Contrast-enhanced Magnetic Resonance Angiography Research Articles

Type 2 endoleak embolization and utilization of non-contrast-enhanced magnetic resonance angiography (NCE-MRA) as a non-invasive imaging follow-up method.

Endovascular aneurysm repair (EVAR) is a minimally invasive technique widely used in abdominal aortic aneurysm treatment. The most common complications after EVAR remain endoleaks, type 2 endoleak (T2EL) being the most prevalent. T2EL detection and surveillance require imaging techniques such as computed tomography angiography (CTA), contrast-enhanced magnetic resonance angiography (CE-MRA), Doppler ultrasound, or digital subtraction angiography (DSA). However, these modalities are associated with numerous limitations, including exposure to ionizing radiation, contrast media administration, or operator dependency, as in the case of ultrasonography. A non-contrast-enhanced MRA could be a substitute non-invasive method for endoleak monitoring. Our case report describes an 83-year-old female patient with type 2 endoleak and enlarging aneurysm sac detected on a CT scan. Despite the enormous aneurysm size, the patient underwent endovascular treatment owing to multiple comorbidities. Due to challenging feeding vessel anatomy, catheterization of the aneurysmal sac was impossible. Attempted polymerization of the aneurysmal sac with Glubran-2 partially sealed the sac and obliterated the feeders' inflow. Unfortunately, a non-targeted embolization resulted in the loss of patency of the right feeder and adjacent communicating branch. The patient underwent follow-up imaging that included non-contrast-enhanced as well as contrast-enhanced MRA. The examination revealed the presence of a small residual endoleak, a freshly formed thrombus, and areas of old thrombi. The NCE-MR appeared to be a valuable tool in endoleak detection and provided a detailed clot morphology.

TH4.1 Systematic review of preoperative magnetic resonance angiography, computed tomography angiography and duplex ultrasonography for diagnosis and planning of surgical, endovascular or hybrid procedures for lower limb revascularisation

Abstract Aims This systematic review assessed literature concerning preoperative magnetic resonance angiography (MRA), computed tomography angiography (CTA), and duplex ultrasonography to determine the sensitivity and specificity at detecting lower limb arterial stenosis and/or occlusion, with digital subtraction angiography (DSA) as the reference standard. The aim was to see if any, or a combination of, methods could replace DSA in peripheral arterial disease diagnosis and treatment planning. Methods 10 databases were searched on Ovid for studies involving MRA, CTA and/or duplex ultrasonography of the lower limb arteries. The period of interest was 1995-April 2021. The papers were assessed for their relevance to the review against the exclusion criteria. Results 41 studies were included. For detecting ≥50% stenosis or occlusion, multi-detector CTA had the highest median sensitivity of 93.9% and specificity of 93.4%. Contrast-enhanced MRA and duplex ultrasonography reported median sensitivities and specificities of 91.1% and 91.9%, and 82.7% and 90.6%, respectively. For detecting occlusions, duplex ultrasonography had the best median sensitivity of 92.3% and specificity of 99.5%. Contrast-enhanced MRA and multi-detector CTA had median sensitivities and specificities 92.0% and 96.5%, and 88.6% and 98.3%, respectively. Conclusion Contrast-enhanced MRA had the best overall diagnostic accuracy. Multi-detector CTA detected ≥50% stenosis or occlusion well, but the sensitivity for occlusions was lower than MRA and duplex ultrasonography. Though duplex ultrasonography detected occlusions better than MRA and CTA, it was less sensitive and specific at detecting ≥50% stenosis or occlusion. Consequently, contrast-enhanced MRA could be used as an alternative to DSA.

