MRA Images Research Articles

Magnetic resonance angiography and perfusion mapping by arterial spin labeling using Fourier transform-based velocity-selective pulse trains: Examination on a commercial perfusion phantom.

Purpose:Benchmarking of flow and perfusion MR techniques on standardized phantoms can facilitate the use of advanced angiography and perfusion-mapping techniques across multiple sites, field strength, and vendors. Here, MRA and perfusion mapping by arterial spin labeling (ASL) using Fourier transform (FT)–based velocity-selective saturation and inversion pulse trains were evaluated on a commercial perfusion phantom.Methods:The FT velocity-selective saturation–based MRA and FT velocity-selective inversion–based ASL perfusion imaging were compared with time-of-flight and pseudo-continuous ASL at 3 T on the perfusion phantom at two controlled flow rates, 175 mL/min and 350 mL/min. Velocity-selective MRA (VSMRA) and velocity-selective ASL (VSASL) were each performed with three velocity-encoding directions: foot–head, left–right, and oblique 45°. The contrast-to-noise ratio for MRA scans and perfusion-weighted signal, as well as labeling efficiency for ASL methods, were quantified.Results:On this phantom with feeding tubes having only vertical and transverse flow directions, VSMRA and VSASL exhibited the dependence of velocity-encoding directions. The foot–head-encoded VSMRA and VSASL generated similar signal contrasts as time of flight and pseudo-continuous ASL for the two flow rates, respectively. The oblique 45°–encoded VSMRA yielded more uniform contrast-to-noise ratio across slices than foot–head and left–right-encoded VSMRA scans. The oblique 45°–encoded VSASL elevated labeling efficiency from 0.22–0.68 to 0.82–0.90 through more uniform labeling of the entire feeding tubes.Conclusion:Both FT velocity-selective saturation–based VSMRA and FT velocity-selective inversion–based VSASL were characterized on a commercial perfusion phantom. Careful selection of velocity-encoding directions along the major vessels is recommended for their applications in various organs.

Abstract P344: Validation of Computational Fluid Dynamics Against PC-MRI Measurements of Blood Flow in Healthy Intracranial Arteries: On the Threshold to Clinical Utility for Stroke Prediction

Aim: Computational Fluid Dynamics (CFD) modeling of blood flow is a promising technique to obtain hemodynamic biomarkers and predict recurrent strokes. Few studies, however, have validated CFD against other methods for measuring hemodynamics, e.g. phase contrast MRI (PC-MRI). To resolve the uncertainties about the accuracy of CFD, this study validates the results of an automated software that combines deep learning and CFD for simulating blood flow given an MR angiogram against PC-MRI. Methods: Intracranial arteries in 10 healthy volunteers (60% male, mean age 38 ± 16 years) were automatically segmented from TOF MRA obtained at 3T using deep learning. Subject-specific CFD modelling was undertaken. PC-MRI flow rate for each subject was used at the inlet boundary condition, but not at the outlets. Outlet boundary condition was set to lumped parameter Windkessel model, with the resistance programmatically determined using allometric scaling laws based on the dimension and branching of vasculature. For comparison, two commonly used outlet conditions (exponent 2 & 3 in Murray’s Law) were also considered. CFD results for flow rate and wall shear stress were compared against PC-MRI using Pearson’s correlation coefficient. Results: The flow rate across major intracranial arteries from CFD was in excellent agreement with the PC-MRI (MCA: r = 0.83, ACA: r = 0.81 & PCA: r = 0.82). In addition, there was good correlation for both wall shear stress (WSS) and WSS Ratio (WSSR, i.e. the ratio of WSS between a branch and its parent vessel) (MCA (WSS/WSSR): r = 0.6/0.77, ACA (WSS/WSSR): r = 0.86/0.93 & PCA (WSS/WSSR): r = 0.72/0.85). The inter-subject variability of the flow rate (i.e. standard deviation) obtained from CFD matched closely the variation range observed from PC-MRI and the literature. The two alternative outlet models behaved similarly but suffered from vessel truncation and high errors in some cases. Conclusion: CFD modelling of blood flow in intracranial arteries from static images has good agreement with PC-MRI measurements when allometric scaling laws are applied for setting Windkessel outflow conditions. This lays the foundation for using CFD to predict recurrent strokes as the technique uses standard MRA images already commonly acquired for stroke evaluation.

