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Alzheimer's disease (AD) is one of the most common neurodegenerative diseases, commonly affecting the aged, with pathophysiological changes presenting 15 to 20 years before clinical symptoms. Early diagnosis and intervention are crucial in effectively slowing the progression of AD. In the current study, poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC)-functionalized NaGdF 4 nanoparticles (NaGdF 4 -PMPC) were developed as magnetic resonance imaging (MRI) contrast agents for targeting alpha 7 nicotinic acetylcholine receptors (α7 nAChRs) in AD mice. NaGdF 4 -PMPC showed excellent biocompatibility, targeting ability, and MRI performance, with the longitudinal molar relaxivity ( r 1 ) being 1.21-fold and 1.33-fold higher than those of the clinical contrast agent Gd-DTPA, respectively, resulting in higher-sensitive MR angiography. After intravenous injection, 3D dynamic contrast-enhanced (DCE) MR images with high-resolution vasculature of the mouse brain were obtained. In addition, by using NaGdF r 2 ) being 1.21-fold and 1.33-fold higher than those of the clinical contrast agent Gd-DTPA, respectively, resulting in higher-sensitive MR angiography. After intravenous injection, 3D dynamic contrast-enhanced (DCE) MR images with high-resolution vasculature of the mouse brain were obtained. In addition, by using NaGdF 4 -PMPC, susceptibility-weighted imaging (SWI) signals in AD mouse brains were greatly retained compared to those in healthy mice for 24 h, emphasizing the excellent targeting ability of NaGdF 4 -PMPC. Furthermore, the CD31, α7 nAChRs, and Thioflavin S staining were also utilized to investigate the relationship among vascular inflammation, α7 nAChRs, and amyloid-β (Aβ) deposition in AD mice. This work highlights a promising targeted imaging strategy for the timely diagnosis of AD.

Arteriovenous malformations (AVMs) of the brain are quite rare vascular pathologies, but they are life-threatening, due to the risk of intracerebral hemorrhage. Stereotactic radiosurgical treatment of patients with cerebral AVM is performed in cases where surgical removal is impossible or embolization with a stable occlusive effect cannot be performed. Currently, for the diagnosis of AVM, magnetic resonance imaging (MRI) is increasingly used because of its noninvasiveness and minimal risks. When a malformation is located in a functionally significant area, then a non-invasive technique is used to assess its interposition and mapping - functional magnetic resonance imaging.We have presented the experience of radiosurgical treatment of a 43-year-old male patient with a ruptured AVM located in the left temporal lobe, near Wernicke’s area. The patient underwent stereotactic radiosurgical treatment with Elekta Leksell Gamma Knife Perfection device, taking into account the location of the AVM in a functionally significant area, preoperative mapping was performed. After two years, according to MR angiography, the arterial component in the projection of the irradiated AVM was not visualized, which was confirmed by the data of cerebral angiography. Thus, a clinical example has demonstrated the high efficiency of MRI in the diagnosis and assessment of the results of the performed stereotactic radiosurgical treatment of AVMs.

Cystic hydatidosis is an endemic parasitic disease with usual localization in liver and lungs. Rarely it localizes in uncommon sites, the right ventricle being an exceptional localization.We present an extremely rare case of a young man with hydatid pulmonary embolism complicating right-ventricle hydatid cysts. Echocardiography, CT pulmonary angiogram and MR-angiography were performed for the diagnostic evaluation. Our patient did not undergo surgery. He was discharged on a regimen of albendazole, and is still being followed-up.Hydatid disease rarely presents with pulmonary embolism. It has uncharacteristic clinical features, requiring particular diagnosis and therapy.

Vessel wall MR imaging (VW-MRI) has been introduced into clinical practice and applied to a variety of diseases, and its usefulness has been reported. High-resolution VW-MRI is essential in the diagnostic workup and provides more information than other routine MR imaging protocols. VW-MRI is useful in assessing lesion location, morphology, and severity. Additional information, such as vessel wall enhancement, which is useful in the differential diagnosis of atherosclerotic disease and vasculitis could be assessed by this special imaging technique. This review describes the VW-MRI technique and its clinical applications in arterial disease, venous disease, vasculitis, and leptomeningeal disease. [ABSTRACT FROM AUTHOR]

OBJECTIVE:We report here an initial experience using 4D flow MRI in pelvic imaging-specifically, in imaging uterine fibroids. We hypothesized that blood flow might correlate with fibroid volume and that quantifying blood flow might help to predict the amount of embolic required to achieve stasis at subsequent uterine fibroid embolization (UFE). MATERIALS AND METHODS:Thirty-three patients with uterine fibroids and seven control subjects underwent pelvic MRI with 4D flow imaging. Of the patients with fibroids, 10 underwent 4D flow imaging before UFE and seven after UFE; in the remaining 16 patients with fibroids, UFE had yet to be performed. Four-dimensional flow measurements were performed using Arterys CV Flow. The flow fraction of the internal iliac artery was expressed as the ratio of internal iliac artery flow to external iliac artery flow and was compared between groups. The flow ratios between the internal iliac arteries on each side were calculated. Fibroid volume versus internal iliac flow fraction, embolic volume versus internal iliac flow fraction, and embolic volume ratio between sides versus the ratio of internal iliac artery flows between sides were compared. RESULTS:The mean internal iliac flow fraction was significantly higher in the 26 patients who underwent imaging before UFE (mean ± standard error, 0.78 ± 0.06) than in the seven patients who underwent imaging after UFE (0.48 ± 0.07, p < 0.01) and in the seven control patients without fibroids (0.48 ± 0.08, p < 0.0001). The internal iliac flow fraction correlated well with fibroid volumes before UFE (r = 0.7754, p < 0.0001) and did not correlate with fibroid volumes after UFE (r = -0.3051, p = 0.51). The ratio of embolic required to achieve stasis between sides showed a modest correlation with the ratio of internal iliac flow (r = 0.6776, p = 0.03). CONCLUSION:Internal iliac flow measured by 4D flow MRI correlates with fibroid volume and is predictive of the ratio of embolic required to achieve stasis on each side at subsequent UFE and may be useful for preprocedural evaluation of patients with uterine fibroids.

PurposeTo develop and validate a cardiac-respiratory self-gating strategy for the recently proposed multiphase steady-state imaging with contrast enhancement (MUSIC) technique.MethodsThe proposed SG strategy uses the ROtating Cartesian K-space (ROCK) sampling, which allows for retrospective k-space binning based on motion surrogates derived from k-space center line. The k-space bins are reconstructed using a compressed sensing algorithm. Ten pediatric patients underwent cardiac MRI for clinical reasons. The original MUSIC and 2D-CINE images were acquired as a part of the clinical protocol, followed by the ROCK-MUSIC acquisition, all under steady-state intravascular distribution of ferumoxytol. Subjective scores and image sharpness were used to compare the images of ROCK-MUSIC and original MUSIC.ResultsAll scans were completed successfully without complications. The ROCK-MUSIC acquisition took 5 ± 1 min, compared to 8 ± 2 min for the original MUSIC. Image scores of ROCK-MUSIC were significantly better than original MUSIC at the ventricular outflow tracts (3.9 ± 0.3 vs. 3.3 ± 0.6, P

Immunoglobulin G4-related aortitis (IgG4-RA) is histologically characterized by the infiltration of IgG4 positive plasma cells and fibrosis in systemic organs and the elevation of serum IgG4 levels. The cardiovascular system is commonly involved with various possible presentations such as aortitis, arteritis, periaortitis, periarteritis, and inflammatory aneurysm. We present a case of a 48-year-old male without known previous medical history, admitted for further workup of long-standing chest pain and shortness of breath with suspected aortic dissection on initial assessment. Investigation with computed tomography angiography (CTA) and magnetic resonance angiography (MRA) indicated severe thoracic and abdominal aortoarteritis associated with an ascending thoracic aortic aneurysm, which was confirmed to be IgG4-RA on histopathologic analysis. Thoracic and abdominal IgG4-RA clinical and radiological presentation may simulate other causes of acute aortic syndrome such as aortic dissection, atherosclerotic aneurysm and inflammatory conditions. Accurate recognition of IgG4-RA diagnostic imaging features are essential for early diagnosis and treatment surveillance.