Application of locating supratrochlear artery and supraorbital artery in combined transfrontal and intranasal endoscopic approaches

Objective: To investigate the localization methods of supratrochlear artery (STA) and supraorbital artery (SOA), and to explore the clinical benefit of locating nerve via accompanying vascular localization in combined transfrontal and intranasal endoscopic approaches. Methods: From June 2019 to May 2021, 14 patients, including 11 males and 3 females, aging from 18 to 69 years old, were underwent frontal sinus surgery through the combined transfrontal and intranasal endoscopic approaches in the Department of Otorhinolaryngology Head and Neck Surgery of the Third Affiliated Hospital of Sun Yat-sen University. Before the surgery, localization of STA and SOA was determined by color doppler flow imaging (CDFI), computerized topographic angiography (CTA) and contrast enhanced magnetic resonance angiography (CE-MRA) respectively, and the distances between STA and SOA from facial midline were measured on 28 eyebrows. The position of external incision was determined according to the preoperative localization of STA and SOA. The examination time, cost and postoperative complications of the three methods were recorded. The accuracy of localization at 14 sides was verified by the surgery. GraphPad Prism 8.3 software was used for statistical analysis. Results: STA and SOA could be located by CDFI, CTA and CE-MRA. There was no significant difference in the measurement of the distance between STA and SOA from the facial midline among 3 methods (all P>0.05). Determining the position of external incision according to the localization of STA and SOA could protect both the blood vessels and accompanying nerves. No postoperative complications such as numbness of the forehead skin occurred. The measurement time of CDFI, CTA and CE-MRA was 22.50 (15.75, 30.00), 30.00 (28.00, 34.25) and 48.00 (44.00, 52.75) min (M (Q1, Q3)), respectively (all P<0.05). CDFI incurred the lowest costs and took the shortest time. Conclusions: CDFI is an efficient and economic localization method. The localization of STA and SOA facilitates the precise selection of the position of external incision, protects the accompanying nerve and reduces postoperative complications.

Contrast-enhanced MR Angiography without Gadolinium-based Contrast Material: Clinical Applications Using Ferumoxytol

Vascular imaging can be challenging because of the wide variability of contrast dynamics in different vascular territories and potential safety concerns in patients with renal insufficiency or allergies. Off-label diagnostic use of ferumoxytol, a superparamagnetic iron nanoparticle approved for therapy, is a promising alternative to gadolinium-based contrast agents for MR angiography (MRA). Ferumoxytol has exhibited a reassuring safety profile when used within the dose range recommended for diagnostic imaging. Because of its prolonged and stable intravascular residence, ferumoxytol can be used in its steady-state distribution for a wide variety of imaging indications, including some where conventional MRA is unreliable. In this article, authors discuss some of the major vascular applications of ferumoxytol and highlight how it may be used to provide highly diagnostic images and improve the quality, workflow, and reliability of vascular imaging. Keywords: MR Angiography, MRI Contrast Agent, Cardiac, Vascular © RSNA, 2022

Quantitative Assessment of Regional Pulmonary Transit Times in Pulmonary Hypertension.

Pulmonary hypertension (PH) contributes to restricted flow through the pulmonary circulation characterized by elevated mean pulmonary artery pressure acquired from invasive right heart catheterization (RHC). MRI may provide a noninvasive alternative for diagnosis and characterization of PH. To characterize PH via quantification of regional pulmonary transit times (rPTT). Retrospective. A total of 43 patients (58% female); 24 controls (33% female). RHC-confirmed patients classified as World Health Organization (WHO) subgroups 1-4. A 1.5 T/time-resolved contrast-enhanced MR Angiography (CE-MRA). CE-MRA data volumes were combined into a 4D matrix (3D resolution + time). Contrast agent arrival time was defined as the peak in the signal-intensity curve generated for each voxel. Average arrival times within a vessel region of interest (ROI) were normalized to the main pulmonary artery ROI (t0 ) for eight regions to define rPTT for all subjects. Subgroup analysis included grouping the four arterial and four venous regions. Intraclass correlation analysis completed for reproducibility. Analysis of covariance with age as covariate. A priori Student's t-tests or Wilcoxon rank-sum test; α=0.05. Results compared to controls unless noted. Significant without listing P value. ICC ran as two-way absolute agreement model with two observers. PH patients demonstrated elevated rPTT in all vascular regions; average rPTT increase in arterial and venous branches was 0.85 ± 0.15 seconds (47.7%) and 1.0 ± 0.18 seconds (16.9%), respectively. Arterial rPTT was increased for all WHO subgroups; venous regions were elevated for subgroups 2 and 4 (group 1, P=0.86; group 3, P=0.32). No significant rPTT differences were found between subgroups (P=0.094-0.94). Individual vessel ICC values ranged from 0.58 to 0.97. Noninvasive assessment of PH using standard-of-care time-resolved CE-MRA can detect increased rPTT in PH patients of varying phenotypes compared to controls. 1 TECHNICAL EFFICACY: Stage 3.

