Conventional MRA Research Articles

Dynamic contrast-enhanced MRA of the aorta using a Golden-angle RAdial Sparse Parallel (GRASP) sequence: comparison with conventional time-resolved cartesian MRA (TWIST).

To compare the application of two contrast-enhanced time-resolved magnetic resonance angiography sequences on an aortic disease patient cohort: the conventional Cartesian-sampling-based, Time-resolved angiography With Interleaved Stochastic Trajectories (TWIST) sequence, and the radial-sampling-based Golden-angle RAdial Sparse Parallel (GRASP) sequence. TWIST is highly sensitive to patient movement, which can lead to blurring and reduced sharpness of vascular structures, particularly in dynamic regions like the aorta. Such motion artifacts can compromise diagnostic accuracy. Radial-sampling-based techniques are less sensitive to motion than cartesian sampling and are expected to improve the image quality in body parts subjected to motion. 30 patients (60.9 ± 16.1y.o.) with various aortic diseases underwent a 1.5T magnetic resonance angiography examination. Assessment of image quality in the ascending aorta (AA), descending aorta (DA), and abdominal aorta (AbA) on a 4-point Likert scale (1 = excellent, 4 = non-diagnostic) as well as max. aortic diameters (Dmax) were performed. T-test and multilevel mixed-effect proportional-odds models were used for the image analysis. GRASP offered superior depiction of vascular structures in terms of vascular contrast for qualitative analysis(TWIST, reader 1: 1.6 ± 0.5; reader 2: 1.9 ± 0.4; reader 3: 1.1 ± 0.4; GRASP, reader 1: 1.5 ± 0.5; reader 2: 1.4 ± 0.5; reader 3: 1.0 ± 0.2) and vessel sharpness for qualitative (TWIST, reader 1: 1.9 ± 0.6; reader 2: 1.6 ± 0.6; reader 3: 2.0 ± 0.3; GRASP, reader 1: 1.4 ± 0.6; reader 2: 1.2 ± 0.4; reader 3: 1.3 ± 0.6) and quantitative analysis (TWIST, AA = 0.12 ± 0.04, DA = 0.12 ± 0.03, AbA = 0.11 ± 0.03; GRASP, AA = 0.20 ± 0.05, DA = 0.22 ± 0.06, AbA=0.20 ± 0.05). Streaking artefacts of GRASP were more visible compared to TWIST (TWIST, reader 1: 2.2 ± 0.6; reader 2: 1.9 ± 0.3; reader 3: 2.0 ± 0.5; GRASP, reader 1: 2.6 ± 0.6; reader 2: 2.3 ± 0.5; reader 3: 2.8 ± 0.6).Aortic Dmax comparison among the sequence showed no clinical relevance. GRASP outperformed TWIST in SNR, vessel sharpness, and reduction in image blurring; streaking artefacts were stronger with GRASP, but did not affect diagnostic image quality.

An Improved Voltage Sag Monitor Placement Method by using Simple Probability Reach Area Matrix

Aim: A novel optimization model is introduced in this paper to achieve monitor placements of voltage sag. Background: Considering the uncertainty of system parameters, calculation errors and measurement errors, the method of MRA is not suitable. Objective: The contradiction between the number of monitors and observation areas can be coordinated to achieve voltage sag observation with fewer monitor quantities. Method: A new generalized approach defined as a simple probability reach area matrix (SPMRA) is proposed. Result: SPMRA method is simulated by the IEEE-39 bus system, which reveals that monitor placement quantities can be reduced effectively under probabilistic observability. Conclusion: SPMRA method is a general method for monitor placements of voltage sag. This method not only performs the functions of conventional MRA methods, but also addresses the challenges of errors and conflicts between observation requirements and installation costs.

High-Resolution Time-of-Flight Magnetic Resonance Angiography with a Volume Rendering Algorithm for Detection of Unruptured Aneurysms: Correlations with Digital Subtraction Angiography

