Metabolic imaging of human kidney triglyceride content: reproducibility of proton magnetic resonance spectroscopy.

OBJECTIVE: To assess the feasibility of renal proton magnetic resonance spectroscopy for quantification of triglyceride content and to compare spectral quality and reproducibility without and with respiratory motion compensation in vivo. MATERIALS AND METHODS: The Institutional Review Board of our institution approved the study protocol, and written informed consent was obtained. After technical optimization, a total of 20 healthy volunteers underwent renal proton magnetic resonance spectroscopy of the renal cortex both without and with respiratory motion compensation and volume tracking. After the first session the subjects were repositioned and the protocol was repeated to assess reproducibility. Spectral quality (linewidth of the water signal) and triglyceride content were quantified. Bland-Altman analyses and a test by Pitman were performed. RESULTS: Linewidth changed from 11.5±0.4 Hz to 10.7±0.4 Hz (all data pooled, p<0.05), without and with respiratory motion compensation respectively. Mean % triglyceride content in the first and second session without respiratory motion compensation were respectively 0.58±0.12% and 0.51±0.14% (P = NS). Mean % triglyceride content in the first and second session with respiratory motion compensation were respectively 0.44±0.10% and 0.43±0.10% (P = NS between sessions and P = NS compared to measurements with respiratory motion compensation). Bland-Altman analyses showed narrower limits of agreement and a significant difference in the correlated variances (correlation of -0.59, P<0.05). CONCLUSION: Metabolic imaging of the human kidney using renal proton magnetic resonance spectroscopy is a feasible tool to assess cortical triglyceride content in humans in vivo and the use of respiratory motion compensation significantly improves spectral quality and reproducibility. Therefore, respiratory motion compensation seems a necessity for metabolic imaging of renal triglyceride content in vivo.

Site-specific coupling between vascular wall thickness and function: an observational MRI study of vessel wall thickening and stiffening in hypertension.

OBJECTIVES: The objective of this study was to evaluate associations between aortic pulse wave velocity (PWV) and aortic and carotid vessel wall thickness (VWT) using cardiovascular magnetic resonance imaging (MRI) in patients with hypertension as compared with healthy adult volunteers. MATERIALS AND METHODS: Local medical ethics approval was obtained and the participants gave informed consent. Fifteen patients with hypertension (5 men and 10 women; mean [SD] age, 49 [14] years) and 15 age- and sex-matched healthy volunteers were prospectively included and compared. All participants underwent MRI examination for measuring aortic and carotid VWT and aortic PWV with well-validated MRI techniques at 1.5- and 3-T MRI systems: PWV was assessed from velocity-encoded MRI and VWT was assessed by using dual-inversion black-blood gradient-echo imaging techniques. Paired t tests were used for testing differences between the volunteers and the patients and Pearson correlation (r) and univariable and multivariable stepwise linear regression analyses were used to test associations between aortic and carotid arterial wall thickness and stiffness. RESULTS: Mean values for aortic PWV and aortic and carotid VWT (indexed for body surface area [BSA]) were all significantly higher in patients with hypertension as compared with the healthy volunteers (ie, aortic PWV, 7.0 ± 1.4 m/s vs 5.7 ± 1.3 m/s; aortic VWT/BSA, 0.12 ± 0.03 mL/m vs 0.10 ± 0.03 mL/m; carotid VWT/BSA, 0.04 ± 0.01 mL/m vs 0.03 ± 0.01 mL/m; all P < 0.01). Aortic PWV was highly correlated with aortic VWT/BSA (r = 0.76 and P = 0.002 in the patients vs r = 0.63 and P = 0.02 in the volunteers), and in the patients, aortic PWV was moderately correlated with carotid VWT/BSA (r = 0.50; P = 0.04). In the volunteers, correlation between aortic PWV and carotid VWT/BSA was not significant (r = 0.40; P = 0.13). In addition, aortic VWT/BSA was significantly correlated with carotid VWT/BSA, in both the patients (r = 0.60; P = 0.005) and volunteers (r = 0.57; P = 0.007). CONCLUSIONS: In the patients with hypertension and the healthy volunteers, the aortic PWV is associated more strongly with aortic wall thickness than with carotid wall thickness, reflecting site-specific coupling between vascular wall thickness and function.

Gastric volume changes in response to a meal: validation of magnetic resonance imaging versus the barostat.