Imaging of the extracranial internal carotid artery in acute ischemic stroke: assessment of stenosis, plaques, and image quality using relaxation-enhanced angiography without contrast and triggering (REACT).

In stroke magnetic resonance imaging (MRI), contrast-enhanced magnetic resonance angiography (CE-MRA) is the clinical standard to depict extracranial arteries but native MRA techniques are of increased interest to facilitate clinical practice. The purpose of this study was to assess the detection of extracranial internal carotid artery (ICA) stenosis and plaques as well as the image quality of cervical carotid arteries between a novel flow-independent relaxation-enhanced angiography without contrast and triggering (REACT) sequence and CE-MRA in acute ischemic stroke (AIS). In this retrospective, single-center study, 105 consecutive patients (65.27±18.74 years, 63 males) were included, who received a standard stroke protocol at 3T in clinical routine including Compressed SENSE (CS) accelerated (factor 4) 3D isotropic REACT (fixed scan time: 02:46 min) and CS accelerated (factor 6) 3D isotropic CE-MRA. Three radiologists independently assessed scans for the presence of extracranial ICA stenosis and plaques (including hyper-/hypointense signal) with concomitant diagnostic confidence using 3-point scales (3= excellent). Vessel quality, artifacts, and image noise of extracranial carotid arteries were subjectively scored on 5-point scales (5= excellent/none). Wilcoxon tests were used for statistical comparison. Considering CE-MRA as the standard of reference, REACT provided a sensitivity of 89.8% and specificity of 95.2% for any and of 93.5% and 95.8% for clinically relevant (≥50%) extracranial ICA stenosis and yielded a to CE-MRA comparable diagnostic confidence [mean ± standard deviation (SD), median (interquartile range): 2.8±0.5, 3 (3-3) vs. 2.7±0.5, 3 (2-3), P=0.03]. Using REACT, readers detected more plaques overall (n=57.3 vs. 47.7, P<0.001) and plaques of hyperintense signal (n=12.3 vs. 5.7, P=0.02) with higher diagnostic confidence [2.8±0.5, 3 (3-3) vs. 2.6±0.7, 3 (2-3), P<0.001] than CE-MRA. After analyzing a total of 1,260 segments, the vessel quality of all segments combined [4.61±0.66 vs. 4.58±0.68, 5 (4-5) vs. 5 (4-5), P=0.0299] and artifacts [4.51±0.70 vs. 4.44±0.73, 5 (4-5) vs. 5 (4-5), P>0.05] were comparable between the sequences with REACT showing a lower image noise [4.43±0.67 vs. 4.25±0.71, 5 (4-5) vs. 4 (4-5), P<0.001]. Without the use of gadolinium-based contrast agents or triggering, REACT provides a high sensitivity and specificity for extracranial ICA stenosis and a potential improved depiction of adjacent plaques while yielding to CE-MRA comparable vessel quality in a large patient cohort with AIS.

Perfusion Maps Acquired From Dynamic Angiography MRI Using Deep Learning Approaches.

A typical stroke MRI protocol includes perfusion-weighted imaging (PWI) and MR angiography (MRA), requiring a second dose of contrast agent. A deep learning method to acquire both PWI and MRA with single dose can resolve this issue. To acquire both PWI and MRA simultaneously using deep learning approaches. Retrospective. A total of 60 patients (30-73 years old, 31 females) with ischemic symptoms due to occlusion or ≥50% stenosis (measured relative to proximal artery diameter) of the internal carotid artery, middle cerebral artery, or anterior cerebral artery. The 51/1/8 patient data were used as training/validation/test. A 3 T, time-resolved angiography with stochastic trajectory (contrast-enhanced MRA) and echo planar imaging (dynamic susceptibility contrast MRI, DSC-MRI). We investigated eight different U-Net architectures with different encoder/decoder sizes and with/without an adversarial network to generate perfusion maps from contrast-enhanced MRA. Relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), mean transit time (MTT), and time-to-max (Tmax ) were mapped from DSC-MRI and used as ground truth to train the networks and to generate the perfusion maps from the contrast-enhanced MRA input. Normalized root mean square error, structural similarity (SSIM), peak signal-to-noise ratio (pSNR), DICE, and FID scores were calculated between the perfusion maps from DSC-MRI and contrast-enhanced MRA. One-tailed t-test was performed to check the significance of the improvements between networks. P values < 0.05 were considered significant. The four perfusion maps were successfully extracted using the deep learning networks. U-net with multiple decoders and enhanced encoders showed the best performance (pSNR 24.7 ± 3.2 and SSIM 0.89 ± 0.08 for rCBV). DICE score in hypo-perfused area showed strong agreement between the generated perfusion maps and the ground truth (highest DICE: 0.95 ± 0.04). With the proposed approach, dynamic angiography MRI may provide vessel architecture and perfusion-relevant parameters simultaneously from a single scan. 3 TECHNICAL EFFICACY: Stage 5.

