Coronary magnetic resonance angiography for the detection of coronary stenoses.

BACKGROUND: An accurate, noninvasive technique for the diagnosis of coronary disease would be an important advance. We investigated the accuracy of coronary magnetic resonance angiography among patients with suspected coronary disease in a prospective, multicenter study. METHODS: Coronary magnetic resonance angiography was performed during free breathing in 109 patients before elective x-ray coronary angiography, and the results of the two diagnostic procedures were compared. RESULTS: A total of 636 of 759 proximal and middle segments of coronary arteries (84 percent) were interpretable on magnetic resonance angiography. In these segments, 78 (83 percent) of 94 clinically significant lesions (those with a > or = 50 percent reduction in diameter on x-ray angiography) were also detected by magnetic resonance angiography. Overall, coronary magnetic resonance angiography had an accuracy of 72 percent (95 percent confidence interval, 63 to 81 percent) in diagnosing coronary artery disease. The sensitivity, specificity, and accuracy for patients with disease of the left main coronary artery or three-vessel disease were 100 percent (95 percent confidence interval, 97 to 100 percent), 85 percent (95 percent confidence interval, 78 to 92 percent), and 87 percent (95 percent confidence interval, 81 to 93 percent), respectively. The negative predictive values for any coronary artery disease and for left main artery or three-vessel disease were 81 percent (95 percent confidence interval, 73 to 89 percent) and 100 percent (95 percent confidence interval, 97 to 100 percent), respectively. CONCLUSIONS: Among patients referred for their first x-ray coronary angiogram, three-dimensional coronary magnetic resonance angiography allows for the accurate detection of coronary artery disease of the proximal and middle segments. This noninvasive approach reliably identifies (or rules out) left main coronary artery or three-vessel disease.

Quality Assessment of Cardiac Magnetic Resonance Images at 1.5/3.0 T: Description and Validation of Standardized Criteria

PURPOSE: Cardiovascular magnetic resonance (CMR) has become a robust and important diagnostic imaging modality in cardiovascular medicine. However,insufficient image quality may compromise its diagnostic accuracy. No standardized criteria are available to assess the quality of CMR studies. We aimed todescribe and validate standardized criteria to evaluate the quality of CMR studies including: a) cine steady-state free precession, b) delayed gadoliniumenhancement, and c) adenosine stress first-pass perfusion. These criteria will serve for the assessment of the image quality in the setting of the Euro-CMR registry.METHOD AND MATERIALS: First, a total of 45 quality criteria were defined (35 qualitative criteria with a score from 0-3, and 10 quantitative criteria). Thequalitative score ranged from 0 to 105. The lower the qualitative score, the better the quality. The quantitative criteria were based on the absolute signal intensity (delayed enhancement) and on the signal increase (perfusion) of the anterior/posterior left ventricular wall after gadolinium injection. These criteria were then applied in 30 patients scanned with a 1.5T system and in 15 patients scanned with a 3.0T system. The examinations were jointly interpreted by 3 CMR experts and 1 study nurse. In these 45 patients the correlation between the results of the quality assessment obtained by the different readers was calculated.RESULTS: On the 1.5T machine, the mean quality score was 3.5. The mean difference between each pair of observers was 0.2 (5.7%) with a mean standarddeviation of 1.4. On the 3.0T machine, the mean quality score was 4.4. The mean difference between each pair of onservers was 0.3 (6.4%) with a meanstandard deviation of 1.6. The quantitative quality assessments between observers were well correlated for the 1.5T machine: R was between 0.78 and 0.99 (pCONCLUSION: The described criteria for the assessment of CMR image quality are robust and have a low inter-observer variability, especially on 1.5T systems.CLINICAL RELEVANCE/APPLICATION: These criteria will allow the standardization of CMR examinations. They will help to improve the overall quality ofexaminations and the comparison between clinical studies.

Breathhold three-dimensional coronary magnetic resonance angiography using real-time navigator technology.

