Magnetic Resonance Angiography Protocol Research Articles

Pre-Procedural Assessment of the Femoral Access Route for Transcatheter Aortic Valve Implantation: Comparison of a Non-Contrast Time-of-Flight Magnetic Resonance Angiography Protocol with Contrast-Enhanced Dual-Source Computed Tomography Angiography.

Background: We aimed to evaluate the feasibility of a non-contrast time-of-flight magnetic resonance angiography (TOF-MRA) protocol for the pre-procedural access route assessment of transcatheter aortic valve implantation (TAVI) in comparison with contrast-enhanced cardiac dual-source computed tomography angiography (CTA). Methods and Results: In total, 51 consecutive patients (mean age: 82.69 ± 5.69 years) who had undergone a pre-TAVI cardiac CTA received TOF-MRA for a pre-procedural access route assessment. The MRA image quality was rated as very good (median of 5 [IQR 4-5] on a five-point Likert scale), with only four examinations rated as non-diagnostic. The TOF-MRA systematically underestimated the minimal effective vessel diameter in comparison with CTA (for the effective vessel diameter in mm, the right common iliac artery (CIA)/external iliac artery (EIA)/common femoral artery (CFA) MRA vs. CTA was 8.04 ± 1.46 vs. 8.37 ± 1.54 (p < 0.0001) and the left CIA/EIA/CFA MRA vs. CTA was 8.07 ± 1.32 vs. 8.28 ± 1.34 (p < 0.0001)). The absolute difference between the MRA and CTA was small (for the Bland-Altman analyses in mm, the right CIA/EIA/CFA was -0.36 ± 0.77 and the left CIA/EIA/CFA was -0.25 ± 0.61). The overall correlation between the MRA and CTA measurements was very good (with a Pearson correlation coefficient of 0.87 (p < 0.0001) for the right CIA/EIA/CFA and a Pearson correlation coefficient of 0.9 (p < 0.0001) for the left CIA/EIA/CFA). The feasibility agreement between the MRA and CTA for transfemoral access was good (the right CIA/EIA/CFA agreement was 97.9% and the left CIA/EIA/CFA agreement was 95.7%, Kohen's kappa: 0.477 (p = 0.001)). Conclusions: The TOF-MRA protocol was feasible for the assessment of the access route in an all-comer pre-TAVI population. This protocol might be a reliable technique for patients at an increased risk of contrast-induced nephropathy.

Impact of MRA Echo Time on Stroke Prevention Therapy in Pediatric Patients with Sickle Cell Disease

Background and Purpose: Magnetic Resonance Angiography (MRA) is performed on pediatric patients with sickle cell disease (SCD) to classify degree of cerebrovascular stenosis, informing stroke risk and treatment plan for stroke prevention. Flow artifact intrinsic to MRA and influenced primarily by TE (echo time) can lead to overinterpretation of stenosis. A standardized MRA protocol with shorter TE for patients with sickle cell disease was implemented at our institution. The primary objective of this study was to document any change in stroke prevention therapy that could be attributed to the implementation of this standardized MRA scanning protocol. Methods: A standardized MRA scanning protocol with an TE of <5msec based on the SWiTCH study protocol for patients with SCD was implemented at Montefiore Medical Center, NY (MMC) May 2016. This project included a retrospective chart review of patients at MMC ≤ 21 years with SCD who had one MRA head pre- AND one MRA post-May 2016. Of the 81 patients that met inclusion criteria, 29 patients were found to have vasculopathy on pre-May 2016 imaging and were included in this analysis. Level of arterial stenosis on MRA, TE, and treatment plans were documented both pre- and post-May 2016. McNemar analysis was used to determine the significance of change in treatment plans before and after implementation of the standardized scanning protocol. Results: 24/29 (83%) patients were on chronic transfusion therapy for CNS vasculopathy pre-May 2016 whereas 18/29 (62%) were on chronic transfusion therapy post May 2016. Notably, 6 patients had a resolution of vasculopathy on MRA post implementation of the scanning protocol, leading to discontinuation of chronic transfusion therapy. McNemar analysis showed this difference to be statistically significant (p = 0.042). Conclusion: Implementing a standardized MRA scanning protocol allowed for chronic transfusion therapy to be discontinued in 6 out of 24 patients due to minimizing flow artifact. Screening for arterial stenosis with TE <5msec can improve accurate interpretation of true cerebrovascular disease and ensure appropriate treatment plans are in place for SCD stroke prevention.

