Steady-state Magnetic Resonance Angiography Research Articles

Non-contrast free-breathing 3D cardiovascular magnetic resonance angiography using REACT (relaxation-enhanced angiography without contrast) compared to contrast-enhanced steady-state magnetic resonance angiography in complex pediatric congenital heart disease at 3T

BackgroundTo evaluate the great vessels in young children with complex congenital heart disease (CHD) using non-contrast cardiovascular magnetic resonance angiography (CMRA) based on three-dimensional relaxation-enhanced angiography without contrast (REACT) in comparison to contrast-enhanced steady-state CMRA.MethodsIn this retrospective study from April to July 2021, respiratory- and electrocardiogram-gated native REACT CMRA was compared to contrast-enhanced single-phase steady-state CMRA in children with CHD who underwent CMRA at 3T under deep sedation. Vascular assessment included image quality (1 = non-diagnostic, 5 = excellent), vessel diameter, and diagnostic findings. For statistical analysis, paired t-test, Pearson correlation, Bland–Altman analysis, Wilcoxon test, and intraclass correlation coefficients (ICC) were applied.ResultsThirty-six young children with complex CHD (median 4 years, interquartile range, 2–5; 20 males) were included. Native REACT CMRA was obtained successfully in all patients (mean scan time: 4:22 ± 1:44 min). For all vessels assessed, diameters correlated strongly between both methods (Pearson r = 0.99; bias = 0.04 ± 0.61 mm) with high interobserver reproducibility (ICC: 0.99 for both CMRAs). Native REACT CMRA demonstrated comparable overall image quality to contrast-enhanced CMRA (3.9 ± 1.0 vs. 3.8 ± 0.9, P = 0.018). With REACT CMRA, better image quality was obtained at the ascending aorta (4.8 ± 0.5 vs. 4.3 ± 0.8, P < 0.001), coronary roots (e.g., left: 4.1 ± 1.0 vs. 3.3 ± 1.1, P = 0.001), and inferior vena cava (4.6 ± 0.5 vs. 3.2 ± 0.8, P < 0.001). In all patients, additional vascular findings were assessed equally with native REACT CMRA and the contrast-enhanced reference standard (n = 6).ConclusionIn young children with complex CHD, REACT CMRA can provide gadolinium-free high image quality, accurate vascular measurements, and equivalent diagnostic quality compared to standard contrast-enhanced CMRA.

Improving the accuracy of pre-operative evaluation of neurovascular conflict in trigeminal neuralgia using magnetic resonance subtraction.

To investigate the ability of magnetic resonance (MR) subtraction to evaluate neurovascular conflict (NVC) and to compare it with conventional MR protocols. This prospective study included 82 patients with trigeminal neuralgia who underwent microvascular decompression for NVC. All patients had a pre-operative examination using 3T MRI. The MRI protocols used comprised 3D balanced (B)-fast field echo (FFE), 3D steady-state magnetic resonance angiography (MRA), and 3D T1-FFE sequences. MR subtraction images were obtained by subtracting native images from B-FFE and steady-state MRA. NVC evaluation was performed using subtraction images (MR subtraction) and combination images (conventional MR protocols using B-FFE and T1-FFE in combination). Clinical assessment of the degree of compression, the type of compressing vessel, and the location of conflict were undertaken by two independent observers. The two methods were then compared using surgical criteria. MR subtraction exhibited greater accuracy than the conventional method in terms of the estimated severity of conflict (87.80% vs. 57.32%, p < 0.05), and demonstrated better consistency with surgical findings (k= 0.794 vs. k= 0.365, p < 0.05). For the type of compressing vessel and the location of conflict, both methods were highly accurate and agreed to a similar extent with surgical findings (p = 0.987, compressing vessel; p = 0.665, location of conflict). MR subtraction proved reliable in NVC pre-operative evaluation, with increased accuracy when estimating severity. This result strongly supports the wider use of MR subtraction as the preferred choice in clinical application.

