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Biomedical subjects

D C Newman

Publications and source records attributed to D C Newman.

At least 19 recordsLinked to original sources
PubMed2001

Planar strip array (PSA) for MRI.

Parallel, spatial-encoded MRI requires a large number of independent detectors that simultaneously acquire signals. The loop structure and mutual coupling in conventional phased arrays limit the number of coils and therefore the potential reduction in minimum scan time achievable by parallel MRI tchniques. A new near-field MRI detector array, the planar strip array (PSA), is presented that eliminates the coupling problems and can be extended to a very large number of detectors and high MRI frequencies. Its basic structure is an array of parallel microstrips with a high permittivity substrate and overlay. The electromagnetic (EM) wavelength can be adjusted with the permittivity, and the strip lengths tuned to a preselected fraction of the wavelength of the MRI frequency. EM wave analysis and measurements on a prototype four-element PSA reveal that the coupling between the strips vanishes when the strip length is either an integer times a quarter wavelength for a standing-wave PSA, or a half wavelength for a travelling-wave PSA, independent of the spacing between the strips. The analysis, as well as phantom and human MRI experiments performed by conventional and parallel-encoded MRI with the PSA at 1.5 T, show that the decoupled strips produce a relatively high-quality factor and signal-to-noise ratio, provided that the strips are properly terminated, tuned, and matched or coupled to the preamplifiers. Magn Reson Med 45:673-683, 2001.

Humans↗
PubMed2001

Ultra-low dose aprotinin decreases transfusion requirements and is cost effective in coronary operations.

BACKGROUND: The recommended dose of aprotinin has been shown to reduce blood loss and need for blood transfusions, but the cost precludes its routine use. This study was designed to determine whether a less expensive, ultra-low dose of aprotinin is effective when used in coronary artery bypass grafting with left internal mammary artery. METHODS: Patients (n = 202) were randomized to receive either placebo or aprotinin, 0.5 million KIU before incision and 0.5 million KIU during initiation of cardiopulmonary bypass. Differences in quantity of blood transfused were analyzed. Further groups were analyzed to account for the effect of aspirin. Multivariable analysis was performed to determine risk factors for transfusion. Direct costs of blood products and aprotinin were tabulated for each group. RESULTS: There was an important reduction in the proportion of patients transfused, and number of blood units transfused when aprotinin was given before coronary artery bypass grafting. These differences were even more important in patients on aspirin preoperatively. Independent predictors for increased number of transfusions were aspirin continued before operation, smaller body surface area, and the use of placebo instead of ultra-low dose aprotinin. There was no difference in morbidity between treatment groups. There was a reduction in direct costs associated with the use of aprotinin. CONCLUSIONS: These data support the routine use of aprotinin 1 million KIU in coronary artery bypass grafting with left internal mammary artery to reduce cost and transfusion requirements.

Adult↗
PubMed1988

Combined carotid and coronary artery surgery: a review of the literature.

This article reviews 41 different reports that describe various means of surgical management of coexistent carotid and coronary artery disease in almost 1,500 patients. Stroke is the major risk for patients undergoing myocardial revascularization in the presence of symptomatic carotid artery disease or an asymptomatic carotid bruit that reflects an ulcerative lesion or stenosis exceeding 75%. However, patients with asymptomatic carotid stenosis should not routinely undergo prophylactic carotid endarterectomy. Myocardial infarction is the major hazard in patients undergoing carotid endarterectomy who have coronary artery disease. This risk is magnified when the disease is silent. A high level of awareness and rigorous screening are essential in all patients suspected of having coexistent disease. Although a protocol for the management of these patients is important, individual assessment is essential.

Carotid Artery Diseases↗
PubMed1986

Plasma levels of cortisol, corticotropin, and beta-endorphin in patients with major depression.

Efforts to elucidate the abnormal mechanism of corticotropin and beta-endorphin in major depression have yielded conflicting findings. The relationship of plasma levels of cortisol, corticotropin, and beta-endorphin in 42 patients with a Research Diagnostic Criteria diagnosis of major depression, endogenous subtype was examined. Following the DST, 32 patients were nonsuppressors and 10 were suppressors. The differences between the median values for plasma corticotropin and beta-endorphin immunoreactivity were not significant at any time of measurement after the DST.

Adrenocorticotropic Hormone↗
PubMed1986

Emergency treatment for primary Ewing's sarcoma of the ribs.

Two cases of primary Ewing's sarcoma of the ribs necessitating emergency treatment are reported. Treatment consisted of a combination of radiotherapy, chemotherapy, and surgical therapy. The operation was urgent and early in one patient and delayed in the other. Both remain disease free 12 and 14 months after operation, respectively.

Adolescent↗
PubMed1984

Early and long-term results of coronary artery bypass grafting with severely depressed left ventricular performance.