Objective: We investigated the diagnostic accuracy of high-resolution magnetic resonance angiography (HR-MRA) with volume rendering (VR) post-processing techniques for the detection of cerebral aneurysms compared with conventional MRA (C-MRA) using digital subtraction angiography (DSA) as the gold standard.Methods: HR-MRA was performed for 51 possible aneurysms of 38 patients on C-MRA. For each possible aneurysm, readers recorded their level of confidence on a 5-point scale. All patients underwent DSA, which was used as the standard of reference. Receiver-operating characteristic (ROC) analysis and the area under the ROC curves (AUC) were used to determine the effectiveness of C-MRA and HR-MRA in detecting cerebral aneurysm with and without VR algorithm. The increased discriminative value was examined by calculation of Net Reclassification Index (NRI) and Integrated Discrimination Improvement (IDI) index.Results: DSA revealed 37 aneurysms in 26 patients. In aneurysm-based analysis, HR-MRA showed higher diagnostic accuracy than C-MRA, and increased diagnostic accuracy on adding VR (C-MRA vs. HR-MRA, P< 0.01; C-MRA with VR vs. HR-MRA with VR, P< 0.01, respectively). The differences in AUC, IDI (19.38%, Z= 3.18, P< 0.01) and NRI (46.3%, Z= 6.32, P< 0.01), on adding VR to the HR-MRA, were also statistically significant. The application of HR-MRA with VR increased the detection rate of aneurysms less than 3 mm.Conclusion: The application of HR-MRA with VR algorithm improves diagnostic performance for the detection of intracranial aneurysms, especially when the aneurysm is less than 3 mm. Clinically, HR-MRA with VR algorithm could facilitate the accurate differentiation of aneurysms from infundibula and prevent unnecessary, invasive procedure before aneurysmal rupture.

Subtractionless compressed-sensing-accelerated whole-body MR angiography using two-point Dixon fat suppression with single-pass half-reduced contrast dose: feasibility study and initial experience

PurposeTo investigate the feasibility and clinical utility of a compressed-sensing-accelerated subtractionless whole-body MRA (CS-WBMRA) protocol with only contrast injection for suspected arterial diseases, by comparison to conventional dual-pass subtraction-based whole-body MRA (conventional-WBMRA) and available computed tomography angiography (CTA). Materials and methodsThis prospective study assessed 86 patients (mean age, 56 years ± 16.4 [standard deviation]; 25 women) with suspected arterial diseases from May 2021 to December 2022, who underwent CS-WBMRA (n = 48, mean age, 55.9 years ± 16.4 [standard deviation]; 25 women) and conventional-WBMRA (n = 38, mean age, 48 years ± 17.4 [standard deviation]; 20 women) on a 3.0 T MRI after random group assignment based on the chronological order of enrolment. Of all enrolled patients administered the CS-WBMRA protocol, 35% (17/48) underwent CTA as required by clinical demands. Two experienced radiologists independently scored the qualitative image quality and venous enhancement contamination. Quantitative image assessment was carried out by determining and comparing the apparent signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of four representative arterial segments. The total examination time and contrast-dose were also recorded. The independent samples t-test or the Wilcoxon rank sum test was used for statistical analysis. ResultsThe overall scores of CS-WBMRA outperformed those of conventional-WMBRA (3.40 ± 0.60 vs 3.22 ± 0.55, P < 0.001). In total, 1776 and 1406 arterial segments in the CS-WBMRA and conventional-WBMRA group were evaluated. Qualitative image scores for 7 (of 15) vessel segments in the CS-WMBRA group had statistically significantly increased values compared to those of the conventional-WBMRA groups (P < 0.05). Scores from the other 8 segments showed similar image quality (P > 0.05) between the two protocols. In the quantitative analysis, overall apparent SNRs were significantly higher in the conventional-WBMRA group than in the CS-WBMRA group (214.98 ± 136.05 vs 164.90 ± 118.05; P < 0.001), while overall apparent CNRs were not significantly different in these two groups (CS vs conventional: 107.13 ± 72.323 vs 161.24 ± 118.64; P > 0.05). In the CS-WBMRA group, 7 of 1776 (0.4%) vessel segments were contaminated severely by venous enhancement, while in the convention-WBMRA group, 317 of 1406 (23%) were rated as severe contamination. In the CS-WBMRA group, total examination and reconstruction times were only 7 min and 10 min, respectively, vs 20 min and < 30 s for the conventional WBMRA group, respectively. The contrast agent dose used in the CS-WBMRA protocol was reduced by half compared to conventional-WBMRA protocol (18.7 ± 3.5 ml vs 37.2 ± 5.4 ml, P = 0.008). ConclusionThe CS-WBMRA protocol provides excellent image quality and sufficient diagnostic accuracy for whole-body arterial disease, with relatively faster workflow and half-dose reduction of contrast agent, which has greater potential in clinical practice compared with conventional-WBMRA.