PURPOSE: To determine the accuracy of magnetic resonance imaging (MRI) volume scans: 1) to measure known meal volumes in vitro, and 2) to compare volume changes in response to a meal measured with the barostat with those measured with MRI in vivo. MATERIALS AND METHODS: Polyethylene bags were filled with known volumes and MRI volume scans were performed to determine the accuracy of the volume measurements. Barostat measurements and MRI volume scans were performed simultaneously in 14 healthy subjects before and up to 90 minutes after ingestion of a liquid meal. RESULTS: In vitro MRI-determined volumes showed an excellent linear relationship (r = 0.995, P < 0.001) with actual meal volumes. Although fasting gastric volume, postprandial gastric volume, and relaxation volume measured with MRI were significantly larger compared to volumes measured with the barostat, volumes determined with both techniques showed excellent correlation. CONCLUSION: Volumes in the range of postprandial meal volumes are accurately measured with MRI. MRI is a noninvasive technique to measure stomach volumes and volume changes in response to a meal. Volume changes in response to a meal measured with MRI correlate perfectly with those measured with the barostat device.

Right coronary artery flow velocity and volume assessment with spiral K-space sampled breathhold velocity-encoded MRI at 3 tesla: accuracy and reproducibility.

PURPOSE: To evaluate accuracy and reproducibility of flow velocity and volume measurements in a phantom and in human coronary arteries using breathhold velocity-encoded (VE) MRI with spiral k-space sampling at 3 Tesla. MATERIALS AND METHODS: Flow velocity assessment was performed using VE MRI with spiral k-space sampling. Accuracy of VE MRI was tested in vitro at five constant flow rates. Reproducibility was investigated in 19 healthy subjects (mean age 25.4 +/- 1.2 years, 11 men) by repeated acquisition in the right coronary artery (RCA). RESULTS: MRI-measured flow rates correlated strongly with volumetric collection (Pearson correlation r = 0.99; P < 0.01). Due to limited sample resolution, VE MRI overestimated the flow rate by 47% on average when nonconstricted region-of-interest segmentation was used. Using constricted region-of-interest segmentation with lumen size equal to ground-truth luminal size, less than 13% error in flow rate was found. In vivo RCA flow velocity assessment was successful in 82% of the applied studies. High interscan, intra- and inter-observer agreement was found for almost all indices describing coronary flow velocity. Reproducibility for repeated acquisitions varied by less than 16% for peak velocity values and by less than 24% for flow volumes. CONCLUSION: 3T breathhold VE MRI with spiral k-space sampling enables accurate and reproducible assessment of RCA flow velocity.

Initial results on in vivo human coronary MR angiography at 7 T.

Seven tesla (T) MR imaging is potentially promising for the morphologic evaluation of coronary arteries because of the increased signal-to-noise ratio compared to lower field strengths, in turn allowing improved spatial resolution, improved temporal resolution, or reduced scanning times. However, there are a large number of technical challenges, including the commercial 7 T systems not being equipped with homogeneous body radiofrequency coils, conservative specific absorption rate constraints, and magnified sample-induced amplitude of radiofrequency field inhomogeneity. In the present study, an initial attempt was made to address these challenges and to implement coronary MR angiography at 7 T. A single-element radiofrequency transmit and receive coil was designed and a 7 T specific imaging protocol was implemented, including significant changes in scout scanning, contrast generation, and navigator geometry compared to current protocols at 3 T. With this methodology, the first human coronary MR images were successfully obtained at 7 T, with both qualitative and quantitative findings being presented.

Phosphorus-31 magnetic resonance spectroscopy of skeletal muscle in maternally inherited diabetes and deafness A3243G mitochondrial mutation carriers.

PURPOSE: To investigate high-energy phosphate metabolism in striated skeletal muscle of patients with Maternally Inherited Diabetes and Deafness (MIDD) syndrome. MATERIALS AND METHODS: In 11 patients with the MIDD mutation (six with diabetes mellitus [DM] and five non-DM) and eight healthy subjects, phosphocreatine (PCr) and inorganic phosphate (Pi) in the vastus medialis muscle was measured immediately after exercise using (31)P-magnetic resonance spectroscopy (MRS). The half-time of recovery (t1/2) of monoexponentially fitted (PCr+Pi)/PCr was calculated from spectra obtained every 4 seconds after cessation of exercise. A multiple linear regression model was used for statistical analysis. RESULTS: Patients with the MIDD mutation showed a significantly prolonged t1/2 (PCr+Pi)/PCr after exercise as compared to controls (13.6+/-3.0 vs. 8.7+/-1.3 sec, P = 0.01). No association between the presence of DM and t1/2 (PCr + Pi)/PCr was found (P = 0.382). CONCLUSION: MIDD patients showed impaired mitochondrial oxidative phosphorylation in skeletal muscle shortly after exercise, irrespective of the presence of DM.