Analisis Variasi Flip Angle terhadap Informasi Citra Anatomi pada Sekuen 3D TOF MRA Brain dengan MRI 3 Tesla

Background : Magnetic Resonance Angiography is a diagnostic imaging method that can display images of blood vessels. MRA imaging on MRI 3 Tesla provides high spatial resolution making blood vessel contrast increased so that the intracranial vessels are clearer. The efficient technique that does not use contrast media in MRA is Time of Flight. 3D TOF imaging is good for visualizing intracranial vessels. In this method the appropriate flip angle will produce a hyperintense picture of the blood vessels. This study aims to determine the effect of flip angle on anatomical image information on 3D TOF MRA Brain.Methods : This type of research is a quantitative experimental approach, conducted in February 2020 in Pertamina Central Hospital, South Jakarta. Research by conducting flip angle variations of 15°, 20°, 25°, 30° in the 3D TOF sequence of the Brain against 10 volunteers. Criteria for volunteers are healthy people aged 18-25 years. The results of the images were assessed by 3 respondent, including Internal Carotid Artery, Vertebral Artery, Basilar Artery, Anterior Cerebral Artery, Posterior Cerebral Artery, Middle Cerebral Artery, Anterior Communicating Artery, Posterior Communicating Artery. Then the Kappa test was carried out followed by the Friedman test to find the highest mean rank and comparison of flip angle in anatomical information of 3D TOF MRA Brain.Results : The results showed that there was an effect of changes in the values of the flip angle to the anatomical information on 3D TOF MRA Brain with p 0,05. The optimal Flip angle value is obtained based on the highest mean rank value which is flip angle 25° with a value of 3,22. The higher the value of flip angle, the greater the signal and contrast, but many slow flowing blood vessels will hypointens.Conclussion : There are difference in anatomical image information of 3D TOF sequence among 4 variation flip angle on examination MRA Brain. Flip angle 25° is better than 15°, 20° and 30° at anatomy information on 3D TOF sequences to show intracranial artery because it has a higher mean rank value.

A comparative analysis framework of 3T and 7T TOF-MRA based on automated cerebrovascular segmentation.

High field strength 3T and 7T Time-Of-Flight Magnetic Resonance Angiography (TOF- MRA) achieves better visualization of intracranial vessels, so it attracts much attention. However, quantitative comparison between 3T and 7T MRA is lacking in the aspects of image quality and the practical application of cerebrovascular diseases. In this paper, a quantitative framework of 3T and 7T TOF-MRA comparison is proposed, which contains two steps including the automated cerebrovascular segmentation and statistical analysis. Firstly, the whole vascular structures on both 3T and 7T TOF-MRA images are segmented automatically, especially those small blood vessels in 7T MRA. The skeleton extraction-based automatic seed point detection is implemented to ensure the segmented vascular structure complete and precise. Secondly, the statistical analysis of the differences between 3T and 7T MRA is carried out in the aspects of image quality and the characteristics of some important vessels. The objects of statistical analysis are achieved and analyzed automatically without needing the time- consuming human beings' participation, therefore, it is efficient and objective. The comparison experiments on seven pairs of 3T and 7T TOF MRA images validated that about image quality, the contrast-to-noise ratio of 7T MRA was about 4.53 ± 0.95 times as much as that of 3T MRA. About the cerebrovascular information, small vessels were more abundant in 7T MRA compared with 3T MRA (branches number: 462.0 ± 58.5 vs 393.1 ± 63.3). The proposed framework can segment the whole cerebrovascular structure automatically and compare TOF-MRA with different field strengths objectively and quantitatively. It is helpful for clinical cerebrovascular disease, especially cerebral small vessel diseases.

Assessment of 4D MR Angiography at 3T Compared with DSA for the Follow-up of Embolized Brain Dural Arteriovenous Fistula: A Dual-Center Study.

4D contrast-enhanced MRA in the follow-up of treated dural arteriovenous fistulas has rarely been evaluated. Our aim was to evaluate its diagnostic performance at 3T in the follow-up of embolized dural arteriovenous fistulas using DSA as the standard of reference. Patients treated for dural arteriovenous fistulas in 2 centers between 2008 and 2019 were included if they met the following criteria: 1) dural arteriovenous fistula embolization, and 2) follow-up imaging with <6 months between DSA and 4D contrast-enhanced MRA. Two readers reviewed the 4D contrast-enhanced MRA images, first independently, then in consensus to detect any residual/recurrent dural arteriovenous fistula and to grade cases according to the Cognard classification system. Interobserver and intermodality agreement for the detection of a residual dural arteriovenous fistula and stratification of bleeding risk (0-I-IIa; IIb-IIa+b-III-IV-V) was calculated using κ coefficients. A total of 51 pairs of examinations for 44 patients (median age, 65 years; range, 25-81 years) were analyzed. Interobserver agreement for the detection and stratification of bleeding risk was, respectively, κ = 0.8 (95% CI, 0.6-1) and κ = 0.8 (95% CI, 0.5-1). After consensus review, the sensitivity and specificity of 4D contrast-enhanced MRA for the detection of residual/recurrent dural arteriovenous fistula was 63.6% (95% CI, 40.7%-82.8%) and 96.6% (95% CI, 82.2%-99.9%), respectively. The positive and negative predictive values of 4D contrast-enhanced MRA were 93.3% (95% CI, 68.1%-99.8%) and 77.8% (95% CI, 60.8%-89.9%). Intermodality agreement for the detection and stratification of bleeding risk was good, with κ = 0.60 (95% CI, 0.3-0.8). 4D contrast-enhanced MRA at 3T is of interest in the follow-up of treated dural arteriovenous fistulas but lacks the sensitivity to replace arteriography.