Detection of vascularity of femoral head using sub-millimeter resolution steady-state magnetic resonance angiography-initial experience.

The purpose of this study was to use the steady-state (SS) magnetic resonance angiography (MRA) with a sub-millimeter resolution to detect the arteries supplying to the femoral head (FH). SS MRA scanning of hips was performed bilaterally in 15 healthy volunteers. A blood pool contrast agent was used. The scanning protocol included a 0.8-mm3 isotropic T1-fast field echo sequence with spectral fat suppression technique. Two highly qualified radiologists independently evaluated the medial circumflex femoral artery (MCFA), the lateral circumflex femoral artery (LCFA), and the three retinacular arteries including superior retinacular artery (SRA), inferior retinacular artery (IRA), and anterior retinacular artery (ARA). The intraosseous branches of the three retinacular arteries were also evaluated. An orthopaedic surgeon was consulted in case of disagreement. Observation by the two radiologists and support from the orthopaedic surgeon served as the end result. Agreement between the two observer radiologists was evaluated. Interobserver agreement between the two radiologists was found to be substantial to perfect. Of the 30 hips, the LCFA and MCFA were detected in all hips; the SRA and IRA were detected in most hips (100%, 90%), and the ARA was detected in 13 hips (43%). The intraosseous branches of SRA and IRA were detected in 30 and 22 hips (100%, 73%), respectively, while the intraosseous branches of ARA were detected in 11 hips (37%). The main arteries supplying the FH can be detected by the SS MRA, making it a novel method to detect the vascularity of FH.

Steady State Magnetic Resonance Angiography of the Thoracic Aorta Using Inversion-recovery Steady-State Free Precession and a High Relaxivity Contrast Agent.

To evaluate image quality and aortic dimension measurement accuracy of high resolution, motion compensated steady-state magnetic resonance angiography (SS-MRA) with a high relaxivity, extracellular fluid gadolinium-based contrast agent compared with standard first-pass contrast enhanced MRA (FP-CEMRA) in patients with thoracic aortic aneurysms. Sixty-nine patients (mean age, 51.7 y, 25% female) diagnosed with thoracic aortic aneurysms who underwent MRA on a 1.5 T scanner using FP-CEMRA and SS-MRA techniques were retrospectively identified. Quantitative analysis was performed by measuring the aortic diameters at 6 locations within the thoracic aorta for each technique. Two radiologists independently performed the qualitative analysis by assessing the image quality (1 to 5), presence of artifact (1 to 4), signal-to-noise (1 to 4), contrast-to-noise (1 to 4), and wall conspicuity (1 to 4) in the aorta at 4 different locations: the aortic root, the ascending aorta, the aortic arch, and the descending aorta. The aortic dimensions obtained by SS-MRA had a good correlation with FP-CEMRA. Means for the aortic diameters between the FP-CEMRA and the SS-MRA at all 6 locations demonstrated minimal mean differences (0.013 to 0.044 mm).Qualitative assessment of aorta at 4 locations by 2 reviewers demonstrated that SS-MRA had on average superior image quality at the aortic root and ascending aorta for both reviewers (P<0.05) and at the descending aorta for one reader (P<0.05). Otherwise, both techniques were comparable at the ascending aorta. SS-MRA demonstrated less artifact at the aortic root and the ascending aorta (P<0.05). Aortic dimension measurements provided by SS-MRA with a high relaxivity, extracellular fluid gadolinium-based contrast agent are comparable to the conventional FP-CEMRA. Furthermore, SS-MRA qualitatively demonstrated comparable to better overall image quality than FP-CEMRA at different aortic locations. Therefore, SS-MRA may provide a comparable alternative, or complementary examination to conventional FP-CEMRA in patients who have difficulty breath holding, or in situations where contrast bolus timing was poor.

