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The authors sought to define a method to use magnetic resonance (MR) to assess cardiac function by obtaining short-axis images of the left ventricle (LV) in humans. Sagittal and axial scout1H MR images were used in the protocol. The long axis of the LV was defined in both planes using the mitral valve and left ventricular apex as references. Based on this double angulation, the acquisition planes were created for a series of parallel short-axis images extending from the base to the apex of the left ventricular cavity. Cardiac images acquired with a fast-field echo technique, six slices with 16-20 phases per RR interval, were analyzed, representing the initial 75-80% of the cardiac cycle. For each slice, the endocardial border of the left ventricular chamber was manually traced. Using Simpson's rule, the total LV volume at a given phase was determined, considering the traced area, thickness, and position in three-dimensional space of each of the six constituent slices. The calculated volumes were plotted against time, and the stroke volume, ejection fraction, and cardiac output were determined. These parameters are clinically significant indices of cardiac function. Accurate and useful estimates of LV function can be obtained using MRI according to this protocol.

We report on our experience with the fat suppression technique of spectral presaturation with inversion recovery MR in imaging certain spinal disorders. This technique may assist in demonstrating or excluding the presence of fat within a lesion (such as lipoma, dermoid, teratoma) or within a normal structure (i.e., vertebral body or epidural space). The method can also be used to suppress normal fat (such as marrow or epidural fat) thus increasing the conspicuity of adjacent high signal intensity lesions seen on T1-weighted images (such as blood and contrast-enhancing tumors or inflammatory lesions).

The goals of this study were to determine whether abnormalities in phosphorus metabolism could be noninvasively detected using phosphorus-31 nuclear magnetic resonance spectroscopy in patients with dilated cardiomyopathy and left ventricular hypertrophy, and whether these patient groups could be distinguished from each other based on parameters obtained using this technique. Seventeen patients and 14 control subjects were studied using nuclear magnetic resonance spectroscopy. Spectra were obtained from the human heart at rest using 3-dimensional spectroscopic imaging as a localization technique. Data were acquired over an average volume of 48 cc in 26.3 minutes using a 2 tesla imaging and spectroscopy unit. The ratio of phosphocreatine to adenosine triphosphate was 0.89 +/- 0.88 (mean +/- standard error) in normal subjects and did not differ significantly in patients with dilated cardiomyopathy or left ventricular hypertrophy. A prominent peak in the phosphodiester region was seen much more frequently in patients with dilated cardiomyopathy, resulting in significantly higher ratios of phosphodiester to phosphocreatine (1.28 +/- 0.35) and phosphodiester to adenosine triphosphate (0.79 +/- 0.18) in this group compared to normal subjects (0.33 +/- 0.08 and 0.29 +/- 0.08, respectively). However, the various patient groups could not be reliably distinguished from each other based on spectral patterns. These studies demonstrate the feasibility of performing phosphorus-31 nuclear magnetic resonance spectroscopic imaging in patients with myocardial disease. The initial results indicate that, under resting conditions, the ratio of phosphocreatine to adenosine triphosphate is not consistently altered in patients with severe global cardiomyopathies or hypertrophy. Phosphodiesters are elevated in some patients with dilated cardiomyopathy, a finding that may signify abnormal phospholipid metabolism in this condition.

Previous studies have noted that myocardial blood flow and high energy phosphates are heterogeneous across the myocardial wall during ischemia. In order to determine whether differences in metabolites between the subendocardium and subepicardium could be detected using 31P magnetic resonance spectroscopy, the Fourier series window (FSW) experiment was implemented on a porcine model of graded regional ischemia. FSW experiments using a planar phantom showed a 46% improvement in localization to the subendocardium compared to a one-pulse experiment. Animal studies of graded ischemia demonstrated a gradient in the phosphocreatine to inorganic phosphate ratio in the myocardium that paralleled the gradient in blood flow. These studies demonstrate the ability of spatially localized 31P magnetic resonance spectroscopy to detect regional changes in myocardial high energy phosphates localized to the subepicardium and subendocardium.

A 13C-NMR study of the long-acting opiate antagonists naloxazone (I) and naltrexazone (II) and the long-acting opiate agonist oxymorphazone (III) revealed that these compounds are formed as mixtures of their anti and syn isomers. The less crowded anti isomer was found to be the major product in all cases (ca. 80%). N,N-Dimethyl derivatives of naloxazone (IV), naltrexazone (V), and oxymorphazone (VI), which are sterically more crowded than the corresponding unsubstituted hydrazones I-III, were formed as almost exclusively anti isomers. Pure anti isomer of II was obtained as a 1:1 complex with ethanol. No syn-anti equilibration was observed during the 13C-NMR experiment in any of the cases studied. The relevance of our finding about the syn-anti isomerism of the opiate hydrazones to the understanding of their interactions with the opiate receptor is discussed.

Magnetic resonance spectroscopy (MRS) is a valuable tool for the study of myocardial ischemia. Phosphorus (31P) MRS can detect changes in high-energy phosphates resulting from ischemia and has been used to determine the sensitivity of metabolic changes to ischemia as well as to investigate the metabolic factors important for myocardial dysfunction. The mechanisms mediating postischemic dysfunction have been investigated using 31P MRS, as have interventions to limit metabolic and functional damage from ischemia. These investigations have laid the groundwork for human cardiac studies. While abnormalities following myocardial infarction have been shown in man, further work must be performed to reliably acquire localized spectra under conditions of ischemia.