Arterial Spin-Labeling Perfusion for PHACE Syndrome.

Arterial stroke is a rare-but-reported complication in patients with posterior fossa brain malformations, hemangiomas, arterial anomalies, coarctation of the aorta and cardiac defects, and eye abnormalities (PHACE) syndrome. Currently, stroke risk is inferred by the severity of arterial anomalies identified on MRA, though no evidenced-based data exist. The purpose of our study was to determine whether arterial spin-labeling MR imaging perfusion can detect alterations in CBF in patients with PHACE syndrome. Records were reviewed from 3 institutions for all patients with PHACE syndrome who underwent arterial spin-labeling from 2000 to 2019. CBF was qualitatively investigated with arterial spin-labeling to determine whether there was decreased or normal perfusion. Arterial anomalies were characterized on MRA imaging, and parenchymal brain findings were evaluated on conventional MR imaging sequences. Forty-one patients with PHACE syndrome had arterial spin-labeling imaging. There were 30 females and 11 males (age range, 7 days to 15 years). Of the 41 patients, 10 (24%) had decreased CBF signal corresponding to a major arterial territory. Ten of 10 patients had decreased CBF signal in the anterior circulation, 2/10 had decreased anterior and posterior circulation CBF signal, 2/10 had decreased bilateral anterior circulation CBF signal, and 1/10 had globally decreased CBF signal. Forty of 41 (97.5%) patients had at least 1 arteriopathy, and in those with decreased CBF signal, the arteriopathy corresponded to the CBF signal alteration in 10/10 patients. Arterial spin-labeling can potentially characterize hemodynamic changes in patients with PHACE syndrome.

1D CNN-Based Intracranial Aneurysms Detection in 3D TOF-MRA

How to automatically detect intracranial aneurysms from Three-Dimension Time of Flight Magnetic Resonance Angiography (3D TOF MRA) images is a typical 3D image classification problem. Currently, the commonly used method is the Maximum Intensity Projection- (MIP-) based way. It transfers 3D classification into 2D case by projecting the 3D patch into 2D planes along different directions on the basis of voxel’s intensity. After then, the 2D Convolutional Neural Network (CNN) is established to do classification. It has been shown that the MIP-based method can reduce the demands for the samples and increase the computation efficiency. Meanwhile, the accuracy is comparable with that of 3D image classification. Inspired by the strategy of MIP, we want to further reduce the demands for samples and accelerate the training by transferring the 2D image classification into 1D case, i.e., we want to generate the 1D vectors from the MIP images and then establish a 1D CNN to do intracranial aneurysm detection and classification for 3D TOF MRA image. Specifically, our method first extracts a series of patches as the Region of Interests (ROIs) along the blood vessels from the original 3D TOF MRA 3D image. The corresponding MIP images of each ROI will be obtained through maximum intensity projecting. Then, we generate a series of 1D vectors by accumulating each MIP image along different directions. Meanwhile, a 1D CNN is established to detect aneurysms, in which, the input is the obtained 1D vectors and the output is the binary classification result denoting whether there are intracranial aneurysms in the considered patch. Generally, compared with 2D- and 3D-CNN, the 1D CNN-based way greatly accelerates the training and shows stronger robustness in the case of fewer samples. The efficiency of the proposed method outperforms the 2D CNN about 10 times in CPU training. Yet, their accuracies are close.