Incidentally enhancing supraclavicular lymphatic convolutes in magnetic resonance angiography in patients with Fontan circulation.

PURPOSE Fontan procedure and its modifications are the preferred approach to definitive palliation in uni- ventricular hearts though often with short-term or long-term complications. It is believed that a dysfunction in lymphatic circulation is responsible for part of the complications. Occasionally, abnormal supraclavicular lymphatic vessel convolutes can be observed in contrast-enhanced magnetic resonance angiography (ceMRA). This study aims to determine the frequency of this phenomenon as well as a possible correlation with the functional status after Fontan procedure. METHODS CeMRA of 37 patients after Fontan surgery was retrospectively screened and grouped for the presence or absence of abnormal lymphatic convolute. An attempt was made to identify differ- ences in the level of dysfunction of the Fontan circulation between the 2 groups. RESULTS In 6 of 37 patients (16%), an abnormal cervical lymphatic convolute was found in the cervical venous angle. The surrogate parameters for a malfunction of the Fontan circulation did not sig- nificantly differ between both groups. CONCLUSION This is the first description of cervical lymphatic vessels in Fontan patients enhancing incidentally in ceMRA, probably due to venous-to-lymphatic reflux. As the likelihood of various complica- tions of Fontan circulation increases with the severity of lymphatic dysfunction, this observation could help to select patients who require closer monitoring or advanced lymphatic imaging.

Evaluation of the Abdominal Aorta and External Iliac Arteries Using Three-Dimensional Time-of-Flight, Three Dimensional Electrocardiograph-Gated Fast Spin-Echo, and Contrast-Enhanced Magnetic Resonance Angiography in Clinically Healthy Cats.

Arterial thromboembolism is associated with high morbidity and mortality rates in cats. Definitive diagnosis requires advanced imaging modalities, such as computed tomography angiography (CTA) and contrast-enhanced (CE) magnetic resonance angiography (MRA). However, CTA involves exposure to a large amount of ionized radiation, and CE-MRA can cause systemic nephrogenic fibrosis. Non-contrast-enhanced (NE) MRA can help accurately diagnose vascular lesions without such limitations. In this study, we evaluated the ability of NE-MRA using three-dimensional electrocardiograph-gated fast spin-echo (3D ECG-FSE) and 3D time-of-flight (3D TOF) imaging to visualize the aorta and external iliac arteries in clinically healthy cats and compared the results with those obtained using CE-MRA. All 11 cats underwent 3D ECG-FSE, 3D TOF, and CE-MRA sequences. Relative signal intensity (rSI) for quantitative image analysis and image quality scores (IQS) for qualitative image analysis were assessed; the rSI values based on the 3D TOF evaluations were significantly lower than those obtained using 3D ECG-FSE (aorta 3D TOF: 0.57 ± 0.06, aorta 3D ECG-FSE: 0.83 ± 0.06, P < 0.001; external iliac arteries 3D TOF: 0.45 ± 0.06, external iliac arteries 3D ECG-FSE:0.80 ± 0.05, P < 0.001) and similar to those obtained using CE-MRA (aorta: 0.58 ± 0.05, external iliac arteries: 0.57 ± 0.03). Moreover, IQS obtained using 3D TOF were significantly higher than those obtained using 3D ECG-FSE (aorta 3D TOF: 3.95 ± 0.15, aorta 3D ECG-FSE: 2.32 ± 0.60, P < 0.001; external iliac arteries 3D ECG-FSE: 3.98 ± 0.08, external iliac arteries 3D ECG-FSE: 2.23 ± 0.56, P < 0.001) and similar to those obtained using CE-MRA (aorta: 3.61 ± 0.41, external iliac arteries: 3.57 ± 0.41). Thus, 3D TOF is more suitable and produces consistent image quality for visualizing the aorta and external iliac arteries in clinically healthy cats and this will be of great help in the diagnosis of FATE.

