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Biomedical subjects

W Stewart

Publications and source records attributed to W Stewart.

At least 91 records · Page 5Linked to original sources
PubMed1983

Risk factors in schizophrenia: season birth in Maryland, USA.

The association between the risk for schizophrenia and season of birth was studied using a standard actuarial life table method. This method of analysis eliminates the possibility of the previously described statistical artifacts from the data. An increased risk for schizophrenia for winter born individuals was demonstrated. The analysis also supported the hypothesis that season of birth is associated with an increased risk for a subtype of schizophrenia.

Actuarial Analysis↗
PubMed1983

Aspects of the design of performance measuring test objects.

In order for medical ultrasonics to achieve a high and universal standard of systematic and scientific implementation, methods for assessing the imaging performance of scanners must be developed which are both rigorous and simple to use. The difficulty that has been found in this task comes from the complex interaction of the performance parameters. Measurements of parameters should not be presented in mutual isolation. Further, the performance of a scanner, as measured using electronically generated external stimuli, might not be generalised to realistic acoustic situations. If the assessment is to be relevant to the clinical situation these factors must be taken into account. Test objects employing tissue mimicking materials provide the simplest, and possibly the only way to achieving this. In this paper the authors' designs for such test objects together with an indication of a comprehensive test system are presented.

Acoustics↗
PubMed1982

A simple calibration and evaluation phantom for ultrasound scanners.

It is argued that performance measuring phantoms containing tissue mimicking material should be considered as a series of combined test features. Each test feature should be capable of yielding quantitative data if desired and the inclusion of a comprehensive set of such features in a single phantom would allow the mutual interdependence of performance parameters to be assessed. These ideas are demonstrated in scans of several phantoms which utilise new features for measuring grey scale performance and relative beam width orthogonal to the scan plane. The relation of this work to research on low contrast detectability of lesions is discussed.

Biophysical Phenomena↗
PubMed1976

Carcinoembryonic antigen in colorectal practice: report of three cases.

CEA, in combination with the time-honored barium enema, sigmoidoscopy, rectal examination with guaiac determinations, and thorough clinical history, is a useful tool for the colorectal surgeon in following the progression of disease in both colorectal carcinoma patients and patients who have certain premalignant conditions. In this high-risk group of patients, CEA determinations as well as colonoscopy are becoming increasingly useful. That tumors on the left side are associated with higher CEA levels than those on the right side, due to vascular invasion or the grades of the tumors, and that often CEA antigenicity and severity of symptoms in ulcerative colitis correlate well, are emphasized. Finally, following total colectomy in five cases of ulcerative colitis, all CEA titers decreased to the normal range and have remained there.

Adult↗