Steady-state Free Precession Magnetic Resonance Angiography Research Articles

Reliability of non-contrast magnetic resonance angiography-derived aortic diameters in Marfan patients: comparison of inner vs. outer vessel wall measurements

Aortic diameter measurements play a crucial role for the indication of aortic root surgery in Marfan patients. However, for magnetic resonance angiography (MRA)-derived measurements, there is no consensus on whether the aortic wall should be included or excluded in the aortic diameter. The purpose of this retrospective study was to compare the reliability of non-contrast bright blood MRA aortic inner-to-inner and outer-to-outer edge measurements in patients with Marfan syndrome. Forty Marfan patients underwent ECG-gated balanced steady-state free-precession MRA of the aorta at 1.5 T. Two readers independently performed inner and outer measurements at different aortic levels. They rated the image quality of the delineation of both inner and outer vessel wall edges on a four-point scale. MRA-derived diameters of the sinuses of Valsalva were compared with echocardiography-derived diameters. Aortic vessel wall delineation score was rated higher at all levels for inner than for outer vessel walls (p < 0.001). Inter- and intraobserver variances of aortic measurements were smaller for inner-to-inner measurements at the sinuses of Valsalva, sinotubular junction and ascending aorta (p < 0.03). There was a difference of 1.1 ± 2.3 mm for inner MRA measurements (p = 0.014) and 6.9 ± 3.1 mm for outer MRA measurements (p < 0.001) when compared to echocardiographic leading-edge measurements. Inner-to-inner vessel wall diameter measurements in non-contrast bright blood MRA provide more reliable diameters when compared to outer-to-outer vessel wall measurements of the aortic root. Therefore, we propose to rely on inner rather than outer aortic wall measurements in non-contrast-MRA when monitoring aortic diameters in patients with Marfan syndrome.

276Non contrast 3D steady-state free-precession magnetic resonance angiography: the more relevant magnetic resonance technique for the assessment prior to Ross procedure?

276Non contrast 3D steady-state free-precession magnetic resonance angiography: the more relevant magnetic resonance technique for the assessment prior to Ross procedure?

Can visual analogue scale be used in radiologic subjective image quality assessment?

BackgroundAssessment of qualitative or subjective image quality in radiology is traditionally performed using a fixed-point scale even though reproducibility has proved challenging.ObjectiveImage quality of 3-T coronary magnetic resonance (MR) angiography was evaluated using three scoring methods, hypothesizing that a continuous scoring scale like visual analogue scale would improve the assessment.Materials and methodsAdolescents corrected for transposition of the great arteries with arterial switch operation, ages 9–15 years (n=12), and healthy, age-matched controls (n=12), were examined with 3-D steady-state free precession magnetic resonance imaging. Image quality of the coronary artery origin was evaluated by using a fixed-point scale (1–4), visual analogue scale of 10 cm and a visual analogue scale with reference points (figurative visual analogue scale). Satisfactory image quality was set to a fixed-point scale 3=visual analogue scale/figurative visual analogue scale 6.6 cm. Statistical analysis was performed using Cohen kappa coefficient and agreement index.ResultsThe mean interobserver scores for the fixed-point scale, visual analogue scale and figurative visual analogue scale were, respectively, in the left main stem 2.8, 5.7, 7.0; left anterior descending artery 2.8, 4.7, 6.6; circumflex artery 2.5, 4.5, 6.2, and right coronary artery 3.2, 6.3, 7.7. Scoring with a fixed-point scale gave an intraobserver κ of 0.52–0.77 while interobserver κ was lacking. For visual analogue scale and figurative visual analogue scale, intraobserver agreement indices were, respectively, 0.08–0.58 and 0.43–0.71 and interobserver agreement indices were up to 0.5 and 0.65, respectively.ConclusionQualitative image quality evaluation with coronary 3-D steady-state free precession MR angiography, using a visual analogue scale with reference points, had better reproducibility compared to a fixed-point scale and visual analogue scale. Image quality, being a continuum, may be better determined by this method.

