cases(p=0.12). However, there were no patients whose symptoms progressed in Group C. Conclusion: 7 T-MRA can provide a clear visualization of perforating arteries and occluded lesions. It can be a useful and noninvasive diagnostic tool to study clinical prognosis after treatment in acute subcortical infarction.

EHMTI-0016. Examples of problematic use of references in the headache literature. A problem for readers, authors, referees, and editors ?

Methods Uncontrolled personal observations of dubious references in the headache literature. Examples: Statement: Nagata et al. (4) reported that spontaneous migraine was not associated with any dilation of the middle meningeal artery as measured by MRA. Reference: 4. Nagata E, et al. The middle meningeal artery during a migraine attack: 3T magnetic resonance angiography study. Intern Med 2009; 48: 2133–2135. Comment: Note that only one migraine attack was studied. Statement (from a kinetic study on orally inhaled DHE): Other routes of administration such as nasal delivery (40% bioavailability) have erratic and somewhat unpredictable pharmacokinetic (PK) properties that pose therapeutic challenges (eg, unpredictable clinical response or adverse events)(4) Reference: 4. Saper JR, Silberstein S. Pharmacology of dihydroergotamine and evidence for efficacy and safety in migraine. Headache 2006;46 (Suppl 4): S171-81(in this reference no mention at all of inconsistent kinetics of nasal DHE). Comment: The statement is from an industry-sponsored paper on kinetics of the new orally inhaled DHE and discredits to some extent nasal DHE. However, an extensive study of nasal DHE from 1996 demonstrated “the reliability and reproducibility” of nasal DHE’s pharmacokinetics (Humbert H, et al. Human pharmacokinetics of dihydroergotamine administered by nasal spray. Clin Pharmacol Ther 1996; 60: 265–275).

Intracranial microvascular imaging at 7 T MRI with transceiver RF coils

PurposeTo investigate intracranial microvascular images with transceiver radio-frequency (RF) coils at ultra-high field 7T magnetic resonance imaging (MRI). Materials and methodsWe designed several types of RF coils for the study of 7T magnetic resonance angiography and analyzed quantitatively each coil's performance in terms of the signal-to-noise ratio (SNR) profiles to evaluate the usefulness of RF coils for microvascular imaging applications. We also obtained the microvascular images with different resolutions and parallel imaging technique. ResultsThe overlapped 6-channel (ch) transceiver coil exhibited the highest performance for angiographic imaging. Although other multi-channel coils, such as 4- or 8-ch, were also suitable for fast imaging, these coils performed poorly in homogeneity or SNR for angiographic imaging. Furthermore, the 8-ch coil was poor in SNR at the center of the brain, while it had the highest SNR at the periphery. ConclusionThe present study has demonstrated that the overlapped 6-ch coil with large-size loop coils provided the best performance for microvascular imaging or angiography with the ultra-high-field 7T MRI, mainly because of its long penetration depth together with high SNR.

Micro‐vascular imaging experiences of time‐of‐flight MRA at 7T for cerebrovascular diseases

ABSTRACTSurgical or endovascular approaches have proved effective for large‐vessel diseases over the past decade. However, approaches for small vessel diseases are unlikely to be accomplished by those for large vessels and only few have been applied, because it is hard to access to those small vessels and one could not directly delineate the affected small vessels due to a lack of detection modalities. This study is to examine patients with vascular diseases using ultra‐high field 7T MRI with conventional time‐of‐flight (TOF) sequence, 3D fast low‐angle shot (FLASH) gradient‐echo. We have evaluated several radio‐frequency (RF) coils to find the optimal one for 7T magnetic resonance angiography (MRA), especially for micro‐vascular imaging. We have conducted several comparison studies with vascular disease patients. The results showed that micro‐vessels such as lenticulostriate arteries in the subjects with risk factors like hypertension or stroke patients were significantly less than in the healthy subjects. 7T MRA images in steno‐occlusive patients also showed clearly numerous collateral vessels not visible by 1.5T or 3T MRA. Furthermore, 7T MRA images were comparable to those obtained by digital subtraction angiography (DSA), particularly for micro‐vascular imaging. In this article, we would like to share the clinical experiences on 7T MRA that vascular images of 7T MRA were superior to conventional angiography images including 1.5T and 3T MRA, and even comparable to DSA. We also expect that further technical development and clinical applications of 7T MRA would be a clinically important diagnostic tool, in terms of an early detection of the stroke in a totally non‐invasive manner. © 2014 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 24, 121–128, 2014

Morphometric, geographic, and territorial characterization of brain arterial trees

Morphometric information of the brain vascularization is valuable for a variety of clinical and scientific applications. In particular, this information is important when creating arterial tree models for imposing boundary conditions in numerical simulations of the brain hemodynamics. The purpose of this work is to provide quantitative descriptions of arterial branches, bifurcation patterns, shape, and geographical distribution of the arborization of the main cerebral arteries as well as estimations of the corresponding vascular territories. For this purpose, subject-specific digital reconstructions of the brain vascular network created from 3T magnetic resonance angiography images of healthy volunteers are used to derive population-averaged morphometric characteristics of the cerebral arterial trees. Copyri