Red Blood Cell Membrane-Coated Ultrasmall NaGdF4 Nanoprobes for High-Resolution 3D Magnetic Resonance Angiography.

Enhanced angiography based on magnetic resonance imaging (MRI) has emerged as a noninvasive, robust, and high-resolution imaging technique for the clinical evaluation of vascular diseases. However, the effects of clinical Gd-chelating contrast agents are unsatisfactory for MRI contrast enhancement owing to their short blood half-life caused by rapid vascular extravasation, especially in microvessels. To address these issues, nanoprobes based on red blood cell membrane-coated ultrasmall NaGdF4 nanoparticles that exhibit much higher longitudinal molar relaxivity (r1) than the clinically used contrast agent gadolinium diethylenetriaminepentaacetic acid have been developed. Furthermore, the appropriate hydrodynamic diameter and stealth nature aid the nanoprobes to reside longer within the blood vessels without extravasation, thereby increasing the contrast between the blood vessels and surrounding tissues. Through probe-enhanced three-dimensional (3D) dynamic contrast-enhanced MR angiography, the main arteries and veins of the mouse were readily discernible, and even tiny vessels with sub-millimeter diameters could be clearly depicted. With this level of outstanding MR angiography performance, the embolization and recanalization processes of the carotid artery can be serially monitored with high imaging resolution using only a single injection. Additionally, the results of clearance studies and the toxicity tests further highlight the safety features of the nanoprobe. To summarize, the nanoprobes used in this study exhibit less extravascular leakage and a longer blood half-life, thus successfully overcoming the defects of the conventional low-molecular-weight Gd-based contrast agents and demonstrating their potential usefulness in enhanced MR angiography.

Cerebrovascular segmentation in phase-contrast magnetic resonance angiography by multi-feature fusion and vessel completion.

Phase-Contrast Magnetic Resonance Angiography (PC-MRA) is a potential way of cerebrovascular imaging, which can suppress non-vascular tissue while presenting vessels. But PC-MRA will bring much noise and is easy to result in partially broken vessels. Usually, deep learning is an effective way to quantify vessels. However, how to choose an appropriate deep learning model is an important and difficult issue. In this work, we adopted the Dempster-Shafer (DS) evidence theory to fuse multi-feature from different models. Also, the vessel thinning and completion method were proposed to fill in information of broken cerebrovascular in PC-MRA images. For quantitative analysis, we chose Precision (PRE), Recall (REC), and Dice Similarity Coefficient (DSC) as assessment metrics, and established U-Net, V-Net, and Dense-Net. The 22 subjects tested this method. Comparison with different fusion strategies and common deep learning models have confirmed the effectiveness of the proposed method. In addition, we scanned Contrast-Enhanced MRA (CE-MRA) for 12 patients to verify reliability of vessel completion. Experiments show that the completion vessel can improve the matching ratio with CE-MRA, which has clinical potential.

Botulinum toxin injections in jaw-opening dystonia. The lateral pterygoid – maxillary artery problem