Feasibility of performing non-contrast magnetic resonance angiography in pregnant subjects with familial aortopathies

BackgroundPregnancy is associated with an increased risk of aortic pathology. We sought to assess the feasibility of performing non-contrast 3D steady-state free-precession (SSFP) magnetic resonance angiography (MRA) in pregnant subjects with inherited aortopathy. MethodsFifteen pregnant subjects (age 27±4yr) with positive genotyping for aortopathy (Marfan, Loeys-Dietz, Ehlers-Danlos) and/or a family history of aortic dissection underwent non-contrast 3D-SSFP MRA at 1.5T (Avanto, Siemens Healthcare, Erlangen, Germany) using a modified ECG-triggered orientated in a sagittal-oblique plane with a respiratory navigator at the diaphragmatic level (mean acquisition time 4.1±1.9min). Imaging was performed during the mid-trimester (21±5weeks). Image analysis was performed off-line using Cvi42 software (Circle Cardiovascular Imaging, Calgary, Canada). An assessment of image quality (score 0–3) was made before performing inner edge to inner edge measurements of the thoracic aorta at 7 levels from the multiplanar reconstructions by two independent blinded observers. ResultsNon-contrast 3D-MRA was successfully acquired in all 15 subjects. Image quality was deemed excellent in 87% (13/15) of cases after a mean acquisition time of 4.1±1.9min. There was a high level of agreement for aortic measurements, with low intra- and inter-observer variability (ICC ranges; 0.95–0.99 and 0.92–0.98, respectively). All pregnancies reached term (≥37/40) with a mean gestation at delivery of 38.0±0.5weeks. The mode of delivery was vaginal in 9 out of 15 subjects (60%). ConclusionsNon-contrast SSFP MRA imaging provides a quick and reproducible method of assessing the thoracic aorta in pregnancy.

19 Feasibility of native high-resolution 3D SSFP MR angiography for assessment of the thoracic aorta in pregnant subjects with familial aortopathies

<h3>Introduction</h3> Native magnetic resonance angiography (MRA) is recommended to assess the thoracic aorta during pregnancy, avoiding the risks of ionising radiation and contrast agent administration. This guidance is however, based only on consensus opinion supported by limited case reports (level of evidence C). <h3>Aim</h3> To evaluate the feasibility of performing native 3D steady-state free-precession (SSFP) MRA in pregnant subjects with inherited aortopathy to guide timing and mode of delivery. <h3>Methods</h3> Prospective patients (n = 15) with known thoracic aortic disease underwent native 3D-SSFP MRA at 1.5T (Avanto, Siemens) with high isotropic spatial resolution (1.3×1.3×1.3mm³) using a modified ECG-triggered sequence orientated in a sagittal-oblique plane, aligned along the aortic arch, with a respiratory navigator at the diaphragmatic level (slice thickness 2.00mm; TR/TE: 274/1.5ms). Subjects were imaged during “free breathing” adopting a “left uterine displacement” position, with a wedge under the right buttock, offloading the gravid uterus from the inferior vena cava. Aortic dimensions were measured at 7 levels by two independent blinded observers after an assessment of image quality (score 0–3: 0=poor, 3=excellent). <h3>Results</h3> Native 3D-MRA was successfully acquired in all subjects during the mid-trimester (20.6 ± 4.9wk). Subject characteristics and pregnancy outcomes are available in Table 1. Image quality was deemed excellent in 87% after a mean acquisition time of 3.1 ± 1.5min. Figure 1 provides a typical example of a 3D-MRA image. There was a high level of agreement for aortic measurements, with low intra- and inter-observer variability (ICC ranges; 0.95–0.99 and 0.92–0.96, respectively). All pregnancies reached term (≥37/40) with a mean gestation at delivery of 38.0 ± 0.5wk. Imaging surveillance in combination with satisfactory haemodynamic status permitted vaginal delivery in 60%. <h3>Conclusion</h3> Native SSFP MRA provides a robust and safe method to accurately measure the thoracic aorta in pregnant subjects with aortopathy, helping to inform decisions regarding the timing and mode of delivery.

Comparison of native high-resolution 3D and contrast-enhanced MR angiography for assessing the thoracic aorta