Carotid Webs in Pediatric Acute Ischemic Stroke

IntroductionCarotid web is a radiographic entity located in the posterior aspect of the origin of the internal carotid arteries, considered to be a pathologic equivalent to intimal fibromuscular dysplasia, and has been implicated in acute ischemic strokes. The mechanism underlying its development is unknown and it remains unclear if this lesion is congenital or acquired. The aim of our study was to determine the frequency of carotid webs in a pediatric population with acute ischemic stroke (AIS). MethodsA retrospective review of neck CTA, MRA, or DSA images in a pediatric population with acute ischemic stroke was performed to determine the occurrence of carotid webs. Two fellowship-trained neurointerventionists performed independent vascular imaging review. ResultsWe identified forty-seven cases of childhood acute ischemic stroke (55% male; median age, 9 years). Congenital heart disease, sickle cell disease, infection, and recent head/neck trauma were the most common risk factors. Eight of the ischemic stroke cases were located in multiple vascular territories. Neck arterial imaging was undertaken in twenty-four patients. No carotid webs were detected in the studied pediatric stroke population. (The correlation coefficient for the determination of webs was Kappa = 1.00; p < 0.001). ConclusionThis study failed to find evidence that carotid webs are congenital. More studies are needed for a better understanding of carotid web origin, natural evolution, and the potential implications for treatment.

A novel sequence for simultaneous measurement of whole-brain static and dynamic MRA, intracranial vessel wall image, and T1 -weighted structural brain MRI.

To propose a highly time-efficient imaging technique named improved simultaneous noncontrast angiography and intraplaque hemorrhage (iSNAP) for simultaneous assessment of lumen, vessel wall, and blood flow in intracranial arteries. iSNAP consists of pulsed arterial spin labeling preparations and 3D golden angle radial acquisition. Images were reconstructed by k-space weighted image contrast (KWIC) method with optimized data-sharing strategies. Dynamic MRA for blood flow assessment was obtained from iSNAP by reconstruction at multiple inversion times and image subtraction, static MRA by both image subtraction approach and phase-sensitive inversion recovery technique, and vessel wall images by both reconstruction at zero-crossing time-point of blood and phase-sensitive inversion recovery. A T1 -weighted brain MRI was also reconstructed from iSNAP. Preliminary comparison of iSNAP against the dedicated dynamic MRA sequence 4D-TRANCE, MRA/vessel wall imaging sequence SNAP, and vessel wall imaging sequence T1 -weighted VISTA was performed in healthy volunteers and patients. iSNAP has whole-brain coverage and takes ~6.5 min. The dedicated reconstruction strategies are feasible for each iSNAP image contrast and beneficial for image SNR. iSNAP-dynamic MRA yields similar dynamic flow information as 4D-TRANCE and allows more flexible temporal resolution. The 2 types of iSNAP static MRA images complement each other in characterizing both proximal large arteries and distal small arteries. Depiction of vessel wall lesions in iSNAP vessel wall images is better than SNAP and may be similar to T1 -weighted VISTA, although the images are slightly blurred. iSNAP provides a time-efficient evaluation of intracranial arteries and may have great potential for comprehensive assessment of intracranial vascular conditions using a single sequence.

Quantitative Analysis of the Cerebral Vasculature on Magnetic Resonance Angiography

The arterial connections in the Circle of Willis are a central source of collateral blood flow and play an important role in pathologies such as stroke and mental illness. Analysis of the Circle of Willis and its variants can shed light on optimal methods of diagnosis, treatment planning, surgery, and quantification of outcomes. We developed an automated, standardized, objective, and high-throughput approach for categorizing and quantifying the Circle of Willis vascular anatomy using magnetic resonance angiography images. This automated algorithm for processing of MRA images isolates and automatically identifies key features of the cerebral vasculature such as branching of the internal intracranial internal carotid artery and the basilar artery. Subsequently, physical features of the segments of the anterior cerebral artery were acquired on a sample and intra-patient comparisons were made. We demonstrate the feasibility of using our approach to automatically classify important structures of the Circle of Willis and extract biomarkers from cerebrovasculature. Automated image analysis can provide clinically-relevant vascular features such as aplastic arteries, stenosis, aneurysms, and vessel caliper for endovascular procedures. The developed algorithm could facilitate clinical studies by supporting high-throughput automated analysis of the cerebral vasculature.