It has been suggested that the variations in the trajectory of the maxillary artery (MA) near the lateral pterygoid muscle (LPM) play a critical role in Botulinum neurotoxin (BoNT) injections in patients with jaw-opening/deviation dystonia (JOD). In the case of a lateral course to the LPM, an extraoral injection entails risks of MA injury, pain, and hematoma. Previous reports suggest geographical differences in variations of the MA-LPM relationship. We aimed to determine these variations in Turkish individuals and highlight the need to establish a consensus on approach to LPM injections. In 284 individuals, contrast-enhanced magnetic resonance angiography (MRA) images were evaluated by two radiologists on both sides for the variations in the course of the MA in the infratemporal fossa. Images of 44 were excluded due to trauma, arteriovenous malformation, mass, surgery, and imaging artifacts. Of the included, 62.1% were female. In 480 evaluations of 240 individuals, the MA passed lateral to the LPM in 65.6% (n = 315). No sex difference was noted. In 51 individuals (21.3%), the MA course differed on the right and left sides (medial–lateral asymmetry). These results confirm that the lateral course of the MA is more frequent. In patients with JOD, the trajectory of the MA should be determined with imaging prior to extraoral BoNT injections. In the case of a lateral course, an intraoral approach seems to be safer to avoid a potential MA injury.

Fast three-dimensional contrast-enhanced magnetic resonance angiography of the canine lumbar spinal cord vascular supply: A feasibility study.

Magnetic resonance angiography (MRA) is the noninvasive spinal cord vascular imaging modality of choice in human medicine. The aim of this exploratory, prospective, descriptive study was to assess the feasibility of fast three-dimensional (3D) contrast-enhanced (CE) MRA for visualization of spinal vascular structures in the canine lumbar region. Fourteen canine patients weighing>5kg were included. The lumbar arteries were consistently visualized (14/14;100%). Spinal arteries, radicular branches, great radicular artery (of Adamkiewicz), ventral spinal artery, and dorsal spinal arteries were not visualized (0/14;0%). The internal vertebral venous plexus was visualized in 11 of 14 (79%) dogs. Overall, the results of this study show that fast 3D CE-MRA of the lumbar region in dogs is feasible. However, the smaller arteries responsible for the spinal cord vascular supply were not visualized in this study.

MR Angiography Series: MR Angiography of the Extremities.

MR angiography (MRA) is a powerful tool for imaging of the extremities, allowing a thorough assessment of the arteries and veins in both the upper and lower limbs. Both contrast-enhanced and noncontrast MRA techniques are described in the online presentation, including practical tips and tricks to obtain all necessary information at every examination. This module is the sixth and final segment in a series created on behalf of the Society for Magnetic Resonance Angiography (SMRA), a group of researchers and clinicians who are passionate about the benefits of MRA but understand its challenges. The full digital presentation is available online. ©RSNA, 2022.

Volumetric surveillance of brain aneurysms: Pitfalls of MRA.

Untreated brain aneurysms are usually surveilled with serial MR imaging and evaluated with 2D multiplanar measurements. The assessment of aneurysm growth may be more accurate with volumetric analysis. We evaluated the accuracy of a magnetic resonance angiography (MRA) segmentation pipeline for aneurysm volume measurement and surveillance. A pipeline to determine aneurysm volume was developed and tested on two aneurysm phantoms imaged with time-of flight (TOF) MRA and 3D rotational angiography (3DRA). The accuracy of the pipeline was then evaluated by reconstructing 10 aneurysms imaged with contrast enhanced-MRA (CE-MRA) and 3DRA. This calibrated and refined post-processing pipeline was subsequently used to analyse aneurysms from our prospectively acquired database. Volume changes above the threshold of error were considered true volume changes. The accuracy of these measurements was analysed. TOF-MRA reconstructions were not as accurate as CE-MRA reconstructions. When compared to 3DRA, CE-MRA underestimated aneurysm volume by 7.8% and did not accurately register the presence of blebs. Eighteen aneurysms (13 saccular and 5 fusiform) were analysed with the optimized 3D volume reconstruction pipeline, with a mean follow-up time of 11 months. Artifact accounted for 10.2% error in volume measurements using serial CE-MRA. When this margin of error was used to assess aneurysms volume in serial imaging with CE-MRA, only two fusiform aneurysms changed in volume. The variations in volume of these two fusiform aneurysms were caused by intra-mural and intrasaccular thrombosis. CE-MRA and TOF-MRA 3D volume reconstructions may not register minor morphological changes such as the appearance of blebs. CE-MRA underestimates volume by 7.8% compared to 3DRA. Serial CE-MRA volume measurements had a larger margin of error of approximately 10.2%. MRA-based volumetric measurements may not be appropriate for aneurysm surveillance.