To omit risks of contrast agent administration, native magnetic resonance angiography (MRA) is desired for assessing the thoracic aorta. The aim was to evaluate a native steady-state free precession (SSFP) three-dimensional (3D) MRA in comparison with contrast-enhanced MRA as the gold standard. Seventy-six prospective patients with known or suspicion of thoracic aortic disease underwent MRA at 1.5 T using (i) native 3D SSFP MRA with ECG and navigator gating and high isotropic spatial resolution (1.3 × 1.3 × 1.3 mm(3)) and (ii) conventional contrast-enhanced ECG-gated gradient-echo 3D MRA (1.3 × 0.8 × 1.8 mm(3)). Datasets were compared at nine aortic levels regarding image quality (score 0-3: 0 = poor, 3 = excellent) and aortic diameters, as well as observer dependency and final diagnosis. Statistical tests included paired t-test, correlation analysis, and Bland-Altman analysis. Native 3D MRA was acquired successfully in 70 of 76 subjects (mean acquisition time 8.6 ± 2.7 min), while irregular breathing excluded 6 of 76 subjects. Aortic diameters agreed close between both methods at all aortic levels (r = 0.99; bias ± SD -0.12 ± 1.2 mm) with low intra- and inter-observer dependency (intraclass correlation coefficient 0.99). Native MRA studies resulted in the same final diagnosis as the contrast-enhanced MRA. The mean image quality score was superior with native compared with contrast-enhanced MRA (2.4 ± 0.6 vs. 1.6 ± 0.5; P < 0.001). Accuracy of aortic size measurements, certainty in defining the diagnosis and benefits in image quality at the aortic root, underscore the use of the tested high-resolution native 3D SSFP MRA as an appropriate alternative to contrast-enhanced MRA to assess the thoracic aorta.

Comparison of Nonenhanced MR Angiographic Subtraction Techniques for Infragenual Arteries at 1.5 T: A Preliminary Study

To evaluate diagnostic performance of three nonenhanced methods: variable-refocusing-flip angle (FA) fast spin-echo (SE)-based magnetic resonance (MR) angiography (variable FA MR) and constant-refocusing-FA fast SE-based MR angiography (constant-FA MR) and flow-sensitive dephasing (FSD)-prepared steady-state free precession MR angiography (FSD MR) for calf arteries, with dual-injection three-station contrast material-enhanced MR angiography (gadolinium-enhanced MR) as reference. This prospective study was institutional review board approved and HIPAA compliant, with informed consent. Twenty-one patients (13 men, eight women; mean age, 62.6 years) underwent calf-station variable-FA MR, constant-FA MR, and FSD MR at 1.5 T, with gadolinium-enhanced MR as reference. Image quality and stenosis severity were assessed in 13 segments per leg by two radiologists blinded to clinical data. Combined constant-FA MR and FSD MR reading was also performed. Methods were compared (logistic regression for correlated data) for diagnostic accuracy. Of 546 arterial segments, 148 (27.1%) had a hemodynamically significant (≥ 50%) stenosis. Image quality was satisfactory for all nonenhanced MR sequences. FSD MR was significantly superior to both other sequences (P < .0001), with 5-cm smaller field of view; 9.6% variable-FA MR, 9.6% constant-FA MR, and 0% FSD MR segmental evaluations had nondiagnostic image quality scores, mainly from high diastolic flow (variable-FA MR) and motion artifact (constant-FA MR). Stenosis sensitivity and specificity were highest for FSD MR (80.3% and 81.7%, respectively), compared with those for constant-FA MR (72.3%, P = .086; and 81.8%, P = .96) and variable-FA MR (75.9%, P = .54; and 75.6%, P = .22). Combined constant-FA MR and FSD MR had superior sensitivity (81.8%) and specificity (88.3%) compared with constant-FA MR (P = .0076), variable-FA MR (P = .0044), and FSD MR (P = .0013). All sequences had an excellent negative predictive value (NPV): 93.2%, constant-FA MR; 94.7%, variable-FA MR; 91.7%, FSD MR; and 92.9%, combined constant-FA MR and FSD MR. At 1.5 T, all evaluated nonenhanced MR angiographic methods demonstrated satisfactory image quality and excellent NPV for hemodynamically significant stenosis. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120859/-/DC1.

Unenhanced MR Angiography: Techniques and Clinical Applications in Patients with Chronic Kidney Disease

Alongside the two conventional unenhanced magnetic resonance (MR) angiographic techniques, namely time-of-flight and phase-contrast MR angiography, several novel techniques have since been developed, including electrocardiograph (ECG)-gated fast spin echo (FSE), steady-state free precession (SSFP), and arterial spin labeling. These techniques are increasingly being used to avoid severe complications caused by contrast materials, such as iodinated contrast material-induced nephropathy and gadolinium-induced nephrogenic systemic fibrosis. However, image acquisition and interpretation with these techniques are more complicated than with contrast-enhanced MR angiography because of numerous types of artifacts. Appropriate use of these techniques can allow diagnosis of vascular diseases in patients with chronic kidney disease without using contrast materials. For example, time-of-flight angiography is the main technique for evaluating intracranial arteries. Phase-contrast imaging is increasingly being used for physiologic evaluation rather than morphologic evaluation. Meanwhile, ECG-gated FSE MR angiography can show peripheral arteries in more detail. SSFP MR angiography with or without arterial spin labeling can provide high-resolution images of blood vessels including renal arteries, the aorta, and coronary arteries. Black-blood imaging is also used to evaluate vessel walls and intravascular abnormalities including plaque, dissection, and thrombi. The authors review the principles of the currently available unenhanced MR angiographic techniques, along with their advantages and limitations, and describe their clinical applications. This article should help readers select the most appropriate unenhanced MR angiographic technique to assess vascular diseases in patients with chronic kidney disease. Supplemental material available at http://radiographics.rsna.org/lookup/suppl/doi:10.1148/rg.312105075/-/DC1.