Comparison of conventional MRI, MR arthrography, MR arthrography with traction, MR arthrography with pressure in the evaluation of articular distension

ObjectiveTo evaluate the performance of conventional MRI, standard MR arthrography, MR arthrography with traction and MR arthrography with pressure in articular distension in patients with ACL injury. Design and patientsThe consecutive patients (7 female, 21 male) with acute ACL injured conventional MRI, MR arthrography, MR arthrography with traction and MR arthrography with pressure were evaluated. ResultsThe amount of distension in the joint was evaluated in the posterior, femorotibial and anterior compartments. Medially, between the meniscus posterior horn and the tibial corner, MRA with pressure was found to be more effective in showing this distance than MRA with traction (p < 0,05). Laterally, in measurements made between the posterior horn of the meniscus and the capsule, MRA with traction and MRA with pressure are more effective showing this distance than conventional MRI and standard MRA (p < 0,05). In measurements made medially, between the posterior horn of the meniscus and the capsule, MRA with traction is more effective in showing this distance than standard MRA (p < 0,05). In all three different MRA modalities, the lateral femorotibial joint distance was found to be statistically higher than conventional MRI (p < 0,05). Medial femorotibial joint distance was found to be statistically higher in MRA with pressure than in conventional MRI and standard MRA (p < 0,05). The medial infrapatellar distance was found to be statistically higher in MRA with pressure than standard MRA and MRA with traction (p < 0,05). The lateral infrapatellar distance is higher in MRA with pressure than in MRA with traction, and this height is statistically significant (p < 0,05). ConclusionTraction and pressure applications added to MRA will increase the effectiveness of the method by increasing the distension in the knee joint. Although both seem to be effective in creating distension in posterior compartment and femorotibial joint distance, MRA with pressure is more effective especially in anterior compartment.

Non-contrast MR angiography versus contrast enhanced MR angiography for detection of renal artery stenosis: a comparative analysis in 400 renal arteries.

In this study, we compared non-contrast MR angiography (NC-MRA) with conventional 3D contrast-enhanced MRA (CE-MRA) in patients suspected to have renal artery stenosis (RAS). From March 2014 to March 2020, patients who were evaluated for RAS and had a glomerular filtration rate > 30ml/min/1.73 m2 underwent MR imaging on a 3T MR Scanner (Signa Hdxt General Electrics, Milwaukee, USA) using a Torso PA coil. The NC-MRA sequence was performed using a 3D fat-suppressed inflow inversion recovery balanced steady state free precession (SSFP) sequence (Inhance 3D Inflow IR, GE Medical) whereas the CE-MRA sequence was a 3D fast spoiled gradient echo (FSPGR). Overall quality of images was rated 1 to 4. Stenosis was reported as grade 1 (Normal), 2 (< 50% narrowing), 3 (> 50% narrowing) and 4 (Total occlusion). Grade 3 and 4 were considered haemodynamically significant. During the study period, 201 patients were enrolled (400 renal arteries). For hemodynamically significant (grade 3/4) stenosis, NC-MRA correctly diagnosed 72 patients (95 arteries) while in 2 patients (2 arteries), NC-MRA underdiagnosed the stenosis as grade 2 (these were found to have grade 3 stenosis on CE-MRA). The kappa value of agreement between NC-MRA and CE-MRA for detection of RAS showing excellent agreement (p < 0.001). In one of the largest series of patients so far, we found that NC-MRA is a viable alternative to CE-MRA for detection of RAS, highly correlating with CE-MRA for grade of stenosis and with additional advantage of lack of gadolinium based contrast agents toxicity.

Feasibility and Robustness of 3T Magnetic Resonance Angiography Using Modified Dixon Fat Suppression in Patients With Known or Suspected Peripheral Artery Disease.