Development and practical evaluation of a saturation effect learning simulator for inflow magnetic resonance angiography.

The quality of visualization in inflow magnetic resonance angiography (MRA) depends highly on the excitation state of the longitudinal magnetization obtained using specified imaging parameters. In addition, signal intensity changes controlled by the preparation pulse-such as inversion recovery (IR) and saturation recovery (SR)-can potentially be used as quantitative physiological values. Although having practitioners understand these relationships both qualitatively and quantitatively is important, handling clinical equipment in practical learning or experiments involves limited opportunities. The simulator corresponds to a three-dimensional spoiled gradient echo sequence and allows users to freely input multiple virtual excitation effects in space and time. The purpose of this study was to quantitatively evaluate the agreement between the measured MRAs obtained in flow phantom tests and virtual MRAs simulated under similar conditions. We imaged two vascular flow phantoms on a 3.0T MR system using three-dimensional (3D) time-of-flight (TOF) MRA and 3D inversion recovery tissue signal suppression (IR-suppression) MRA protocols. We evaluated quantitative values for consistency between the measured and virtual MRAs images with matched spatial resolution. Then we assessed the coincidence by reformatting maximum-intensity projection images with 1mm isotropic pixels, with it ranging from 89.6 to 92.0% and 89.1 to 92.9% for TOF MRA and IR-suppression MRA, respectively. These results may be useful as a reference index for the theoretical study of MRA images by practitioners, for complementary validation by phantom testing, or for the development of MRI-related simulators.

Ferumoxytol-enhanced magnetic resonance angiography provides comparable vascular conspicuity to CT angiography in dogs with intrahepatic portosystemic shunts.

Computed tomography angiography (CTA) is currently the gold standard imaging modality for anatomically characterizing canine hepatic vascular anomalies; with conventional, gadolinium-enhanced MR angiography being less frequently utilized. However, both imaging modalities are limited by a brief, first pass peak of contrast medium in the vasculature that necessitates precisely timed image acquisition. A long-acting purely intravascular magnetic resonance imaging (MRI) contrast agent, ferumoxytol, offers the potential to reduce complexity of magnetic resonance angiography (MRA) protocol planning by ensuring diagnostic contrast medium concentration in all the vessels that are targeted for imaging. Aims of this prospective, pilot, methods comparison study were to develop an optimized MRA protocol using ferumoxytol in dogs with hepatic vascular anomalies, perform a dose escalation trial to compare image quality with four-dose regimens of ferumoxytol, and compare accuracy of vascular anatomic depiction based on the gold standard of CTA. Six dogs (10.7-36.1kg) with portosystemic shunts (four intrahepatic left divisional shunts and two intrahepatic right divisional shunts) were recruited for inclusion in the study. A dose-escalation trial was performed to compare image quality at four incremental dose levels of ferumoxytol (1, 2, 3, and 4mg/kg) and to compare the accuracy of vascular anatomic detection to CTA. Ferumoxytol contrast-enhanced MRA (CE-MRA) at 4mg/kg provided similar conspicuity of normal and abnormal vasculature compared to CTA with a minimal decrease in spatial resolution. Findings indicated that ferumoxytol holds promise for comprehensive, single breath hold CE-MRA of all abdominal vessels in dogs with portosystemic shunts. Background information provided in this study can be used to support development of other future applications such as intracranial and cardiac MRA, real-time imaging, flow quantification, and potentially sedated MRI imaging.

High spatial resolution whole-neck MR angiography using thin-slab stack-of-stars quiescent interval slice-selective acquisition.