The acquisition duration of most three-dimensional (3D) coronary magnetic resonance angiography (MRA) techniques is considerably prolonged, thereby precluding breathholding as a mechanism to suppress respiratory motion artifacts. Splitting the acquired 3D volume into multiple subvolumes or slabs serves to shorten individual breathhold duration. Still, problems associated with misregistration due to inconsistent depths of expiration and diaphragmatic drift during sustained respiration remain to be resolved. We propose the combination of an ultrafast 3D coronary MRA imaging sequence with prospective real-time navigator technology, which allows correction of the measured volume position. 3D volume splitting using prospective real-time navigator technology, was successfully applied for 3D coronary MRA in five healthy individuals. An ultrafast 3D interleaved hybrid gradient-echoplanar imaging sequence, including T2Prep for contrast enhancement, was used with the navigator localized at the basal anterior wall of the left ventricle. A 9-cm-thick volume, with in-plane spatial resolution of 1.1 x 2.2 mm, was acquired during five breathholds of 15-sec duration each. Consistently, no evidence of misregistration was observed in the images. Extensive contiguous segments of the left anterior descending coronary artery (48 +/- 18 mm) and the right coronary artery (75 +/- 5 mm) could be visualized. This technique has the potential for screening for anomalous coronary arteries, making it well suited as part of a larger clinical MR examination. In addition, this technique may also be applied as a scout scan, which allows an accurate definition of imaging planes for subsequent high-resolution coronary MRA.

EuroCMR (European Cardiovascular Magnetic Resonance) registry: results of the German pilot phase.

OBJECTIVES: During its German pilot phase, the EuroCMR (European Cardiovascular Magnetic Resonance) registry sought to evaluate indications, image quality, safety, and impact on patient management of routine CMR. BACKGROUND: CMR has a broad range of applications and is increasingly used in clinical practice. METHODS: This was a multicenter registry with consecutive enrollment of patients in 20 German centers. RESULTS: A total of 11,040 consecutive patients were enrolled. Eighty-eight percent of patients received gadolinium-based contrast agents. Twenty-one percent underwent adenosine perfusion, and 11% high-dose dobutamine-stress CMR. The most important indications were workup of myocarditis/cardiomyopathies (32%), risk stratification in suspected coronary artery disease/ischemia (31%), as well as assessment of viability (15%). Image quality was good in 90.1%, moderate in 8.1%, and inadequate in 1.8% of cases. Severe complications occurred in 0.05%, and were all associated with stress testing. No patient died during or due to CMR. In nearly two-thirds of patients, CMR findings impacted patient management. Importantly, in 16% of cases the final diagnosis based on CMR was different from the diagnosis before CMR, leading to a complete change in management. In more than 86% of cases, CMR was capable of satisfying all imaging needs so that no further imaging was required. CONCLUSIONS: CMR is frequently performed in clinical practice in many participating centers. The most important indications are workup of myocarditis/cardiomyopathies, risk stratification in suspected coronary artery disease/ischemia, and assessment of viability. CMR imaging as used in the centers of the pilot registry is a safe procedure, has diagnostic image quality in 98% of cases, and its results have strong impact on patient management.

Impact of navigator timing on free-breathing submillimeter 3D coronary magnetic resonance angiography.

The purpose of this study was to investigate the impact of navigator timing on image quality in navigator-gated and real-time motion-corrected, free-breathing, three-dimensional (3D) coronary MR angiography (MRA) with submillimeter spatial image resolution. Both phantom and in vivo investigations were performed. 3D coronary MRA with real-time navigator technology was applied using variable navigator time delays (time delay between the navigator and imaging sequences) and varying spatial resolutions. Quantitative objective and subjective image quality parameters were assessed. For high-resolution imaging, reduced image quality was found as a function of increasing navigator time delay. Lower spatial resolution coronary MRA showed only minor sensitivity to navigator timing. These findings were consistent among volunteers and phantom experiments. In conclusion, for submillimeter navigator-gated and real-time motion-corrected 3D coronary MRA, shortening the time delay between the navigator and the imaging portion of the sequence becomes increasingly important for improved spatial resolution.

B1-insensitive T2 preparation for improved coronary magnetic resonance angiography at 3 T.

