Biomedical subjects
Publications and source records attributed to B Breyer.
Ultrasound of time average acoustic intensities between 0.5 and 3 W cm-2 is widely used in physiotherapy. A simple device for semiquantitative checking of output power and beam shape has been designed. The beam tester consists of an absorbing plate and a sheath liquid crystal thermometer for temperature distribution display. The ultrasonic beam is fed to the absorber through a simple water tank.
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46 persons have been tested in their ability to resolve grey tones in quantitatively callibrated transparencies. The transparencies were designed as phantoms matched in lightness and dynamics to TV monitors. The results show that on average not more than 9 grey tones can be counted in such phantoms and that dark gaps between the fields decrease the confidence of viewers.
Ultrasonic mammography has been compared with clinical examination and X-ray mammography. Results for the years 1977-79 are shown. A general purpose compound scanner and a custom made water delay bath are used. Twenty three percent of patients undergoing breast examination had an ultrasonic scan. The lowest limit for cyst detection in 4 mm diameter and for solid tumours about 10 mm. Comparison of the three methods shows an agreement of approx. 87% in benign lesions (i.e. agreement in the type of benign disease), and between 16/18 and 17/18 in malignant lesions (comparison of suspicion of malignancy only). As a result of these findings ultrasound is used in our department as a useful auxiliary method.
The feasibility of noise measurement in medical ultrasonic imaging has been studied and a theoretical evaluation of stochastic noise influence upon the perceived image has been undertaken. The influence of noise on a perceived image has been calculated by considering the light intensity perception characteristic of the human eye and it has been found taht the additive noise in the video signal pushes the small signals in the image towards the invisible (black) region. Impulse noise measurements of amplitude and time jitter have been set up using a standard water/CCl4 interface and pulse amplitude analysis to take into account the random nature of noise by distribution measurements.
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Correct patient positioning is essential for good aiming in radiotherapy. This can be achieved using back and side pointers, but sometimes these devices are not being used in order to simplify and make the positioning faster. The effects of such a simplification have been studied and measured. The results of this experimental study show that in thicker patients (over 24 cm) the use of back and side pointers is of great importance, because the variation of the patient thickness and angulation can significantly influence the aiming angles and dose percentages.
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The fetal abdomen was measured with an ultrasonic contact scanner in order to correlate abdomenal circumference and birth weight. A sample of 134 measurements was used to calculate a standard graph, which was then tested against a subsequent 280 measurements, giving a mean estimation error of 105 Gm. Head-to-abdomen circumference ratio measurements were used to assess the type of growth retardation.
Three hundred ninety fetal crown-rump measurements by ultrasound echography were performed in order to correlate the crown-rump length with gestational age between the sixth and fourteenth weeks of gestation. A blind trial in 58 patients showed a good correlation of ultrasonically determined age and menstrual age. A graph of normal values was designed and is currently being used in routine work.
The physical responses of LiF, film and a chemical dosemeter in high energy photon and electron beams has been studied. It is shown that the response for film and the chemical dosemeter does not change significantly up to 42 MeV, while for LiF it decreases by about 10%. Analysis of calculations and measurements showed that this decrease could not be explained by existing theories.
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Birthweight estimation has clinical importance in routine practice. The method used at present is the measuring of the circumference of the fetal abdomen at the umbilical vein level. The aim of this study was to check the theoretical hypothesis that a simple method of the trunk area measurement is a better birthweight estimator than the circumference measurement (when elliptic elongation is changed). In order to make this measurement simple, an ellypsoid approximation of the trunk cross section was used, i.e. the longest and the shortest diameters were measured. The area is proportional to the product of the diameters while the circumference is proportional to the sum of the two. The longest and the shortest diameters were measured in 200 patients up to two days prior to delivery, perpendicular to the spine at the umbilical vein level. The results have shown that in fetuses whose cross-section of the abdomen is elongated, the product of the longest and the shortest diameter gives a significantly better correlation to birthweight than their sum.