To report a 3D multi-echo thin-slab stack-of-stars (tsSOS) quiescent-interval slice-selective (QISS) strategy for high-resolution magnetic resonance angiography (MRA) of the entire neck in under seven minutes. The neck arteries of eight subjects were imaged at 3 Tesla. Multi-echo 3D tsSOS QISS using a FLASH readout was compared with 3D tsSOS FLASH, 2D QISS, 2D TOF, and 3D TOF. A root-mean-square (RMS) combination of echo time images was tested. Evaluation metrics included arterial signal-to-noise ratio (SNR), arterial-to-muscle contrast-to-noise ratio (CNR), and image quality. 3D multi-echo tsSOS QISS using a RMS combination of echo time images increased SNR and CNR by 60% and 63% with respect to the reconstruction obtained with the shortest echo time. 3D tsSOS QISS showed superior CNR with respect to 3D tsSOS FLASH imaging, and more than 3-fold higher SNR and CNR with respect to 2D radial QISS when normalized for voxel size. 3D tsSOS QISS provided good to excellent image quality that exceeded the image quality of 2D QISS, 2D TOF, and 3D TOF (P<.05). Whole-neck high-resolution nonenhanced MRA is feasible using 3D tsSOS QISS, and produced image quality that exceeded those of competing nonenhanced MRA protocols at 3 Tesla.

Diagnostic Accuracy of Noncontrast MR Angiography Protocols at 3T for the Detection and Characterization of Lower Extremity Peripheral Arterial Disease

PurposeTo compare the diagnostic accuracy of established non–gadolinium (Gd)-enhanced magnetic resonance (MR) angiography protocols with Gd-enhanced MR angiography at 3T for evaluating lower extremity peripheral arterial disease (PAD). Materials and MethodsFrom February 2014 to 2015, 20 patients with PAD and intermittent claudication (16 men; age range, 51–76 y; Fontaine stage II) underwent 3-station (abdominopelvic, thigh, and calf) non-Gd MR angiography and bolus-chase Gd MR angiography protocols performed at 3T (Siemens Tim Trio), including quiescent-interval single-shot (QISS) MR angiography for all 3 stations and a combination of quadruple inversion recovery (QIR) MR angiography for the abdominopelvic station and electrocardiogram-gated fast spin echo (ECG-FSE) MR angiography for the extremities. Two radiologists independently evaluated vessel segments for vascular stenosis, diagnosis confidence, graft presence, and Trans-Atlantic Inter-Society Consensus (TASC) II classification for each station. Diagnostic accuracies and κ agreement were assessed. ResultsOf 573 vascular segments imaged, 16.9% (97/573, 19/20 patients) demonstrated hemodynamically significant abnormalities. Reader confidence was sufficient for diagnosis in 98% of segments with Gd MR angiography, 93% with QIR/ECG-FSE, and 95% with QISS. Overall reader confidence was higher with QISS than QIR/ECG-FSE within all 3 stations combined (P < .05). With low-confidence segments treated as misdiagnosis, sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and κ agreement for all 3 stations combined were 81.4/87.2/57.0/95.8/86.2%/0.578 for QIR/ECG-FSE and 75.0/90.6/61.6/94.7/88.0%/0.597 for QISS. Using TASC II criteria to assess severity, QISS and QIR/ECG-FSE had no statistical difference in agreement with Gd MR angiography. ConclusionsQISS and QIR/ECG-FSE MR angiography protocols demonstrate comparable diagnostic accuracies with high specificity. Either protocol provides an alternative to Gd MR angiography at 3T for patients with PAD.

Technical Feasibility of a Combined Noncontrast Magnetic Resonance Protocol for Preoperative Transcatheter Aortic Valve Replacement Evaluation.