Purpose: 3D time‐of‐flight MRA can accurately visualize the intracranial vasculature but is limited by long acquisition times. Compressed sensing reconstruction can be used to substantially accelerate acquisitions. The quality of those reconstructions depends on the undersampling patterns used. In this work, we optimize sets of undersampling parameters for various acceleration factors of Cartesian 3D time‐of‐flight MRA. Methods: Fully sampled datasets, acquired at 7 Tesla, were retrospectively undersampled using variable‐density Poisson disk sampling with various autocalibration region sizes, polynomial orders, and acceleration factors. The accuracy of reconstructions from the different undersampled datasets was assessed using the vessel‐masked structural similarity index. Identified optimal undersampling parameters were then evaluated in additional prospectively undersampled datasets. Compressed sensing reconstruction parameters were chosen based on a preliminary reconstruction parameter optimization. Results: For all acceleration factors, using a fully sampled calibration area of 12 × 12 k‐space lines and a polynomial order of 2 resulted in the highest image quality. The importance of parameter optimization of the sampling was found to increase for higher acceleration factors. The results were consistent across resolutions and regions of interest with vessels of varying sizes and tortuosity. The number of visible small vessels increased by 7.0% and 14.2% when compared to standard parameters for acceleration factors of 7.2 and 15, respectively. Conclusion: The image quality of compressed sensing time‐of‐flight MRA can be improved by appropriate choice of undersampling parameters. The optimized sets of parameters are independent of the acceleration factor and enable a larger number of vessels to be visualized. [ABSTRACT FROM AUTHOR]

Objective  The primary objective of the study was to assess the location of cerebral infarction and look for corresponding magnetic resonance angiography (MRA) changes in patients with tuberculous meningitis (TBM). We also evaluated the predictors of ischemic stroke in TBM and the impact of these infarctions on patient's outcome. Methods  This was a single-center prospective study between September 2018 and September 2020. Demographic and laboratory parameters were noted. Cranial magnetic resonance imaging and MRA were performed at the time of admission to the hospital. Results  Among 120 patients with TBM, 46 had stroke. Nineteen (15.8%) patients died, of which 12 (10%) suffered from stroke. The most common site of infarction was the basal ganglia (54.3%). The commonest site of MRA abnormalities was the middle cerebral artery (39.1%). British Medical Research Council (BMRC) stage 3, cerebrospinal fluid (CSF) sugar, CSF adenosine deaminase (ADA) level, basal exudates, hydrocephalus, and hyponatremia were found to be predictors of stroke in TBM, while BMRC stage 3, CSF cell count, CSF ADA level, and anemia were found to be significantly associated with mortality in TBM patients with stroke. Conclusion  The basal ganglia were the most common site of ischemic stroke in TBM, and middle cerebral artery was the most often involved intracranial blood vessel. BMRC stage 3 was significantly associated with both stroke and mortality in TBM patients with stroke. [ABSTRACT FROM AUTHOR]

Introduction The anterior choroidal artery is a branch of the terminal internal carotid artery (ICA) that is often an incidentally detected anomaly. The hyperplastic variant has been linked with an increased risk of aneurysms. We explore the role of magnetic resonance (MR) angiography in the detection of this variant and its impact of presentation of patients. Patient Presentation A 62-year-old diabetic and hypertensive male came to the casualty with complaints of giddiness, left-sided weakness, and loss of coordination for the last 2 to 3 days. He was provisionally diagnosed with a posterior circulation stroke. Management and Outcome Magnetic resonance imaging of brain revealed an acute infarct in the right thalamus and the midbrain. Time-of-flight angiography sequences were done that showed hypoplasia of the A1 segment of the left anterior cerebral artery, fetal origin of the right posterior cerebral artery, narrowing of the left ICA, and a hyperplastic left anterior choroidal artery. He was managed conservatively with antiplatelets. He later underwent a digital subtraction angiography that revealed significant narrowing of the left ICA for which he was advised carotid stenting. However, the patient was unwilling for the procedure and was discharged on oral medication with stable vitals. Conclusion Anatomical variations in the intracranial vasculature impact ischemia territory and the approach to intracranial pathology. Hyperplastic anterior choroidal artery results from the abnormal persistence of fetal pattern of vascular supply. It is important to recognize the presence of a hyperplastic anterior choroidal artery as it impacts both disease presentation and management of these patients. MR angiography allows for noninvasive and reliable detection of these anomalies in patients without the risks associated with radiation or contrast exposure in conventional/computed tomography angiography. [ABSTRACT FROM AUTHOR]

Background and purpose: Endovascular treatment (EVT) is a time-dependent procedure that aims to remove the arterial blood flow obstruction in brain vessels in acute ischemic stroke. In our center, the MRI patient selection protocol in acute ischemic stroke is performed with DWI, FLAIR, MR angiography (MRA) and MR cisternography (MRC) sequences. MRA and MRC are promptly and automatically fused in order to have a clear detection of vessel anatomy, before and during EVT.Our study aim is to evaluate if the fusion process between MRA and MRC could be considered time-safe and could influence EVT duration or outcome. Materials and methods: 45 patients were retrospectively selected for the study and divided into 2 groups according to the presence of MRC sequence fused with MRA (Group 1) or not (Group 2 - controls). Results: MRA and MRC fusion was able to depict vessel anatomy in all subjects of Group 1 (22 patients, 12 females; age 75.59 years ± 10.87). Group 1 presented EVT time reduction (p < 0.05; p = 0.040) (51.59 min ± 30.94) when compared to Group 2 (23 patients, 13 females; age 75.04 years ± 12.12) (71.96 min ± 34.55) of 20.37 min average. No differences between groups were detected evaluating: NIHSS at admission (p = 0.49) and discharge (p = 0.67), pre-stroke mRS (p = 0.89), mRS at 90 days (p = 0.62), ASPECT (p = 0.98) and ASPECT-DWI scores (p = 0.93), time from symptom onset to groin puncture (p = 0.80), thromboaspiration vs combined technique (p = 0.67), EVT success (p = 0.63). Conclusion: Fusion of MRA and MRC is a safe and promising technique in promptly revealing vascular anatomy beyond vessel obstruction, and can play a role in EVT duration reduction.

