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.
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.
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).
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.
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 × 10− 3± 2.24 × 10− 3 mmHg− 1 vs. 7.42 × 10− 3± 3.34 × 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.
We investigated the additional value of magnetic resonance (MR) angiography in 12 patients with clinically significant coronary anomalies. In 5 patients, the referring cardiologist requested ...additional evaluation because coronary arteriography was inconclusive about the course of the anomaly. For comparison, 7 patients with known anomalous coronary arteries were collected from our database. In these patients, there had been no doubt about the course of the anomalous coronary arteries. MR angiography provided the diagnosis in all 5 patients in whom the diagnosis was inconclusive beforehand. From the 7 patients in whom diagnosis had been established previously by contrast arteriography, the anomaly was confirmed in 5 by MR angiography. In 1 patient, the initial diagnosis at contrast arteriography had to be changed as a result of MR angiography. In 1 patient, the MR image was of insufficient quality to be conclusive.
In conclusion, in patients with angiographically suspected coronary anomalies, fast gradient echo MR angiography is a helpful adjunct to coronary arteriography in identifying and confirming the origin and course of clinically significant coronary anomalies. The additional value of fast gradient echo MR coronary angiography is the visualization of both the artery and its surrounding structures.
In 12 patients with angiographically suspected clinically significant coronary anomalies, we investigated the additional value of magnetic resonance angiography to delineate the course of the coronary artery. Fast gradient echo magnetic resonance angiography appeared to be a helpful adjunct to coronary arteriography in identifying and confirming the course of the clinically significant coronary anomalies.
Plasma leptin concentrations were measured every 20 min for 24 h
in eight normal weight women and in eight upper body and eight lower
body obese women matched for body mass index. The circadian ...rhythm of
leptin, which could mathematically be described by a cosine, was
characterized by an acrophase just after midnight in all subjects. The
amplitude of a cosine fit as well as the average 24-h leptin
concentration were increased by 280% and 420%, respectively, in obese
compared to normal weight women. All characteristics of leptin
concentration profiles were similar in upper body and lower body obese
women, except for a significantly higher amplitude in the lower body
obese group. Visceral and sc body fat depots were measured using
magnetic resonance imaging in all three groups. Average 24-h leptin
concentrations were strongly correlated with sc fat (r = 0.84),
whereas visceral fat was not an independent predictor of the plasma
leptin level. A loss of 50% of the overweight was associated with a
55% decrease in the average 24-h leptin concentrations in obese women
(95% confidence interval, 12.3, 26.6), whereas the characteristics of
the circadian rhythm of leptin remained unchanged. Finally, it was
observed that a fasting plasma leptin concentration is not an
acceptable indicator of the average leptin concentration over 24
h.
With a newly developed magnetic resonance (MR) technique for blood flow measurements, qualitative and quantitative information on both flow volume and flow velocity in the great vessels can be ...obtained. MR flow quantitation is performed with a gradient-echo MR sequence with high temporal resolution enabling measurements at frequent intervals throughout the cardiac cycle. MR flow quantitation uses the phase rather than the amplitude of the MR signal to reconstruct the images. These images, often referred to as MR velocity maps or velocity-encoded cine MR images, are two-dimensional displays of flow velocity. From these velocity maps, velocity and volume flow data can be obtained. Previous validation experiments have demonstrated the accuracy of MR velocity mapping, and this technique is now being applied successfully in several clinical fields. MR velocity mapping may be of considerable value when Doppler echocardiography results are unsatisfactory or equivocal, particularly because MR is suited for the analysis of volumetric flow and complex flow patterns. Among the vastly growing number of clinical cardiovascular applications that have been reported are the great arteries and veins, coronary vessels, valvular disease, and the abdominal and peripheral vessels. These items are reviewed, and some aspects of the technique that need improvement are discussed.
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.
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.
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).
Use of 3D three-directional VE MR imaging enables accurate MV and TV flow quantification, even in patients with valve regurgitation.
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