Objective: Contrast-enhanced magnetic resonance angiography (CE-MRA) is a well-established non-invasive imaging technique for the assessment of peripheral artery disease (PAD). A subtractionless method using modified Dixon (mDixon) fat suppression showed superior image quality at 1.5T over the common subtraction method, using a three-positions stepping table approach with a single dose of contrast agent. The aim of this study was to investigate the feasibility of subtractionless first-pass peripheral MRA at 3T in patients with known or suspected PAD and to compare the performance in terms of vessel-to-background contrast (VBC), signal-to-noise ratio (SNR), and subjective image quality to conventional subtraction MRA.Methods: Ten patients [mean age 69 years ± 12 standard deviation (SD)] with known or suspected PAD were examined on a clinical 3T scanner (Ingenia, Philips Healthcare, Best, Netherlands) at three table positions using subtractionless and subtraction first-pass peripheral MRA. Two readers rated image quality on a four- point scale. Interobserver agreement was expressed in quadratic weighted κ values. VBC was assessed with a semi-automated process and SNR was compared in a healthy volunteer.Results: Subjective image quality was significantly better with the subtractionless method overall (mean image quality for mDixon imaging: 2.88 ± 0.32 SD vs. for subtraction imaging: 2.57 ± 0.48 SD; P < 0.001) and per table position (abdominal position: 2.88 ± 0.32 vs. 2.57 ± 0.48 SD; P < 0.001); upper leg position: (2.97 ± 0.15 SD vs. 2.68 ± 0.37 SD; P < 0.001; lower leg position: 2.60 ± 0.50 SD vs. 2.13 ± 0.60 SD; P < 0.001). Vessel-to-background contrast increased by 22% with the subtractionless method overall (mean VBC for mDixon imaging: 23.16 ± 8.4 SD vs. for subtraction imaging: 19.00 ± 8.1 SD; factor 1.22, P < 0.001). SNR was 82% higher with the subtractionless method (overall SNR gain 1.82; P < 0.001).Conclusion: This study demonstrated the feasibility and robustness of subtractionless first-pass peripheral MRA at 3T in patients with known or suspected PAD using a three- positions stepping table approach with a single dose of contrast agent. It showed increased image quality compared to the conventional subtraction method and superior performance in terms of SNR and vessel-to-background contrast.

Image diagnosis of Trigeminal Neuralgia caused by Vascular Compression

Trigeminal Neuralgia (TGN) is a disease frequently encountered by the neurologists and neurosurgeons. The typical pain of TGN is lancinating in nature in one side of face along the distribution of Trigeminal nerve. Pain is sharp shooting and periodic in nature, aggravated by various factors, like eating, talking, laughing. A typical trigeminal neuralgia is caused by compression to the Root exit zone (REZ) by superior cerebellar artery (SCA), aberrant loop of Antero inferior cerebellar artery (AICA), dolichobasilar artery or a large sized vein. However facial pain mimicking TGN may occur by a tumor, plaque of Multiple sclerosis or may be idiopathic. So this is very important to know the cause of TGN/ facial pain for planning of specific treatment. Most of the patients remain pain free by medical management by using Carbamazepine, oxycarbazepine, Pregabalin, Gabapentin, Clonazepam etc. But medically refractory TGN can be treated by Microvascular decompression (MVD) with significantly satisfactory results if the cause is by vascular compression. However during MVD no significant blood vessels are seen and surgery become failed. Clinical examination and evaluation is very important, however to become confirmed about the pathogenesis needs imaging of brain. MRI of brain can differentiate any tumor or Plaque of MS. But conventional MRI images can not show us clearly the blood vessel causing TGN. Conventional MRA could show the blood vessels, which might be causing compression to REZ but does not confirm the fact. Constructive interference in steady state (CISS) MR images were evaluated in our 15 cases to find neurovascular relationship at the REZ. In 11 cases CISS images showed excellent visualization of fifth nerve and blood vessels causing compression to REZ in all case of TGN who underwent Microvascular decompression (MVD) with excellent result. In 2 patients we depended on clinical findings and T2 MR Images. In one of them we could find Offending vessels who were also improved clinically. In one case we did not find any significant offending vessel except a small vein and this patient did not show any improvement. In rest two cases, in one patient CISS showed a tiny vessel and after MVD the patient did not improve. In one patient no significant vessels were not seen in CISS images. We did not go for MVD for this case. So the pre-operative CISS MR images are more precise to show the neurovascular relationship and determine the offending blood vessel causing TGN. Thus we can avoid an unnecessary MVD.&#x0D; Bang. J Neurosurgery 2020; 10(1): 3-8

Feasibility and optimization of ultra-short echo time MRI for improved imaging of IVC-filters at 3.0T.

