Assessment of magnetic field interactions and heating for cerebral aneurysm flow diverters during 7T MRI.

Flow diverters (FDs) are utilized for a wide range of aneurysms, but show safety issues such as adverse interactions with static magnetic fields (displacement force and torque) and radiofrequency-induced heating during magnetic resonance imaging (MRI). The present study aimed to assess these adverse interactions in a 7-tesla (7T) static magnetic field and radiofrequency-induced heating during a 7T MRI for two types of FD. Displacement force and magnetically induced torque were assessed using the deflection angle method and low friction surface method, respectively. To assess heating, each FD was set in a phantom filled with gelled-saline mixed with polyacrylic acid and underwent a 7T MRI using a three-dimensional fast spin echo method. Displacement force and magnetically induced torque in the 7T static magnetic field were undetectable, and radiofrequency-induced heating during 7T MRI remained ≤ 0.6 °C for both types of FD, suggesting that magnetic field interactions and heating on FDs during a 7T MRI are acceptable from a safety perspective.

Feasibility of Diffusion-weighted Imaging (DWI) for Assessing Cerebrospinal Fluid Dynamics: DWI-fluidography in the Brains of Healthy Subjects.

PURPOSE: The present study aimed to investigate whether diffusion-weighted imaging (DWI) can qualify and quantify cerebrospinal fluid (CSF) dynamics in the brains of healthy subjects. For this purpose, we developed new DWI-based fluidography and compared the CSF dynamics seen on the fluidography with two apparent diffusion coefficients obtained with different DWI signal models at anatomical spaces filled by CSF. METHODS: DWI with multiple b values was performed for 10 subjects using a 7T MRI scanner. DWI-fluidography based on the DWI signal variations in different motion probing gradient directions was developed for visualizing the CSF dynamics voxel-by-voxel. DWI signals were measured using an ROI in the representative CSF-filled anatomical spaces in the brain. For the multiple DWI signals, the mono-exponential and kurtosis models were fitted and two kinds of apparent diffusion coefficients (ADCC and ADCK) were estimated in each space using the Gaussian and non-Gaussian diffusion models, respectively. RESULTS: DWI-fluidography could qualitatively represent the features of CSF dynamics in each anatomical space. ADCs indicated that the motions at the foramen of Monro, the cistern of the velum interpositum, the quadrigeminal cistern, the Sylvian cisterns, and the fourth ventricle were more drastic than those at the subarachnoid space and anterior horns of the lateral ventricle. Those results seen in ADCs were identical to the findings on DWI-fluidography. CONCLUSION: DWI-fluidography based on the features of DWI signals could show differences of CSF dynamics among anatomical spaces.

Using a low-metal-density stent for thrombectomy-resistant vertebrobasilar occlusion due to thrombus migration from a thrombosed vertebral artery aneurysm: illustrative case.

BACKGROUND: Thrombosed intracranial aneurysms can lead to large vessel occlusion as a result of spontaneous thrombosis. Although mechanical thrombectomy is likely effective, recurrent thromboembolism can occur if the thrombotic source remains untreated. The authors describe a case of recurrent vertebrobasilar artery occlusion due to thrombus migration from a large thrombosed vertebral artery (VA) aneurysm that was successfully treated with mechanical thrombectomy followed by stenting. OBSERVATIONS: A 61-year-old male previously diagnosed with a large, thrombosed VA aneurysm presented with right hypoesthesia. Imaging on admission showed left VA occlusion and an acute ischemic lesion in the left medial medulla. His symptoms worsened, with complete right hemiparesis and tongue deviation occurring 3 hours after admission, and mechanical thrombectomy was performed to recanalize the left-dominant VA. Despite several attempts, reocclusion of the vertebrobasilar system occurred after each mechanical thrombectomy because of repeated thrombus formation in the thrombosed aneurysm. Therefore, a low-metal-density stent was deployed to prevent thrombus migration into the parent artery, which resulted in complete recanalization and rapid improvement of the symptoms. LESSONS: Stenting with a low-metal-density stent for recurrent embolism secondary to thrombus migration from a large thrombosed aneurysm was feasible in the acute stroke setting.

Predicting Intracardiac Thrombus Formation in the Left Atrial Appendage Using Machine Learning and CT Images.

This paper proposes a comprehensive method for estimating thrombus formation factors in the left atrial appendage (LAA). First, using 3D CT (Computer Tomography) image data as input, classification of thrombus presence/absence is learned using 3D ResNet. Besides, 3D Grad-CAM is applied to the prediction results to visualize regions of interest in thrombus formation. Second, features are extracted based on the visualization of regions of interest. Using the extracted features and numerical data obtained from the hospital as input, a regression analysis is performed to predict the presence/absence of thrombus using LightGBM. Visualization of regions of interest using 3D ResNet and 3D Grad-CAM shows that the right inferior pulmonary vein and the LAA were particularly correlated with thrombus formation. Estimation of important factors for thrombus formation using LightGBM shows that the LAA ostium area has the greatest influence on thrombus formation.Clinical Relevance-This paper shows the factors that contribute to thrombus formation in the LAA from the viewpoint of three-dimensional structure. In addition, the features considered important in thrombus formation were identified by comparing a variety of features.

Ruptured Aneurysm at the Origin of an Anomalous Callosomarginal Artery Arising from the A1 Segment of the Anterior Cerebral Artery-A Case Report.

Aneurysms of the A1 segment of the anterior cerebral artery tend to develop in combination with various vascular anomalies of the A1 segment. Arterial branches that originate from the A1 segment and perfuse cortical regions are known to be rare. In this report, we describe a 48-year-old woman who presented with a ruptured aneurysm at the origin of an anomalous cortical artery arising from the A1 segment, for which microsurgical neck clipping was performed. Intraoperatively, the anomalous artery was seen to originate from the A1 segment, running into the interhemispheric fissure. An aneurysm was located at the bifurcation of the anomalous artery and the A1 segment. Postoperative angiography showed that the anomalous artery has branched into the fronto-orbital artery and the frontopolar artery and terminated as the anterior internal frontal arteries. We report a rare case of an aneurysm arising from an anomalous callosomarginal artery that arose from the A1 segment and perfused the cortical region. It is of significance to recognize that an aneurysm can develop at the origin of an anomalous artery that arises from the A1 segment.