Aortic vessel wall magnetic resonance imaging at 3.0 Tesla: a reproducibility study of respiratory navigator gated free-breathing 3D black blood magnetic resonance imaging.

The purpose of this study was to evaluate a free-breathing three-dimensional (3D) dual inversion-recovery (DIR) segmented k-space gradient-echo (turbo field echo [TFE]) imaging sequence at 3T for the quantification of aortic vessel wall dimensions. The effect of respiratory motion suppression on image quality was tested. Furthermore, the reproducibility of the aortic vessel wall measurements was investigated. Seven healthy subjects underwent 3D DIR TFE imaging of the aortic vessel wall with and without respiratory navigator. Subsequently, this sequence with respiratory navigator was performed twice in 10 healthy subjects to test its reproducibility. The signal-to-noise (SNR), contrast-to-noise ratio (CNR), vessel wall sharpness, and vessel wall volume (VWV) were assessed. Data were compared using the paired t-test, and the reproducibility of VWV measurements was evaluated using intraclass correlation coefficients (ICCs). SNR, CNR, and vessel wall sharpness were superior in scans performed with respiratory navigator compared to scans performed without. The ICCs concerning intraobserver, interobserver, and interscan reproducibility were excellent (0.99, 0.94, and 0.95, respectively). In conclusion, respiratory motion suppression substantially improves image quality of 3D DIR TFE imaging of the aortic vessel wall at 3T. Furthermore, this optimized technique with respiratory motion suppression enables assessment of aortic vessel wall dimensions with high reproducibility.

Mitral valve and tricuspid valve blood flow: accurate quantification with 3D velocity-encoded MR imaging with retrospective valve tracking.

PURPOSE: To validate flow assessment performed with three-dimensional (3D) three-directional velocity-encoded (VE) magnetic resonance (MR) imaging with retrospective valve tracking and to compare this modality with conventional two-dimensional (2D) one-directional VE MR imaging in healthy subjects and patients with regurgitation. MATERIALS AND METHODS: Patients and volunteers gave informed consent, and local medical ethics committee approval was obtained. Patient data were selected retrospectively and randomly from a database of MR studies obtained between July 2006 and July 2007. The 3D three-directional VE MR images were first validated in vitro and compared with 2D one-directional VE MR images. Mitral valve (MV) and tricuspid valve (TV) flow were assessed in 10 volunteers without valve insufficiency and 20 patients with valve insufficiency, with aortic systolic stroke volume (ASSV) as the reference standard. RESULTS: Phantom validation showed less than 5% error for both techniques. In volunteers, 3D three-directional VE MR images showed no bias for MV or TV flow when compared with ASSV, whereas 2D one-directional VE MR images showed significant bias for MV flow (15% overestimation, P < .01). TV flow showed 25% overestimation; however, this was insignificant because of the high standard deviation. Correlation with ASSV was strong for 3D three-directional VE MR imaging (r = 0.96, P < .01 for MV flow; r = 0.88, P < .01 for TV flow) and between MV and TV flow (r = 0.91, P < .01); however, correlation was weaker for 2D one-directional VE MR imaging (r = 0.80, P < .01 for MV flow; r = 0.22, P = .55 for TV flow) and between MV flow and TV flow (r = 0.34, P = .34). In patients (mean regurgitation fractions of 13% and 10% for MV flow and TV flow, respectively), correlation between MV flow and TV flow for 3D three-directional VE MR imaging was strong (r = 0.97, P < .01). CONCLUSION: Use of 3D three-directional VE MR imaging enables accurate MV and TV flow quantification, even in patients with valve regurgitation.

Metabolic MRI of myocardial and hepatic triglyceride content in response to nutritional interventions.