To determine the feasibility of ultra-short echo time (UTE) MRA for assessment of inferior vena cava (IVC) filters and evaluate the impact of different imaging protocols at 3.0T, using conventional Cartesian MRA (cMRA) as the reference standard. Patients with IVC-filters were recruited for this prospective IRB-approved, HIPAA-compliant study. Subjects underwent contrast-enhanced breath-held and a free-breathing 3D radial acquisition UTE-MRA (bhUTE, fbUTE) at three different flip angles (FA: 10°, 15°, 20°) to optimize T1-weighted image quality. Two radiologists performed a direct comparison consensus reading to assess the optimal FA. Image quality (IQ) of both UTE techniques at the best FA was rated independently on a 4-point Likert scale (0 = non-diagnostic, 3 = excellent) and compared to 3D T1-weighted breath-held cMRA. Nine subjects were recruited. Low FAs of 10° were rated best for both UTE techniques. fbUTE was excellent (3, IQR: 2; 3) and significantly better for IVC-filter depiction than cMRA (2, IQR: 0.75; 2, p = 0.001) and bhUTE (1.5, IQR: 0.75; 2, p < 0.001). Both UTE techniques showed significantly less filter-related artifacts (fbUTE: 28%, bhUTE: 33%) than cMRA (89%, p = 0.001 and p = 0.002, respectively). However, IQ of bhUTE was generally degraded due to high image noise and low image contrast. IQ of the IVC venogram was best with cMRA. Clinically relevant signal voids were only observed with the cage-shaped OptEase filter. UTE-MRA is feasible at 3.0T for the assessment of IVC-filters, particularly using a free-breathing protocol. Larger studies are needed to investigate the clinical utility of free-breathing UTE-MRA for assessment of IVC-filter-related complications.

Abstract No. 487 Role of time-resolved magnetic resonance angiography in appropriate diagnosis of patients with Klippel-Trenaunay syndrome

Vascular malformations associated with genetic mutations are rare and patient presentation can be complex. Misdiagnosis in this patient population is not uncommon. Time-resolved magnetic resonance angiography (TR-MRA) provides essential information about flow dynamics of a malformation that aids in establishing the correct diagnosis and appropriate treatment planning. A retrospective chart review at one institution was performed after obtaining Institutional Review Board approval. The charts of patients previously diagnosed or suspected to have Klippel-Trenaunay syndrome (KTS) at the time of referral were analyzed to assess the value of TR-MRA in the patient’s diagnosis and treatment. TR-MRA delineates arterial and venous phases of vascular enhancement. TR-MRA involves rapid sequential T1-weighted imaging during the passage of the contrast bolus to document the first pass through the vasculature. This technique provides dynamic information that is not available with conventional single-phase MRA and was previously only available with diagnostic catheter angiography. Of 17 patients referred to IR clinic with a suspected diagnosis of KTS, TR-MRA was performed in 76% of the cases (11 performed at the treating institution and 2 performed at an outside hospital). TR-MRA provided an alternate diagnosis in 2 of 13 cases (15%). In one case, TR-MRA demonstrated an arteriovenous malformation (AVM) rather than a purely venous malformation, which in the presence of a port wine stain and limb hypertrophy is consistent with Parkes-Weber syndrome (PWS). The second case demonstrated no evidence of vascular malformation despite the presence of a port wine stain. In both cases, TR-MRA changed patient management. TR-MRA definitely identifies and differentiates fast-flow and slow-flow vascular malformations impacting patient diagnosis and management. In our study, time-resolved MRA confirmed the presumed diagnosis of KTS in 85% of patients, and revealed new information leading to change of diagnosis and management in 15% of patients initially referred with a presumed diagnosis of KTS.

Non-Contrast-Enhanced Carotid MRA: Clinical Evaluation of a Novel Ungated Radial Quiescent-Interval Slice-Selective MRA at 1.5T.

Non-contrast-enhanced MRA techniques have experienced a renaissance due to the known correlation between the use of gadolinium-based contrast agents and the development of nephrogenic systemic fibrosis and the deposition of gadolinium in some brain regions. The purpose of this study was to assess the diagnostic performance of ungated non-contrast-enhanced radial quiescent-interval slice-selective MRA of the extracranial supra-aortic arteries in comparison with conventional contrast-enhanced MRA in patients with clinical suspicion of carotid stenosis. In this prospective study, both MRA pulse sequences were performed in 31 consecutive patients (median age, 68.8 years; 19 men). For the evaluation, the cervical arterial system was divided into 35 segments (right and left side). Three blinded reviewers separately evaluated these segments. An ordinal scoring system was used to assess the image quality of arterial segments and the stenosis grading of carotid arteries. Overall venous contamination in quiescent-interval slice-selective MRA was rated as "none" by all readers in 84.9% of cases and in 8.1% of cases in contrast-enhanced MRA (P < .0001). The visualization quality of arterial segments was considered good to excellent in 40.2% for the quiescent-interval slice-selective MRA and in 52.2% for the contrast-enhanced MRA (P < .0001). The diagnostic accuracy of ungated quiescent-interval slice-selective MRA concerning the stenosis grading showed a total sensitivity and specificity of 85.7% and 90.0%, respectively. Ungated quiescent-interval slice-selective MRA can be used clinically as an alternative to contrast-enhanced MRA without a significantly different image quality or diagnostic accuracy for the detection of carotid stenosis at 1.5T.