At 3 T, the effective wavelength of the RF field is comparable to the dimension of the human body, resulting in B1 standing wave effects and extra variations in phase. This effect is accompanied by an increase in B0 field inhomogeneity compared to 1.5 T. This combination results in nonuniform magnetization preparation by the composite MLEV weighted T2 preparation (T2 Prep) sequence used for coronary magnetic resonance angiography (MRA). A new adiabatic refocusing T2 Prep sequence is presented in which the magnetization is tipped into the transverse plane with a hard RF pulse and refocused using a pair of adiabatic fast-passage RF pulses. The isochromats are subsequently returned to the longitudinal axis using a hard RF pulse. Numerical simulations predict an excellent suppression of artifacts originating from B1 inhomogeneity while achieving good contrast enhancement between coronary arteries and surrounding tissue. This was confirmed by an in vivo study, in which coronary MR angiograms were obtained without a T2 Prep, with an MLEV weighted T2 Prep and the proposed adiabatic T2 Prep. Improved quantitative and qualitative coronary MRA image measurement was achieved using the adiabatic T2 Prep at 3 T.

Direct magnetic resonance arthrography of the knee: utility of axial traction.

The purpose of this study was to determine the impact of axial traction during acquisition of direct magnetic resonance (MR) arthrography examination of the knee in terms of joint space width and amount of contrast material between the cartilage surfaces. Direct knee MR arthrography was performed in 11 patients on a 3-T MR imaging unit using a T1-weighted isotropic gradient echo sequence in a coronal plane with and without axial traction of 15 kg. Joint space widths were measured at the level of the medial and the lateral femorotibial joint with and without traction. The amount of contrast material in the medial and lateral femorotibial joint was assessed independently by two musculoskeletal radiologists in a semiquantitative manner using three grades ('absence of surface visualization, 'partial surface visualization or 'complete surface visualization'). With traction, joint space width increased significantly at the lateral femorotibial compartment (mean = 0.55 mm, p = 0.0105) and at the medial femorotibial compartment (mean = 0.4 mm, p = 0.0124). There was a trend towards an increased amount of contrast material in the femorotibial compartment with axial traction. Direct MR arthrography of the knee with axial traction showed a slight and significant increase of the width of the femorotibial compartment with a trend towards more contrast material between the articular cartilage surfaces.

Fetal MRI as complement to US in the diagnosis and characterization of anomalies of the genito-urinary tract.

The purpose of this study is to compare the accuracy of prenatal ultrasound (US) and prenatal magnetic resonance imaging (MRI) in the diagnosis and characterization of congenital abnormalities of the genito-urinary tract and to determine if the additional information obtained by MRI may influence the management of the fetus. We retrospectively evaluate 15 cases of congenital genito-urinary tract anomalies detected by prenatal US and with echographic inconclusive diagnosis. We compare the MRI findings with the US findings and the final diagnosis, obtained from neonatal outcomes, imaging studies and pathology records. Fetal US diagnosis was correct in 9 cases (60%) and MRI in 13 cases (86.7%). Prenatal MRI revealed additional information to US in 9 cases (60%), which modified the initial US diagnosis in 5 cases (33.3%) and changed the therapeutic approach in 5 fetuses (33.3%). Fetal MRI was better than US in cases of oligoamnios and in fetuses with genito-urinary pathology concerning the pelvic and perineum region. We believe that MRI should be considered as a complementary diagnostic method in cases of echographic suspicion of congenital pathology of the genito-urinary tract and inconclusive prenatal US.

Quality assessment of cardiovascular magnetic resonance in the setting of the European CMR registry: description and validation of standardized criteria.