PURPOSE OF REVIEW: To discuss the technique and clinical applications of myocardial and hepatic H magnetic resonance spectroscopy to study myocardial and hepatic triglyceride content, in relation to changes in plasma nonesterified fatty acids induced by nutritional interventions. RECENT FINDINGS: Progressive caloric restriction induces a dose-dependent increase in myocardial triglyceride content and a dose-dependent decrease in diastolic function in lean healthy men. Hepatic triglyceride content shows a differential response to progressive caloric restriction, indicating that redistribution of endogenous triglyceride stores is tissue specific, at least in lean healthy men. A short-term high-fat high-energy diet in healthy men results in major increases in hepatic fat content, whereas it does not influence myocardial triglyceride content or myocardial function. Apparently, there is a differential, tissue-specific partitioning of either triglyceride or fatty acids or both between nonadipose organs such as the human heart and liver during different physiological conditions. SUMMARY: Metabolic MRI of myocardial and hepatic triglyceride content is a promising new tool to study the effects of nutritional interventions on myocardial and hepatic lipid metabolism in relation to heart function. Future studies should aim to apply these magnetic resonance techniques to obesity and type 2 diabetes mellitus.

Metabolic imaging of myocardial triglyceride content: reproducibility of 1H MR spectroscopy with respiratory navigator gating in volunteers.

Institutional review board approval and informed consent were obtained. The purpose of the study was to prospectively compare spectral resolution and reproducibility of hydrogen 1 (1H) magnetic resonance (MR) spectroscopy, with and without respiratory motion compensation based on navigator echoes, in the assessment of myocardial triglyceride content in the human heart. In 20 volunteers (14 men, six women; mean age+/-standard error, 31 years+/-2.8 [range, 19-60 years]; body mass index, 19-30 kg/m2) without history of cardiovascular disease, 1H MR spectroscopy of the myocardium was performed at rest, with and without respiratory motion compensation. Unsuppressed water signal linewidth changed from 11.9 Hz to 10.7 Hz (P<.001) with the use of the navigator, which indicated better spectral resolution. The navigator improved the intraclass correlation coefficient for the assessment of myocardial triglyceride content from 0.32 to 0.81. Therefore, the authors believe that respiratory motion correction is essential for reproducible assessment of myocardial triglycerides.

Reproducibility of wall shear stress assessment with the paraboloid method in the internal carotid artery with velocity encoded MRI in healthy young individuals.

PURPOSE: To verify whether wall shear stress (WSS) can be assessed in a reproducible manner using automatic model-based segmentation of phase-contrast MR images by determination of flow volume and maximum flow velocity (Vmax) in cross-sections of these vessels. MATERIALS AND METHODS: The approach is based on fitting a 3D paraboloid to the actual velocity profiles and on determining Vmax. WSS was measured in the internal carotid arteries of two groups of healthy young volunteers. The reproducibility of rescanning and repositioning was studied in the first group. In the second group a 1-week and a 1-month interval was investigated. Reproducibility was calculated by the intraclass correlation (ICC). RESULTS: The flow volume, Vmax, and WSS averaged over the cardiac cycle were found to be 287.8 +/- 29.7 mL/min, 37.0 +/- 4.6 cm/s, and 1.13 +/- 0.16 Pa, respectively. The diastolic WSS varied between 1.00 +/- 0.21 Pa without averaging to 0.88 +/- 0.16 Pa with temporal and spatial averaging. Systolic WSS was 1.67 +/- 0.33 Pa without averaging and 1.67 +/- 0.25 Pa with averaging. ICC varied between 0.58 and 0.87 without averaging and between 0.75 and 0.90 with averaging for WSS. CONCLUSION: WSS in MR images of the internal carotid artery can be assessed semiautomatically with good to excellent reproducibility without inter- or intraobserver variability using model-based postprocessing.

Magnetic resonance assessment of aortic pulse wave velocity, aortic distensibility, and cardiac function in uncomplicated type 2 diabetes mellitus.

