No abstract

In the examination of intact muscles by 31P nuclear magnetic resonance spectroscopy, a number of signals have been detected in the phosphodiester region (-0.5 to 0.5 ppm) of the spectrum which could not be correlated with the known common phosphates of muscle tissue. These signals arise from perchloric acid extractable compounds with several common chemical properties, one of which is a ready solubility in nearly anhydrous ethanol solutions. A component contributing to the major resonance has been identified as glycerol-3-phosphorylcholine. This characterization is based on both 31P nuclear magnetic resonance and chromatographic data.

The risks to patients with metal surgical implants who are undergoing nuclear magnetic resonance (NMR) imaging and the artifacts caused by such implants were studied. Twenty-one aneurysm and other hemostatic clips and a variety of other materials (e.g., dental amalgam, 14 karat gold) were used. Longitudinal forces and torques were found to be exerted upon 16 of the 21 clips. With five aneurysm clips, forces and torques sufficient to produce risk of hemorrhage from dislocation of the clip from the vessel or aneurysm, or cerebral injury by clip displacement without dislodgement were identified. The induced ferromagnetism was shown to be related to the composition of the alloys from which the clips were manufactured. Clips with 10-14% nickel are evidently without sufficient induced ferromagnetism to cause hazard. The extent of NMR imaging artifacts was greater for materials with measurable ferromagnetic properties, but metals without measurable ferromagnetism in our tests also resulted in significant artifacts. Dental amalgam and 14 karat gold produced no imaging artifacts, but stainless steels in dentures and orthodontic braces produced extensive artifacts in the facial region.

SUMMARY Determination of myocardial infarct size is important for clinical management of patients with ischemic heart disease and for research on limiting infarct size. Nuclear magnetic resonance (NMR) imaging permits tomographic depiction of the distribution of mobile tissue protons. NMR images have demonstrated high spatial resolution and contrast. To evaluate the potential of this technique in measuring myocardial infarct size, NMR imaging was performed in six canine hearts excised 24 hours after circumflex coronary artery ligation. Before sacrifice, the dogs received i.v. manganous chloride (0.05 mmol/kg). After NMR imaging, the hearts were sectioned and the myocardial slices were stained with triphenyl tetrazolium chloride. The pathologically determined infarct size was compared with the infarct size measured by NMR imaging. The correlation was good (regression line slope 1.06; r = 0.94). We conclude that NMR imaging with paramagnetic contrast agents can be used to determine infarct size in excised hearts.THE ACCURATE determination of myocardial infarct size has been a topic of major interest over the past decade. Previous work has demonstrated that prognosis depends upon infarct size."A Careful measurement of infarct size is important in determining the efficacy of interventions designed to limit infarction. Methods used clinically to quantify infarct size rely on assessment of wall motion (radionuclide angiography or ultrasound), myocardial perfusion (thallium-201), radioisotopic labeling of necrotic myocardium (technetium-99m stannous pyrophosphate), or release of intracellular enzymes into the bloodstream (CK-MB). Nuclear magnetic resonance (NMR) imaging is a noninvasive, high-resolution technique that uses no ionizing radiation and allows tomographic depiction of the distribution of mobile tissue protons. Image contrast can be enhanced by using paramagnetic substances that are markers of myocardial blood flow and alter NMR properties of tissue in their distribution. We have used NMR imaging with paramagnetic ion contrast enhancement to detect acute myocardial infarction in excised canine hearts.5 To evaluate the potential utility of NMR imaging in quantifying myocardial infarction, we studied a canine model of myocardial infarction with paramagnetic ion contrast enhancement using manganous ion. Methods Infarct ProductionSix adult mongrel dogs of either sex that weighed 15-20 kg were anesthetized with intravenous pentobarbital, 60 mg/kg (Veterinary Lab Inc.), intubated, and ventilated with 100% oxygen by positive pressure ventilator (Bird Corp.). The pericardium was opened through a left lateral thoracotomy, and the left circumflex coronary artery was isolated and ligated with 3-0 silk suture. The thoracotomy was closed and pleural air was evacuated. One gram of cephaloridine (Eli Lilly and Co.), and 1 g of procainamide (E.R. Squibb and Sons) were administered intramuscularly. The dogs were allowed to recover. Twenty-four hours after coronary ligation, the dogs were reanesthetized with i.v. pentobarbita...

Nuclear magnetic resonance is a new method for assaying the content of phosphate metabolites in intact tissues. Its nondestructive nature allows simultaneous and repeated determinations of these compounds with a minimum perturbation of tissue. Changes in the concentrations of the phosphates as a function of time characterize the metabolic machinery of the tissue and reveal alterations in enzymic activity that result from drug treatment or disease. The entire phosphate profile shows differences between normal and diseased muscle which should be of diagnostic value. Further, by examining phosphate profiles we detected a family of chemical compounds that were not previously known to exist as major constituents in muscle. Of these, two have been isolated and one has been identified as glycerol 3-phosphorylcholine. Finally, shifts in the positions of resonances monitor the internal environment of the living system, its hydrogen ion concentration, the complexing of alkaline earth metals with ATP, and compartmentalization within the cell.