Low Carotid Flow Pulsatility Index Correlates With the Presence of Unruptured Intracranial Aneurysms.

Background We assessed cases of incidental unruptured intracranial aneurysm (UIA) discovered on screening magnetic resonance angiography to identify hemodynamic and atherosclerotic risk factors. Methods and Results The data of 1376 healthy older subjects (age range, 31-91 years) without cerebro- or cardiovascular diseases who underwent brain magnetic resonance angiography as part of a medical checkup program at a health screening center were examined retrospectively. We looked for an increase in classical risk factors for UIAs (age, sex, hypertension, and smoking) and laboratory data related to lifestyle diseases among subjects with UIAs. Brachial-ankle pulse wave velocity, central systolic blood pressure, radial augmentation index, and carotid flow pulsatility index were also compared between those with and without UIAs. We found UIAs in 79 (5.7%) of the subjects. Mean age was 67.1±9.0 years, and 55 (70%) were women. Of the 79 aneurysms, 75 (95%) were in the anterior circulation, with a mean diameter of 3.1 mm (range, 2.0-8.0 mm). Subjects with UIAs were significantly older and had more severe hypertension. The carotid flow pulsatility index was significantly lower in subjects with UIAs and negatively and independently correlated with UIAs. Tertile analysis stratified by carotid flow pulsatility index revealed that subjects with lower indices had higher levels of low-density lipoprotein cholesterol. Conclusions The presence of UIAs correlated with lower carotid flow pulsatility index and elevated low-density lipoprotein cholesterol in the data from a population of healthy older volunteers. A reduced carotid flow pulsatility index may affect low-density lipoprotein cholesterol elevation by some molecular pathways and influence the development of cerebral aneurysms. This may guide aneurysm screening indications for institutions where magnetic resonance angiography is not routine.

Focused Ultrasound Thalamotomy for Refractory Essential Tremor: A Japanese Multicenter Single-Arm Study.

BACKGROUND: Several feasibility studies and a randomized, controlled, multicenter trial have demonstrated the safety and efficacy of unilateral transcranial magnetic resonance-guided focused ultrasound (FUS) lesioning of the ventral intermediate thalamic nucleus in treating essential tremor. OBJECTIVE: To evaluate the safety and efficacy of FUS thalamotomy in a Japanese patient cohort through a prospective, multicenter, single-arm confirmatory trial. METHODS: A total of 35 patients with disabling refractory essential tremor underwent unilateral FUS thalamotomy and were followed up for 12 post-treatment months. Safety was measured as the incidence and severity of treatment-related adverse events. Efficacy was measured as the tremor severity and quality of life improvements using the Clinical Rating Scale for Tremor and Questionnaire for Essential Tremor. RESULTS: The mean skull density ratio (SDR) was 0.47. There was a significant decrease in the mean postural tremor score of the treated hand from baseline to 12 mo by 56.4% (95% CI: 46.7%-66.1%; P < .001), which was maintained at last follow-up. Quality of life improved by 46.3% (mean overall Questionnaire for Essential Tremor score of 17.4 [95% CI: 12.1-22.7]) and there were no severe adverse events. The most frequent adverse event was gait disturbance and all events resolved. CONCLUSION: Unilateral FUS thalamotomy allowed significant and sustained tremor relief and improved the quality of life with an outstanding safety profile. The observed safety and efficacy of FUS thalamotomy were comparable to those reported in a previous multicenter study with a low SDR, and inclusion of the low SDR group did not affect effectiveness.

Mismatch between TOF MR Angiography and CT Angiography of the Middle Cerebral Artery may be a Critical Sign in Cerebrovascular Dynamics.

PURPOSE: Although time-of-flight (TOF)-magnetic resonance angiography (MRA) can clearly depict intracranial arteries, the arterial flow of middle cerebral artery (MCA) is occasionally not detected. We evaluated this phenomenon with reference to cerebrovascular dynamics. MATERIALS AND METHODS: Seventeen patients with suspected occlusion of MCA or internal carotid artery on TOF-MRA were enrolled. All patients underwent CT angiography (CTA) and quantitative cerebral blood flow (CBF) examination for measurement of resting CBF and cerebrovascular reactivity (CVR). Depending on appearance, patients were categorized into three groups. Group A (n=6) had MCA delineation on both MRA and CTA, while groups B (n=6) and C (n=5) had no signal on MRA, but Group B had a MCA delineation on CTA. RESULTS: No significant difference between resting CBF and CBF after the administration of acetazolamide was seen among 3 groups. In contrast, mean CVR in group B was -19.7±18.1%, which was significantly lower than group A [36.4±21.7% (p<0.05)], but not than group C (21.4±35.2%). Furthermore, all patients in group B displayed a so-called steal phenomenon. CONCLUSION: This study is the first to show that visualization of MCA on TOF-MRA closely correlates with CVR, and that a vascular pattern showing no MCA signal intensity on MRA but with MCA delineation on CTA indicates a critical cerebrovascular condition.