Image quality and diagnostic accuracy of unenhanced SSFP MR angiography compared with conventional contrast-enhanced MR angiography for the assessment of thoracic aortic diseases

ObjectivesThe purpose of this study was to determine the image quality and diagnostic accuracy of three-dimensional (3D) unenhanced steady state free precession (SSFP) magnetic resonance angiography (MRA) for the evaluation of thoracic aortic diseases.MethodsFifty consecutive patients with known or suspected thoracic aortic disease underwent free-breathing ECG-gated unenhanced SSFP MRA with non-selective radiofrequency excitation and contrast-enhanced (CE) MRA of the thorax at 1.5 T. Two readers independently evaluated the two datasets for image quality in the aortic root, ascending aorta, aortic arch, descending aorta, and origins of supra-aortic arteries, and for abnormal findings. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were determined for both datasets. Sensitivity, specificity, and diagnostic accuracy of unenhanced SSFP MRA for the diagnosis of aortic abnormalities were determined.ResultsAbnormal aortic findings, including aneurysm (n = 47), coarctation (n = 14), dissection (n = 12), aortic graft (n = 6), intramural hematoma (n = 11), mural thrombus in the aortic arch (n = 1), and penetrating aortic ulcer (n = 9), were confidently detected on both datasets. Sensitivity, specificity, and diagnostic accuracy of SSFP MRA for the detection of aortic disease were 100% with CE-MRA serving as a reference standard. Image quality of the aortic root was significantly higher on SSFP MRA (P < 0.001) with no significant difference for other aortic segments (P > 0.05). SNR and CNR values were higher for all segments on SSFP MRA (P < 0.01).ConclusionOur results suggest that free-breathing navigator-gated 3D SSFP MRA with non-selective radiofrequency excitation is a promising technique that provides high image quality and diagnostic accuracy for the assessment of thoracic aortic disease without the need for intravenous contrast material.

ECG-gated Nonenhanced 3D Steady-State Free Precession MR Angiography in Assessment of Transplant Renal Arteries: Comparison with DSA

To evaluate noncontrast material-enhanced steady-state free precession (SSFP) magnetic resonance (MR) angiography in the assessment of transplant renal arteries (RAs) by using digital subtraction angiography (DSA) as the reference standard. This prospective study was approved by the institutional review board; written informed consent was obtained from all participants. In 20 renal allograft recipients scheduled for DSA, the transplant RAs were assessed with electrocardiographically gated nonenhanced SSFP MR angiography performed at 1.5 T; the degree of stenosis was compared with that of DSA. Subjective image quality for SSFP MR angiography was assessed independently by two radiologists on a four-point scale (from 1, nondiagnostic to 4, excellent) in four predefined segments (I, the iliac artery; II, the main transplant artery; III, segmental branches; and IV, parenchymal branches). Sensitivity, specificity, and accuracy of SSFP MR angiography for the detection of relevant (> or =50%) transplant RA stenosis (TRAS) were calculated on a per-artery basis. One patient was excluded because SSFP MR angiography failed to adequately visualize the allograft vasculature owing to low cardiac output. The mean image quality assessed by both readers was 3.98 +/- 0.16 (standard deviation), 3.5 +/- 0.68, 2.71 +/- 1.12 and 2.03 +/- 1.09 for segments I, II, III, and IV, respectively (kappa = 0.80). DSA helped identify eight relevant (> or =50%) stenoses in six transplant RAs. Kinking of the transplant artery without relevant stenosis was found in seven patients. The degree of stenosis was overestimated in three patients by using SSFP MR angiography. As compared with DSA, the sensitivity, specificity, and accuracy of SSFP MR angiography to help detect relevant TRAS were 100% (six of six), 88% (14 of 16), and 91% (20 of 22), respectively. Nonenhanced SSFP MR angiography is a reliable alternative imaging technique for the assessment of transplant RAs in patients for whom contrast-enhanced MR angiography is contraindicated.

