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Biomedical subjects

G ter Haar

Publications and source records attributed to G ter Haar.

At least 37 records · Page 2Linked to original sources
PubMed1989

Pregnant adolescents in rural Transkei. Age per se does not confer high-risk status.

No significant differences were found when the obstetric outcome of 515 rural adolescents aged 16 years and younger was compared with that of an equal number of matched young adult rural women aged 20-29 years in respect of booking status, postpartum haemoglobin content, operative/instrumental delivery, mean neonatal birth mass and the incidence of infants weighing under 2,500 g. These results support the conclusions of recent studies in Australia and the USA that adolescence per se confers no increased obstetric risk. On the other hand, unwed motherhood (among all age groups) constitutes a most disturbing social trend in black rural society and this, rather than teenage pregnancy as such, ought to be the focus of concern for social workers and the medical profession.

Adolescent↗
PubMed1989

Biophysical characterisation of diagnostic ultrasound equipment--preliminary results.

The use of diagnostic ultrasound can be justified if it can be shown to provide only negligible or small risk while giving good benefit to the patient. In the absence of biological evidence, one way of assessing a new (or existing) piece of diagnostic equipment would be to predict the biophysical changes (i.e. heat and cavitation) that may be produced by its ultrasonic fields in tissue. An assessment of risk may then be made from our knowledge of thermal and cavitational biology. To this end, this study has sought to measure temperature rise, bubble formation, sonoluminescence and acoustic streaming arising from clinical transducers that have been carefully calibrated using a Beam Calibrator, and to determine whether there is good correlation between measured acoustic parameters in water and any of these biophysical characteristics. The results are inconclusive.

Acoustics↗
PubMed1989

High intensity focused ultrasound--a surgical technique for the treatment of discrete liver tumours.

The treatment of discrete liver tumours is often a difficult clinical problem. High intensity, focused ultrasound may provide one form of therapy for such disease. The ability to focus ultrasound precisely on a predetermined volume allows the possibility of selective tissue destruction at this position without damage to intervening tissues. We have investigated this both in vivo and in excised liver samples in vitro. Quantitative and qualitative studies have been carried out on the relationship between the ultrasonic exposure and the lesion shape, position and volume. In addition, the highly echogenic nature of the ultrasonic lesion has been studied, in an attempt to determine whether 'real time' observation of the extent of tissue damage is feasible.

Animals↗
PubMed1988

An investigation into the combined effects of X-irradiation and 3MHz ultrasound-induced hyperthermia on pig skin.

The thermal enhancement of radiation-induced damage in pig skin has been investigated. Heating at 43 degrees C for 60 min was produced by a scanned 3MHz ultrasound transducer, immediately after single doses of X rays. The ED50 values for the dermal reactions of dusky/mauve erythema and necrosis after irradiation alone were 18.6 +/- 0.5 Gy and 20.5 +/- 0.4 Gy, respectively. The reduction in the ED50 values to 15.3 +/- 0.4 Gy and 17.7 +/- 0.5 Gy after irradiation plus heating was significant and suggested a thermal enhancement ratio (TER) of between 1.15 and 1.22. These TER values were within the range obtained in both pig and rat skin using other 'dry' heating methods. This would suggest that the non-thermal effects of ultrasound do not influence the thermal enhancement of x-irradiation damage.

Animals↗
PubMed1987

The use of ultrasound by physiotherapists in Britain, 1985.

A questionnaire was sent out to physiotherapists in Britain in 1985 requesting information about their use of therapeutic ultrasound. Replies were obtained from National Health Service (NHS) departments and private practitioners. Twenty percent of all physiotherapy treatments in NHS departments involved ultrasound, and 54% of all private treatments. Information was obtained about the range and pattern of ultrasonic frequencies and intensities used. The conditions for which ultrasound is used as a treatment modality are listed, as are the contraindications for its use.

England↗
PubMed1985

The induction of hyperthermia by ultrasound; its value and associated problems: II. Scanned-plane transducer.

A system is described in which large superficial areas of tissue may be heated using a single plane ultrasonic transducer scanned in a raster fashion. The shape of the heated area is determined by the movement of a microswitch which is activated when it strikes the rigid edge of a hole of the required shape cut in a plate. Temperature profiles are presented. They are measured in pig thigh muscle, and are generated by 0.75 and 3.0 MHz ultrasound scanned over areas up to 7 cm X 7 cm. It was found that uniform heating could be obtained over the area scanned by the central portion of the ultrasonic beam.

Animals↗
PubMed1983

The induction of hyperthermia by ultrasound: its value and associated problems. I. Single, static, plane transducer.

The temperature distributions that may be achieved in mammalian tissues by ultrasonic heating have been studied. Thigh muscle of Large White pigs has been irradiated with 0.75 and 3.0 MHz ultrasound at spatial average intensities in the range 1.5-3.0 W cm-2 in both pulsed and continuous modes of delivery. Resultant temperature profiles are described and some of the problems arising are discussed.

Animals↗
PubMed1980

Ultrasonic irradiation of mammalian cells in vitro at hyperthermic temperatures.

Suspensions of V79 cells and HeLa cells have been irradiated with continuous 3 MHz ultrasound at a spatial average intensity of 3W cm-2. This irradiation condition did not give rise to cell lysis. When the cells were irradiated with ultrasound for up to six hours at 37 degrees C no cell killing was observed. However, at temperatures in the hyperthermia range 42--45 degrees C the increase in cell killing that resulted from the irradiation was greater than that which could be attributed to its heating effect alone.

Animals↗