PENGARUH TIME REPETITION (TR) DAN FLIP ANGLE (FA) TERHADAP INFORMASI ANATOMI PADA 3D TOF MRA PEMERIKSAAN BRAIN DENGAN MRI 1.5 TESLA

Background: In MR angiography examination of the brain, there are many clinical situations where radiologist want to optimal suppression of stasionary nuclei. So stasionary nuclei and flowing nuclei will produce a good contrast. One of the most commonly used method MR angiography of the brain is a 3D TOF because it can show the blood vessels by hyperintens with more hypointens of background. Parameters TR and flip angle is one of the parameters that will determine a stasionary nuclei experiencing suppression well and the flowing nuclei will still generate a signal that more hyperintens. The porpose of this study was to determine the influence of repetition time and flip angle of the anatomical information of 3D TOF MRA examination of the brain, and also to determine value the repetition time and flip angle best to display anatomical information of 3D TOF MRA examination of the brain.&#x0D; Methods: This research is an experimental approach to the pre-experimental research design and post-test only research design. This research was conducted in Bintaro Premier Hospital. The data in the form of 54 3D TOF MRA images brain of 6 volunteers with nine variations repetitions time and flip angle. Assessment anatomical information performed by the two respondents or reviewer. The data analysis is done by testing the influence is multiple linear regression to determine the value of repetition time and flip angle optimal use friedman mean rank test.&#x0D; Result: The result showed that there is the influence of repetition time and flip angle of the anatomical information on 3D TOF MRA examination of the brain with a significance level of p &lt;0.001 (p &lt;0.05). The repetition time 30 ms and flip angle 30o is and optimal value for anatomical information showing 3D TOF MRA examination of the brain. application of repetition time 30 ms and flip angle 30o can be properly saturate or suppression the stasionary nuclei so that is displays excellent contrast between the nuclei.&#x0D; Conclution: There are influence of repetition time and flip angle to the anatomical information on 3D TOF MRA examination of the brain with a significance level of p &lt;0.001 (p &lt;0.05). The repetition time 30 ms and a flip angle of 30o is an optimal value for anatomical information showing 3D TOF MRA examination of the brain.

Surface Point Cloud Ultrasound with Transcranial Doppler: Coregistration of Surface Point Cloud Ultrasound with Magnetic Resonance Angiography for Improved Reproducibility, Visualization, and Navigation in Transcranial Doppler Ultrasound.

Transcranial Doppler (TCD) ultrasound is a standard tool used in the setting of recent sub-arachnoid hemorrhage (SAH). By tracking velocity in the circle-of-Willis vessels, vasospasm can be detected as interval velocity increase. For this disease process, repeated TCD velocity measurements over many days is the basis for its usefulness. However, a key limitation to TCD is its user dependence, which is itself largely due to the fact that exact information about probe positioning is lost between subsequent scans. Surface point cloud ultrasound (SPC-US) was recently introduced as a general approach combining ultrasound and three-dimensional surface imaging of patient + probe. In the present proof-of-principle demonstration, we have applied SPC-US to TCD and co-registered the skin surface with that from MRA images to provide a roadmap of the vasculature in 3D space for better speed, accuracy, reproducibility, and potential semi-automation of TCD. Collating the acronyms, we call the combined approach SPC-US-TCD. TCD of the M1 was obtained while three-dimensional photographic images were obtained with the Structure Sensor camera. MRA imaging was also obtained. SPC-US-TCD and corresponding MRA 3D reconstruction images were co-registered in MeshMixer using the skin surfaces for alignment. A cylinder the width of the TCD probe was placed over the fused images and aligned with the direction and orientation of the TCD probe to demonstrate the acoustic beam. In the fused images, the acoustic beam intersects the right M1 segment of the middle cerebral artery (MCA). The angle of insonation is well demonstrated and measurable in various planes. Distance measurements made in Blender localized the TCD probe position based on three skin surface landmarks, and tabulated orientation based on three angles along the corresponding directions. SPC-US-TCD provides valuable information that is otherwise not present in TCD studies. By co-registering SPC-US-TCD data with that from cross sectional vessel imaging, precise probe location relative to external skin surface landmarks as well as 3D vessel location relative to TCD probe placement offers the potential to provide a roadmap that improves exam reproducibility, speed of acquisition, and accuracy. The goal of future work is to demonstrate this improvement statistically by application to multiple patients and scans.

Reconstruction of undersampled 3D non-Cartesian image-based navigators for coronary MRA using an unrolled deep learning model.