Three-Dimensional Imaging of Pulmonary Veins by a Novel Steady-State Free-Precession Magnetic Resonance Angiography Technique Without the Use of Intravenous Contrast Agent

To evaluate the feasibility of 3-dimensional (3D) steady-state free-precession (SSFP) magnetic resonance angiography (MRA) using nonselective radiofrequency excitation for imaging of pulmonary veins (PVs) without intravenous gadolinium chelate and to correlate the results with conventional contrast-enhanced MRA (CE-MRA). Forty consecutive patients with history of atrial fibrillation underwent free-breathing respiratory navigator-gated electrocardiogram-triggered SSFP MRA without contrast administration and conventional high-resolution 3D CE-MRA of the thorax at 1.5 T. Two readers assessed both datasets for vascular definition (from 0, not visualized, to 3, excellent definition), artifacts, and ostial diameters. Statistical analysis was performed using Wilcoxon, paired t test, and kappa coefficient. On SSFP MRA, readers 1 and 2 graded 96.4% (160/166) and 97% (161/166) of the segments as having diagnostic visibility and sharpness, respectively (k = 0.82). On CE-MRA datasets, all segments were graded as having diagnostic visibility and sharpness by both readers (k = 0.86). No significant difference existed for visibility and sharpness of pulmonary venous segments between the datasets for each reader (P[r] > 0.05). Reader 1 (2) identified 27 (28) and 35 (32) motion artifacts on SSFP and CE-MRA datasets, respectively. No significant difference was found to exist between ostial diameters on CE-MRA and SSFP datasets (P > 0.05). Our study shows that 3D depiction of PVs without intravenous contrast is feasible with nonslice-selective SSFP MRA. This novel MRA technique may be used in certain patients with atrial fibrillation to assess the number and size of PV ostia draining to the left atrium prior to radiofrequency ablation.

In vivo quantification of femoral‐popliteal compression during isometric thigh contraction: Assessment using MR angiography

To quantify femoral-popliteal vessel deformation during thigh contraction. Eleven subjects underwent a magnetic resonance (MR) examination of the femoral-popliteal vasculature on a 1.5 T system. A custom 3D balanced steady-state free precession (SSFP) sequence was implemented to image a 15-20-cm segment of the vasculature during relaxation and voluntary isometric thigh contraction. The arterial and venous lumina were outlined using a semiautomated method. For the artery, this outline was fit to an ellipse whose aspect ratio was used to describe arterial deformation, while venous deformation was characterized by its cross-sectional area. Focal compression of the femoral-popliteal artery during contraction was observed 94-143 mm superior to the condyle that corresponds to the distal adductor canal (AC) immediately superior to the adductor hiatus. This was illustrated by a significant reduction (P < or = 0.05) in aspect ratio from 0.88 +/- 0.06 during relaxation to 0.77 +/- 0.09 during contraction. A negligible change in arterial aspect ratio was observed inferior to the AC and in the proximal AC. Similarly, venous area was dramatically reduced in the distal AC region during contraction. Rapid 3D SSFP MR angiography of the femoral-popliteal vasculature during thigh contraction demonstrated focal compression of the artery in the distal AC region. This may help explain the high stent failure rate and the high likelihood of atherosclerotic disease in the AC. J. Magn. Reson.

Renal Transplant: Nonenhanced Renal MR Angiography with Magnetization-prepared Steady-State Free Precession

The institutional review board approved this HIPAA-compliant study and waived informed consent. The purpose was to investigate nonenhanced magnetic resonance (MR) angiography with steady-state free precession (SSFP) with inversion recovery for assessing renal arteries in patients with renal transplants. Thirteen recipients of renal transplants underwent SSFP MR angiography before contrast material-enhanced MR angiography. Three stenoses (two mild, one severe) were identified at SSFP MR angiography in agreement with findings at contrast-enhanced MR angiography. There was no significant difference in image quality between the two methods. Results suggest SSFP MR angiography permits image quality of renal transplant arteries and detection of arterial stenosis comparable with those at contrast-enhanced MR angiography.

