Automated observer-independent acquisition of cardiac short-axis MR images: a pilot study.

The authors compared an automated observer-independent acquisition planning method for short-axis multisection multiphase cardiac magnetic resonance imaging studies with conventional manual image planning. Systematic and random differences and reproducibility of left ventricular function measurements and image geometry were evaluated in five healthy adult volunteers and 20 patient studies. Results with the automated planning method were as accurate and reproducible as those with the manual planning method.

Left ventricular function: correlation of quantitative gated SPECT and MR imaging over a wide range of values.

In 21 patients, the authors compared results with quantitative gated single photon emission computed tomography (SPECT) to results with magnetic resonance imaging in the assessment of left ventricular (LV) end-diastolic volume (LVEDV), end-systolic volume (LVESV), and ejection fraction (LVEF). Between the two methods, correlations were good for LVEF (r = 0.85), LVEDV (r = 0.94), and LVESV (r = 0.95). Quantitative gated SPECT can help determine LVEF, LVEDV, and LVESV.

Arrhythmogenic right ventricular dysplasia: MRI findings.

Arrhythmogenic right ventricular dysplasia (ARVD) is a heart muscle disorder of unknown cause that is characterized pathologically by fibrofatty replacement of the right ventricular myocardium. Clinical manifestations include structural and functional malformations of the right ventricle, electrocardiographic abnormalities, and presentation with ventricular tachycardias with left bundle branch pattern or sudden death. The disease is often familial with an autosomal inheritance. In addition to right ventricular dilatation, right ventricular aneurysms are typical deformities of ARVD and they are distributed in the so-called "triangle of dysplasia", i.e., right ventricular outflow tract, apex, and infundibulum. Ventricular aneurysms at these sites can be considered pathognomonic of ARVD. Another typical hallmark of ARVD is fibrofatty infiltration of the right ventricular free wall. These functional and morphologic characteristics are relevant to clinical imaging investigations such as contrast angiography, echocardiography, radionuclide angiography, ultrafast computed tomography, and magnetic resonance imaging (MRI). Among these techniques, MRI allows the clearest visualization of the heart, in particular because the right ventricle is involved, which is usually more difficult to explore with the other imaging modalities. Furthermore, MRI offers the specific advantage of visualizing adipose infiltration as a bright signal of the right ventricular myocardium. MRI provides the most important anatomic, functional, and morphologic criteria for diagnosis of ARVD within one single study. As a result, MRI appears to be the optimal imaging technique for detecting and following patients with clinical suspicion of ARVD.

Right ventricular function in patients after acute myocardial infarction assessed with phase contrast MR velocity mapping encoded in three directions.

The purpose of the study was to assess global and regional myocardial function of the right ventricle (RV) with the use of phase contrast (PC) velocity mapping in patients after acute myocardial infarction. We examined 8 patients after acute myocardial wall infarction and 10 healthy volunteers for comparison. PC velocity mapping was performed in a single midventricular short-axis slice with velocity encoding in three different directions. RV displacement during systole in the through-plane direction differed significantly between patients and volunteers (P = 0.009). RV myocardial velocity in the through-plane and radial directions, evaluated at time of peak ejection rate, was significantly lower in patients than in healthy volunteers (P<0.05). RV abnormalities may be detected in patients after acute myocardial infarction using PC velocity mapping with velocity encoding in three different directions. Owing to their short acquisition times and relatively easy postprocessing, PC techniques are time-efficient and promising tools for the evaluation of RV function.

Functional and metabolic evaluation of the athlete's heart by magnetic resonance imaging and dobutamine stress magnetic resonance spectroscopy.