BACKGROUND: Cardiovascular magnetic resonance (CMR) has become an important diagnostic imaging modality in cardiovascular medicine. However, insufficient image quality may compromise its diagnostic accuracy. We aimed to describe and validate standardized criteria to evaluate a) cine steady-state free precession (SSFP), b) late gadolinium enhancement (LGE), and c) stress first-pass perfusion images. These criteria will serve for quality assessment in the setting of the Euro-CMR registry. METHODS: Thirty-five qualitative criteria were defined (scores 0-3) with lower scores indicating better image quality. In addition, quantitative parameters were measured yielding 2 additional quality criteria, i.e. signal-to-noise ratio (SNR) of non-infarcted myocardium (as a measure of correct signal nulling of healthy myocardium) for LGE and % signal increase during contrast medium first-pass for perfusion images. These qualitative and quantitative criteria were assessed in a total of 90 patients (60 patients scanned at our own institution at 1.5T (n=30) and 3T (n=30) and in 30 patients randomly chosen from the Euro-CMR registry examined at 1.5T). Analyses were performed by 2 SCMR level-3 experts, 1 trained study nurse, and 1 trained medical student. RESULTS: The global quality score was 6.7±4.6 (n=90, mean of 4 observers, maximum possible score 64), range 6.4-6.9 (p=0.76 between observers). It ranged from 4.0-4.3 for 1.5T (p=0.96 between observers), from 5.9-6.9 for 3T (p=0.33 between observers), and from 8.6-10.3 for the Euro-CMR cases (p=0.40 between observers). The inter- (n=4) and intra-observer (n=2) agreement for the global quality score, i.e. the percentage of assignments to the same quality tertile ranged from 80% to 88% and from 90% to 98%, respectively. The agreement for the quantitative assessment for LGE images (scores 0-2 for SNR <2, 2-5, >5, respectively) ranged from 78-84% for the entire population, and 70-93% at 1.5T, 64-88% at 3T, and 72-90% for the Euro-CMR cases. The agreement for perfusion images (scores 0-2 for %SI increase >200%, 100%-200%,<100%, respectively) ranged from 81-91% for the entire population, and 76-100% at 1.5T, 67-96% at 3T, and 62-90% for the Euro-CMR registry cases. The intra-class correlation coefficient for the global quality score was 0.83. CONCLUSIONS: The described criteria for the assessment of CMR image quality are robust with a good inter- and intra-observer agreement. Further research is needed to define the impact of image quality on the diagnostic and prognostic yield of CMR studies.

Training and accreditation in cardiovascular magnetic resonance in Europe: a position statement of the working group on cardiovascular magnetic resonance of the European Society of Cardiology.

Cardiovascular magnetic resonance (CMR) has become an established imaging modality which provides often unique information on a wide range of cardiovascular diseases. The European Society of Cardiology (ESC) training curriculum reflects the emerging role of CMR by recommending that all trainees obtain a minimum level of training in CMR and by defining criteria for subspecialty training in CMR. 1 The wider use of CMR requires the definition of standards for data acquisition, reporting, and training in CMR across Europe. At the same time, training and accreditation in all cardiac imaging methods should be harmonized and integrated to promote the training of cardiac imaging specialists. The recommendations presented in this document are intended to inform the discussion about standards for accreditation and certification in CMR in Europe and the discussion on integrated imaging training. At present, the recommendations in this position statement are not to be interpreted as guidelines. Until such guidelines are available and nationally ratified, physicians will be able to train and practice CMR according to current national regulations.

Robust volume-targeted balanced steady-state free-precession coronary magnetic resonance angiography in a breathhold at 3.0 Tesla: a reproducibility study.