Contrast-enhanced MR angiography (MRA) is a critical technique for vascular imaging. Nevertheless, the efficacy of MRA is often limited by the low rate of relaxation, short blood-circulation time, and metal ion-released potential long-term toxicity of clinical available Gd-based contrast agents. In this work, we report a facile and efficient strategy to achieve Gd-chelated organic nanoparticles with high relaxivity for T1-weighted MRA imaging. The Gd-chelated PEG-TCPP nanoparticles (GPT NPs) have been engineered composite structured consisting of Gd-chelated TCPP and PEG. The spherical structure of TCPP offers more chemical sites for Gd3+ coordination to improve the relaxivity and avoid leakage of the Gd3+ ions. The synthesized GPT NPs exhibit a high relaxation rate of 35.76 mM− 1 s− 1 at 3.0 T, which is higher than the rates for most reported MR contrast agents. Therefore, GPT NPs can be used for MRA with much stronger vascular signals, longer circulation time, and high-resolution arterial vascular visualization than those using clinical MR contrast agents at the same dose. This work may make the T1 MRI contrast agents for high-resolution angiography possible and offer a new candidate for preclinical and clinical applications of MR vascular imaging and vascular disease diagnosis. [ABSTRACT FROM AUTHOR]

Abstract Background The purpose of this study was to clarify the effect of asymmetric COW variants on carotid flow changes, and proposed an easy estimate of the representative carotid flow volume for accurate numerical simulation. Methods A total of 210 healthy adults receiving magnetic resonance angiography and carotid duplex sonography were included. Three anterior cerebral artery asymmetry (AA) groups were defined based on the diameter ratio difference (DRD) of bilateral A1 segments: AA1 group, one-side A1 aplasia; AA2, A1 DRD ≥ 50%; AA3, A1 DRD between 10 and 50%. Similarly, 3 posterior communicating artery (PcomA) asymmetry (PA) groups were defined: PA1 group, one fetal-origin posterior cerebral artery and absent contralateral PcomA; PA2, PcomA DRD ≥ 50%; PA3, PcomA DRD between 10 and 50%. Results With A1 asymmetry, the ICA diameter of the dominant A1 is significantly greater than the contralateral side. Significant differences of bilateral ICA flow were present in the AA1 and AA2 groups (mean flow difference 42.9 and 30.7%, respectively). Significant bilateral ICA diameter and flow differences were only found in the PA1 group. Linear regression analysis of ICA diameter and flow found a moderately positive correlation between ICA diameter and flow in all AA groups, with a 1 mm increment in vessel diameter corresponding to a 62.6 ml increment of flow volume. The product of bilateral ICA diameter and flow volume difference (ICA-PDF) could be a potential discriminator with a cutoff of 4.31 to predict A1 asymmetry ≥50% with a sensitivity of 0.81 and specificity of 0.76. Conclusions The study verifies that A1 asymmetry causes unequal bilateral carotid inflow, and consequently different bilateral ICA diameters. Adjustment of the inflow boundary conditions according to the COW variants would be necessary to improve the accuracy of numerical simulation.

Background: The effect of different anticoagulants on recanalization after cerebral venous thrombosis has not been studied in a randomized controlled trial. Methods: RE-SPECT CVT (ClinicalTrials.gov number: NCT02913326) was a Phase III, prospective, randomized, parallel-group, open-label, multicenter, exploratory trial with blinded endpoint adjudication. Acute cerebral venous thrombosis patients were allocated to dabigatran 150 mg twice daily, or dose-adjusted warfarin, for 24 weeks, after 5–15 days' treatment with unfractionated or low-molecular-weight heparin. A standardized magnetic resonance protocol including arterial spin labeling, three-dimensional time-of-flight venography, and three-dimensional contrast-enhanced magnetic resonance angiography was obtained at the end of the treatment period. Cerebral venous recanalization at six months was assessed by two blinded adjudicators, using the difference in a score of occluded sinuses and veins (predefined secondary efficacy endpoint) and in the modified Qureshi scale (additional endpoint), between baseline and the end of the treatment. Results: Of 120 cerebral venous thrombosis patients randomized, venous recanalization could be evaluated in 108 (55 allocated to dabigatran and 53 to warfarin, 1 patient had a missing occlusion score at baseline). No patient worsened in the score of occluded cerebral veins and sinuses, while 33 (60%) on dabigatran and 35 (67%) on warfarin improved. The mean score change from baseline in the occlusion score was similar in the two treatment groups (dabigatran −0.8, SD 0.78; warfarin −1.0, SD 0.92). In the modified Qureshi score, full recanalization was adjudicated in 24 (44%) and 19 (36%), and partial recanalization in 23 (42%) and 26 (49%) patients in the dabigatran and warfarin arms, respectively. No statistically significant treatment difference in the modified Qureshi score could be detected (p = 0.44). Conclusion: The majority of patients with cerebral venous thrombosis, anticoagulated with either dabigatran or warfarin for six months, showed partial or complete recanalization of occluded sinuses and veins at the end of the treatment. Clinical trial registration: Trial registry name: ClinicalTrials.gov URL: https://clinicaltrials.gov Registration number: NCT02913326 [ABSTRACT FROM AUTHOR]

Background: 3.0 T non‐contrast‐enhanced nitroglycerin (NTG)‐assisted whole‐heart coronary magnetic resonance angiography (MRA) employing Dixon water‐fat separation and compressed SENSE (CS‐SENSE) acceleration is a promising method for diagnosing coronary artery disease (CAD). Purpose To evaluate the diagnostic performance of this technique for detecting clinically‐relevant (≥50% diameter reducing) CAD and to evaluate the difference in NTG‐induced coronary vasodilation between patients with and without clinically‐relevant CAD. Study Type: Prospective. Population: Sixty‐six patients with suspected CAD. Field Strength/Sequence: 3.0 T; CSSENSE, Dixon water‐fat separation, three‐dimensional segmented turbo field gradient‐echo sequence for whole‐heart coronary MRA. Assessment Overall image quality of coronary MRA was calculated on the basis of all visible coronary segments. The diagnostic performance of coronary MRA for detecting a ≥50% reduction in coronary artery diameter with and without NTG was compared using X‐ray coronary angiography (CAG) as the reference. According to CAG, patients were divided into a non‐clinically‐relevant CAD group and clinically‐relevant CAD group, and the difference in NTG‐induced vasodilation between the groups was evaluated. Statistical Tests: Unpaired/paired Student's t‐test, Mann–Whitney U test, paired Wilcoxon signed‐rank test, χ2 test, McNemar test. A two‐tailed P value <0.05 was considered significant. Results: Overall image quality was increased significantly in the coronary MRA images after NTG. The diagnostic performance of the non‐NTG vs. NTG‐assisted coronary MRA was as follows on a per‐patient basis: sensitivity 94.3% vs. 94.3%, specificity 64.5% vs. 83.9%, positive predictive value 75.0% vs. 86.8%, negative predictive value 90.9% vs. 92.9%, and accuracy 80.3% vs. 89.4%, respectively. NTG‐induced vasodilation was significantly lower in the clinically‐relevant CAD group than in the non‐clinically‐relevant CAD group (13.7 ± 8.1% vs. 24.1 ± 16.3%). Data Conclusion: Non‐contrast Dixon water‐fat separation CS‐SENSE coronary MRA at 3.0 T can noninvasively detect clinically‐relevant CAD and sublingual NTG improved performance. Combining pre‐ and post‐NTG coronary MRA may provide a simple noninvasive and nonionizing test to evaluate coronary vasodilation function. Level of Evidence: 1 Technical Efficacy Stage: 2 [ABSTRACT FROM AUTHOR]

This study investigated the optimal labeling position and gradient moment for 4D-MR angiography based on superselective pseudo-continuous arterial spin labeling combined with CENTRA-keyhole and view-sharing (4D-S-PACK) for vessel-selective flow visualization of the internal carotid artery (ICA) and vertebrobasilar artery (VBA) systems. Seven healthy volunteers were scanned with a 3.0 T MR scanner. To visualize the ICA system, the labeling focus was placed in the right ICA at 55, 75 and 95 mm below the imaging slab. To visualize the VBA system, the labeling focus was placed in the basilar artery (BA), upper vertebral artery (VA upper), and lower vertebral artery (VA lower). Two sizes of labeling focus were created using gradient moments of 0.5 and 0.75 mT/m ms. The contrast-to-noise ratio (CNR) was measured in the middle cerebral artery (MCA) and posterior cerebral artery (PCA) branches. CNRs increased as the distance between the center of the imaging slab and the labeling position decreased in all MCA segments. CNRs obtained with VA lower tended to be higher than those obtained with BA and VA upper in all PCA segments. Selective vessel visualization was achieved with the gradient moment of 0.75 mT/m ms for the ICA and VBA system. The optimal 4D-S-PACK gradient moment was found to be 0.75 mT/m ms for the ICA and VBA systems. When visualizing the ICA system, the labeling position should be placed as close as possible to the imaging slab. When visualizing the VBA system, the labeling position should be placed at VA lower. [ABSTRACT FROM AUTHOR]