MR Angiography of Renal Transplant Vasculature with Ferumoxytol:: Comparison of High-Resolution Steady-State and First-Pass Acquisitions

This work aimed to quantify the differences in signal-to-noise ratio (SNR) and vessel sharpness between steady-state and first-pass magnetic resonance angiography (MRA) with ferumoxytol in renal transplant recipients. We performed a retrospective study of adult patients who underwent steady-state and first-pass MRA with ferumoxytol to evaluate renal transplant vasculature. SNR was calculated in the external iliac artery, and vessel sharpness was calculated in the external iliac and renal transplant arteries for both acquisitions. Data were compared using Student's t test. Fifteen patients were included (mean age 56.9 years, 10 males). The mean SNR of the external iliac artery was 42.2 (SD, 11.9) for the first-pass MRA and 41.8 (SD, 9.7) for the steady-state MRA (p = 0.92). The mean vessel sharpness was significantly higher for the steady-state MRA compared to first-pass MRA for both external iliac (1.24 vs. 0.80 mm(-1), p < 0.01) and renal transplant arteries (1.26 vs. 0.79 mm(-1), p < 0.01). Steady-state MRA using ferumoxytol improves vessel sharpness while maintaining equivalent SNR compared to conventional first-pass MRA in renal transplant patients.

Multimodality Imaging of Lower Extremity Peripheral Arterial Disease

Patients with symptomatic peripheral arterial disease (PAD) affecting the lower extremities are initially evaluated with an ankle-brachial index (ABI) and segmental pressure measurements. An ABI 50% stenosis) with a sensitivity and specificity of 79% and 96%, respectively.1 An ABI between 0.90 and 1.0 is considered borderline. The localization of the stenosis can be inferred by an abnormal decrease (>20 mm Hg) in segmental lower extremity pressures. In the presence of calcified atherosclerosis, arteries may become stiff and noncompressible, which results in a falsely elevated ABI (often >1.3). For patients with suspected PAD and a normal ABI at rest, it is valuable to obtain postexercise ABI measurements, which if <0.85 are consistent with PAD and is an independent predictor of mortality.2 Imaging is then needed to confirm the location and degree of stenosis before revascularization or if the diagnosis of PAD is uncertain. Characterization of PAD can be performed with noninvasive angiography using computed tomography (CTA) or magnetic resonance angiography (MRA), as well as with duplex ultrasonography (US), depending on patient specific characteristics (Table 1). Advances in both CTA and MRA provide clinicians with the opportunity to obtain a high resolution, 3-dimensional (3-D) road map of the peripheral arterial tree in patients, particularly when planning revascularization strategies. Invasive digital subtraction angiography (DSA) has been the accepted standard for evaluation of lower extremity atherosclerosis. Although DSA is a robust technique for diagnosing significant arterial stenosis or obstruction, it provides a 2-D view of the vessels, which may underestimate the degree of stenosis for tortuous vessels.3 Furthermore, there are inherent risks with arterial access, ionizing radiation, and the use of iodinated contrast media (CM).4 View this table: Table 1. Comparison Between CTA, MRA, and Duplex US for Diagnosis of PAD This review aims to deliver a comprehensive, yet concise …

Steady state imaging of the thoracic vasculature using inversion recovery FLASH and SSFP with a blood pool contrast agent