BACKGROUND: The question of whether training-induced left ventricular hypertrophy in athletes is a physiological rather than a pathophysiological phenomenon remains unresolved. The purpose of the present study was to detect any abnormalities in cardiac function in hypertrophic hearts of elite cyclists and to examine the response of myocardial high-energy phosphate metabolism to high workloads induced by atropine-dobutamine stress. METHODS AND RESULTS: We studied 21 elite cyclists and 12 healthy control subjects. Left ventricular mass, volume, and function were determined by cine MRI. Myocardial high-energy phosphates were examined by 31P magnetic resonance spectroscopy. There were no significant differences between cyclists and control subjects for left ventricular ejection fraction (59+/-5% versus 61+/-4%), left ventricular cardiac index (3.4+/-0.4 versus 3.4+/-0.4 L x min(-1) x m[-2]), peak early filling rate (562+/-93 versus 535+/-81 mL/s), peak atrial filling rate (315+/-93 versus 333+/-65 mL/s), ratio of early and atrial filling volumes (3.0+/-1.0 versus 2.6+/-0.6), mean acceleration gradient of early filling (5.2+/-1.4 versus 5.8+/-1.9 L/s2), mean deceleration gradient of early filling(-3.1 +/- 0.9 versus -3.2 +/- 0.7 L/s2), mean acceleration gradient of atrial filling (3.6+/-1.8 versus 4.5+/-1.7 L/s2), and atrial filling fraction (0.23+/-0.06 versus 0.26+/-0.04, respectively). Cyclists and control subjects showed similar decreases in the ratio of myocardial phosphocreatine to ATP measured with 31P magnetic resonance spectroscopy during atropine-dobutamine stress (1.41+/-0.20 versus 1.41+/-0.18 at rest to 1.21+/-0.20 versus 1.16+/-0.13 during stress, both P=NS). CONCLUSIONS: Left ventricular hypertrophy in cyclists is not associated with significant abnormalities of cardiac function or metabolism as assessed by MRI and spectroscopy. These observations suggest that training-induced left ventricular hypertrophy in cyclists is predominantly a physiological phenomenon.

Diagnosis of cardiac abnormalities in patients with nonischemic tachyarrhythmias: additional value of MR imaging.

PURPOSE: To assess the contribution of cardiac magnetic resonance (MR) imaging in the evaluation of patients with nonischemic tachyarrhythmias and equivocal diagnosis following echocardiography and cardiac angiography. METHODS AND RESULTS: Twenty-five patients with nonischemic tachyarrhythmias and equivocal diagnosis were studied using MR imaging. Before the MR examination all patients underwent two-dimensional echocardiography and cardiac catheterization. The type of additional information, obtained with MR imaging, ranged from confirming a suspected diagnosis in 5 patients (20%) to the identification of new important anatomic or functional information, allowing a correct diagnosis in 18 patients (72%). In two patients (8%) the MR diagnosis was incomplete. CONCLUSION: MR imaging may be an important additional diagnostic tool in the evaluation of cardiac abnormalities in patients with nonischemic tachyarrhythmias.

MR velocity mapping of tricuspid flow: correction for through-plane motion.

We evaluated the effect of through-plane motion on tricuspid flow measurements performed with MR velocity mapping in nine normal subjects and 15 patients with possible right ventricular (RV) disease. Eight parameters of RV diastolic function were derived from the tricuspid flow measurements, both before and after a correction for through-plane motion. Measurements of E-peak, A-peak, and time-to-peak filling rate changed significantly after correction for through-plane motion (P < .05). Tricuspid flow as a marker of RV diastolic function should be corrected for the effect of through-plane motion to improve functional evaluation of the RV.

Total-body MR imaging in as little as 18 seconds.

Eighteen human subjects underwent echo-planar magnetic resonance (MR) imaging of the whole body at 1.5 T. A stack of axial images was obtained from the top of the head to the feet with gradient-echo, spin-echo, and inversion-recovery spin-echo pulse sequences by moving the patient table through the magnet isocenter. In all examinations, the subjects tolerated the procedure well and table motion was uniform. Image quality depended on careful setting of the transmit frequency, gain, and shims. Results were easily obtained and reproducible in all cases in as little as 18 seconds.