To rapidly reconstruct undersampled 3D non-Cartesian image-based navigators (iNAVs) using an unrolled deep learning (DL) model, enabling nonrigid motion correction in coronary magnetic resonance angiography (CMRA). An end-to-end unrolled network is trained to reconstruct beat-to-beat 3D iNAVs acquired during a CMRA sequence. The unrolled model incorporates a nonuniform FFT operator in TensorFlow to perform the data-consistency operation, and the regularization term is learned by a convolutional neural network (CNN) based on the proximal gradient descent algorithm. The training set includes 6,000 3D iNAVs acquired from 7 different subjects and 11 scans using a variable-density (VD) cones trajectory. For testing, 3D iNAVs from 4 additional subjects are reconstructed using the unrolled model. To validate reconstruction accuracy, global and localized motion estimates from DL model-based 3D iNAVs are compared with those extracted from 3D iNAVs reconstructed with -ESPIRiT. Then, the high-resolution coronary MRA images motion corrected with autofocusing using the -ESPIRiT and DL model-based 3D iNAVs are assessed for differences. 3D iNAVs reconstructed using the DL model-based approach and conventional -ESPIRiT generate similar global and localized motion estimates and provide equivalent coronary image quality. Reconstruction with the unrolled network completes in a fraction of the time compared to CPU and GPU implementations of -ESPIRiT (20× and 3× speed increases, respectively). We have developed a deep neural network architecture to reconstruct undersampled 3D non-Cartesian VD cones iNAVs. Our approach decreases reconstruction time for 3D iNAVs, while preserving the accuracy of nonrigid motion information offered by them for correction.

Abstract TP51: Comparison of Recanalization Rate Between Intravenous Actilyse and Intravenous Actilyse With Mechanical Thrombectomy in Larger Artery Occlusion Ischemic Stroke Patients

Background and Purpose: According to the guidelines for acute ischemic stroke treatment, intravenous tissue plasminogen activator (IV-tPA) administration is the first line treatment and intraarterial thrombolysis (IA-Tx) with retrieval stent is regarded as additional treatment. But recanalization rate of large artery intracranial occlusion disease (LAICOD) after IV-tPA is very low and inconsistent according to the reports. Authors tried to find out the early recanalization rate of IV-tPA in patients with LAICOD. Methods: 278 with anterior circulation occlusion patients were included in this analysis. Brain CT-angiography (CTA) was an initial imaging study and acute stroke MRI was following after the IV-tPA. Recanalization rate was studied with initial CTA and followed MRA image. And other clinical outcomes were compared with IV-tPA, IA-Tx or perfusion/diffusion-mismatching (P/D-mismatching) or not. Results: The overall recanalization rate of LAICOD after IV-tPA was 15.5% (43/278), 86.0% (86/100) in patients treated with IA-Tx after IV-tPA, and 78.7% (48/61) in IA-Tx without IV-tPA. In patients who underwent IA-Tx after IV-tPA, P/D-mismatching patients showed higher recanalization rate (88.2% = 67/76 vs. 66.7% = 16/27, p = 0.020), and higher incidence of favorable outcomes (63.2% = 48/76 vs. 12.5% = 3/27, p = 0.000) compared to P/D-matching patients. Conclusion: This study suggests that recanalization rate after IV-tPA for the patients with acute ischemic stroke due to LAICOD is very low and IV-tPA before IA-Tx does not significantly influence on the neurologic outcomes and complication rates. Bridging treatment is effective, for stroke patient management, but authors would like to propose that IA-Tx might be applied as the first therapy option, just like in the management of acute myocardial infarction patients.

Silent MRA: arterial spin labeling magnetic resonant angiography with ultra-short time echo assessing cerebral arteriovenous malformation.

MR angiography using the silent MR angiography algorithm (silent MRA), which combines arterial spin labeling and an ultrashort time echo, has not been used for the evaluation of cerebral arteriovenous malformations (CAVMs). We aimed to determine the usefulness of silent MRA for the evaluation of CAVMs. Twenty-nine CAVMs of 28 consecutive patients diagnosed by 4D CT angiography or digital subtraction angiography, who underwent both time-of-flight (TOF) MRA and silent MRA, were enrolled. Two observers independently assessed the TOF-MRA and silent MRA images of CAVMs. Micro AVM was defined as AVM with a nidus diameter less than 10mm. The detection rate, visualization of the components, and accuracy of Spetzler-Martin grade were evaluated with statistical software R. For all 29 CAVMs, 23 (79%) lesions were detected for TOF-MRA and all for silent MRA. Of 10 micro AVMs, only 4 (40%) lesions were detectable on TOF-MRA and all (100%) on silent MRA. The visibility of the nidus and drainer was significantly better for silent MRA than TOF-MRA (p < 0.001), while there was no significant difference in the feeder between the two sequences. The accuracy rates of the Spetzler-Martin grade for the TOF and silent MRA were 38% (11/29) and 79.3% (23/29), respectively (p < 0.001). Silent MRA is useful for evaluating CAVM components and detecting micro AVM.

Assessing the Risk of Intracranial Aneurysm Rupture Using Morphological and Hemodynamic Biomarkers Evaluated from Magnetic Resonance Fluid Dynamics and Computational Fluid Dynamics.