The aim of this study was to prospectively evaluate the technical feasibility of a noncontrast magnetic resonance angiography (MRA) protocol using investigational prototype self-navigated 3D (SN3D) radial whole-heart and quiescent-interval single-shot (QISS) pulse sequences regarding their potential in planning transcatheter aortic valve replacement (TAVR). Five patients (76±7 y) with severe aortic valve stenosis and prior computed tomographic angiography (CTA) for TAVR planning and 10 healthy volunteers (28±6 y) underwent noncontrast MRA on a 1.5 T system. A SN3D whole-heart acquisition was used to assess the aortic root anatomy. Evaluation of the aortoiliac access route was performed with both SN3D and QISS. Measurements were compared among SN3D, QISS, and CTA using a paired t test or 1-way analysis of variance. Image quality ratings and contrast-to-noise ratios (CNR) were analyzed using Mann-Whitney U tests. Interobserver agreement was evaluated using Cohen's κ. The combined SN3D and QISS protocol provided a 10.1±1.6-minute acquisition time. TAVR-relevant evaluation was technically feasible in healthy volunteers. All measurements showed good agreement with CTA in patients (all P>0.098). SN3D and QISS produced similar image quality both in volunteers and in patients (all P>0.122). There was no difference in qualitative ratings between MRA and CTA (all P>0.119). Interobserver agreement was good for MRA (κ=0.71 to 0.76) and excellent for CTA (κ=0.82 to 0.84). Thoracic SN3D provided a similar CNR compared with CTA (P=0.117). CTA yielded higher CNR in the abdominopelvic region compared with QISS (P=0.006). A noncontrast MRA protocol combining SN3D and QISS acquisitions for the assessment of cardiac and vascular access route anatomy has technical feasibility for TAVR planning.

Image Quality and Stenosis Assessment of Non-Contrast-Enhanced 3-T Magnetic Resonance Angiography in Patients with Peripheral Artery Disease Compared with Contrast-Enhanced Magnetic Resonance Angiography and Digital Subtraction Angiography.

PurposeTo evaluate the diagnostic performance of flow-sensitive dephasing (FSD)-prepared steady-state free precession (SSFP) magnetic resonance angiography (MRA) at 3 T for imaging infragenual arteries relative to contrast-enhanced MRA (CE-MRA) and digital subtraction angiography (DSA).Materials and MethodsA series of 16 consecutive patients with peripheral arterial disease (PAD) underwent a combined peripheral MRA protocol consisting of FSD-MRA for the calves and large field-of-view CE-MRA. DSA was performed on all patients within 1 week of the MR angiographies. Image quality and degree of stenosis was assessed by two readers with rich experience. Inter-observer agreement was determined using kappa statistics. Receiver operating characteristic (ROC) curve analysis determined the diagnostic value of FSD-MRA, CE-MRA, and CE-MRA combined with FSD-MRA (CE+FSD MRA) in predicting vascular stenosis.ResultsAt the calf station, no significantly difference of subjective image quality scores was found between FSD-MRA and CE-MRA. Inter-reader agreement was excellent for both FSD-MRA and CE-MRA. Both of FSD-MRA and CE-MRA carry a stenosis overestimation risk relative to DSA standard. With DSA as the reference standard, ROC curve analysis showed that the area under the curve was largest for CE+FSD MRA. The greatest sensitivity and specificity were obtained when a cut-off stenosis score of 2 was used.ConclusionIn patients with severe PAD,3 T FSD-MRA provides good-quality diagnostic images without a contrast agent and is a good supplement for CE-MRA. CE+FSD MRA can improve the accuracy of vascular stenosis diagnosis.

Arterial spin labeled carotid MR angiography: A phantom study examining the impact of technical and hemodynamic factors.

To quantify the accuracy of three-dimensional (3D) radial arterial spin labeled (ASL) magnetic resonance angiography (MRA) using vascular models of carotid stenosis. Eight vascular models were imaged at 1.5 Tesla using pulsatile flow waveforms at rates found in the internal carotid arteries (100-400 mL/min). The impacts of the 3D ASL imaging readout (fast low angle shot (FLASH) versus balanced steady-state free precession (bSSFP)), ultrashort echo time imaging using a pointwise encoding time reduction with radial acquisition (PETRA), and model stenosis severity on the accuracy of vascular model display at the location of stenosis were quantified. Accuracy was computed vis-à-vis a reference bSSFP volume acquired under no flow. Comparisons were made with standard-of-care contrast-enhanced MRA (CEMRA) and Cartesian time-of-flight (TOF) MRA protocols. For 50% and 70% stenoses, CEMRA was most accurate (respective accuracies of 81.7% and 78.6%), followed by ASL FLASH (75.7% and 71.8%), ASL PETRA (69.6% and 70.6%), 3D TOF (66.6% and 57.1%), ASL bSSFP (68.7% and 51.2%), and 2D TOF (65.1% and 50.6%). Flow phantom imaging studies show that ASL MRA can improve the display of hemodynamically significant carotid arterial stenosis compared with TOF MRA, with FLASH and ultrashort echo time readouts being most accurate.