Comparison of two different measurement methods in evaluating basilar atherosclerotic plaque using high-resolution MRI at 3\u2009tesla

BackgroundTo compare the Self-referenced and Referenced measurement methods in assessing basilar artery (BA) atherosclerotic plaque employing dark blood high-resolution MRI at 3 Tesla.MethodsForty patients with > 20% stenosis as identified by conventional MRA were recruited and evaluated on a 3 Tesla MRI system. The outer wall, inner wall and lumen areas of maximal lumen narrowing site and the outer wall and lumen areas of sites that were proximal and distal to the maximal lumen narrowing site were manually traced. Plaque area (PA), stenosis rate (SR) and percent plaque burden (PPB) were calculated using the Self-referenced and Referenced measurement methods, respectively. To assess intra-observer reproducibility, BA plaque was measured twice with a 2-week interval in between measurements.ResultsThirty-seven patients were included in the final analysis. There were no significant differences in PA, SR and PPB measurements between the two methods. The intra-class coefficients and coefficient of variations (CV) ranged from 0.976 to 0.990 and from 3.73 to 5.61% for the Self-referenced method and ranged from 0.928 to 0.971 and from 4.64 to 9.95% for the Referenced method, respectively. Both methods are effective in the evaluation of BA plaque. However, the CVs of the Self-referenced method is lower than the Referenced measurement method. Moreover, Bland-Altman plots showed that the Self-referenced method has a narrower interval than the Referenced measurement method.ConclusionsThe Self-referenced method is better and more convenient for evaluating BA plaque, and it may serve as a promising method for evaluation of basilar atherosclerotic plaque.

Reliability of fast magnetic resonance imaging for acute ischemic stroke patients using a 1.5-T scanner.

To determine whether fast scanned MRI using a 1.5-T scanner is a reliable method for the detection and characterization of acute ischemic stroke in comparison with conventional MRI. From May 2015 to June 2016, 862 patients (FLAIR, n = 482; GRE, n = 380; MRA, n = 190) were prospectively enrolled in the study, with informed consent and under institutional review board approval. The patients underwent both fast (EPI-FLAIR, ETL-FLAIR, TR-FLAIR, EPI-GRE, parallel-GRE, fast CE-MRA) and conventional MRI (FLAIR, GRE, time-of-flight MRA, fast CE-MRA). Two neuroradiologists independently assessed agreements in acute and chronic ischemic hyperintensity, hyperintense vessels (FLAIR), microbleeds, susceptibility vessel signs, hemorrhagic transformation (GRE), stenosis (MRA), and image quality (all MRI), between fast and conventional MRI. Agreements between fast and conventional MRI were evaluated by generalized estimating equations. Z-scores were used for comparisons of the percentage agreement among fast FLAIR sequences and fast GRE sequences and between conventional and fast MRA. Agreements of more than 80% were achieved between fast and conventional MRI (ETL-FLAIR, 96%; TR-FLAIR, 97%; EPI-GRE, 96%; parallel-GRE, 98%; fast CE-MRA, 86%). ETL- and TR-FLAIR were significantly superior to EPI-FLAIR in the detection of acute ischemic hyperintensity and hyperintense vessels, while parallel-GRE was significantly superior to EPI-GRE in the detection of susceptibility vessel sign (p value < 0.05 for all). There were no significant differences in the other scores and image qualities (p value > 0.05). Fast MRI at 1.5T is a reliable method for the detection and characterization of acute ischemic stroke in comparison with conventional MRI. • Fast MRI at 1.5 T may achieve a high intermethod reliability in the detection and characterization of acute ischemic stroke with a reduction in scan time in comparison with conventional MRI.

