Acquisition and measurement of left ventricular (LV) volumes with a three-dimensional data set of cine magnetic resonance (MR) images from apex to base is a time-consuming process. Results of a study with 10 healthy volunteers and 10 patients with LV hypertrophy were prospectively evaluated. The heart was shown in the anatomic short- and horizontal long-axis planes with cine MR imaging. LV volumes were measured with various geometric models, and ejection fractions were calculated. In both groups, the values of LV stroke volume obtained with a modified Simpson rule and biplane ellipsoid models correlated well to the analysis of the three-dimensional data set of cine MR images. There were no significant differences for the calculated ejection fraction between values obtained with the modified Simpson rule or the biplane ellipsoid model versus the three-dimensional data set. A high inter-observer reproducibility of cine MR measurements with the two former models was found. Therefore, modified Simpson rule and biplane ellipsoid models, with their shorter acquisition and processing times, may increase the clinical utility of cine MR imaging.
The interstudy reproducibility of velocity-encoded cine (VEC) magnetic resonance (MR) imaging for quantification of regurgitant volume (RV) and regurgitant fraction (RF) was studied in 10 patients with chronic aortic regurgitation. Each patient underwent two VEC MR imaging studies. RV and RF were measured on the aortic flow curve by quantifying antegrade and retrograde flow per cardiac cycle. VEC MR imaging measurements for RV and RF correlated closely with volumetric measurements for both studies (r greater than .97). Interstudy reproducibility for VEC MR imaging measurement of RV and RF was high (r greater than .97), and the interstudy variability for VEC MR imaging measurements was low. These results demonstrate a high accuracy of VEC MR imaging for measurement of RV and RF in patients with chronic aortic regurgitation. The level of interstudy reproducibility of VEC MR imaging for quantitative assessment of RV and RF indicates the potential of this technique for follow-up and monitoring of response to therapy.
OBJECTIVE.Gadodiamide injection (Omniscan, Sanofi Winthrop Pharmaceuticals, New York) is a new nonionic MR contrast medium that has been shown in animal studies to provide persistent differential enhancement of myocardial infarction.Because differential enhancement of normal and infarcted myocardium may be useful for the diagnosis and sizing of myocardial infarctions, we assessed the effectiveness of gadodiamide injection in enhancing signal-intensity differences between infarcted and normal myocardium on spin-echoTi-weighted images. SUBJECTS AND METHODS. Signal intensity of normal and infarcted myocardium, contrast ratio, contrast-to-noise ratio, and signal-to-noise ratio were measured in 12 patients with subacute myocardial infarction (mean, 16 days after diagnosis) before and after injection of contrast medium. Precontrast Ti-weighted and T2-weighted images were obtained with a 1.5-T MR imager. Ti-weighted images were acquired 5, 15, and 30 mm after gadodiamide injection (0.2 mmollkg) and Ti-weighted images with fat saturation were acquired 10 mm after gadodiamide injection. RESULTS. Gadodiamide injection significantly increased signal intensity of normal (34 ±%) and infarcted (90 ±%) myocardium compared with their signal intensities on precontrast TI-weighted images. The contrast ratio was significantly increased, and the augmented ratios persisted throughout the 45-mm observation period. The contrast ratio on T2-weighted images was comparable to that on contrast-enhanced Tiweighted images (with or without the use of fat saturation).However, the signal-tonoise and contrast-to-noise ratios of T2-weighted images were significantly lower than those of contrast-enhanced Ti-weighted images. The maximum contrast-tonoise ratio for visualizing myocardial infarction was achieved on contrast-enhanced Ti-weighted Images with fat saturation. CONCLUSION.Improved and persistent contrast between infarcted and normal myocardium can be produced on MR images by injecting gadodiamide at a dose of 0.2 mmol/kg, which provides prolonged delineation of myocardial infarctions. Maximum contrast-to-noise ratios for detecting myocardial infarction can be produced by using fat-saturated Ti-weighted imaging after a high dose of this nonionic contrast medium has been administered.
The sites of deposition of atherosclerotic plaque on the aortic wall are considered to be influenced by secondary and retrograde flow patterns that cause regions of altered shear stress. To detect secondary flow patterns and areas of retrograde flow in the abdominal aorta, velocity-encoded cine (VEC) magnetic resonance (MR) imaging was performed at five different levels of the abdominal aorta in nine healthy volunteers. Net retrograde flow (expressed as a percentage of antegrade flow) increased from proximal to distal levels and was maximal (13.8% +/- 11.8) just distal to the origin of the renal arteries. An increase in the duration of retrograde flow over the cardiac cycle was observed from proximal to distal levels. Whereas retrograde flow was present at end systole and early diastole in each volunteer at every level, the duration and amount of retrograde flow during diastole showed high interindividual variation. Such differences suggest the possibility of variable vascular geometric risk factors in the population for the development of atherosclerotic plaque. The location of retrograde flow in the abdominal aorta demonstrated in vivo with VEC MR imaging was close to that obtained with in vitro flow visualization studies in models of the abdominal aorta.
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