Gadofosveset trisodium in coronary magnetic resonance angiography at 3 Tesla

Background Coronary magnetic resonance angiography (MRA) at 3T suffers from imaging inconsistencies compared to 1.5T despite the use of gadolinium-based contrast agents (GBCAs). Gadofosveset Trisodium (Ablavar ® ,L antheus Medical Imaging), with its high relaxivity and long intravascular residence time, offers greater potential over standard GBCAs to improve evaluation of the coronary arteries. Compared to its validation in larger arteries, the optimum dosage for coronary MRA has yet to be assessed. The purpose of the study was to evaluate the diagnostic potential of a 0.06 mmol/kg dose of Gadofosveset compared to a standard clinical dose of 0.03 mmol/kg, using a free-breathing whole-heart coronary MRA protocol with 1.0 mm3 spatial resolution and 100% navigator efficiency. The injection protocol was optimized for the prolonged pharmacokinetics of Gadofosveset. Methods Twenty two contrast enhanced CMR scans were performed in 11 subjects [2 (18.2%) male; 27.3 ± 6 years; BMI = 23.1 ± 3 kg/m2] on a 3.0T Verio Siemens scanner, using

Time-of-Flight Magnetic Resonance Angiography at 7 T Using Venous Saturation Pulses With Reduced Flip Angles

The visibility of the vasculature in time-of-flight (TOF) magnetic resonance angiography (MRA) highly profits from increased magnetic field strengths. However, the application of additional saturation pulses for suppression of the venous system is often not possible at 7 T; to remain within the regulatory specific absorption rate (SAR) limits, the repetition time (TR) needs to be prolonged, preventing the acquisition of high-resolution MRA data sets within clinically acceptable acquisition times. In this work, saturation pulses were modified regarding flip angle and duration to meet SAR constraints and minimize total measurement time. To ameliorate SAR restrictions, the variable-rate selective excitation (VERSE) algorithm was used for both excitation and saturation radio frequency pulses. In this way, saturation pulses (executed every TR) become applicable in high-resolution TOF MRA protocols but still lengthen total measurement time notably. In this work, saturation pulses were further modified in terms of flip angle and duration to meet SAR constraints and minimize total measurement time. In the considered parameter range for excitation flip angle α of 15° to 35° and TR of 20 ms to 35 ms, sufficient saturation flip angles (αSAT) were 30° to 50°. This work shows that by lowering the flip angle αSAT, saturation pulses can be applied in high-resolution clinical TOF protocols using a TR as short as 20 ms. An αSAT of α + 15° is sufficient for suppression of the venous system in TOF MRA protocols in the parameter range normally used at 7 T. Instead of the standard 90° saturation pulse, only half the flip angle (or even less) is necessary, substantially ameliorating SAR constraints and enabling acquisition of high resolution in acceptable imaging time.

