Biomedical subjects
Publications and source records attributed to G Kossoff.
Ultrasonic beams are distorted during propagation between two media with different velocities if the traversed interface is curved within the ultrasonic beamwidth. The distorting effects of various interfaces on a beam generated by a multi-element transducer are analyzed and a technique to reduce these by controlling the time delays to the individual elements is presented.
A form of range ambiguity in Doppler ultrasound has been identified. It occurs when a high pulse repetition frequency (prf) is used with a superficial range gate. "Phantom" range gates are then generated at depths beyond the desired range gate, and these may produce artifactual signals. Extremely high prf values should not normally be used, and duplex machines should be programmed to display phantom range gates wherever they fall within the displayed field of view.
As ultrasonic beams propagate through tissues, there is a loss of energy by absorption, reflection and scattering. This loss is displayed in the image as shadowing and is an important sonographic sign for the detection and diagnosis of breast disease. Shadowing may result because of reflection of most of the energy by a large impedance discontinuity. The degree of shadowing by interfaces is dependent on their size relative to the ultrasonic beam. Interfaces smaller than the beam may allow sufficient energy to bypass the reflector to permit good visualization of posterior detail. Shadowing may also result from beam spreading due to refraction. Attenuation is the acoustic parameter which specifies total loss of energy and is due predominantly to absorption. Echogenicity is determined by the reflecting and scattering characteristics and therefore attenuation and echogenicity should be regarded as independent entities in the interpretation of breast images.
The waveforms of vessels supplying the ovaries of women on an in-vitro fertilization (IVF) programme were studied using transvaginal B-mode and Doppler ultrasound. There were 125 scans recorded in 65 women at weekly intervals from 3 days after embryo transfer or 5 days after gamete intrafallopian transfer (GIFT) until confirmation of pregnancy or onset of menses. At each examination the signals obtained from vessels supplying the ovaries were recorded and quantified using a resistance index (RI). Fifteen patients became pregnant of whom one has subsequently miscarried. There was a highly significant difference in the RI values between patients who became pregnant and those who did not; no patient who became pregnant had a RI greater than 0.5. Oestrogen to progesterone ratios were calculated in the subgroup of non-pregnant patients and there was no correlation between these values and the RI values. This new technique enables prediction of IVF treatment failure earlier than has been reported previously and may reflect the inadequacy of the corpus luteum.
The aim of this study is to determine whether sister chromatid exchange (SCE) frequency increases in human lymphocytes that are exposed to pulsed ultrasound conditions within the range typically employed in ultrasound Doppler measurements of fetal blood flow. Whole blood diluted with culture medium was exposed in vitro to 3.1 MHz pulsed ultrasound at spatial peak pulse average (SPPA) intensities from 15 to 135 W/cm2. Insonation for 5 min did not significantly alter the base level frequency of SCEs compared to that observed in sham-insonated controls. To avoid missing an effect, due to differing sensitivities of the division stages within the mitotic cycle, insonation was also applied for 24 hr to include one complete cell division cycle. No change in SCE was observed after this extended insonation at SPPA intensity of 33 W/cm2.
The review presents a perspective on ultrasonic techniques which place numerical values on properties of tissue or physiological function. Two distinct approaches to tissue characterisation are identified and the various techniques employed are reviewed. The range of Doppler techniques currently in use or under development are described. The potential roles of the various techniques are discussed, using clinical results from the Ultrasonics Institute as a basis. Attenuation measurements show a considerable spread in results, but sound speed appears to correlate closely with the degree of fibrosis in liver and spleen. Other methods have been found useful in specialised areas. The use of pulsed Doppler with a resolution cell sufficiently large to encompass the entire vessel, in conjunction with B-mode imaging to determine geometry, permits volumetric flow measurements to be made in deep vessels and reveals previously inaccessible physiological data. The use of analysis techniques to provide quantitative information in the physiological state or function of tissue promises to add a new dimension to diagnostic ultrasound.
Explore the source record for details and available documents.
