Donald L. Johnston

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The T2-weighted spin-echo technique is currently the most frequently used magnetic resonance imaging (MRI) method to visualize acute myocardial infarction. However, image quality is often degraded by ghost artifacts from blood flow, and respiratory and cardiac contractile motion. To enhance the usefulness of this technique for detailed characterization of(More)
A dynamic MR angiography technique, MR digital subtraction angiography (MR DSA), is proposed using fast acquisition, contrast enhancement, and complex subtraction. When a bolus of contrast is injected into a patient, data acquisition begins, dynamically acquiring a thick slab using a fast gradient echo sequence for 10-100 s. Similar to x-ray DSA, a mask is(More)
Knowledge of left ventricular ejection fraction has been shown to provide diagnostic and prognostic information in patients with known or suspected heart disease. In clinical practice, the ejection fraction can be determined by using one of the five currently available imaging techniques: contrast angiography, echocardiography, radionuclide techniques of(More)
In order to establish normal values for left heart dimensions by magnetic resonance imaging (MRI), electrocardiographically gated MRI was performed in 16 normal asymptomatic subjects using a whole-body 0.6-T superconducting magnet with a spin-echo pulse sequence and an echo delay (TE) of 30 msec. Images were oriented along the long and short axes of the(More)
ECG gating and monitoring during NMR imaging may be achieved reliably by applying the principles in this tutorial. In order to use the ECG signal both for triggering and for patient monitoring it must have a prominent R-wave, while at the same time must have little artifact from gradient switches or the Lorentz voltage across the aorta, and not be(More)
Proton (hydrogen-1) magnetic resonance imaging techniques have potential for the detection and characterization of changes associated with myocardial ischemia. Since image contrast is dependent on T1 and T2 relaxation times, we examined these parameters in a canine preparation of occlusion of the left anterior descending coronary artery. Of 16 dogs studied,(More)
A time-varying filter electrocardiographic gating device designed to reduce NMR-induced gradient artifacts during NMR imaging of the acutely ill cardiac patient is described. When used in conjunction with multiple electrocardiographic display monitors, accurate assessment of the electrocardiogram for morphologic changes and arrhythmias during all phases of(More)
Balloon dilation is effective in the immediate relief of obstruction due to unoperated coarctation of the aorta. However, the long-term benefits and complications of this procedure have not been established. Thirty-three patients underwent balloon dilation of unoperated coarctation using a percutaneous technique from November 1983 to December 1985. High(More)
The effects of inosine (INO) on substrate metabolism and rigor formation in ischemic myocardium were examined in isolated rabbit hearts. Metabolite content was assessed in tissue extracts by chemical analysis and in the whole heart by 13C and 31P nuclear magnetic resonance spectroscopy. In ischemic hearts metabolizing either [3-13C]pyruvate or(More)
Detection of myocardial rejection is difficult in patients with heterotopic heart transplantation because of the complex vascular anatomy present after transplant surgery. To determine whether magnetic resonance imaging might be useful for the assessment of heart rejection, eight patients with heterotopic heart transplantation were serially studied on 27(More)