Magnetic Resonance Evaluation of Renal Artery Stenosis in a Swine Model

The aim of this study was to compare low-dose imaging with gadobutrol and gadoterate meglumine (Gd-DOTA) for evaluation of renal artery stenosis with 3-T magnetic resonance angiography (MRA) in a swine model. A total of 12 experimental animals were evaluated using equivalently dosed gadobutrol and Gd-DOTA for time-resolved and static imaging. For time-resolved imaging, the time-resolved imaging with stochastic trajectories (TWIST) technique (temporal footprint, 4.4 seconds) was used; a dose of 1 mL of gadobutrol was injected at 2 mL/s and a dose of 2 mL of Gd-DOTA was injected at both 2 and 4 mL/s. For a separate static acquisition, doses were doubled. The static scans were used for stenosis gradation and the time-resolved scans for comparison of enhancement dynamics, signal-to-noise ratio (SNR), and qualitative assessments. The average magnitude of difference in the stenosis measurements with static gadobutrol scans relative to digital subtraction intra-arterial catheter angiography (mean [SD], 7.4% [5.6%]) was less than with both the 2 mL/s (10.6% [6.2%]) and 4 mL/s (11.5% [7.8%]) Gd-DOTA MRA protocols. On time-resolved scans, peak signal-to-noise ratio was greatest with the gadobutrol protocol (P < 0.05), and the gadobutrol TWIST scan was preferred to the TWIST Gd-DOTA scan in terms of image quality and stenosis visualization in every case for every reader. Low-dose gadobutrol (~0.05 mmoL/kg) contrast-enhanced MRA results in improved accuracy of renal artery stenosis assessments relative to equivalently dosed Gd-DOTA at 3 T.

Anomalous origin of the occipital artery diagnosed by magnetic resonance angiography

It is well known that the occipital artery (OA) can arise from the internal carotid artery (ICA) or vertebral artery (VA). However, the incidence of an anomalously originating OA has not been reported. We investigate its incidence and characteristic features on magnetic resonance angiography (MRA). We retrospectively reviewed MRA images of 2,866 patients that included the carotid bifurcation; images were obtained using a standard noncontrast MRA protocol and two 1.5-T MR units. We diagnosed six cases (seven arteries) of anomalously originating OA, which represented an incidence of 0.21%. The OA arose from the ICA in four patients (five arteries), from the carotid bifurcation in one, and from the VA in one. Five of the seven arteries occurred on the right. Anomalously originating OA is rare and occurs with right-side predominance. Correct diagnosis is necessary before or during cerebral angiography, especially when selective catheterization to the OA is required.

A free-breathing non-contrast-enhanced pulmonary magnetic resonance angiography at 3 Tesla.

The breathhold contrast-enhanced three-dimensional magnetic resonance angiography (MRA) using T1-weighted gradient-echo imaging sequence is the standard technique for MRA of the thorax. However, this technique is not desirable for certain patients with respiratory insufficiency, serious renal impairment, or allergy to contrast agents. The objective of this study was to optimize and evaluate a non-contrast-enhanced free-breathing pulmonary MRA protocol at 3 Tesla. The time-of-flight protocol was based on a two-dimensional T1-weighted turbo field echo sequence with slice-selective inversion recovery and magnetization transfer preparation together with respiratory navigator gating, cardiac gating, and parallel imaging. Optimal values for time of inversion delay, flip angle and slice thickness were experimentally determined and used for all subjects. Excellent pulmonary MRA images, in which the 7th order branches of pulmonary arteries could be reliably identified, were obtained in the 12 free-breathing healthy volunteers. TI of approximately 300 ms provides the best suppression of background thoracic and cardiac muscles and effective inflow enhancement. With increasing flip angle, the pulmonary vessels gradually brightened and exhibited optimal contrast at 20 degrees-30 degrees. The 2 mm slice thickness and 0.5 mm slice overlap is suitable for visualization of the peripheral pulmonary vessel. The MRA protocol at 3 Tesla may have clinical significance for pulmonary vascular imaging in patients who are not available for contrast-enhanced 3D MRA and CT angiography examination or are unable to sustain a long breath-hold.