The use of MR guidance for endovascular intervention is appealing because of its lack of ionizing radiation, high-contrast visualization of vessel walls and adjacent soft tissues, multiplanar capabilities, and potential to incorporate functional information such as flow, fluid dynamics, perfusion, and cardiac motion. This review highlights state-of-the-art imaging techniques and hardware used for passive tracking of endovascular devices in interventional MR imaging, including negative contrast, passive contrast, nonproton multispectral, and direct current techniques. The advantages and disadvantages of passive tracking relative to active tracking are also summarized.

ObjectiveFerumoxytol is increasingly reported as an alternative to gadolinium-based contrast agents for MR angiography (MRA), particularly for patients with renal failure. This article summarizes more than 3 years of clinical experience with ferumoxytol-enhanced MRA for a range of indications and anatomic regions.ConclusionFerumoxytol-enhanced MRA has many advantages including that it is safe for patients with renal failure and provides a lengthy plateau of vascular signal as a blood pool agent that allows longer navigated MRA sequences.

Background and Purpose: To determine the feasibility of time-resolved angiography with stochastic trajectories (TWIST) in the diagnosis of spinal dural arteriovenous fistula (SDAVF) and perimedullary arteriovenous fistula (PAVF).Methods: A total of 11 negative patients with TWIST examination were retrospective analyzed and then 18 patients with suspected spinal vascular diseases underwent TWIST. For negative patients, Adamkiewicz artery (AKA), great anterior radiculomedullary vein (GARV) and anterior spinal artery (ASA) were retrospective analyzed. In patients, the results of TWIST were compared with those of DSA.Results: The displaying rates of the ASA, AKA and GARV in 11 negative patients were 100, 90.9, and 90.9%, respectively. The AKA and GARV were separated on TWIST. Of 18 patients, 11 and three were diagnosed with SDAVF and PAVF, respectively. The spinal cord vascular malformation diagnosed on TWIST was consistent with DSA with an excellent intermodality agreement (Kappa = 0.92, p < 0.001). The feeding artery and side of all 11 SDAVF patients were displayed on TWIST and the results were consistent with DSA. For PAVF patients, the feeding artery in two patients and the sides as displayed on TWIST were consistent with DSA.Conclusions: TWIST enables the differentiation of the spinal artery and vein and the differential diagnosis of SDAVF and PAVF.

Background and Purpose: To determine the feasibility of time-resolved angiography with stochastic trajectories (TWIST) in the diagnosis of spinal dural arteriovenous fistula (SDAVF) and perimedullary arteriovenous fistula (PAVF). Methods: A total of 11 negative patients with TWIST examination were retrospective analyzed and then 18 patients with suspected spinal vascular diseases underwent TWIST. For negative patients, Adamkiewicz artery (AKA), great anterior radiculomedullary vein (GARV) and anterior spinal artery (ASA) were retrospective analyzed. In patients, the results of TWIST were compared with those of DSA. Results: The displaying rates of the ASA, AKA and GARV in 11 negative patients were 100, 90.9, and 90.9%, respectively. The AKA and GARV were separated on TWIST. Of 18 patients, 11 and three were diagnosed with SDAVF and PAVF, respectively. The spinal cord vascular malformation diagnosed on TWIST was consistent with DSA with an excellent intermodality agreement (Kappa = 0.92, p < 0.001). The feeding artery and side of all 11 SDAVF patients were displayed on TWIST and the results were consistent with DSA. For PAVF patients, the feeding artery in two patients and the sides as displayed on TWIST were consistent with DSA. Conclusions: TWIST enables the differentiation of the spinal artery and vein and the differential diagnosis of SDAVF and PAVF. [ABSTRACT FROM AUTHOR]

Background: Contrast‐enhanced magnetic resonance angiography (MRA) is used to assess various cardiovascular conditions. However, gadolinium‐based contrast agents (GBCAs) carry a risk of dose‐related adverse effects. Purpose: To develop a deep learning method to reduce GBCA dose by 80%. Study Type: Retrospective and prospective. Population: A total of 1157 retrospective and 40 prospective congenital heart disease patients for training/validation and testing, respectively. Field Strength/Sequence: A 1.5 T, T1‐weighted three‐dimensional (3D) gradient echo. Assessment: A neural network was trained to enhance low‐dose (LD) 3D MRA using retrospective synthetic data and tested with prospective LD data. Image quality for LD (LD‐MRA), enhanced LD (ELD‐MRA), and high‐dose (HD‐MRA) was assessed in terms of signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), and a quantitative measure of edge sharpness and scored for perceptual sharpness and contrast on a 1–5 scale. Diagnostic confidence was assessed on a 1–3 scale. LD‐ and ELD‐MRA were assessed against HD‐MRA for sensitivity/specificity and agreement of vessel diameter measurements (aorta and pulmonary arteries). Statistical Tests: SNR, CNR, edge sharpness, and vessel diameters were compared between LD‐, ELD‐, and HD‐MRA using one‐way repeated measures analysis of variance with post‐hoc t‐tests. Perceptual quality and diagnostic confidence were compared using Friedman's test with post‐hoc Wilcoxon signed‐rank tests. Sensitivity/specificity was compared using McNemar's test. Agreement of vessel diameters was assessed using Bland–Altman analysis. Results: SNR, CNR, edge sharpness, perceptual sharpness, and perceptual contrast were lower (P < 0.05) for LD‐MRA compared to ELD‐MRA and HD‐MRA. SNR, CNR, edge sharpness, and perceptual contrast were comparable between ELD and HD‐MRA, but perceptual sharpness was significantly lower. Sensitivity/specificity was 0.824/0.921 for LD‐MRA and 0.882/0.960 for ELD‐MRA. Diagnostic confidence was 2.72, 2.85, and 2.92 for LD, ELD, and HD‐MRA, respectively (PLD‐ELD, PLD‐HD < 0.05). Vessel diameter measurements were comparable, with biases of 0.238 (LD‐MRA) and 0.278 mm (ELD‐MRA). Data Conclusion: Deep learning can improve contrast in LD cardiovascular MRA. Level of Evidence Level: 2 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Purpose: Follow-up MRI/MRA is historically obtained as outpatient when patients with a spontaneous intracerebral hemorrhage (ICH) have an initial MRI/MRA that is negative for an underlying structural lesion. However, the utility of repeating MR imaging in a delayed fashion remains uncertain. Methods: We retrospectively reviewed 396 patients with spontaneous ICH admitted at our institution between 2015 and 2017 and selected those whose initial MRI/MRA was negative for an underlying structural lesion and those who underwent follow-up MR imaging in a delayed fashion. Results: A total of 113 patients met the study criteria. The average age of those with negative follow-up MRI/MRA was 65.0 ± 12.6 (IQR: 55.0–74.0) years old. None of the 113 patients with a negative inpatient MRI/MRA had an underlying structural lesion on follow-up MRI/MRA (0%, 95% CI 0.0–0.032, p < 0.001). The mean time of the follow-up imaging from the initial study was 105.7 days (median: 62 days; IQR: 42.5–100.5). Of the 113, 83 (73.5%) underwent follow-up MRI with and without gadolinium, while 30 (26.5%) patients did not receive gadolinium. Conclusion: Delayed follow-up MRI in patients with a negative initial MRI/MRA for workup of spontaneous ICH was not diagnostic in any of the patients included in the study. Our study suggests that a routine follow-up MRI for this patient population is not necessary. [ABSTRACT FROM AUTHOR]