BACKGROUND: Type 2 diabetes mellitus (DM2) may augment arterial stiffening and thereby modulates left ventricular (LV) function. Cardiovascular magnetic resonance (CMR) is well suited to assess aortic pulse wave velocity (PWV) and aortic distensibility, both markers of arterial stiffness, without the use of geometric assumptions. Furthermore, CMR is a reliable method for assessing left ventricular (LV) function. The purpose of this study was to assess LV function, PWV, and aortic distensibility in patients with DM2 using MR. METHODS: Fourteen patients with well controlled, uncomplicated DM2, and 16 age and gender matched healthy subjects were included. PWV was calculated based on MR velocity mapping at two predefined aortic locations. Aortic distensibility was measured in the mid ascending aorta. LV volumes were measured by fast gradient-echo imaging to assess systolic function. Furthermore, mitral inflow was measured by MR velocity mapping to assess diastolic LV function. RESULTS: Mean PWV was higher in patients as compared to healthy subjects (6.83 +/- 1.60 m/s vs. 5.65 +/- 0.75 m/s, p < 0.05). This difference was independent of blood pressure. PWV correlated significantly (p < 0.05) with fasting plasma glucose and insulin levels. Aortic distensibility was lower in patients as compared to healthy subjects (4.50 x 10(- 3)+/- 2.24 x 10(- 3) mmHg(- 1) vs. 7.42 x 10(- 3)+/- 3.34 x 10(- 3) mmHg(- 1), p < 0.05). Distensibility correlated negatively with PWV and positively with LV diastolic function (p < 0.05). CONCLUSION: A combined CMR assessment of aortic PWV, aortic distensibility, and heart function reveals abnormal PWV and distensibility in patients with DM2, independent of blood pressure. Furthermore, aortic distensibility correlates with diastolic left ventricular function.

Assessment of the carotid artery by MRI at 3T: a study on reproducibility.

PURPOSE: To examine the reproducibility of carotid artery dimension measurements using 3T MRI. MATERIALS AND METHODS: Ten healthy volunteers underwent three scans on two occasions for assessment of total vessel wall area (TVWA), total luminal area (TLA), and minimum (MinT) and maximum (MaxT) vessel wall thickness. A double inversion-recovery (IR) fast gradient-echo (FGRE) sequence was used on a commercial 3T system. During the first visit the subjects were scanned twice. The third scan was performed at least four days later. One observer traced all scans, and a second observer retraced the first scan series. RESULTS: For TVWA an interclass correlation (ICC) of 0.994 was calculated with all three scans taken into account. The interobserver ICC was 0.984. The agreement between the scans for TLA showed an ICC of 0.982 with an interobserver ICC of 0.998. For MinT and MaxT an ICC of 0.843 and 0.935 were calculated, with interobserver ICCs of 0.860 and 0.726, respectively. CONCLUSION: With the use of a commercial 3T MR system, TVWA, TLA, and wall thickness measurements of the carotid artery can be assessed with good reproducibility.

Validation of a high-resolution, phase contrast cardiovascular magnetic resonance sequence for evaluation of flow in coronary artery bypass grafts.

The aim was to validate a magnetic resonance high-resolution, phase-contrast sequence for quantifying flow in small and large vessels and to demonstrate its feasibility to measure flow in coronary artery bypass grafts. A breathhold, echo planar imaging (EPI) sequence was developed and validated in a flow phantom using a fast field echo (FFE) sequence as reference. In 17 volunteers aortic flow was measured using both sequences. In 5 patients flow in the left internal mammary artery (LIMA) and aorta was measured at rest and during adenosine stress, and coronary flow reserve (CFR) was calculated; in 7 patients, vein graft flow velocity was measured. In the flow phantom measurements, the EPI sequence yielded an excellent correlation with the FFE sequence (r = 0.99; p < 0.001 for all parameters). In healthy volunteers, aortic volume flow correlated well (r = 0.88; p < 0.01), with a minor overestimation. It was feasible to measure flow velocity in the LIMA and vein grafts of the 12 patients. The high-resolution, breathhold cardiovascular magnetic resonance velocity-encoded sequence correlated well with a free-breathing, FFE sequence in a flow phantom and in the aortae of healthy volunteers. Using the EPI sequence, it is feasible to measure flow velocity in both LIMA and vein grafts, and in the aorta.

Aortic root dysfunctioning and its effect on left ventricular function in Ross procedure patients assessed with magnetic resonance imaging.