Effect of Contrast Agent Dose Reduction on Vascular Enhancement and Image Quality in Thoracoabdominal Dynamic 3-Dimensional Magnetic Resonance Angiography: A Systematic Intraindividual Analysis in Pigs.

High spatial and temporal resolution contrast-enhanced magnetic resonance angiography (MRA) with gadolinium-based contrast agents (GBCAs) at standard dose offers both detailed anatomic information on both arterial and venous vessels and hemodynamic characteristics. Several preclinical and clinical dynamic 3-dimensional (3D) MRA studies that focused on arterial vessels only proposed that high image quality may also be achieved with significantly reduced GBCA doses, calling into question the need to use standard doses. A systematic analysis of GBCA doses and resulting image quality for both arteries and veins has not yet been performed. The purpose of this study was therefore to systematically analyze dose-dependent vascular enhancements in dynamic 3D-MRA of the thoracoabdominal vasculature at 1.5 T in an animal model to determine the optimal contrast agent protocol for optimized vascular assessment. The vascular enhancement in thoracoabdominal dynamic 3D-MRA (time-resolved angiography with interleaved stochastic trajectories, TWIST at 1.5 T) was interindividually and intraindividually compared in 5 anesthetized Göttingen minipigs using gadobutrol at the standard dose (0.1 mmol/kg body weight, ie, 0.1 mL/kg) and at reduced doses (0.08, 0.06, 0.04, 0.02 mmol/kg) in a randomized order. All injections were performed at 2 mL/s followed by 20 mL saline. Images were quantitatively analyzed, measuring signal intensities in 5 regions that covered the passage of the GBCA through the body at different representative stages of circulation (pulmonary, arterial, and venous system). The evaluation of GBCA dose-dependent signal intensity changes in the different vascular regions was performed by linear regression analysis.The qualitative image analysis of dynamic 3D-MRA by 3 independent radiologists included the visibility of 25 arterial and venous vessel segments at different stages of GBCA passage. Possible quality losses were statistically tested by comparing image quality ratings at the reduced dose with that of the standard dose using Friedman test followed by Dunn post hoc test for multiple comparison. Significance was stated at P < 0.05. Quantitative analysis revealed shorter time-to-peak intervals and bolus durations in line with decreasing GBCA dose and volume in all vessels. Although the peak signal was almost independent of the administered GBCA dose at the level of the pulmonary trunk, a linear signal decrease in the abdominal aorta ( r2 = 0.96), the renal arteries ( r2 = 0.99), the inferior vena cava ( r2 = 0.99), and the portal vein ( r2 = 0.97) was observed. Cumulative analysis of arterial segments revealed significantly lower image quality at doses below 40% of the standard dose, whereas in venous segments, significantly lower image quality was observed at doses below 60% of the standard dose. In dynamic 3D-MRA at 1.5 T, dose reduction leads to a signal loss that is most pronounced in the venous system and results in significantly lower image quality according to the dose and vessels of interest. Careful dose reduction is thus required according to the specific diagnostic needs. For dynamic 3D-MRA of the arterial and venous system, GBCA doses of at least 60% of the standard dose up to the full dose are preferable, whereas 40% of the standard dose seems feasible if only the arterial system is to be imaged.

High relaxivity Gd3+-based organic nanoparticles for efficient magnetic resonance angiography

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.Graphical

Bilateral carotid artery geometry using magnetic resonance angiography: a 10-year longitudinal single center study

Aging and atherosclerotic progression can lead to geometric changes in the carotid arteries. We conducted a longitudinal study to investigate geometric changes in the bilateral carotid arteries. We conducted a retrospective study of 177 subjects who underwent carotid contrast-enhanced magnetic resonance angiography (MRA) at our clinic at baseline and 10 years after the procedure. Semi-automated methods were used to segment the bilateral carotid arteries to obtain carotid artery geometric measurements. The mean age for the total population after 10 years was 70.7 ± 10.6 years (male, 40.1%). The mean time interval between baseline and after 10 years for all subjects was 130.2 ± 8.1 months. The bilateral bifurcation angle, the diameters for both common carotid arteries (CCAs), and areas of both CCAs significantly increased (p < 0.001) over a 10-year period. The maximum diameter and internal carotid artery area did not significantly change. The bifurcation angle of the right carotid artery was significantly increased compared to the left carotid artery. However, the diameter and area of the CCA of the left carotid artery was significantly increased compared to the right carotid artery. The bifurcation angle, diameter and area of both CCAs significantly increased over a decade. The change in the bifurcation angle over a 10-year period was predominant in the right carotid artery and the change of the area and diameter of the CCA was dominant in the left carotid artery.