Pulmonary Vein Imaging with Unenhanced Three-dimensional Balanced Steady-State Free Precession MR Angiography: Initial Clinical Evaluation

To determine whether unenhanced magnetic resonance (MR) angiography performed with a three-dimensional (3D) segmented steady-state free precession (SSFP) sequence would be an alternative to contrast material-enhanced MR angiography for evaluating pulmonary veins (PVs) prior to and following radiofrequency (RF) ablation for atrial fibrillation. MR angiographic examinations of PVs, performed in 20 patients (nine men, 11 women; mean age, 56.4 years +/- 12.7 [standard deviation]), were retrospectively reviewed according to an institutional review board-approved protocol. The number of PVs and their orthogonal measurements obtained from the 3D SSFP images were compared with those obtained from contrast-enhanced MR angiography. Signal-to-noise and contrast-to-noise ratios were also compared. Qualitative assessment of both techniques was performed by independent reviewers who scored the image quality (on a scale of 1 to 5) on the basis of PV conspicuity. The presence of cardiac and extracardiac pathologic indicators was also determined. Bland-Altman and Wilcoxon signed rank statistical analyses were performed. The mean difference in PV diameter measurements between contrast-enhanced MR angiography and 3D SSFP was -0.02 cm +/- 0.25. Signal-to-noise and contrast-to-noise ratios were higher for 3D SSFP images than for contrast-enhanced MR angiograms. Qualitatively, there was no significant difference in PV conspicuity between the techniques. Noncardiac pathologic indicators were detected in 10 of 20 patients on 3D SSFP images but not on contrast-enhanced MR angiograms. Unenhanced PV MR angiography performed by using a free-breathing 3D SSFP technique is as accurate as contrast-enhanced MR angiography for measuring PV diameter. This technique can be used for patients in whom contrast-enhanced computed tomographic or MR angiography is contraindicated and may be sufficient in all patients.

Noncontrast 3D Steady-State Free-Precession Magnetic Resonance Angiography of the Whole Chest Using Nonselective Radiofrequency Excitation over a Large Field of View: Comparison With Single-Phase 3D Contrast-Enhanced Magnetic Resonance Angiography

To evaluate the feasibility of three-dimensional (3D) steady-state free-precession (SSFP) magnetic resonance angiography (MRA) using nonselective radiofrequency excitation in the assessment of cardiac morphology, thoracic aorta, main pulmonary, and proximal coronary arteries. Thirty consecutive patients (19 males; 11 females; age range, 20-74) with various cardiac and thoracic vascular diseases underwent free-breathing respiratory navigator-gated electrocardiogram-triggered noncontrast SSFP MRA and conventional high-resolution 3D contrast-enhanced MRA (CE-MRA) of the thorax at 1.5 T. Two readers evaluated both datasets for findings, vascular delineation and sharpness (from 0, not visualized to 3, excellent definition), artifacts, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in 14 vascular segments including aorta, supra-aortic, pulmonary, and coronary arteries, and in cardiac chambers. Statistical analysis was performed using Wilcoxon test for vessel delineation, and [kappa] coefficient for interobserver variability. 3D SSFP and CE-MRA were successfully performed in all patients. Scan time for SSFP MRA ranged from 5 to 10 minutes (mean +/- standard deviation, 7 +/- 2 minutes). On SSFP MRA, readers 1 and 2 graded 233 (97.1%) and 234 (97.5%) coronary arterial segments and cardiac chambers, and 275 (91.7%) and 278 (92.7%) noncoronary arterial segments with diagnostic definition (grades 2 and 3) (k = 0.86). On conventional CE-MRA, readers 1 and 2 graded 10 (4.2%) and 12 (5%) coronary arterial segments and cardiac chambers, and 272 (90.7%) and 270 (90%) noncoronary arterial segments with diagnostic definition (grades 2 and 3) (k = 0.89). Segmental visibility was higher for aortic root, pulmonary trunk, proximal coronary arteries, and heart chambers (P < 0.001), and lower for supra-aortic arteries (P < 0.001) on SSFP MRA for each reader. SNR and CNR values were higher for aortic root and aorta on SSFP MRA (P < 0.001 for both). No significant difference existed between SNR and CNR values for the other vascular segments and cardiac chambers on SSFP and CE-MRA (P > 0.05 for all). The 2 readers demonstrated vascular stenosis and dilatation/aneurysm in 7 and 35 segments on both datasets, respectively. Noncontrast 3D SSFP MRA with nonselective radiofrequency excitation provides high image quality and sufficient SNR and CNR for confident assessment of cardiac and thoracic vascular diseases including congenital heart diseases. Our results suggest that noncontrast SSFP MRA outperforms CE-MRA in visualization of cardiac chambers, proximal coronary arteries, pulmonary trunk, and aortic root.