BACKGROUND: This study evaluated the diameters and distensibility of the aortic root as well as the degree of aortic regurgitation (AR) and its effect on left ventricular (LV) function in patients 8.2 +/- 3.1 years after they underwent the Ross procedure, with a comparison of these parameters between patients and matched healthy subjects. METHODS: Eighteen Ross procedure patients (16 male patients, age [mean +/- SD] 19.2 +/- 3.8 years) and 18 matched healthy subjects (16 male patients, age [mean +/- SD] 19.7 +/- 4.2 years) underwent magnetic resonance imaging. Measurements for diameters (at 4 levels) and the distensibility of the aortic root were performed using a steady-state free precession sequence. Aortic flow was assessed with a velocity-encoded phase-contrast sequence. Left ventricular systolic function was assessed with a gradient-echo sequence in the short-axis plane. Comparison of parameters was performed using the Mann-Whitney U test. Correlations between diameters, distensibility, AR fraction, and LV systolic function were expressed with Spearman rank correlation coefficients. Linear regression analysis was used to identify predictors of LV systolic dysfunction. RESULTS: Aortic root diameters were increased in Ross procedure patients as compared with healthy subjects (mean difference 6.3-11.6 mm, P < or = .02 at all 4 levels). Distensibility of the aortic root was lower in patients (1.9 +/- 1.1 vs 7.8 +/- 3.3 mm Hg(-1), P < .01). An AR fraction > 5% was present in 14 of the 18 patients (mean AR fraction 8% +/- 5% vs 1% +/- 1%, P < .01). Left ventricular ejection fraction was lower in patients (50% +/- 6% vs 57% +/- 6%, P < .01). Dilatation, decreased distensibility, and AR fraction were correlated with impaired LV systolic function (P < .05 for all). The AR fraction predicted impaired LV systolic function (P < .01). CONCLUSIONS: Magnetic resonance imaging shows dilatation and decreased distensibility of the aortic root, AR, and consequent impaired LV systolic function in patients after the Ross procedure.

MDCT assessment of right ventricular systolic function.

OBJECTIVE: The objective of our study was to validate using MDCT for the assessment of right ventricular (RV) function. MDCT with retrospective ECG gating was performed in 15 patients being evaluated for suspected cardiovascular disease. Echocardiography was performed for comparison. The MDCT images were reconstructed at 20 phase points over the cardiac cycle. The end-diastolic and end-systolic volumes of both ventricles were measured. Stroke volumes and ejection fractions were calculated from these data. CONCLUSION: RV volumes can be accurately assessed using MDCT.

The effect of corticosteroid medication on quantitative MR parameters of the brain.

BACKGROUND AND PURPOSE: Quantitative MR imaging techniques such as magnetization transfer imaging (MTI), diffusion-weighted imaging (DWI), and MR spectroscopy are promising diagnostic tools for use with patients with diffuse brain diseases such as neuropsychiatric systemic lupus erythematosus (NPSLE). Such patients are often on corticosteroid (CS) treatment. Presently, it is unknown whether CSs per se influence quantitative MR imaging measurements. The aim of this study was to evaluate the effect of low-dose oral CSs on MTI, DWI, and MR spectroscopy parameters of the brain. METHODS: Twenty-seven rheumatoid arthritis (RA) patients with and without CS medication and 15 healthy controls were subjected to conventional MR imaging, whole-brain MTI and DWI, and single-voxel MR spectroscopy. Oral CSs were used by 13 of the RA patients. Univariate analyses with age as a covariate were performed on MTI, DWI, and MR spectroscopy parameters between RA patients with and without CSs and healthy controls. Pearson correlations were calculated between all imaging parameters and duration of disease, duration of CS use, and CS dosage. RESULTS: No significant differences between the groups of subjects or significant correlations with clinical parameters were found for MTI, DWI and MR spectroscopy parameters. CONCLUSION: In this study, we found no evidence for an effect of low-dose oral CSs on whole-brain MTI and DWI histogram parameters and single-voxel MR spectroscopy measurements of the brain. The results of this study demonstrate that it is unlikely that MTI, DWI, and MR spectroscopy parameters reported in NPSLE studies are confounded by low-dose oral CS.

MRI to evaluate left atrial and ventricular reverse remodeling after restrictive mitral annuloplasty in dilated cardiomyopathy.