Purpose: Time-of-flight (TOF)-MR angiography (MRA) is an important imaging sequence for the surveillance and analysis of cerebral arteriovenous shunt (AVS), including arteriovenous malformation (AVM) and arteriovenous fistula (AVF). However, this technique has the disadvantage of a relatively long scan time. The aim of this study was to compare diagnostic accuracy between compressed sensing (CS)-TOF and conventional parallel imaging (PI)-TOF-MRA for detecting and characterizing AVS. Methods: This study was approved by the institutional review board for human studies. Participants comprised 56 patients who underwent both CS-TOF-MRA and PI-TOF-MRA on a 3-T MR unit with or without cerebral AVS between June 2016 and September 2018. Imaging parameters for both sequences were almost identical, except the acceleration factor of 3× for PI-TOF-MRA and 6.5× for CS-TOF-MRA, and the scan time of 5 min 19 s for PI-TOF-MRA and 2 min 26 s for CS-TOF-MRA. Two neuroradiologists assessed the accuracy of AVS detection on each sequence and analyzed AVS angioarchitecture. Concordance between CS-TOF, PI-TOF, and digital subtraction angiography was calculated using unweighted and weighted kappa statistics. Results: Both CS-TOF-MRA and PI-TOF-MRA yielded excellent sensitivity and specificity for detecting intracranial AVS (reviewer 1, 97.3%, 94.7%; reviewer 2, 100%, 100%, respectively). Interrater agreement on the angioarchitectural features of intracranial AVS on CS-MRA and PI-MRA was moderate to good. Conclusion: The diagnostic performance of CS-TOF-MRA is comparable to that of PI-TOF-MRA in detecting and classifying AVS with a reduced scan time under 2.5 min. [ABSTRACT FROM AUTHOR]

Background: Carotid plaque morphology and tissue composition help assess risk stratification of stroke events. Many post-processing image techniques based on CT and MR images have been widely used in related research, such as image segmentation, 3D reconstruction, and computer fluid dynamics. However, the criteria for the 3D numerical model of carotid plaque established by CT and MR angiographic image data remain open to questioning.Method: We accurately duplicated the geometry and simulated it using computer software to make a 3D numerical model. The initial images were obtained by CTA and TOF-MRA. MIMICS (Materialize’s interactive medical image control system) software was used to process the images to generate three-dimensional solid models of blood vessels and plaques. The subsequent output was exported to the ANSYS software to generate finite element simulation results for the further hemodynamic study.Results: The 3D models of carotid plaque of TOF-MRA and CTA were simulated by using computer software. CTA has a high-density resolution for carotid plaque, the boundary of the CTA image is obvious, and the main component of which is a calcified tissue. However, the density resolution of TOF-MRA for the carotid plaque and carotid artery was not as good as that of CTA. The results show that there is a large deviation between the TOF-MRA and CTA 3D model of plaque in the carotid artery due to the unclear recognition of plaque boundary during 3D reconstruction, and this can further affect the simulation results of hemodynamics.Conclusion: In this study, two-dimensional images and three-dimensional models of carotid plaques obtained by two angiographic techniques were compared. The potential of these two imaging methods in clinical diagnosis and fluid dynamics of carotid plaque was evaluated, and the selectivity of image post-processing analysis to original medical image acquisition was revealed.

Functional magnetic resonance imaging (fMRI) in the resting state, particularly fMRI based on the blood-oxygenation level-dependent (BOLD) signal, has been extensively used to measure functional connectivity in the brain. However, the mechanisms of vascular regulation that underlie the BOLD fluctuations during rest are still poorly understood. In this work, using dual-echo pseudo-continuous arterial spin labeling and MR angiography (MRA), we assess the spatio-temporal contribution of cerebral blood flow (CBF) to the resting-state BOLD signals and explore how the coupling of these signals is associated with regional vasculature. Using a general linear model analysis, we found that statistically significant coupling between resting-state BOLD and CBF fluctuations is highly variable across the brain, but the coupling is strongest within the major nodes of established resting-state networks, including the default-mode, visual, and task-positive networks. Moreover, by exploiting MRA-derived large vessel (macrovascular) volume fraction, we found that the degree of BOLD-CBF coupling significantly decreased as the ratio of large vessels to tissue volume increased. These findings suggest that the portion of resting-state BOLD fluctuations at the sites of medium-to-small vessels (more proximal to local neuronal activity) is more closely regulated by dynamic regulations in CBF, and that this CBF regulation decreases closer to large veins, which are more distal to neuronal activity.

We describe a unique case of bilateral cervical spinal dural arteriovenous fistulas mimicking an intracranial dural arteriovenous fistula near the foramen magnum. We review its detection via MRI and digital subtraction angiography and subsequent management through surgical intervention. Pitfalls in diagnostic angiography are discussed with reference to accurate location of the fistula site. The venous anastomotic connections of the posterior midline spinal vein to the medial posterior medullary vein, posterior fossa bridging veins, and dural venous sinuses of the skull base are discussed with reference to problem-solving in this complex case. The mechanism of myelopathy through venous hypertension produced by spinal dural fistulas is also emphasized.

A modern vascular service cannot function without high quality, timely and relevant diagnostic imaging. In this age of evidence-based medicine, radiological findings and their expert interpretation are fundamental in aiding decisions with regard to patient management and surgical intervention. In this chapter we present the basic principles, clinical indications, advantages and limitations of the different imaging modalities used to assess vascular patients including duplex ultrasound (DUS), computed tomography (CT), magnetic resonance imaging (MR) and digital subtraction angiography (DSA). [ABSTRACT FROM AUTHOR]

Background: Carotid plaque morphology and tissue composition help assess risk stratification of stroke events. Many post-processing image techniques based on CT and MR images have been widely used in related research, such as image segmentation, 3D reconstruction, and computer fluid dynamics. However, the criteria for the 3D numerical model of carotid plaque established by CT and MR angiographic image data remain open to questioning. Method: We accurately duplicated the geometry and simulated it using computer software to make a 3D numerical model. The initial images were obtained by CTA and TOF-MRA. MIMICS (Materialize's interactive medical image control system) software was used to process the images to generate three-dimensional solid models of blood vessels and plaques. The subsequent output was exported to the ANSYS software to generate finite element simulation results for the further hemodynamic study. Results: The 3D models of carotid plaque of TOF-MRA and CTA were simulated by using computer software. CTA has a high-density resolution for carotid plaque, the boundary of the CTA image is obvious, and the main component of which is a calcified tissue. However, the density resolution of TOF-MRA for the carotid plaque and carotid artery was not as good as that of CTA. The results show that there is a large deviation between the TOF-MRA and CTA 3D model of plaque in the carotid artery due to the unclear recognition of plaque boundary during 3D reconstruction, and this can further affect the simulation results of hemodynamics. Conclusion: In this study, two-dimensional images and three-dimensional models of carotid plaques obtained by two angiographic techniques were compared. The potential of these two imaging methods in clinical diagnosis and fluid dynamics of carotid plaque was evaluated, and the selectivity of image post-processing analysis to original medical image acquisition was revealed. [ABSTRACT FROM AUTHOR]