Noncontrast 3D Steady State Free Precession Magnetic Resonance Angiography of the Thoracic Central Veins Using Nonselective Radiofrequency Excitation Over a Large Field of View

To evaluate the feasibility of three-dimensional (3D) steady state free precession (SSFP) magnetic resonance angiography (MRA) using nonselective radiofrequency excitation for the assessment of thoracic central veins. Thirty consecutive patients (17 males, 13 females, age range 22-76) with various cardiac and thoracic vascular diseases underwent free-breathing electrocardiogram-gated noncontrast SSFP MRA and conventional high-resolution 3D contrast-enhanced (CE) MRA of the thorax at 1.5 T. Two readers evaluated both datasets for findings: venous visibility and sharpness (from 0, not visualized to 3, excellent definition); artifacts; signal-to-noise ratio (SNR); and contrast-to-noise ratio (CNR) in 8 venous segments including superior vena cava (SVC), supra-diaphragmatic inferior vena cava, bilateral brachiocephalic, proximal subclavian, and lower internal jugular veins. Statistical analysis was performed using Wilcoxon test for overall image quality and vessel visibility, t test for SNR and CNR analysis, and kappa coefficient for inter-observer variability. 3D SSFP and CE-MRA were successfully performed in all patients. Scan time for SSFP MRA ranged from 5 to 10 minutes (mean +/- standard deviation, 7 +/- 2 minutes). Reader 1 (2) graded the overall image quality as excellent and good on SSFP MRA in 23 (25) and 7 (5) patients, and on CE-MRA in 22 (23) and 8 (9) patients, respectively. On SSFP MRA, readers 1 and 2 graded 234 (97.5%) and 233 (97.1%) venous segments with diagnostic definition (grades 2 and 3) (kappa = 0.69), respectively. On conventional CE-MRA, readers 1 and 2 graded 231 (96.3%) and 232 (96.7%) venous segments with diagnostic definition (grades 2 and 3) (kappa = 0.68), respectively. Segmental visibility and sharpness were higher for lower internal jugular veins on CE-MRA for each reader (P < 0.001). No significant difference existed for venous visibility and sharpness scores for other venous segments between the 2 techniques for both readers (P > 0.05). SNR and CNR values were lower for internal jugular veins on SSFP MRA (P < 0.001). No significant difference existed between SNR and CNR values for the other venous segments on SSFP and CE-MRA (P > 0.05 for all). The 2 readers demonstrated patent SVC Glenn shunt to main pulmonary artery (n = 3), patent extra cardiac Fontan shunt from inferior vena cava to pulmonary artery confluence (n = 2), and dilatation and thrombosis of SVC (n = 1) and right brachiocephalic vein (n = 1) on both datasets. Free breathing navigator-gated noncontrast 3D SSFP MRA with nonselective radiofrequency excitation provides high image quality and sufficient SNR and CNR for confident evaluation of thoracic central veins.

Renal Artery Assessment with Nonenhanced Steady-State Free Precession versus Contrast-enhanced MR Angiography

To prospectively assess the diagnostic accuracy of nonenhanced three-dimensional (3D) steady-state free precession (SSFP) magnetic resonance (MR) angiography for detection of renal artery stenosis (RAS), with breath-hold contrast material-enhanced MR angiography performed as the reference standard. The study was local ethics committee approved; all patients gave written informed consent. Fifty-three patients (30 male, 23 female; mean age, 58 years) with arterial hypertension and suspected of having RAS were examined with 1.5-T 3D SSFP renal MR angiography. Stenosis grade, maximal visible vessel length, and subjective image quality were compared. Sensitivity, specificity, accuracy, and negative predictive value (NPV) were calculated on artery-by-artery and patient-by-patient bases. The significance of the results was assessed with the paired two-sided t test for continuous variables and with the marginal homogeneity test for categorical variables. Cohen kappa statistics were used to estimate interobserver agreement. One hundred eight renal arteries with 20 significant (>or=50%) stenoses were detected with contrast-enhanced MR angiography. At artery-by-artery analysis, sensitivity, specificity, accuracy, and NPV of nonenhanced SSFP MR angiography for RAS detection were 100%, 93%, 94%, and 100%, respectively, for observer 1 and 95%, 95%, 95%, and 99%, respectively, for observer 2. Corresponding patient-by-patient values were 100%, 92%, 94%, and 100%, respectively, for observer 1 and 100%, 95%, 96%, and 100%, respectively, for observer 2. Overestimation of stenosis grade with SSFP MR angiography resulted in six and four false-positive findings for readers 1 and 2, respectively. Mean maximal visible lengths of the renal arteries were 69.9 mm at contrast-enhanced MR angiography and 61.1 mm at SSFP MR angiography (P<.001). Both techniques yielded good to excellent image quality. Slab-selective inversion-prepared 3D SSFP MR angiography had high sensitivity, specificity, accuracy, and NPV for RAS detection, without the need for contrast material. However, RAS severity was overestimated in some patients.