Background Although contrast-enhanced first-pass MRA (FP-MRA) is frequently used to visualize the thoracic vasculature, it may not be ideal for the assessment of the aortic root due to poor image quality and motion artifact. Bloodpool contrast agents remain within the intravascular space for several hours, allowing vessels to be imaged longer and therefore improving spatial resolution. The purpose of this study is to compare steady-state magnetic resonance angiography (SS-MRA) following injection of a blood-pool contras agent to first-pass MR angiography (FP-MRA) in adults with thoracic aortic disease. Methods 25 patients (14 men, 11 women) with suspect thoracic aortic disease disease underwent MRA on a 1.5 T scanner (Magnetom Aera and Avanto; Siemens Medical Solutions). The MRA protocol consisted of FP-MRA followed by SS-MRA after intravenous injection of gadofosveset trisodium (Ablavar, Lantheus Medical Imaging). FP-MRA consisted of a breath-held ECG-gated FLASH acquisition in a sagittal oblique orientation with the following imaging parameters: TR/TE: 2.8/1.0, flip angle 25°, FOV 343x500 mm, matrix 264x512, slice thickness 1.5 mm, voxel size 1.3 x 1.0 x 1.0 mm, GRAPPA x 2, 20 second acquisition. 0.03 mmol/kg of gadofosveset was injected intravenously at 1cc/sec in an antecubital vein. Contrast bolus timing was achieved using care bolus technique. SS-MRA consisted of free-breathing ECGgated IR-FLASH and IR-SSFP in a sagittal oblique orientation. IR-FLASH had the following parameters: TR/TE/TI: 3.5/1.5/260, flip angle 18°, and IR-SSFP had: TR/TE/TI: 3.3/1.5/260, flip angle 70°. Both sequences had FOV 326x380, matrix 440x512, slice thickness 1.5 mm, voxel 0.7 x 0.7 x 1.0 mm, GRAPPA x 2, and 3 minute acquisition. Respiratory gating was achieved using a navigator acquisition with an average acceptance window of 35%. For quantitative analysis, orthogonal dimensions of the thoracic aorta were measured at several locations. Signal-to-noise ratio (SNR) was also measured for both techniques by placing regions of interest in the aortic root and the ascending aorta. For qualitative analysis, two independent reviewers evaluated both FP-MRA and SS-MRA images separately. The aortic root and the ascending aorta were scored on an image quality scale of 1-4.

Steady-state magnetic resonance angiography of the thoracic vasculature in congenital heart disease using a blood pool contrast agent: evaluation of two different techniques

Background Although contrast-enhanced first-pass MRA (FP-MRA) is frequently used to visualize the vasculature, it may not be suitable for the assessment of congenital heart disease. Blood-pool contrast agents remain within the intravascular space for several hours, allowing vessels to be imaged without relying on accurate contrast bolus timing. The purpose of this study is to compare steadystate magnetic resonance angiography (SS-MRA) following injection of a blood-pool contras agent to first-pass MR angiography (FP-MRA) in adults with congenital heart disease.

Improved detection of in-stent restenosis by blood pool agent-enhanced, high-resolution, steady-state magnetic resonance angiography

The aim of this study was to assess whether visualisation of in-stent changes can be improved with high-resolution, steady-state, blood pool contrast-enhanced MR angiography compared with first-pass MR angiography. Intra-arterial digital subtraction angiography (DSA) served as the reference standard. Twenty patients after stent placement in the superficial femoral artery (SFA) underwent MRA prior to reintervention. MRA of the SFA includes first-pass MRA as well as 3D high-resolution MRA in the steady state (SS-MRA) after injection of Gadofosveset trisodium. Sensitivity and specificity values for the detection of significant in-stent lesions by means of SS-MRA were calculated at the proximal, middle and distal stent segments in comparison to DSA. Kappa statistics were used to determine agreement between the two techniques. Sensitivity and specificity values for the detection of significant stenosis with SS-MRA reached 95% in the proximal, 100% in the middle and 100% in the distal stent segment. Kappa coefficients between SS-MRA and DSA were 0.789, 0.797 and 0.859 for the proximal, middle and distal segments, whereas the Kappa coefficients for FP-MRA were 0,211, 0,200 and 0,594 in these segments, respectively. Detection of in stent stenosis is significantly improved using SS MRA, in comparison to state-of-the-art FP-MRA.