Purpose: To determine the diagnostic accuracy of 3D time of flight MR angiography (TOF-MRA), contrast enhanced MR angiography (CE-MRA), and T1-weighted high-resolution isotropic volume examination (THRIVE) at 3 T for the evaluation of intracranial aneurysm occlusion after endovascular treatment and to evaluate the usability of the THRIVE sequence in endovascular treatment follow-up. Methods: In 3 T MR follow-up examinations of 66 aneurysms in 50 patients treated endovascularly, 3D TOF-MRA (index test), THRIVE (index test), and CE-MRA (reference standard) examinations were performed in a retrospective consecutive case series. Source images were classified as class 1, class 2, and class 3 according to the Raymond criteria using MIP (maximum intensity projection) techniques. The compatibility between sequences was evaluated with the Kappa test. The sensitivity and specificity were also calculated. Results: In the evaluation of THRIVE and CE-MRA sequences, compatibility was determined in 61 cases in total, with an overall fit of 61/66 (92.42%). A statistically significant correlation was found between THRIVE and CE-MRA (p < 0.001, κ = 0.800). In the evaluation of TOF and CE-MRA sequences, compatibility was determined in 54 cases in total, and the overall fit was 54/66 (81.8%). A statistically significant agreement was found between TOF and CE-MRA (p < 0.001, κ = 0.502). Assuming that CE-MRA is a reference standard, the sensitivity and specificity of the TOF sequence were 44.4% and 97.9%, respectively, and the sensitivity and specificity of the THRIVE sequence were 77.8% and 97.9%, respectively. Conclusion: The THRIVE sequence can be used as a noncontrast method for monitoring endovascularly treated intracranial aneurysms. [ABSTRACT FROM AUTHOR]

Purpose: To correct the intensity difference of static background signal between bright blood images and dark blood images in subtractive non‐contrast–enhanced MR angiography using robust regression, thereby improving static background signal suppression on subtracted angiograms. Methods: Robust regression (RR), using iteratively reweighted least squares, is used to calculate the regression coefficient of background tissues from a scatter plot showing the voxel intensity of bright blood images versus dark blood images. The weighting function is based on either the Euclidean distance from the estimated regression line or the deviation angle. Results from RR using the deviation angle (RRDA), conventional RR using the Euclidean distance, and ordinary leastsquares regression were compared with reference values determined manually by two observers. Performance was evaluated over studies using different sequences, including 36 thoracic flow‐sensitive dephasing data sets, 13 iliac flow‐sensitive dephasing data sets, and 26 femoral fresh blood imaging data sets. Results: RR deviation angle achieved robust and accurate performance in all types of images, with small bias, small mean absolute error, and high‐correlation coefficients with reference values. Background tissues, such as muscle, veins, and bladder, were suppressed while the vascular signal was preserved. Euclidean distance gave good performance for thoracic and iliac flow‐sensitive dephasing, but could not suppress background tissues in femoral fresh blood imaging. Ordinary least squares regression was sensitive to outliers and overestimated regression coefficients in thoracic flow‐sensitive dephasing. Conclusion: Weighted subtraction using RR was able to acquire the regression coefficients of background signal and improve background suppression of subtractive non‐contrast–enhanced MR angiography techniques. RR deviation angle has the most robust and accurate overall performance among three regression methods. [ABSTRACT FROM AUTHOR]

During acute ischemic stroke evaluations, neurovascular imaging is commonly performed to localize the source of a thromboembolus and to identify vascular stenoses. In this study, we aimed to analyze 1) the usefulness of intracranial and/or cervical CTA and MRA and carotid doppler ultrasound (DUS) for identifying the stroke source and 2) the incidence of vascular stenoses across stroke etiologies. We retrospectively reviewed intracranial and/or cervical CTA, DUS and MRA studies to identify the source of the acute stroke by Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria for 200 consecutive patients admitted with a stroke to our tertiary hospital. Stroke etiologies were ascertained and the rates of intracranial and cervical vascular stenoses were stratified by stroke type. Of 200 patients, the most probable sources of stroke were small vessel disease (29%), cardioembolic (26.0%) and atheroembolic (23.5%). Across all groups, 27.5% of patients had ≥70% stenosis on neurovascular imaging. The rate of ≥70% vascular stenosis in the neck was 6.9% and 5.8% in the small vessel and cardioembolic categories, respectively. The TOAST etiologies of strokes were nearly equally distributed. Neurovascular imaging was of high utility for identifying large vessel intracranial stenoses in patients presenting with acute stroke across all etiologies, although neck CTA/MRA had a lower rate of positive studies with cardiogenic and small vessel strokes. These findings have implications on the use of CTA/MRA in acute stroke work-up. • 24% and 13.5% of 199 stroke patients had ≥70% vascular stenoses in the brain and neck, respectively. • ≥70% Intracranial stenoses were seen in 13.8% of small vessel and 17.4% of cardioembolic strokes. • Patients with atheroembolic strokes showed 44.7% intracranial and 29.8% neck vessel ≥70% stenoses. • Neck CTA/MRA had a lower rate of ≥70% stenoses in cardiogenic (5.8%) and small vessel (6.9%) strokes. [ABSTRACT FROM AUTHOR]

BACKGROUND AND PURPOSE: Aneurysm 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. METHODS: We 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. RESULTS: There 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). CONCLUSION: Our 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. [ABSTRACT FROM AUTHOR]

To study the specific course of the clinical and neurovisual features of the cerebral stroke caused by reversible cerebral vasoconstriction syndrome (RCVS). 30 patients were under our control. The control group consisted of 19 women and 11 men. The age of patients is from 15 to 60 years (the average age (43.3 ± 0.7)). We performed MRI and MR angiographic studies of the brain using the apparatus for MRI "TOSHIBA" (1.5T), conducted USDS of the cerebral vessels, and used the MMSE short mental health assessment scale for an overall assessment of the cognitive system. We used the Reisberg scale (2008) to assess the decrease in overall cognitive activity with an emphasis on memory, the VAS scale to assess the intensity of headaches and the results were statistically processed. Result: the diagnosis of RCVS (Fleming-Call syndrome) is made on the basis of the patient's clinical picture, the nature of the headache (development speed, headache intensity (100%), nausea (90%)), on the basis of vasoconstriction changes in the brain vessels in an MRI study T1, T2, FLAIR and in blood vessel research modes. In the first group (n = 23), there were no focal signs in the brain in the T1, T2, and FLAIR modes; vasoconstriction changes in the cerebral vessels were detected in the MR angiographic. In the second group (n = 7), focal changes in the brain were detected in the T1, T2, and FLAIR modes, as well as vasoconstriction changes in the cerebral vessels in the MR angiographic. USDS examination revealed atherosclerotic changes in cerebral vessels in 42% of patients: grade I or II stenosis, and in 58% of patients atherosclerotic changes in cerebral vessels were not detected. Conclusions: 1. It has been established that most cases of cerebral stroke caused by RCVS (Fleming-Call syndrome) occur in patients under the age of 55 and are accompanied by high-intensity headaches and vasoconstrictive changes in cerebral vessels. [ABSTRACT FROM AUTHOR]

This pilot study tests the feasibility of rapid carotid MR angiography using the liver acquisition with volume acceleration-flex technique (LAVA MRA). Seven healthy volunteers and 21 consecutive patients suspected of carotid stenosis underwent LAVA and conventional time-of-flight (cTOF) MRAs. Artery-to-fat and artery-to-muscle signal intensity ratios were manually measured. LAVA MRA exhibited a significantly larger artery-to-fat signal intensity ratio compared with cTOF MRA in all slices (P < 0.001) and exhibited a larger (P < 0.001) or equivalent (P = 1.0) artery-to-muscle signal intensity ratio in the extracranial carotid arteries. The image quality of the cervical carotid bifurcation and the signal change on each MRA were visually assessed and compared among the MRAs. There was no significant difference between the two MRAs in visual assessment. LAVA MRA can provide visualization similar to cTOF MRA in the evaluation of the cervical carotid bifurcation while reducing scan time by one-fifth. [ABSTRACT FROM AUTHOR]