TIPIT: A randomised controlled trial of thyroxine in preterm infants under 28 weeks gestation: Magnetic Resonance Imaging and Magnetic Resonance Angiography protocol

BackgroundInfants born at extreme prematurity are at high risk of developmental disability. A major risk factor for disability is having a low level of thyroid hormone described as hypothyroxinaemia, which is recognised to be a frequent phenomenon in these infants. Derangements of critical thyroid function during the sensitive window in prematurity when early development occurs, may have a range of long term effects for brain development. Further research in preterm infants using neuroimaging techniques will increase our understanding of the specificity of the effects of hypothyroxinaemia on the developing foetal brain. This is an explanatory double blinded randomised controlled trial which is aimed to assess the effect of thyroid hormone supplementation on brain size, key brain structures, extent of myelination, white matter integrity and vessel morphology, somatic growth and the hypothalamic-pituitary-adrenal axis.MethodsThe study is a multi-centred double blinded randomised controlled trial of thyroid hormone supplementation in babies born below 28 weeks' gestation. All infants will receive either levothyroxine or placebo until 32 weeks corrected gestational age. The primary outcomes will be width of the sub-arachnoid space measured using cranial ultrasound and head circumference at 36 weeks corrected gestational age. The secondary outcomes will be thyroid hormone concentrations, the hypothalamic pituitary axis status and auxological data between birth and expected date of delivery; thyroid gland volume, brain size, volumes of key brain structures, extent of myelination and brain vessel morphology at expected date of delivery and markers of morbidity which include duration of mechanical ventilation and/or oxygen requirement and chronic lung disease.Trial registrationCurrent Controlled Trials ISRCTN89493983

Hybrid contrast-enhanced MR angiography of pelvic and lower extremity vasculature at 3.0 T: Initial experience

Purpose The objective of this study was to describe contrast-enhanced magnetic resonance angiography (MRA) of the lower extremities at 3.0 T system for assessment of high resolution images in patients with peripheral arterial occlusive disease (PAOD). Material and methods 21 Patients with suspected PAOD were examined with four-station MRA at a 3.0 T MR system. The MRA protocol consisted of a hybrid technique with two contrast media injections, the first one for visualization of the calf and foot vasculature (non-moving-table technique), the second one for imaging the aortoiliacal and femoral arteries (moving-table technique). For the femoropopliteal and calf station a randomly segmented central k-space ordering (contrast-enhanced timing-robust angiography [CENTRA]) was used. MR-images were analyzed independently by two radiologists with regard to image quality, venous overlap and grade of stenosis. In 6 patients digital subtraction angiography was performed within the following 7 days and evaluated by two radiologists in consensus with regard to the grade of stenosis. The vasculature-tree of each leg was divided in 12 segments, and 3 anatomical regions (iliacal, femoropopliteal, calf/foot). Results 490 and 488 of 495 arterial segments were visualized with diagnostic image quality by observer 1 and observer 2, respectively. Image quality was excellent in 470 and 457 arterial segments, respectively. Only 4 segments were rendered as non-diagnostic due to venous overlap. Relevant arterial stenoses (50–99%) were detected in 43 and 47 segments by observer 1 and observer 2, 66 and 65 arterial segments, respectively, were interpreted as occluded. Conclusion The hybrid MRA protocol at 3.0 T offers high diagnostic quality for the whole peripheral arterial tree without venous contamination at high spatial resolution.

Assessment of brain aneurysms by using high-resolution magnetic resonance angiography after endovascular coil delivery

Digital subtraction (DS) angiography is the current gold standard of assessing intracranial aneurysms after coil placement. Magnetic resonance (MR) angiography offers a noninvasive, low-risk alternative, but its accuracy in delineating coil-treated aneurysms remains uncertain. The objective of this study, therefore, is to compare a high-resolution MR angiography protocol relative to DS angiography for the evaluation of coil-treated aneurysms. In 2003, the authors initiated a prospective protocol of following up patients with coil-treated brain aneurysms using both 1.5-tesla gadolinium-enhanced MR angiography and biplanar DS angiography. Using acquired images, the subject aneurysm was independently scored for degree of remnant identified (complete obliteration, residual neck, or residual aneurysm) and the surgeon's ability to visualize the parent vessel (excellent, fair, or poor). Thirty-seven patients with 42 coil-treated aneurysms were enrolled for a total of 44 paired MR angiography-DS angiography tests (median 9 days between tests). An excellent correlation was found between DS and MR angiography for assessing any residual aneurysm, but not for visualizing the parent vessel (K = 0.86 for residual aneurysm and 0.10 for parent vessel visualization). Paramagnetic artifact from the coil mass was minimal, and in some cases MR angiography identified contrast permeation into the coil mass not revealed by DS angiography. An intravascular microstent typically impeded proper visualization of the parent vessel on MR angiography. Magnetic resonance angiography is a noninvasive and safe means of follow-up review for patients with coil-treated brain aneurysms. Compared with DS angiography, MR angiography accurately delineates residual aneurysm necks and parent vessel patency (in the absence of a stent), and offers superior visualization of contrast filling within the coil mass. Use of MR angiography may obviate the need for routine diagnostic DS angiography in select patients.