Quantitative assessment of ventricular function using three‐dimensional SSFP magnetic resonance angiography

To evaluate three-dimensional (3D), free-breathing, steady-state free precession (SSFP) magnetic resonance angiography (MRA) for volumetric assessment of ventricular function. In 18 subjects (mean age = 21.5 years) 3D datasets of the heart and great vessels were acquired using an ECG-triggered, free-breathing SSFP technique with a T2-preparation prepulse. Data were acquired during end-systole (ES) and end-diastole (ED) for assessment of stroke volumes (SVs). Through-plane flow measurements of the great arteries were performed as well as 2D-cine SSFP imaging for comparison. For image analysis of the 3D SSFP datasets a simplex mesh model was used. Papillary muscles were excluded from ventricular volumes using thresholds. Intra- and interobserver variability (Bland-Altman analysis) and correlations (Pearson's coefficient) between volumetric and flow measurements were assessed. ES and ED datasets were acquired successfully in all subjects. The best correlation was observed between flow vs. 3D SSFP SV for the LV (r = 0.85, mean difference = -1.0 mL) and the RV (r = 0.89, mean difference = -2.2 mL) with high intra- (LV: r = 0.93; RV: r = 0.94) and interobserver (LV: r = 0.91; RV: r = 0.93) reproducibility. 3D SSFP datasets combined with semiautomatic segmentation algorithms allow highly accurate and reproducible assessment of left (LV) and right ventricular (RV) SVs in free-breathing subjects.

Intraindividual Comparison of 3D Coronary MR Angiography and Coronary CT Angiography

To compare the diagnostic value of magnetic resonance (MR) and computed tomography (CT) for the detection of coronary artery disease (CAD) with special regard to calcifications. Twenty-seven patients with known CAD were examined with a targeted, navigator-gated, free-breathing, steady-state free precession MR angiography sequence (repetition time = 5.6 milliseconds, echo time = 2.8 milliseconds, flip angle 110 degrees ) and 16-slice coronary CT angiography. Segment-based sensitivity, specificity, and accuracy for the detection of stenoses larger than 50% were determined as defined by the gold standard catheter coronary angiography along with the subjective image quality (Grade 1-4). The degree of calcifications in each segment was quantified using a standard calcium scoring tool. Of 115 possible segments, 7% had to be excluded in MR imaging because of poor image quality. In CT, 3% were nondiagnostic because of image quality and 15% were not evaluable because of calcifications. Values for the detection of relevant coronary artery stenoses in the evaluated segments were: sensitivity: MR imaging 85% versus CT 96%; specificity: 88% versus 96%; accuracy: 87% versus. 96%. Average subjective image quality was 1.8 for MR imaging and 1.6 for CT. Of the 15% of segments that had to be excluded from CT evaluation because of calcifications, MR imaging provided the correct diagnosis segments in 67%. CT provided a better image quality with superior accuracy for the detection of CAD. Despite its overall inferiority, MR imaging proved to be helpful method in interpreting coronary stenosis in severely calcified segments.

Renal Arteries: Comparison of Steady-State Free Precession MR Angiography and Contrast-enhanced MR Angiography

All participants provided informed consent to participate in this study, which was approved by the institutional review board. Breath-hold three-dimensional (3D) steady-state free precession (SSFP) magnetic resonance (MR) angiography was compared with 3D contrast material-enhanced MR angiography in patients suspected of having renal artery stenosis. Two radiologists assessed visualization of renal arteries and detection of vascular disease. With SSFP MR angiography, 39 of 41 renal arteries in 19 patients were correctly detected. Relevant stenoses were correctly identified with SSFP MR angiography in two patients. In two patients, SSFP MR angiographic data sets led to false-positive overgrading of vascular disease. Fast breath-hold 3D SSFP MR angiography appears to be feasible for MR angiography of renal arteries.