Utility of 3-dimensional ultrasound imaging to evaluate carotid artery stenosis: comparison with magnetic resonance angiography.

BACKGROUND: We evaluated the utility of 3-dimensional (3-D) ultrasound imaging for assessment of carotid artery stenosis, as compared with similar assessment via magnetic resonance angiography (MRA). METHODS: Subjects comprised 58 patients with carotid stenosis who underwent both 3-D ultrasound imaging and MRA. We studied whether abnormal findings detected by ultrasound imaging could be diagnosed using MRA. Ultrasound images were generated using Voluson 730 Expert and Voluson E8. RESULTS: The degree of stenosis was mild in 17, moderate in 16, and severe in 25 patients, according to ultrasound imaging. Stenosis could not be recognized using MRA in 4 of 17 patients diagnosed with mild stenosis using ultrasound imaging. Ultrasound imaging showed ulceration in 13 patients and mobile plaque in 6 patients. When assessing these patients, MRA showed ulceration in only 2 of 13 patients and did not detect mobile plaque in any of these 6 patients. Static 3-D B mode images demonstrated distributions of plaque, ulceration, and mobile plaque, and static 3-D flow images showed flow configuration as a total structure. Real-time 3-D B mode images demonstrated plaque and vessel movement. Carotid artery stenting was not selected for patients diagnosed with ulceration or mobile plaque. CONCLUSIONS: Ultrasound imaging was necessary to detect mild stenosis, ulcerated plaque, or mobile plaque in comparison with MRA, and 3-D ultrasound imaging was useful to recognize carotid stenosis and flow pattern as a total structure by static and real-time 3-D demonstration. This information may contribute to surgical planning.

Initial experience in evaluating the prevalence of unruptured intracranial aneurysms detected on 3-tesla MRI.

BACKGROUND: Given the very poor outcome of ruptured intracranial aneurysms, detection and treatment of unruptured intracranial aneurysms by a less invasive examination have become important. For this purpose, 3-tesla (3T) magnetic resonance imaging (MRI) is the most suitable candidate, owing to its high signal/noise ratio and frequency resolution. However, few reports have investigated the prevalence of intracranial aneurysms with high-tesla MRI. Here, we evaluated the prevalence of intracranial aneurysms and the effectiveness of a 3T MRI system in their detection. METHODS: During a 1-year period, a total of 3,414 consecutive patients undergoing MR angiography with 3T MRI for the first time were enrolled. Diagnosis of intracranial aneurysm was made by two neuroradiologically trained medical doctors under complete blinding to patient information. When intracranial aneurysm was suspected, volume-rendering images were created for more accurate diagnosis. RESULTS: Surprisingly, 317 unruptured intracranial aneurysms were identified in 286 of 3,414 cases (8.4%); 151 unruptured aneurysms (47.6%) occurred in the internal carotid artery, 85 (26.8%) in the middle cerebral artery, 54 (17.0%) in the anterior cerebral artery, and 27 (8.5%) in the posterior circulation. Of these, 152/317 (47.9%) were <3 mm, 104 (32.8%) ranged from 3 to 5 mm, 5 (11.0%) from 5 to 7 mm, and 26 (8.2%) were >7 mm. No significant difference in size was seen among the four locations. CONCLUSIONS: For the first time, this study assessed the detection rate of intracranial aneurysms using 3T MRI. Results showed a higher detection rate than previously documented. The reason for this higher rate is likely the improved ability of this modality to detect unruptured aneurysms in the internal carotid artery and those <3 mm.

Asymptomatic cerebral microbleeds seen in healthy subjects have a strong association with asymptomatic lacunar infarction.

BACKGROUND: Cerebral microbleed (CMB), which is conspicuous on gradient-echo T2-weighted magnetic resonance imaging, is a risk factor of intracerebral hemorrhage (ICH). CMBs have been detected even in neurologically healthy persons, who also seem prone to be affected by stroke, not only ICH but also cerebral infarction. METHODS AND RESULTS: The presence of CMB was investigated in brain dock participants, making reference to silent lacunar infarction (SLI). Participants comprised 377 neurologically healthy persons and 21 (5.6%) had CMB detected, which was associated with a high incidence of hypertension, other conventional risk factors having no significant correlation with CMB. In a simple correlation analysis, CMB showed a positive association with age and systolic blood pressure (SBP). Logistic regression analysis revealed that SLI was the factor most strongly associated with CMB. Moreover, individuals who had both CMB and SLI had higher SBP than other groups. CONCLUSIONS: The etiology of CMB is similar to that of SLI.