Breast cancer is the second most commonly diagnosed malignancy among women globally. Past MRI studies have linked a high animal fat diet (HAFD) to increased mammary cancer risk in the SV40Tag mouse model of triple‐negative breast cancer. Here, serial MRI examines tumor progression and measures the arterial blood volume feeding mammary glands in low fat diet (LFD) or HAFD fed mice. Virgin female C3(1)SV40Tag mice (n = 8), weaned at 3 weeks old, were assigned to an LFD (n = 4, 3.7 kcal/g, 17.2% kcal from vegetable oil) or an HAFD (n = 4, 5.3 kcal/g, 60% kcal from lard) group. From ages 8 to 12 weeks, weekly fast spin echo MR images and time‐of‐flight (TOF) MR angiography of inguinal mammary glands were acquired at 9.4 T. Following in vivo MRI, mice were sacrificed. Inguinal mammary glands were excised and fixed for ex vivo MRI and histology. Tumor, blood, and mammary gland volumes for each time point were measured from manually traced regions of interest; tumors were classified as invasive by histopathology‐blinded observers. Our analysis confirmed a strong correlation between total tumor volume and blood volume in the mammary gland. Tumor growth rates from weeks 8‐12 were twice as high in HAFD‐fed mice (0.42 ± 0.14/week) as in LFD‐fed mice (0.21 ± 0.03/week), p < 0.004. Mammary gland blood volume growth rate was 2.2 times higher in HAFD mice (0.29 ± 0.11/week) compared with LFD mice (0.13 ± 0.06/week), p < 0.02. The mammary gland growth rate of HAFD‐fed mice (0.071 ± 0.011/week) was 2.7 times larger than that of LFD‐fed mice (0.026 ± 0.009/week), p < 0.01. This is the first non‐invasive, in vivo MRI study to demonstrate a strong correlation between an HAFD and increased cancer burden and blood volume in mammary cancer without using contrast agents, strengthening the evidence supporting the adverse effects of an HAFD on mammary cancer. These results support the potential future use of TOF angiography to evaluate vasculature of suspicious lesions. [ABSTRACT FROM AUTHOR]

Magnetic resonance angiography (MRA) is a powerful clinical tool for evaluation of the thoracic vasculature. MRA can be performed on nearly any magnetic resonance imaging (MRI) scanner, and provides images of high diagnostic quality without the use of ionizing radiation. While computed tomographic angiography (CTA) is preferred in the evaluation of hemodynamically unstable patients, MRA represents an important tool for evaluation of the thoracic vasculature in stable patients. Contrast-enhanced MRA is generally performed unless there is a specific contraindication, as it shortens the duration of the exam and provides images of higher diagnostic quality than noncontrast MRA. However, intravenous contrast is often not required to obtain a diagnostic evaluation for most clinical indications. Indeed, a variety of noncontrast MRA techniques are used for thoracic imaging, often in conjunction with contrast-enhanced MRA, each of which has a differing degree of reliance on flowing blood to produce the desired vascular signal. In this article we review contrast-enhanced MRA, with a focus on contrast agents, methods of bolus timing, and considerations in imaging acquisition. Next, we cover the mechanism of contrast, strengths, and weaknesses of various noncontrast MRA techniques. Finally, we present an approach to protocol development and review representative protocols used at our institution for a variety of thoracic applications. Further attention will be devoted to additional techniques employed to address specific clinical questions, such as delayed contrast-enhanced imaging, provocative maneuvers, electrocardiogram and respiratory gating, and phase-contrast imaging. The purpose of this article is to review basic techniques and methodology in thoracic MRA, discuss an approach to protocol development, and illustrate commonly encountered pathology on thoracic MRA examinations. Level of Evidence 5 Technical Efficacy Stage 3. [ABSTRACT FROM AUTHOR]

Objectives: To use multi-parametric magnetic resonance imaging (MRI) to test the hypothesis that hypertensives would have higher retrograde venous blood flow (RVBF) in the internal jugular veins (IJV) vs. normotensives, and that this would inversely correlate with arterial inflow and gray matter, white matter, and cerebrospinal fluid volumes.Methods: Following local institutional review board approval and written consent, a prospective observational 3-T MRI study of 42 hypertensive patients (53 ± 2 years, BMI 28.2 ± 0.6 kg/m2, ambulatory daytime systolic BP 148 ± 2 mmHg, ambulatory daytime diastolic BP 101 ± 2 mmHg) and 35 normotensive patients (48 ± 2 years, BMI 25.2 ± 0.8 kg/m2, ambulatory daytime systolic BP 119 ± 3 mmHg, ambulatory daytime diastolic BP 90 ± 2 mmHg) was performed. Phase contrast imaging calculated percentage retrograde venous blood flow (%RVBF), brain segmentation estimated regional brain volumes from 3D T1-weighted images, and pseudo-continuous arterial spin labeling measured regional cerebral blood perfusion. Statistical analysis included two-sample equal variance Student's T tests, two-way analysis of variance with Tukey's post hoc correction, and permutation-based two-group general linear modeling (p < 0.05).Results: In the left IJV, %RVBF was higher in hypertensives (6.1 ± 1.5%) vs. normotensives (1.1 ± 0.3%, p = 0.003). In hypertensives, there was an inverse relationship of %RVBF (permutation-based general linear modeling) to cerebral blood flow in several brain regions, including the left occipital pole and the cerebellar vermis (p < 0.01). Percentage retrograde flow in the left IJV correlated inversely with the total matter volume (gray plus white matter volume) in hypertensives (r = - 0.49, p = 0.004).Conclusion: RVBF in the left IJV is greater in hypertensives vs. normotensives and is linked to regional hypoperfusion and brain total matter volume.Key Points: • Hypertensive humans have higher retrograde cerebral venous blood flow, associated with regional brain hypoperfusion and lower tissue volume, compared with controls. • Cerebral retrograde venous blood flow may add further stress to already hypoperfused tissue in hypertensive patients. • The amount of retrograde venous blood flow in hypertensive patients may predict which patients might be at higher risk of developing cerebral pathologies. [ABSTRACT FROM AUTHOR]

Moyamoya disease (MMD) is characterized by bilateral, chronic progressive stenosis at the terminal portions of the internal carotid arteries and their proximal branches. The "smoke-like" appearance of the arterial collaterals in angiography gives the disease its name. The "ivy-sign" is the less-known magnetic resonance imaging (MRI) pattern of this disease. The leptomeningeal collaterals present as diffuse signal enhancement at the brain surface in contrast-enhanced T1-weighted image and fluid-attenuated inversion recovery sequences "as if overgrown with ivy." We report on three patients with MMD in whom the "ivy-sign" was already present but misinterpreted in the initial MRI of the brain. The correct diagnosis was made only after repeated MRI. Using three case studies, we describe the difficulties in the interpretation of the "ivy-sign" as an MRI pattern. Knowledge of the "ivy-sign" can be helpful, especially in diseases predisposing to MMD. If this MRI pattern is present, MMD should be considered and MR angiography should be added. [ABSTRACT FROM AUTHOR]