First-Pass and High-Resolution Steady-State Magnetic Resonance Angiography of the Peripheral Arteries With Gadobenate Dimeglumine

To assess the feasibility of combined first-pass (FP) and steady-state (SS) contrast-enhanced magnetic resonance angiography (MRA) of the peripheral arteries with gadobenate dimeglumine (MultiHance) and to evaluate diagnostic performance relative to digital subtraction angiography (DSA). A total of 35 patients with symptomatic peripheral arterial occlusive disease (PAOD) underwent FP MRA (repetition time [TR]/echo time [TE]/flip angle [FA]/acquisition time [TA] = 3.5/1.2/30°/14s) at 1.5T after intravenous injection of 10 mL of gadobenate dimeglumine. Thereafter, SS imaging of the calf (TR/TE/FA/TA = 7.5/2.3/20°/40-130s) and femoropopliteal (TR/TE/FA/TA = 7.5/2.3/18°/130-240s) regions was performed after a second injection of 5 mL of gadobenate dimeglumine. All patients underwent conventional DSA. Three readers reviewed separate FP and FP+SS MRA datasets for image quality and presence/absence of clinically relevant PAOD. A fourth independent observer evaluated DSA images. The diagnostic performance (sensitivity, specificity, positive and negative predictive values) achieved with each dataset was determined and compared. Inter-reader agreement was assessed using kappa statistics. The image quality of 134 of 140 vascular regions was optimal or adequate on SS MRA. Inter-reader agreement was good to very good for assessments of FP (κ = 0.725) and combined FP+SS images (κ = 0.866). SS images improved diagnostic confidence in 34 (48.6%) femoropoliteal and 46 (65.7%) crural regions and altered final diagnosis in 8 (11.4%) and 10 (14.3%) regions, respectively. Global diagnostic accuracy increased from 92.9% on FP images to 95.9% on FP+SS images, with significant (P = 0.0384) improvement in the crural region. SS MRA of the peripheral arteries is feasible with gadobenate dimeglumine and potentially improves diagnostic performance in patients with symptomatic PAOD.

Diagnostic accuracy of colour Doppler ultrasonography, CT angiography and blood-pool-enhanced MR angiography in assessing carotid stenosis: a comparative study with DSA in 170 patients

This study was undertaken to prospectively evaluate the diagnostic performance of colour Doppler ultrasonography (CDUS), first-pass (FP) and steady-state (SS) contrast-enhanced magnetic resonance angiography (MRA) and computed tomography angiography (CTA) of the carotid arteries using digital subtraction angiography (DSA) as the reference standard. A total of 170 patients with previous cerebrovascular events and suspected carotid artery stenoses underwent CDUS, blood-pool MRA, CTA and DSA. Accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for CDUS, FP MRA, SS MRA and CTA. The McNemar and Wilcoxon tests and receiver operating characteristic (ROC) curve analysis were used to determine significant differences (p<0.05) between the diagnostic performances of the four modalities, and the degree of stenosis was compared using linear regression. A total of 336 carotid bifurcations were studied. The area under the curve (AUC) for degree of stenosis was: CDUS 0.85±0.02, FP MRA 0.982±0.005, SS MRA 0.994±0.002 and CTA 0.997±0.001. AUC analysis showed no statistically significant difference between CTA and MRA (p=0.0174) and a statistically significant difference between CDUS and the other techniques (p<0.001). Plaque morphology analysis showed no significant difference between CTA and SS MRA; a significant difference was seen between CTA and SS MRA versus FP MRA (p=0.04) and CDUS (p=0.038). Plaque ulceration analysis showed a statistically significant difference between MRA and CTA (0.04< p<0.046) versus CDUS (p=0.019). CTA is the most accurate technique for evaluating carotid stenoses, with a slightly better performance than MRA (97% vs. 95% for SS MRA and 92% for FP MRA) and a greater accuracy than CDUS (97% vs. 76%). Blood-pool contrast-enhanced SS sequences offer improved evaluation of degree of stenosis and plaque morphology with accuracy substantially identical to CTA.

High-Resolution Steady State Magnetic Resonance Angiography of the Carotid Arteries: Are Intravascular Agents Necessary?

