| PMR | patient meta-record; perinatal mortality rate; periodic medical review; physical medicine and rehabi... |
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| PR | by way of the rectum [Lat. per rectum]; far point [of accommodation] [Lat. punctum remotum]; palindr... |
| PRE | photoreacting enzyme; physician's report of examination; pigmented retinal epithelium; preplacement ... |
| PRR | proton relaxation rate; pulse repetition rate |
| RARE | rapid acquisition with relaxation enhancement |
| isovolumic relaxation | That part of the cardiac cycle between the time of aortic valve closure and mitral opening, during which the ventricular muscle decreases its tension without lengthening so that ventricular volume remains unaltered; the heart is never precisely isovolumetric (vs. Isovolumic) except during long diastoles with a midiastolic period of diastasis. Synonym: isovolumetric relaxation. (05 Mar 2000) |
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| endothelium derived relaxation factor | <biochemistry> This compound is produced from L arginine by the enzyme nitric oxide synthase. Acts as a potent vasorelaxant via elevation of intracellular cGMP in vascular smooth muscle. Synthesis of nitric oxide is not confined to endothelium, isoforms of nitric oxide synthase are also found in brain, neutrophils and platelets. Synonym: endothelium derived relaxation factor. Acronym: NO (29 Dec 1997) |
| transverse relaxation | In nuclear magnetic resonance, the rapid decay of the nuclear magnetization vector at right angles to the magnetic field after the 90 |
| longitudinal relaxation | In nuclear magnetic resonance, the return of the magnetic dipoles of the hydrogen nuclei (magnetization vector) to equilibrium parallel to the magnetic field, after they have been flipped 90 |