Comparison of 3D TOF MR angiographic accuracy in predicting Raymond grade of flow-diverted versus coiled intracranial aneurysms

The accuracy of 3D time of Flight Magnetic Resonance Angiography (TOF MRA) has been studied extensively for following coiled intracranial aneurysms. It is used by many clinicians for non-invasive follow-up because of its adequate sensitivity in predicting aneurysmal recanalization compared to diagnostic cerebral angiography. The data on the accuracy of 3D TOF MRA for the Pipeline™ Embolization Device (PED) are sparse. In a retrospective chart review, we compared the accuracy of 3D TOF MRA of PED to coil embolization at our institution. 3D TOF MRA had a lower sensitivity and positive predictive value in detecting aneurysmal filling in PED-treated versus coiled aneurysms (57% versus 87% and 80% versus 100%, respectively). Analysis of discrepancies between conventional diagnostic angiography and 3D TOF MRA revealed that 3D TOF MRA was inaccurate in the setting of small residual necks and slow residual filling of the dome with fluid–fluid layers. Therefore, contrasted studies such as contrast-enhanced MRA may be preferred for non-invasively following PED-treated aneurysms to increase accuracy.

Isolated Posteroinferior Cerebellar Artery Dissection Diagnosed by High-Resolution Vessel Wall MRI

Arterial dissection is an important cause of stroke. We report two cases of isolated posterior inferior cerebellar artery (PICA) dissection diagnosed by high-resolution vessel-wall MRI (HRVW-MRI). One subject complained of abrupt-onset vertigo and headache, and the other subject had headache, vertigo, and Horner syndrome. Conventional MRA showed only focal dilatation of the PICA, but HRVW-MRI revealed intramural hematoma and double-lumen contour in the PICA, suggesting arterial dissection. We suggest that the use of HRVW-MRI should be considered when diagnosing isolated PICA dissection in a PICA infarct with an unknown cause. Key Words: Isolated PICA dissection, High-resolution vessel-wall MRI, Arterial dissection

Abstract WP215: Role of Conventional Mri Brain for Basilar Artery Plaque Detection in Solitary Pontine Infarct

Background: Solitary pontine infarct is divided into paramedian pontine infarct (PPI) and small deep pontine infarct (SDPI). The novel high-resolution MRI is the current useful imaging method to characterize vessel walls and detect atherosclerotic plaques of the intracranial arteries. However, high-resolution MRI is not included in routine imaging protocol for patient with acute stroke. We intend to determine the role of conventional MRI and MRA of the brain in solitary pontine infarct. Material and Method: Fifty patients with pontine infarct undergo imaging study of MRI of the brain on T1-weighted image, T2-weighted image and post-gadolinium T1-weighted image (if available) to assess the presence of atherosclerotic plaque, and MRA of the brain using 3-dimensional time-of-flight MRA (3D TOF MRA) to assess the basilar artery luminography. Basilar artery assesses by axial T2-weighted image was scored as “presence of plaque” or “absence of plaque” and 3D TOF MRA of basilar artery is scored as “normal”, “irregular” or “stenosis” ≥ 30%. Pontine infarction is divided into paramedian pontine infarction (PPI) and small deep pontine infarction (SDPI) groups. Results: Fifty patients with pontine infarction are included, thirty-five with PPI and fifteen with SDPI. Conventional axial T2WI MRI of the brain detected basilar artery atherosclerotic plaques in about 50% of patients with pontine infarction: 51.4% (18 of 35 cases) in PPI and 46.7% (7 of 15 cases) in SDPI. No plaque is found in all cases of normal-appearing basilar luminography on 3D TOF MRA and plaque was identified in all patients with basilar artery stenosis on 3D TOF MRA. Conclusion: Basilar artery atherosclerotic branch disease is frequently detected in both groups of solitary pontine infarct (PPI and SDPI). Conventional MRI and MRA of the brain are the useful imaging methods that may characterize intracranial vessel wall abnormalities and may be helpful in further study of intracranial arterial diseases and in comprehension of stroke mechanisms.

ECG and navigator-free 4D whole-heart coronary MRA

Background Cardiac and respiratory motion artifacts are major challenges to whole-heart coronary MRA. The conventional motion suppression strategies often involve prospective gating based on motion surrogates, e.g. ECG and navigator, which complicates scan setup and prolongs scan time significantly. To address these limitations, an ECG and navigator-free 4D whole-heart coronary MRA technique was recently proposed, providing both cardiac function and coronary artery assessment from a single measurement [1]. In this work, we evaluate the 4D technique by comparing it against conventional cine and coronary MRA protocols.

Fat-subtracted three-dimensional time-of-flight MR angiography of the neck by use of fat-only images with the two-point Dixon technique.