To prospectively evaluate the potential of gadobenate dimeglumine for high-resolution steady-state (SS) contrast-enhanced magnetic resonance angiography (CE-MRA) of the carotid arteries as an adjunct to conventional first-pass (FP) MRA, with computed tomography angiography (CTA) and digital subtraction angiography (DSA) as reference. Institutional ethics committee approval and written informed consent were obtained. Forty consecutive patients underwent conventional FP MRA with 15 mL gadobenate dimeglumine, using a conventional 3D FLASH sequence (14 sec acquisition time). Immediately afterward, SS images were obtained using a high resolution coronal 3D FLASH sequence (240 sec acquisition time). All patients also underwent CTA and conventional DSA within 8 +/- 3 days. Three experienced radiologists assessed FP and SS image quality and calculated sensitivity, specificity, accuracy, and predictive values for stenosis grade and length, plaque morphology, and tandem lesions using DSA as reference. Detected stenoses were quantified and compared (Spearman rank correlation coefficient, [R(s)]; McNemar test) with DSA and CTA findings. Inter-read variability was assessed using kappa (kappa) statistics. The impact of SS acquisitions on diagnostic confidence and patient management was assessed. MRA FP and SS image quality was excellent in 63 (78.8%) and 46 (57.5%) vessels, adequate in 11 (13.8%) and 20 (25.0%) vessels, and poor in 6 (7.5%) and 14 (17.5%) vessels, respectively. Area under the curve analysis revealed no significant differences between MRA FP, MRA FP + SS, and CTA for the grading of stenoses (P = 0.838; accuracy values of 97.4%, 97.4%, and 98.7%, respectively). Greater accuracy (P < 0.001) was noted for FP + SS images over FP images alone for the assessment of plaque morphology (96.1% for FP + SS images vs. 83.3% for FP). Increased diagnostic confidence was noted for 49 (61.3%) vessels because of additional SS images whereas an impact on final diagnosis was noted in 8 (10%) cases. Good correlation was noted between SS image quality and impact on final diagnosis (R(s) = 0.7; P < 0.0001). SS imaging of the carotid arteries is feasible with gadobenate dimeglumine. The increased spatial resolution attainable allows improved evaluation of stenoses and plaque irregularity, yielding comparable diagnostic performance to that of CTA and DSA.

MR Angiography of Infrapopliteal Arteries in Patients with Peripheral Arterial Occlusive Disease by Using Gadofosveset at 3.0 T: Diagnostic Accuracy Compared with Selective DSA

To prospectively compare the diagnostic accuracy of steady-state, high-spatial-resolution magnetic resonance (MR) angiography of the lower leg, performed with a blood pool contrast agent, with selective digital subtraction angiography (DSA) as the reference standard in patients with symptomatic peripheral arterial disease. Local ethics committee approval and written informed consent were obtained. In a nonrandomized trial, selective DSA and MR angiography were performed at 3.0 T with a blood pool contrast agent on 22 calves in 20 patients (mean age, 69.4 years +/- 11.3 [standard deviation]), 16 men (mean age, 67.8 years +/- 12.4) and four women (mean age, 75.6 years +/- 3.6 years), to evaluate 352 arterial segments. DSA and MR angiography were performed within 24 hours of each other and directly compared by three experienced, blinded radiologists by using high-spatial-resolution steady-state MR angiograms. Consensus reading for both DSA and MR angiography served as the reference standard. MR angiography was successful and occurred without serious adverse events in all patients. Seven significantly stenosed and 40 occluded segments were rated equally in both modalities. In three cases, the tibial arteries were shown to be occluded or significantly stenosed at DSA but appeared normal or significantly stenosed at MR angiography. The respective average segment sensitivity, specificity, and accuracy were 98.3% (59 of 60), 98% (113.7 of 116), and 98.1% (172.7 of 176) for DSA and 100% (60 of 60), 100% (116 of 116), and 100% (176 of 176) for MR angiography. Steady-state MR angiography was especially useful for the distal peroneal artery and the proximal anterior tibial artery. MR angiography performed with blood pool agents has an accuracy comparable with that of selective DSA in the lower leg but with less risk involved. Steady-state imaging performed with blood pool agents facilitates evaluation of MR angiography of infrapopliteal arteries.