Comparison of Different Thoracic Aortic Wall Characteristics for Assessment of Disease Activity in Takayasu Arteritis: A Quantitative Study with 3.0 T Magnetic Resonance Imaging

Determination of disease activity in Takayasu arteritis (TAK) is crucial for clinical management but challenging. The value of different magnetic resonance imaging (MRI) characteristics for the assessment of disease activity remains unclear. This study investigated the imaging findings of the thoracic aortic wall and elasticity by using a comprehensive 3.0 T MRI protocol. We prospectively enrolled 52 consecutive TAK patients. TAK activity was recorded according to the ITAS2010. All the patients underwent thoracic aortic MRI. The luminal morphology of the thoracic aorta and its main branches were quantitatively evaluated using a contrast-enhanced magnetic resonance angiography (MRA) sequence. The maximum wall thickness of the thoracic aorta, postcontrast enhancement ratio, and aortic wall edema were analyzed in each patient through pre- and post-enhanced T1-weighted and T2-weighted imaging. Pulse-wave velocity (PWV) of the thoracic aorta was calculated using a four-dimensional flow technique. The majority of the 52 patients had type V disease (34.62%, 18/52). Among all the MRI indicators of the thoracic aorta, the area under the curve was the largest for the maximal wall thickness (0.804, 95% confidence interval [CI] = 0.667-0.941). The maximal wall thickness (93.33%, 95% CI = 68.1%-99.8%) exhibited the highest sensitivity with a cutoff value of 3.12 mm. Wall edema (84.00%, 95% CI = 63.9%-95.5%) presented the highest specificity. A positive correlation was noted between PWV and patients' age (r = 0.54, p < 0.001), disease duration (r = 0.52, p < 0.001), and the maximum wall thickness (r = 0.45, p = 0.001). MRI enabled the comprehensive assessment of aortic wall morphology and functional markers for TAK disease activity. Aortic maximal wall thickness was the most accurate indicator of TAK activity. The early phase was superior to the delay phase for aortic wall enhancement analysis for assessing TAK activity.

Follow-up of Intracranial Aneurysms Treated by Flow Diverters: Evaluation of Parent Artery Patency Using 3D-T1 Gradient Recalled-Echo Imaging with 2-Point Dixon in Combination with 3D-TOF-MRA with Compressed Sensing.

MRA assessment of parent artery patency after flow-diverter placement is complicated by imaging artifacts produced by these devices. The purpose of this study was to assess the accuracy of liver acquisition with volume acceleration-flex technique (LAVA-Flex) MRA in combination with 3D-TOF with HyperSense MRA for the evaluation of parent vessel status after intracranial flow-diverter placement. Fifty-six patients treated by flow diversion and followed with both DSA and 3T MRA between November 2020 and August 2021 were included. All patients were evaluated for parent artery patency using the same imaging protocol (DSA, noncontrast MRA including 3D-TOF with HyperSense and LAVA-Flex, and contrast-enhanced MRA, including time-resolved imaging of contrast kinetics MRA and delayed contrast-enhanced MRA). With DSA as a criterion standard to evaluate the patency of the parent vessel, noncontrast MRA had a good specificity (0.83) and positive predictive value (0.65), better than contrast-enhanced MRA (0.55 and 0.41, respectively). Both had excellent sensitivity and negative predictive value: noncontrast MRA, 0.93 and 0.97, respectively; contrast-enhanced MRA, 0.93 and 0.96, respectively. Specificity and positive predictive value tended to be lower for patients treated with additional devices than for those treated with flow diverters exclusively and for patients treated with a specific type of flow diverter. Noncontrast MRA can be used for noninvasive follow-up of intracranial aneurysms treated by flow diverters. The combined use of LAVA-Flex and 3D-TOF with HyperSense sequences allows monitoring the status of the parent artery and aneurysm occlusion.