For improvement of three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) image quality in the neck, fat-subtracted MRA by use of the two-point Dixon technique was compared with conventional fat-suppressed MRA techniques. Three different types of neck 3D-TOF-MRA were obtained [minimum echo time (TE) (1.9ms), opposed-phase TE (3.4ms), and chemical shift selective fat suppression (CHESS) (TE=1.9ms)] on five volunteers at 3.0 T. MRA was obtained with subtraction of fat-only images (produced by a two-point Dixon sequence) from minimum-TE MRA images, and compared with other fat-suppressed MRA images. Fat-subtracted MRA demonstrated uniform fat suppression compared with other techniques. The mean vessel-to-fat contrast in fat-subtracted MRA was significantly higher (p<0.01) than in other MRA images (minimum-TE: 0.137±0.086, opposed-phase TE: 0.268±0.102, CHESS: 0.307±0.052, fat-subtracted: 0.965±0.101). The mean vessel-to-muscle contrast in opposed-phase TE MRA was significantly lower (p<0.01) than in other MRA images (minimum-TE: 0.526±0.036, opposed-phase TE: 0.419±0.188, CHESS: 0.511±0.023, fat-subtracted: 0.573±0.016). Fat-subtracted MRA by use of the two-point Dixon technique improves the image quality of neck MRA. This technique would be a useful method for MRA, especially in areas with inhomogeneous magnetic fields, such as the neck.

Improvement of the diagnostic accuracy of MRA with subtraction technique in cerebral vasospasm.

Vasospasm has been considered the most severe acute complication after subarachnoid hemorrhage (SAH). MRA is not considered ideal for detecting cerebral vasospasm because of background including the hemorrhage. The aim of this study is to evaluate the efficacy of Subtraction MRA (SMRA) by comparing it to that of conventional MRA (CMRA) for diagnosis of cerebral vasospasm. Arteries were assigned to one of three categories based on the degree of MRA diagnostic quality of vasospasm (quality score): 0, bad … 2, good. Furthermore each artery was assigned to one of four categories based on the degree of vasospasm severity (SV score): 0, no vasospasm … 3, severe. The value of the difference between DSA-SV score and MRA-SV score was defined as the DIF score. CMRA and SMRA were compared for each arterial region with regard to quality score and DIF score. The average CMRA and SMRA quality score were 1.46 and 1.79; the difference was statistically significant. The average CMRA and SMRA DIF score were 1.08 and .60; the difference was statistically significant. Diagnosis of cerebral vasospasm is more accurate by SMRA than by CMRA. The advantages are its noninvasive nature and its ability to detect cerebral vasospasm.

Endovascular coil embolization of unruptured intracranial aneurysms: a Korean multicenter study

Endovascular coil embolization has been a major treatment modality for unruptured intracranial aneurysms (UIAs) in South Korea. However, there are still few reports on the outcomes of this procedure. We performed a retrospective, multicenter study to determine how safe and effective coiling for UIA has been over the most recent 3years in South Korea. We analyzed a total of 2,180 UIAs in 2,035 patients who were treated by coiling from January 2007 to December 2009 at 22 centers in South Korea, with a focus on patient characteristics, the location and size of the aneurysms, procedural complications, and angiographic and clinical outcomes. Coiling was successful in 98.0% of the cases (2,137/2,180 aneurysms). Immediate post-procedural angiography demonstrated complete occlusion in 62.6% (1,337/2,137 aneurysms), residual neck in 32.4% (692/2,137), and residual sac in 5.0% (108/2,137) of the cases. The rate of any procedure-related adverse event was 6.9% (148/2,137 aneurysms). The rates of permanent morbidity and mortality were 1.8% (39/2,137 aneurysms) and 0.1% (2/2,137 aneurysms), respectively. Follow-up conventional angiography or MRA at ≥6months was performed in 85.7% (1,832/2,137 aneurysms) of cases. Among the eligible aneurysms for follow-up angiographic analysis, major recanalization was noted in 3.9% (72/1,832 aneurysms, mean follow-up interval, 12months). Among these, 68 aneurysms (3.7%) were re-treated. An aneurysm of the middle cerebral artery (MCA) was a risk factor for incomplete occlusion (P = 0.049) and major recanalization (P = 0.046). During follow-up, no aneurysmal rupture occurred. Endovascular coil embolization of UIAs has been an effective preventive modality with low procedure-related morbidity in South Korea.