BACKGROUND: Transient balanced steady-state free-precession (bSSFP) has shown substantial promise for noninvasive assessment of coronary arteries but its utilization at 3.0 T and above has been hampered by susceptibility to field inhomogeneities that degrade image quality. The purpose of this work was to refine, implement, and test a robust, practical single-breathhold bSSFP coronary MRA sequence at 3.0 T and to test the reproducibility of the technique. METHODS: A 3D, volume-targeted, high-resolution bSSFP sequence was implemented. Localized image-based shimming was performed to minimize inhomogeneities of both the static magnetic field and the radio frequency excitation field. Fifteen healthy volunteers and three patients with coronary artery disease underwent examination with the bSSFP sequence (scan time = 20.5 ± 2.0 seconds), and acquisitions were repeated in nine subjects. The images were quantitatively analyzed using a semi-automated software tool, and the repeatability and reproducibility of measurements were determined using regression analysis and intra-class correlation coefficient (ICC), in a blinded manner. RESULTS: The 3D bSSFP sequence provided uniform, high-quality depiction of coronary arteries (n = 20). The average visible vessel length of 100.5 ± 6.3 mm and sharpness of 55 ± 2% compared favorably with earlier reported navigator-gated bSSFP and gradient echo sequences at 3.0 T. Length measurements demonstrated a highly statistically significant degree of inter-observer (r = 0.994, ICC = 0.993), intra-observer (r = 0.894, ICC = 0.896), and inter-scan concordance (r = 0.980, ICC = 0.974). Furthermore, ICC values demonstrated excellent intra-observer, inter-observer, and inter-scan agreement for vessel diameter measurements (ICC = 0.987, 0.976, and 0.961, respectively), and vessel sharpness values (ICC = 0.989, 0.938, and 0.904, respectively). CONCLUSIONS: The 3D bSSFP acquisition, using a state-of-the-art MR scanner equipped with recently available technologies such as multi-transmit, 32-channel cardiac coil, and localized B0 and B1+ shimming, allows accelerated and reproducible multi-segment assessment of the major coronary arteries at 3.0 T in a single breathhold. This rapid sequence may be especially useful for functional imaging of the coronaries where the acquisition time is limited by the stress duration and in cases where low navigator-gating efficiency prohibits acquisition of a free breathing scan in a reasonable time period.

Acute Complications of Crohn's Disease: Comparison of Multidetector-Row Computed Tomographic Enterography with Magnetic Resonance Enterography.

Objective: To compare multidetector-row computed tomographic (MDCT) enterography with magnetic resonance (MR) enterography performed upon acute exacerbation of Crohn's disease. Subjects and Methods: Fifty-seven patients (mean age 33.5) with proven Crohn's disease and symptoms suggesting acute exacerbation were prospectively included. After oral administration of 1-2 liters of 5% methylcellulose, MDCT and MR enterography were performed on each patient (mean delay <24 h). Three radiologists blindly and independently evaluated each examination for technical quality and in terms of 8 pathological features of Crohn's disease. Observers' agreement, sensitivity and specificity resulted from comparison with the reference standard [surgery (n = 24), endoscopy (n = 17) and long-term follow-up (n = 16)]. Results: MDCT enterography demonstrated fewer artifacts than MR enterography (p < 0.0001). In 48 MDCT/MR enterography examinations, active disease was demonstrated: abscesses (n = 11), fistulas (n = 13), stenoses (n = 23) and/or intestinal inflammation (n = 38). Observers' agreement (range 0.56-0.87) was not significantly different between MDCT and MR enterography, neither in terms of sensitivity (range 58-95%) nor specificity (range 67-100%) for each of the 8 pathological features. Conclusion: Statistically, MR enterography is of similar diagnostic value as MDCT enterography for acute complications of Crohn's disease. Since the typical Crohn's disease patient is young and will very likely undergo life-long imaging, and given concerns about radiation exposure with MDCT, MR enterography should be the preferred modality.

Real-time motion correction in navigator-gated free-breathing double-oblique submillimeter 3D right coronary artery magnetic resonance angiography.

RATIONALE AND OBJECTIVES: The purpose of this study was the investigation of the impact of real-time adaptive motion correction on image quality in navigator-gated, free-breathing, double-oblique three-dimensional (3D) submillimeter right coronary magnetic resonance angiography (MRA). MATERIALS AND METHODS: Free-breathing 3D right coronary MRA with real-time navigator technology was performed in 10 healthy adult subjects with an in-plane spatial resolution of 700 x 700 microm. Identical double-oblique coronary MR-angiograms were performed with navigator gating alone and combined navigator gating and real-time adaptive motion correction. Quantitative objective parameters of contrast-to-noise ratio (CNR) and vessel sharpness and subjective image quality scores were compared. RESULTS: Superior vessel sharpness, increased CNR, and superior image quality scores were found with combined navigator gating and real-time adaptive motion correction (vs. navigator gating alone; P < 0.01 for all comparisons). CONCLUSION: Real-time adaptive motion correction objectively and subjectively improves image quality in 3D navigator-gated free-breathing double-oblique submillimeter right coronary MRA.