Hand vascular involvement assessed by magnetic resonance angiography in systemic sclerosis

Impairment of the microcirculation is a cardinal feature of systemic sclerosis (SSc). Magnetic resonance angiography (MRA) has improved the assessment of vascular lesions of the hand. The aim of this study was to evaluate vascular abnormalities in the hands of patients with SSc, using MRA. Thirty-eight patients with SSc were compared with 7 healthy subjects and 7 patients with rheumatoid arthritis. Among patients with SSc, the mean +/- SD age was 52 +/- 14 years, the mean +/- SD Health Assessment Questionnaire (HAQ) score was 0.9 +/- 0.8, and the mean +/- SD systolic pulmonary artery pressure (PAP) was 32.2 +/- 8.4 mm Hg. Ten patients had a history of digital ulcers. The MRA protocol consisted of 4 successive acquisitions, each lasting 52 seconds, of 3-dimensional coronal cross-sectional images after gadolinium injection. The primary criteria were distality and quality of arterial opacification, avascular areas, and venous return. Thirty-five of the patients with SSc (92%) had at least 1 true digital artery that did not reach the first phalanx at the initial arterial analysis, and 23 patients (61%) had > or =4 damaged arteries. Twenty-eight patients (74%) had thin arteries, and 20 patients (53%) had >1 avascular area. Nearly all patients (35 of 38 [92%]) had abnormal venous return, and a lack of visible venous return was observed in 16 patients (42%). Results for all of the control subjects were considered normal. Digital ulcers were more frequently observed in patients with SSc who had > or =4 damaged proper digital arteries compared with other patients (P = 0.003), the HAQ score was associated with thin-caliber arteries (P = 0.04), and systolic PAP was associated with tissue enhancement secondary to ischemia (P = 0.04). These results show the substantial vascular involvement in SSc. Lesions were diffuse and involved both arterial and venous vessels of small caliber as well as the microcirculation.

Peripheral Magnetic Resonance Angiography at 3.0 T

Peripheral angiography always has been a challenge for magnetic resonance angiography (MRA) because of the large anatomical area that has to be covered in an arterial phase at high spatial resolution. With conventional stepping table techniques, venous overlay often occurs at the most distal station. To solve these problems, several methods, such as hybrid MRA protocols or venous compression techniques, were used at 1.5-T magnetic resonance systems. The implementation of clinical 3.0-T magnetic resonance systems offers the opportunity of new imaging protocols with an increased image quality. This article explains these new imaging protocols for peripheral MRA and the opportunities that arise from the combination of high field strength and dedicated hardware for MRA.

Renal Magnetic Resonance Angiography at 3.0 T

The increased signal-to-noise ratio at 3.0 T holds promise for high-spatial resolution renal magnetic resonance angiography (MRA). Today, state-of-the-art renal MRA is feasible with submillimeter isotropic spatial resolution in less than 20 seconds acquisition time with sufficient signal-to-noise ratio. This article explains the fundamentals of 3.0-T imaging that are essential for renal MRA, with a focus on the clinical implications. Protocol and imaging recommendations are given based on the physical principles of 3.0-T imaging and underlined by current clinical cases. Apart from pure morphological imaging, the value of functional renal imaging such as renal flow measurements and renal perfusion measurements for a comprehensive 3.0-T renal MRA protocol is discussed.