Diagnosis of unruptured intracranial aneurysms: 3T MR angiography versus 64-channel multi-detector row CT angiography.

BACKGROUND AND PURPOSE: We compared 3-dimensional time-of-flight magnetic resonance angiography (3D TOF MRA) using a 3-tesla (T) MR unit with 64-channel multi-detector row computed tomographic angiography (64-MDCTA) for detection and characterization of angiographically proven unruptured intracranial aneurysms. METHODS: Thirty-eight patients with 47 aneurysms and 8 patients without aneurysms underwent 3T, 3D TOF MRA; 64-MDCTA; and intra-arterial angiography. As a first study, 3 radiologists blinded to pertinent clinical information independently reviewed MRA and CTA images. We evaluated diagnostic accuracy using an alternative free-response receiver operating characteristic (AFROC) analysis and evaluated the sensitivity and specificity of each technique. Next, 2 radiologists used volume-rendering images generated from MRA or CTA data to evaluate the morphology of the 47 aneurysms detected, and MRA and CTA results were compared. Three-dimensional digital angiography (DA) images were used as the standard of reference. RESULTS: On the AFROC analysis, the value of the mean area under the AFROC curve (A(1)) was 0.91 for both modalities. Mean sensitivity of 89% and specificity of 76% for MRA were not significantly different from sensitivity of 87% and specificity of 79% for CTA. Therefore, when used to evaluate aneurysmal morphology, both modalities appear satisfactory for determining these vascular anomalies. CONCLUSION: Three-tesla, 3D TOF MRA and 64-MDCTA are excellent modalities with high diagnostic accuracy for evaluating unruptured intracranial aneurysms and no significant difference between them in diagnostic performance.

Sensitivity of an eight-element phased array coil in 3 Tesla MR imaging: a basic analysis.

PURPOSE: To evaluate the performance advantages of an 8-element phased array head coil (8 ch coil) over a conventional quadrature-type birdcage head coil (QD coil) with regard to the signal-to-noise ratio (SNR) and image uniformity in 3 Tesla magnetic resonance (MR) imaging. MATERIALS AND METHODS: We scanned a phantom filled with silicon oil using an 8 ch coil and a QD coil in a 3T MR imaging system and compared the SNR and image uniformity obtained from T(1)-weighted spin echo (SE) images and T(2)-weighted fast SE images between the 2 coils. We also visually evaluated images from 4 healthy volunteers. RESULTS: The SNR with the 8 ch coil was approximately twice that with the QD coil in the region of interest (ROI), which was set as 75% of the area in the center of the phantom images. With regard to the spatial variation of sensitivity, the SNR with the 8 ch coil was lower at the center of the images than at the periphery, whereas the SNR with the QD coil exhibited an inverse pattern. At the center of the images with the 8 ch coil, the SNR was somewhat lower, and that distribution was relatively flat compared to that in the periphery. Image uniformity varied less with the 8 ch coil than with the QD coil on both imaging sequences. CONCLUSION: The 8 ch phased array coil was useful for obtaining high quality 3T images because of its higher SNR and improved image uniformity than those obtained with conventional quadrature-type birdcage head coil.

[Assessment of hemodynamics of meningioma with dynamic MR imaging].

Dynamic MR imaging provides hemodynamic information about normal and pathologic tissue of the brain. The purpose of our study was to evaluate the usefulness of dynamic MR imaging in the assessment of tumor vascularity and the tumor tissue blood flow of meningiomas. We studied 13 patients with meningiomas using dynamic spin-echo MR imaging. The histological subtypes of meningioma were confirmed by the examination of surgical specimens in all patients, and tumors were meningothelial in 9 cases, fibrous in 2, transitional in 1, and psammomatous in 1. Serial images were obtained every 18-24 sec for 8 minutes and 30 seconds after rapid injection of gadolinium diethylenetriaminepentaacetic acid. Different parameters (time to peak, maximum of signal intensity and the washout ratio) were calculated directly from signal intensity curves. As an indicator of tumor vascularity, microvessel density was counted based on immunohistochemically stained sections and tumor tissue blood flow was measured using an xenon-CT system. The maximum of signal intensity corresponded to the tumor vascularity. With dynamic MR imaging, the time intensity curves (TI curves) were divided into two patterns; type 1 had a steep increase with a peak and type 2 had a slow increase to a peak followed by plateau. The maximum of signal intensity measured from TI curve of dynamic MR imaging correlated significantly with microvessel density (R2 = 0.840, p < 0.0001). Linear regression revealed a significant positive relation between the washout ratio and the tumor tissue blood flow in group showed type 1 on TI curve (R2 = 0.961, p < 0.001). There was also a significant negative correlation between the time to peak and the tumor tissue blood flow (R2 = 0.792, p < 0.01). We suggest that dynamic MR imaging is useful for evaluating hemodynamics of meningiomas.