At 1188 patients we investigated the value of sonography of the breast in the detection of malignancies. We used 2 automatic multitransducer water-bath scanners, at first the 3 MH Octoson, then System 1, a dedicated 4 MH water-bath breast scanner which allows for compound and simple scans in any scanning plane. The sensitivity for detection of 63 malignancies was 87%. Other pathologies were 18 fibroadenomas, 160 cysts, 6 abscesses, 2 fatty necroses, 2 papillomas, 9 prostheses, one of them broken. The difficulties associated with differential diagnosis in breast sonography are discussed in detail.
Common carotid artery (CCA) blood flow was measured noninvasively with a pulsed Doppler duplex scanner modeled after the Octoson (Ultrasonics, Inc., No. Yonkers, N.Y.). The aim of the study was to determine normal values and to assess the accuracy of CCA flow as a predictor of internal carotid artery (ICA) stenosis. One hundred one people who did not have disease were studied; the overall mean flow rate was 395 +/- 79 ml/min (mean +/- S.D.). There was no significant correlation with age, height, or body surface area but there was with body weight (p less than 0.05). A statistically significant difference was evident between men (424 +/- 88 ml/min) and women (371 +/- 62 ml/min) (p less than 0.001). The intrasessional variation (S.D./mean) was 13% and the intersessional variation, 16%. No significant difference was seen between the sides. Ninety-two patients who had carotid angiography were studied and the flow rates compared with the degree of ICA stenosis on each side. The flow rate for mild ICA stenosis (1% to 39%) was 404 +/- 109 ml/min, for moderate stenoses (40% to 69%), 390 +/- 91 ml/min, and for severe stenoses (70% to 99%), 351 +/- 109 ml/min. There was a significant difference in flows only between mild and severe grades of stenosis of the ICA (p less than 0.01). With unilateral stenosis, comparison of flow values in the normal and affected sides showed the greatest discriminatory power when the absolute difference of flow values was taken (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)
This article describes the preliminary findings of a Duplex ultrasound technique that enables the patency of the portal circulation and portosystemic shunt patency to be determined. In addition, the equipment allows the noninvasive measurement of quantitative rates of blood flow in these vessels. Portal vein flow was 952 +/- 273 ml/min in 10 normal subjects after an overnight fast and increased by 50% at 30 minutes in response to a standard 660-calorie liquid meal. Thirteen portosystemic shunts were scanned, and hemodynamic information was obtained from 10. Three of the four patients who had a Warren shunt performed 3 to 4 years earlier had portal vein occlusion. There is evidence of an increase in flow through the Warren shunt on feeding, suggesting a hemodynamic connection to the mesenteric side of the circulation. The apparatus, technique of examination, and the characteristics and difficulties with particular types of shunts are described.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The UI Octoson can provide accurate compound and simple scan cross sectional views of the heart. Sections taken in the transverse, sagittal, and other planes normal and parallel to the long axis of the heart are useful for providing full information that may be obtained by the examination. The views allow the visualization and measurement of most major structures of the heart, giving a more complete description of the geometry of the heart.
Patients with orbital varices form a diagnostically important group of those referred for ultrasonic study of orbital proptosis. Two cases are presented in which diagnosis of dilated orbital blood vessels was established by B scan ultrasonography. The echographic appearance of normal and dilated orbital vessels is discussed.
Explore the source record for details and available documents.
The method of describing acoustic output generated by pulsed equipment has not been fully formalized and is often inadequately specified. This paper discusses the terms that we have found useful to specify the acoustic output generated by pulsed diagnostic equipment and proposes additional terms that allow a more complete description of irradiation dosage. The application of the proposed specification is illustrated by measurements made on a typical contact echoscope.
An ultrasonic window to the upper abdomen is creasted by (a) filling the fasting stomach with methylcellulose suspension, (b) administering glucagon intravenously, and (c) examining the patient prone. Glucagon relaxes the gastric musculature and the prone position allows the stomach gas to rise to the fundus. This enables assessment of the relationships of the stomach to adjacent structures and permits display of structures forming the stomach bed. The equipment used was a commercially available water-delay system with wide-aperture focused transducers. The system gives good resolution and allows the gastric musculature to be distinguished from the mucosa and its overlying mucus.