Purpose: To assess the efficacy of time-resolved MR angiography (MRA) in evaluating penile vasculature in patients with clinically suspected vascular anomalies contributing to their erectile dysfunction correlating with penile doppler ultrasound (PDUS) findings and clinical outcomes after surgical intervention. Methods: Men (n = 26) with signs of early vascular shunting on PDUS underwent time-resolved, contrast-enhanced (0.1 mMol/kg gadobutrol at 1 ml/s followed by saline flush) 3-dimensional spoiled gradient echo T1-weighted MRA sequence performed over 3 min with 4.6 s frame rate after intracavernosal injection of an erectogenic agent. Additional T1- and T2-weighted sequences were performed for anatomic co-localization and tissue characterization. MRA images were evaluated for early filling of draining veins as well as arteriovenous malformations and fistulas and correlated with findings at surgery. Results: 29 MRA examinations on 26 patients (mean age 39 years) demonstrated abnormal early venous drainage (n = 22) as well as diminutive/delayed cavernosal enhancement (n = 3), incomplete tumescence (n = 2), and combined arterial inflow/venous outflow disease (n = 1). The MRA had a concordance of 85.2% at determining the presence, or lack thereof of a shunt/AVM when compared to PDUS. Conclusions: Time-resolved MRA allows for both temporal and spatial resolution with visualization of both arterial and venous abnormalities which may be suggested with a screening PDUS examination. This technique allows us to provide detailed anatomic information prior to any surgical intervention. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study was to clarify the effect of asymmetric COW variants on carotid flow changes, and proposed an easy estimate of the representative carotid flow volume for accurate numerical simulation.Methods: A total of 210 healthy adults receiving magnetic resonance angiography and carotid duplex sonography were included. Three anterior cerebral artery asymmetry (AA) groups were defined based on the diameter ratio difference (DRD) of bilateral A1 segments: AA1 group, one-side A1 aplasia; AA2, A1 DRD ≥ 50%; AA3, A1 DRD between 10 and 50%. Similarly, 3 posterior communicating artery (PcomA) asymmetry (PA) groups were defined: PA1 group, one fetal-origin posterior cerebral artery and absent contralateral PcomA; PA2, PcomA DRD ≥ 50%; PA3, PcomA DRD between 10 and 50%.Results: With A1 asymmetry, the ICA diameter of the dominant A1 is significantly greater than the contralateral side. Significant differences of bilateral ICA flow were present in the AA1 and AA2 groups (mean flow difference 42.9 and 30.7%, respectively). Significant bilateral ICA diameter and flow differences were only found in the PA1 group. Linear regression analysis of ICA diameter and flow found a moderately positive correlation between ICA diameter and flow in all AA groups, with a 1 mm increment in vessel diameter corresponding to a 62.6 ml increment of flow volume. The product of bilateral ICA diameter and flow volume difference (ICA-PDF) could be a potential discriminator with a cutoff of 4.31 to predict A1 asymmetry ≥50% with a sensitivity of 0.81 and specificity of 0.76.Conclusions: The study verifies that A1 asymmetry causes unequal bilateral carotid inflow, and consequently different bilateral ICA diameters. Adjustment of the inflow boundary conditions according to the COW variants would be necessary to improve the accuracy of numerical simulation. [ABSTRACT FROM AUTHOR]

Purpose: To develop a modular magnetization preparation sequence for combined T2‐preparation and multidimensional outer volume suppression (OVS) for coronary artery imaging. Methods: A combined T2‐prepared 1D OVS sequence with fat saturation was defined to contain a 90°−60180°60 composite nonselective tip‐down pulse, two 180°Y hard pulses for refocusing, and a −90° spectral‐spatial sinc tip‐up pulse. For 2D OVS, 2 modules were concatenated, selective in X and then Y. Bloch simulations predicted robustness of the sequence to B0 and B1 inhomogeneities. The proposed sequence was compared with a T2‐prepared 2D OVS sequence proposed by Luo et al, which uses a spatially selective 2D spiral tip‐up. The 2 sequences were compared in phantom studies and in vivo coronary artery imaging studies with a 3D cones trajectory. Results: Phantom results demonstrated superior OVS for the proposed sequence compared with the Luo sequence. In studies on 15 healthy volunteers, the proposed sequence had superior image edge profile acutance values compared with the Luo sequence for the right (P <.05) and left (P <.05) coronary arteries, suggesting superior vessel sharpness. The proposed sequence also had superior signal‐to‐noise ratio (P <.05) and passband‐to‐stopband ratio (P <.05). Reader scores and reader preference indicated superior coronary image quality of the proposed sequence for both the right (P <.05) and left (P <.05) coronary arteries. Conclusion: The proposed sequence with concatenated 1D spatially selective tip‐ups and integrated fat saturation has superior image quality and suppression compared with the Luo sequence with 2D spatially selective tip‐up. [ABSTRACT FROM AUTHOR]

Although age-related changes of cerebral arteries were observed in in vivo magnetic resonance angiography (MRA), standard tools or methods measuring those changes were limited. In this study, we developed and evaluated a model to measure age-related changes in the cerebral arteries from 3D MRA using a 3D deep convolutional neural network. From participants without any medical abnormality, training (n = 800) and validation sets (n = 88) of 3D MRA were built. After preprocessing and data augmentation, a 3D convolutional neural network was trained to estimate each subject's chronological age from in vivo MRA data. There was good correlation between chronological age and predicted age (r = 0.83) in an independent test set (n = 354). The predicted age difference (PAD) of the test set was 2.41 ± 6.22. Interaction term between age and sex was significant for PAD (p = 0.008). After correcting for age and interaction term, men showed higher PAD (p < 0.001). Hypertension was associated with higher PAD with marginal significance (p = 0.073). We suggested that PAD might be a potential measurement of cerebral vascular aging. • There was good correlation between age at the time of MRI and predicted age from brain MRA (r = 0.83). • Using deep learning, we can assess the appropriateness of the overall cerebral vascular aging status of each subject. • This system can be used to assess cerebral vascular aging in subjects with atherosclerosis risk factors, such as hypertension. • A deep learning machine showed potential for assessing age-related changes with brain MRA without knowledge-based features. [ABSTRACT FROM AUTHOR]

Purpose: To develop a method to use information from multiple MRI contrasts to produce a composite angiogram with reduced sequence‐specific artifacts and improved vessel depiction. Methods: Bayesian posterior vessel probability was determined as a function of black blood (BB), contrast enhanced angiography (CE‐MRA), and phase‐contrast MRA (PC‐MRA) intensities from training subjects (N = 4). To generate composite angiogram in evaluation subjects (N = 12), the voxel‐wise vessel probabilities were weighted with a confidence measure and combined as a weighted product to yield angiogram intensity. For 23 internal carotid artery (ICA) segments (N = 23) from evaluation subjects, segmentation accuracy of composite MRA was evaluated and compared against CE‐MRA using dice similarity coefficient (DSC). Results: The composite MRA suppressed venous contaminations in CE‐MRA, reduced flow artifacts, and velocity aliasing seen in PC‐MRA and removed signal ambiguities in BB images. For ICA segmentations, the composite MRA improved segmentation over CE‐MRA per DSC (0.908 ± 0.037 vs. 0.765 ± 0.079). Compared with CE‐MRA, the composite MRA showed conservative changes in vessel appearance to small threshold changes. However, small vessels that are sensitive to registration errors or visible only weakly in CE‐MRA were susceptible to poor depiction in composite MRA. Conclusion: By dynamically weighting vessel information from multiple contrasts and extracting their complementary information, the composite MRA produces reduced sequence‐specific artifacts and improved vessel contrast. It is a promising technique for semi‐automatic segmentation of vessels that are hard to segment because of artifacts. [ABSTRACT FROM AUTHOR]