First‐pass and steady‐state magnetic resonance angiography of the thoracic vasculature using gadofosveset trisodium

To compare a high-resolution, ECG-gated, motion-compensated, steady-state magnetic resonance angiography (SS-MRA) of the thoracic vasculature to standard first-pass MRA (FP-MRA) using a blood-pool contrast agent (gadofosveset trisodium). In all, 25 patients >or=18 years with congenital or acquired disease of the thoracic vasculature, who underwent both FP-MRA and SS-MRA, were retrospectively identified. Diameters of left superior pulmonary vein (LSPV), left pulmonary artery (LPA), and aortic arch (AA) were measured. Image quality for LSPV, LPA, AA, coronary ostia, and coronary sinus were assessed. Vessel sharpness of LPA and LSPV and contrast ratio (CR) of LSPV, LPA, and AA were calculated. SS-MRA yielded significantly higher image quality for all vessels, and significantly higher vessel sharpness for LSPV and LPA compared to the FP-MRA. SS-MRA revealed lower intra- and interobserver variability for vessel diameters compared with the FP-MRA. The FP-MRA showed higher CR compared to the SS-MRA. Motion-compensated high-resolution SS-MRA of the thoracic vasculature using gadofosveset trisodium offers superior image quality compared to standard FP-MRA. Although SS-MRA delivers no dynamic information it may prove specifically helpful as an add-on to FP-MRA for imaging of small vascular structures.

Peripheral MR Angiography with Blood Pool Contrast Agent: Prospective Intraindividual Comparative Study of High-Spatial-Resolution Steady-State MR Angiography versus Standard-Resolution First-Pass MR Angiography and DSA

To prospectively compare the accuracy of high-spatial-resolution steady-state magnetic resonance (MR) angiography with standard-resolution first-pass MR angiography in the lower extremities, with digital subtraction angiography (DSA) as the reference standard. Institutional ethics committee approval and written informed consent were obtained. Twenty-seven patients (16 men, 11 women; mean age, 64.4 years +/- 14.8 [standard deviation]; range, 26-87 years) suspected of having or known to have peripheral arterial disease underwent first-pass and steady-state MR angiography and DSA. First-pass and steady-state MR angiography were performed in the same patient in the same session and with the same dose of blood pool contrast agent. The most severe stenosis grade of each evaluated segment was measured; sensitivity, specificity, and positive and negative predictive values were calculated at first-pass and steady-state MR angiography, with DSA as the reference standard. The kappa coefficient was used to measure the agreement between first-pass MR angiography, steady-state MR angiography, and DSA. A total of 334 arterial segments were available for intraindividual comparison of first-pass MR angiography, steady-state MR angiography, and DSA in 27 patients. In 20 (74%) of 27 patients, the stenosis grade of at least one of the evaluated vessels differed at steady-state MR angiography from that at first-pass MR angiography. In total, stenosis grade was judged as higher at first-pass MR angiography than at DSA (overestimation) in 28 of 334 segments and as lower (underestimation) in 15 of 334 segments. The stenosis grade as judged at steady-state MR angiography matched with that at DSA in 334 of 334 vessel segments. High-spatial-resolution steady-state MR angiography allowed for better agreement with DSA regarding stenosis grade in patients with arterial disease compared with standard-resolution arterial-phase first-pass MR angiography.