Purpose:Evaluate in vivo hemodynamic and morphological biomarkers of intracranial aneurysms, using magnetic resonance fluid dynamics (MRFD) and MR-based patient specific computational fluid dynamics (CFD) in order to assess the risk of rupture.Methods:Forty-eight intracranial aneurysms (10 ruptured, 38 unruptured) were scrutinized for six morphological and 10 hemodynamic biomarkers. Morphological biomarkers were calculated based on 3D time-of-flight magnetic resonance angiography (3D TOF MRA) in MRFD analysis. Hemodynamic biomarkers were assessed using both MRFD and CFD analyses. MRFD was performed using 3D TOF MRA and 3D cine phase-contrast magnetic resonance imaging (3D cine PC MRI). CFD was performed utilizing patient specific inflow–outflow boundary conditions derived from 3D cine PC MRI. Univariate analysis was carried out to identify statistically significant biomarkers for aneurysm rupture and receiver operating characteristic (ROC) analysis was performed for the significant biomarkers. Binary logistic regression was performed to identify independent predictive biomarkers.Results:Morphological biomarker analysis revealed that aneurysm size [P = 0.021], volume [P = 0.035] and size ratio [P = 0.039] were statistically significantly different between the two groups. In hemodynamic biomarker analysis, MRFD results indicated that ruptured aneurysms had higher oscillatory shear index (OSI) [OSI.max, P = 0.037] and higher relative residence time (RRT) [RRT.ave, P = 0.035] compared with unruptured aneurysms. Correspondingly CFD analysis demonstrated significant differences for both average and maximum OSI [OSI.ave, P = 0.008; OSI.max, P = 0.01] and maximum RRT [RRT.max, P = 0.045]. ROC analysis revealed AUC values greater than 0.7 for all significant biomarkers. Aneurysm volume [AUC, 0.718; 95% CI, 0.491–0.946] and average OSI obtained from CFD [AUC, 0.774; 95% CI, 0.586–0.961] were retained in the respective logistic regression models.Conclusion:Both morphological and hemodynamic biomarkers have significant influence on intracranial aneurysm rupture. Aneurysm size, volume, size ratio, OSI and RRT could be potential biomarkers to assess aneurysm rupture risk.

Motion Correction of Dual Volume Reconstruction of Three‑dimensional Digital Subtraction Angiography for Follow‑up Evaluation of Intracranial Coiled Aneurysms.

To evaluate the usefulness of the "Motion Correction" function of the dual volume-3D-volume-rendering technique (DV-3D-VRT) in follow-up digital subtraction angiography (DSA) of intracranial coiled aneurysms. This study used data collected from consecutive, follow-up DSAs after the coiling of 64 intracranial aneurysms in 59 patients. We performed subtracted 3D-rotational angiographies (3D-RAs) on all DSAs and obtained DV-3D-VRT images. We then assessed recurrence using DV-3D-VRT images with and without the motion correction functions (MC(+) vs. MC(-)) and observed which method showed better agreement with the reference assessment (using a combination of 2D DSA and TOF MRA images). The recurrence of MC(-) DV-3D-VRT images showed 51.6% (33/64) agreement with the reference assessment, whereas the MC(+) DV-3D-VRT images showed 78.1% (50/64) (P = 0.035, McNemar test). Motion correction is a useful complementary imaging technique in evaluating aneurysm recurrence after endovascular embolization. MC(+) DV-3D-VRT image showed higher inter-observer agreement than MC(-) DV-3D-VRT.

Improved display of abdominal contrast-enhanced MRA using gadobutrol: comparison with Gd-DTPA

To qualitatively and quantitatively compare gadobutrol with gadopentetate dimeglumine (Gd-DTPA) in abdominal contrast-enhanced magnetic resonance angiography (CE-MRA) and contrast-enhanced magnetic resonance imaging (CE-MRI) during one-stop imaging. This prospective, blinded, multicentre, intra-individual comparison study was approved by the institutional review board. All patients underwent gadobutrol- and Gd-DTPA-enhanced MRA and MRI. Qualitative analysis for vessels was performed using a three-point scale while quantity analysis was performed by signal-to-noise ratio (SNR). Visceral organs enhancements were also analysed. A Wilcoxon matched-pair signed-rank test was used to evaluate the quality and quantity results. One hundred and twelve patients were enrolled. Quality analyses results for large vessels and small vessels of gadobutrol and Gd-DTPA were 18.38±1.51 and 6.76±1.58 and 17.87±1.84 and 6.09±1.55, respectively. Wilcoxon signed-rank tests revealed gadobutrol was significantly superior to Gd-DTPA (p=0.036) for small vessels. For large vessel quantity analysis, gadobutrol demonstrated significantly higher signal-to-noise ratios (SNR; p=0.041) than Gd-DTPA, with mean values of 948.156±349.731 and 838.925±248.197. There was no statistically significant in enhancement of liver, spleen, and renal tissue during gadobutrol- and Gd-DTPA-enhanced imaging (p>0.05). One patient reported an adverse event. Dizziness and vomiting occurred after injection of Gd-DTPA. The present study demonstrates gadobutrol-enhanced MRA was superior to that of Gd-DTPA without statistical significance in visceral organ enhancement. It indicates gadobutrol may be more suitable for abdominal one-stop imaging for CE-MRA and CE-MRI by improving depiction of vessels in MRA images.