The effects of coronary artery bypass grafting (CABG) on ventricular performance and long-term clinical status were studied in 18 consecutive patients with disabling angina pectoris and severely depressed left ventricular (LV) performance (ejection fraction [EF] 27 +/- 9%). All patients survived CABG, although 1 patient had a perioperative myocardial infarction. There was no change in LVEF at rest, 29 +/- 12%, in the other 17 patients. However, LVEF during peak exercise increased from 22 +/- 7% to 27 +/- 14% (p less than 0.05). The 17 patients were separated into 2 groups: those who increased their peak exercise LVEF by at least 10% (group A, 8 patients) and those who increased it by less than 10% (group B, 9 patients). Preoperatively, patients in group A had a higher LVEF at rest (p less than 0.001) and smaller end-systolic and end-diastolic volumes at rest (p less than 0.001) and during exercise (p less than 0.005). Preoperatively, the LVEF in group A decreased with exercise, from 36 +/- 4% to 27 +/- 5% (p less than 0.01), but was unchanged in group B (19 +/- 3% vs 17 +/- 4%, difference not significant). After CABG, patients in group A had a smaller increase in end-systolic volume with exercise than those in group B (13 +/- 7 vs 34 +/- 22 ml/m2, p less than 0.05), but the changes in end-diastolic volume with exercise were not significantly different. At 27 +/- 5 months after CABG, 5 of 8 patients in group A were asymptomatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1983

Clinical use of the dexamethasone suppression test for psychiatric disorders. Need for sensitive method for measuring corticosteroids and cautious interpretation of results.

The corticosteroid levels in 256 plasma samples from 112 patients with the clinical diagnosis of depression were assayed in two ways: by the routine method (sensitivity of 5 to 40 micrograms/dl) and by a newer, more sensitive method (sensitivity of 1 to 10 micrograms/dl). Of the 152 "true-negative" samples measured by the more sensitive method, 81 (53%) were reported as positive ("false-positive") by the routine method. The routine method does not yield accurate results on borderline levels of corticosteroids (5 to 7 micrograms/dl) for the dexamethasone suppression test for psychiatric disorders.

Adrenal Cortex Hormones↗
PubMed1981

The spine and surgical treatment in osteogenesis imperfecta.

In the osteogenesis imperfecta patient, spinal deformity should be expected, particularly in the severely affected nonambulator with chest deformity. Curves develop early (age five to six) and generally progress rapidly. Early bracing, although somewhat effective, may well compress the soft osteoporotic rib cage without controlling the spinal curvature. The pulmonary compromise created by the scoliosis is compounded by the chest cage deformity secondary to bracing. In the patient with severe disease (thin bones and numerous fractures), posterior correction and fusion, with or without Harrington instrumentation, is the preferred approach. This should be done early as the osteoporotic bone does not tolerate the hook forces well; the correction is correspondingly limited. The use of methylmethacrylate bone cement around the hook provides redistribution of forces and more stable fixation. In the patient with mild disease (thick bones and few fractures) treatment should be similar to that of patients with idiopathic scoliosis. The chest cage should be carefully observed to avoid deformity from placement of the lateral or posterior pad.

Bone Cements↗
PubMed1980

Complications with glutaraldehyde-preseved bioprostheses.

Between May, 1975, and May, 1979, 184 glutaraldehyde-preserved valve bioprostheses were implanted (92 aortic, 76 mitral, and 16 multiple). In the last two years, anticoagulants have been administered for the first three post-operative months. Of 176 patients, 10 patients had simultaneous coronary surgery, and five had previous valve surgery; endocarditis had occurred in eight patients before operation, and heart block existed in four patients. In the group of patients who underwent aortic valve replacements, there were four early deaths, all in patients with associated severe coronary artery disease. There was one late death in this group caused by bacterial endocarditis. In the group with mitral valve replacements, there were three early deaths, one related to massive thrombosis of the prosthesis, and two late deaths of unknown cause. Within the whole group, there were seven instances of significant thromboembolism, and nine instances of incompetence, including five mitral periprosthetic leaks which required reoperation. Three patients had stenosis of the mitral prosthesis. There has been no known incidence of intrinsic leaflet incompetence.

Adolescent↗
PubMed1979

Deep hypothermic arrest: observations on later development in children.

Thirty-two children were reviewed following closure of ventricular septal defect in infancy. Fifteen had undergone continuous perfusion and 17 had been subjected to core cooling followed by deep hypothermic arrest. Parental and professional evaluations of intellectual and motor development, at periods between 7 and 72 months following operation, suggest that there is a higher incidence of developmental abnormality in the subgroup treated with deep hypothermic arrest.

Cardiopulmonary Bypass↗