BACKGROUND: Data on reverse remodeling of the left atrium (LA) and left ventricle (LV) after restrictive annuloplasty in patients with dilated cardiomyopathy are scarce, and follow-up studies are performed with echocardiography. METHODS AND RESULTS: Twenty patients with dilated cardiomyopathy and severe mitral regurgitation selected for restrictive mitral annuloplasty underwent serial MRI studies (within 1 week before surgery, and 2 months [n =18] and 1 year [n =13] after surgery). Early mortality was 10%; all patients were free from endocarditis and thromboembolism. New York Heart Association class improved from 3.2+/-0.4 to 1.2+/-0.9. Only 1 patient developed recurrent severe mitral regurgitation during follow-up and it was re-repaired. LA end-systolic volumes decreased significantly over time (from 165+/-48 mL to 109+/-23 mL to 111+/-28 mL; P < 0.01), as did LA end-diastolic volumes (from 92+/-32 mL to 71+/-22 mL to 75+/-17 mL; P = 0.01). LV end-diastolic volumes decreased significantly (from 244+/-56 mL to 184+/-54 mL to 195+/-67 mL; P < 0.01), whereas end-systolic volumes did not change significantly. LV ejection fraction increased significantly (from 35+/-8% to 46+/-13% to 46+/-15%; P < 0.01) and LV mass decreased significantly (from 150+/-43 grams to 132+/-39 grams to 136+/-33 grams; P = 0.02). CONCLUSIONS: Restrictive annuloplasty in patients with dilated cardiomyopathy yielded excellent clinical results associated with significant LA and LV reverse remodeling over time as demonstrated by MRI.

Accurate quantitation of regurgitant volume with MRI in patients selected for mitral valve repair.

OBJECTIVE: Echocardiography, the currently preferred diagnostic approach for mitral valve regurgitation, cannot accurately quantify the amount of regurgitation. Flow quantification with MRI is possible, but the conventional method (1-directional velocity-encoding) acquires the flow at a fixed location during the cardiac cycle, which is not necessarily the location of the mitral valve during the whole cycle. In this study, the exact flow through the mitral valve was quantified with a 3-directional velocity-encoded MRI approach. METHODS: Ten patients with severe mitral valve regurgitation (class 3-4+with echocardiography) resulting from systolic restrictive motion of both leaflets (Carpentier IIIb) which were selected for valve repair and 10 healthy volunteers without cardiac valvular disease confirmed with echocardiography were included in this study. The intra-ventricular flow was sampled with a radial stack of six acquisition planes parallel to the long-axis of the left ventricle. Three-directional velocity-encoded MRI was performed resulting in the intra-ventricular flow velocity vector field for 30 phases during the cardiac cycle. The position of the mitral valvular plane in this vector field was indicated manually for each phase. Velocity values perpendicular to this plane determined the flow through the mitral valve. Both the 3-directional encoded mitral valve flow and the 1-directional encoded mitral valve flow were compared with the flow determined with MRI at the ascending aorta. RESULTS: One-directional velocity-encoded MRI showed a mean overestimation (P<0.01) of 25 ml/cycle compared to the aortic flow. Correlation was very poor (r(P)=0.15, P=0.68). The 3-directional velocity-encoded MRI on the other hand, showed no over/underestimation and a good correlation (r(P)=0.91, P<0.01 for volunteers, r(P)=0.90, P<0.01 for patients). The regurgitant flow fractions were between 3 and 30%. CONCLUSION: With 3-directional velocity-encoded MRI, measurement of the flow through the mitral valve is accurate and reproducible. This is a valuable tool for diagnosing and absolute quantification of regurgitant volume.

Magnetic resonance imaging of knee cartilage using a water selective balanced steady-state free precession sequence.

PURPOSE: To compare an optimized water selective balanced steady-state free precession sequence (WS-bSSFP) with conventional magnetic resonance (MR) sequences in imaging cartilage of osteoarthritic knees. MATERIALS AND METHODS: Flip angles of sagittal and axial WS-bSSFP sequences were optimized in three volunteers. Subsequently, the knees of 10 patients with generalized osteoarthritis were imaged using sagittal and axial WS-bSSFP and conventional MR imaging techniques. We calculated contrast-to-noise ratios (CNR) between cartilage and its surrounding tissues to quantitatively analyze the various sequences. Using dedicated software we compared, in two other patients, the accuracy of cartilage volume measurements with anatomic sections of the tibial plateau. RESULTS: CNRtotal eff (CNR efficiency between cartilage and its surrounding tissue) using WS-bSSFP was maximal with a 20-25 degrees flip angle. CNRtotal eff was higher in WS-bSSFP than in conventional images: 6.1 times higher compared to T1-weighted gradient echo (GE) images, 5.1 compared to proton-density (PD) fast spin echo (FSE) images, and 4.8 compared to T2-weighted FSE images. The mean difference of cartilage volume measurement on WS-bSSFP and anatomic sections was 0.06 mL compared to 0.24 mL for T1-GE and anatomic sections. CONCLUSION: A WS-bSSFP sequence is superior to conventional MR imaging sequences in imaging cartilage of the knee in patients with osteoarthritis.