Validation of Zero TE-MRA in the Characterization of Cerebrovascular Diseases: A Feasibility Study.

Zero TE-MRA is less sensitive to field heterogeneity, complex flow, and acquisition noise. This study aimed to prospectively validate the feasibility of zero TE-MRA for cerebrovascular diseases assessment, compared with TOF-MRA. Seventy patients suspected of having cerebrovascular disorders were recruited. Sound levels were estimated for each MRA subjectively and objectively in different modes. MRA image quality was estimated by 2 neuroradiologists. The degree of stenosis (grades 0-4) and the z-diameter of aneurysms (tiny group ≤3 mm and large group >3 mm) were measured for further quantitative analysis. CTA was used as the criterion standard. Zero TE-MRA achieved significantly lower subjective perception and objective noise reduction (37.53%). Zero TE-MRA images showed higher signal homogeneity (3.29 ± 0.59 versus 3.04 ± 0.43) and quality of venous signal suppression (3.67 ± 0.47 versus 2.75 ± 0.46). The intermodality agreement was higher for zero TE-MRA than for TOF-MRA (zero TE, 0.90; TOF, 0.81) in the grading of stenosis. Zero TE-MRA had a higher correlation than TOF-MRA (zero TE, 0.84; TOF, 0.74) in the tiny group and a higher consistency with CTA (intraclass correlation coefficient, 0.83; intercept, -0.5084-1.1794; slope -0.4952 to -0.2093) than TOF-MRA (intraclass correlation coefficient, 0.64; intercept, 0.7000-2.6133; slope -1.0344 to -0.1923). Zero TE-MRA and TOF-MRA were comparable in the large group. Zero TE-MRA had more accurate details than TOF-MRA of AVM and Moyamoya lesions. Compared with TOF-MRA, zero TE-MRA achieved more robust performance in depicting cerebrovascular diseases. Therefore, zero TE-MRA was shown to be a promising MRA technique for further routine application in the clinic in patients with cerebrovascular diseases.

Building Three-Dimensional Intracranial Aneurysm Models from 3D-TOF MRA: a Validation Study

To create realistic three-dimensional (3D) vascular models from 3D time-of-flight magnetic resonance angiography (3D-TOF MRA) of an intracranial aneurysm (IA). Thirty-two IAs in 31 patients were printed using 3D-TOF MRA source images from polylactic acid (PLA) raw material. Two observers measured the maximum IA diameter at the longest width twice separately. A total mean of four measurements as well as each observer's individual average MRA lengths were calculated. After printing, 3D-printed anatomic models (PAM) underwent computed tomography (CT) acquisition and each observer measured them using the same algorithm as applied to MRA. Inter- and intra-observer consistency for the MRA and CT measurements were analyzed using the intraclass correlation coefficient (ICC) and a Bland-Altman plot. The mean maximum aneurysm diameter obtained from four MRA evaluations was 8.49mm, whereas it was 8.83mm according to the CT 3D PAM measurement. The Wilcoxon test revealed slightly larger mean CT 3D PAM diameters than the MRA measurements. The Spearman's correlation test yielded a positive correlation between MRA and CT lengths of 3D PAMs. Inter and intra-observer consistency were high in consecutive MRA and CT measurements. According to Bland-Altman analyses, the aneurysmal dimensions obtained from CT were higher for observer 1 and observer 2 (a mean of 0.32mm and 0.35mm, respectively) compared to the MRA measurements. CT dimensions were slightly overestimated compared to MRA measurements of the created models. We believe the discrepancy may be related to the Laplacian algorithm applied for surface smoothing and the high slice thickness selection that was used. However, ICC provided high consistency and reproducibility in our cohort. Therefore, it is technically possible to produce 3D intracranial aneurysm models from 3D-TOF MRA images.