Feasibility of Gadofosveset-Enhanced Steady-State Magnetic Resonance Angiography of the Peripheral Vessels at 3 Tesla With Dixon Fat Saturation

To investigate the feasibility and image quality of gadofosveset-enhanced steady-state peripheral MR-angiography using Dixon fat saturation in comparison to spectral fat saturation. After Institutional Review Board (IRB) approval, 10 healthy volunteers underwent peripheral MR-angiography at 3.0 T during the steady state 50 minutes after gadofosveset injection. A steady-state-adapted volume interpolated breathhold examination sequence with an isotropic spatial resolution of 1 mm was acquired with 2-point Dixon fat saturation (DixFS, acquisition time 52 seconds) and with conventional, spectral fat saturation (SFS, acquisition time 58 seconds). The quality of the images was rated on an ordinal 4-point scale (4, very good) by 2 radiologists in consensus. The signal-to-noise ratios (SNRs) of the vessels, the fat, and the muscles as well as the contrast-to-noise-ratio (CNR) between vessels, fat, and muscle were determined. Paired P tests were performed for statistical analysis with a significance level of P < 0.05. Diagnostic image quality was achieved in all examinations. The image quality of the DixFS images was rated superior (median 4) over the SFS images (median 3; P = 0.03). The SNR of muscles and vessels was 40% higher with DixFS (P < 0.008), whereas the SNR of fat was decreased by 40.3% from 40.7 with SFS to 22.4 with DixFS (P < 0.0001). The CNR (fat/muscle) of the DixFS images of 84.1/71.7 was significantly higher than the CNR of the SFS images of 47.7/47.4 (P < 0.001). Two-point Dixon fat suppression for MR-angiography during the steady state after the administration of gadofosveset is feasible with superior image quality and more than 50% increase in CNR (fat/muscle) compared with spectral fat saturation without an additional time penalty.

Surgical dislocation of the adult hip

Surgical dislocation of the hip is rarely undertaken. The potential danger to the vascularity of the femoral head has been emphasised, but there is little information as to how this danger can be avoided. We describe a technique for operative dislocation of the hip, based on detailed anatomical studies of the blood supply. It combines aspects of approaches which have been reported previously and consists of an anterior dislocation through a posterior approach with a 'trochanteric flip' osteotomy. The external rotator muscles are not divided and the medial femoral circumflex artery is protected by the intact obturator externus. We report our experience using this approach in 213 hips over a period of seven years and include 19 patients who underwent simultaneous intertrochanteric osteotomy. The perfusion of the femoral head was verified intraoperatively and, to date, none has subsequently developed avascular necrosis. There is little morbidity associated with the technique and it allows the treatment of a variety of conditions, which may not respond well to other methods including arthroscopy. Surgical dislocation gives new insight into the pathogenesis of some hip disorders and the possibility of preserving the hip with techniques such as transplantation of cartilage.

Contrast agents for MRA: future directions.

The purpose of this review is to outline recent developments in contrast agents for magnetic resonance angiography (MRA) and to give some idea of what the future might hold. Up to now, non-binding gadolinium (Gd) chelates have been the agents used for MRA. Modified paramagnetic Gd-based agents with varying degrees of protein interaction have been developed, and these, together with new superparamagnetic compounds, are currently under clinical evaluation. It is likely that two different types of contrast agent will soon be available: extracellular agents for first-pass MRA and intravascular agents mainly for steady-state MRA. Several agents also exhibit certain tissue specific properties in addition to conventional extracellular properties. This will lead to more comprehensive imaging approaches.

Contrast agents for MRA: Future directions

The purpose of this review is to outline recent developments in contrast agents for magnetic resonance angiography (MRA) and to give some idea of what the future might hold. Up to now, non-binding gadolinium (Gd) chelates have been the agents used for MRA. Modified paramagnetic Gd-based agents with varying degrees of protein interaction have been developed, and these, together with new superparamagnetic compounds, are currently under clinical evaluation. It is likely that two different types of contrast agent will soon be available: extracellular agents for first-pass MRA and intravascular agents mainly for steady-state MRA. Several agents also exhibit certain tissue specific properties in addition to conventional extracellular properties. This will lead to more comprehensive imaging approaches.J. Magn. Reson. Imaging 10:314–316, 1999. © 1999 Wiley-Liss, Inc.