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Biomedical subjects

R W Gill

Publications and source records attributed to R W Gill.

34 records · Page 2Linked to original sources
PubMed1988

Transvaginal pulsed Doppler ultrasound assessment of blood flow to the corpus luteum in IVF patients following embryo transfer.

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.

Corpus Luteum↗
PubMed1987

Splenic blood flow measurements by Doppler ultrasound: a preliminary report.

Splenic blood flow and splenic volume were measured by Doppler and cross sectional ultrasound in 72 human subjects consisting of 61 patients with splenomegaly and 11 normal subjects. This non-invasive and relatively simple method yielded satisfactory results in 76% of the subjects studied; failures were due to obesity, debility, distorted vascular anatomy, and excessive gas in the stomach. These preliminary results suggest that the Doppler ultrasound technique is a practical clinical method for measuring splenic blood flow.

Adult↗
PubMed1986

Quantitative sonography.

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.

Doppler Effect↗
PubMed1981

Fetal umbilical venous flow measured in utero by pulsed Doppler and B-mode ultrasound. I. Normal pregnancies.

Umbilical venous blood flow was measured with a pulsed Doppler unit, which was used in combination with a B-mode ultrasonic imaging system to permit location of the umbilical vein and measurement of its cross-sectional area. The accuracy and limitations of the method are discussed. Forty-seven normal fetuses with gestational ages ranging from 22 weeks to term were studied on a total of 61 occasions. Flow increased with gestational age until 36 weeks, was maximal between 37 and 38 weeks, then decreased during the last 2 weeks of pregnancy. Flow per unit of fetal weight was constant during pregnancy until 36 to 37 weeks, when a reduction occurred.

Blood Flow Velocity↗
PubMed1976

Microtelemetry--the use of integrated circuits in biotelemetry.

Integrated circuits are now in widespread use in such equipment as computers and consumer electronics, where their low cost, high reliability and small size are their principal advantages. In biotelemetry, small size is of particular importance. Here the use of integrated circuits allows systems of considerable complexity to be produced with high reliability in small packages. Commercial integrated circuits with the low power consumption and low voltage operation needed for biotelemetry are now becoming available; some such applications are briefly reviewed. In addition, examples of the use of custom integrated circuits in biotelemetry, and of the use of integrated circuit technology to build unique transducers and assemblies, are described.

Forecasting↗
PubMedDate not supplied

Percutaneous control of a portacaval H-graft: description of a new device and its initial clinical application.

A percutaneously-controlled inflatable cuff which can change the diameter of a portacaval H-graft has been developed and used in 10 patients. When inflated, the cuff narrows the H-graft to increase portal pressure and reduce shunting. Use of the cuff has been of clinical significance in 3 of 7 long-term surviving patients. Narrowing the shunt improved the clinical state in 2 patients with encephalopathy, and reopening a closed shunt improved ascites in the third patient. Duplex ultrasound and deep Doppler have demonstrated an alteration of hepatic portal blood flow following inflation of the cuff after 6 months. It is concluded that further development of this controlled portacaval H-graft is warranted.

Adult↗
PubMedDate not supplied

Umbilical venous flow in normal and complicated pregnancy.

Using pulsed Doppler and B-mode ultrasonic techniques, umbilical venous flow has been measured for the first time under essentially normal physiological conditions. In normal pregnancies, the flow per unit fetal weight remains essentially constant at 110-120 ml/min/kg for most of the pregnancy. In pregnancies with complications, however, abnormally low or high flow values are frequently observed. Low flow values correlate strongly with retarded fetal growth, and with increased incidences of antenatal hypoxia, neonatal morbidity and neonatal death. In some circumstances high flow values suggest the presence of a compensatory mechanism. The results reported here suggest that umbilical flow can be used to separate all fetuses, whether growth retarded or not, into "low risk" and "high risk" groups with better sensitivity and accuracy than existing methods. In addition, low flow values have been measured an average of one week before growth retardation or fetal hypoxia were indicated by the conventional methods. A possible strategy for the diagnostic use of umbilical flow measurements is outlined.

Blood Flow Velocity↗
PubMedDate not supplied

Measurement of blood flow by ultrasound: accuracy and sources of error.

Doppler ultrasound has now developed to the point where the rate of flow of blood in a given vessel can be measured with appropriate instrumentation. The theoretical basis of Doppler flow measurement is reviewed in this paper, with particular emphasis on the potential and actual sources of error. Three distinct approaches are identified, and the strengths and weaknesses of each discussed. The separate errors involved in estimating the vessel cross-sectional area, the angle of approach, and the Doppler shift are analyzed, together with the question of the uniformity of scattering from the blood. In vivo and in vitro tests of the accuracy obtained using a number of Doppler flow measuring instruments are then reviewed. It is concluded that the Doppler methods are capable of good absolute accuracy when suitably designed equipment is used in appropriate situations, with systematic errors of 6% of less. There are, however, considerable random errors, attributable primarily to errors in measuring the cross-sectional area and the angle of approach. Repeating the measurement of flow several times and averaging the results can reduce these random errors to an acceptable level.

Blood Flow Velocity↗
PubMedDate not supplied

Knowledge-based method for segmentation and analysis of lung boundaries in chest X-ray images.

We present a knowledge-based approach to segmentation and analysis of the lung boundaries in chest X-rays. Image edges are matched to an anatomical model of the lung boundary using parametric features. A modular system architecture was developed which incorporates the model, image processing routines, an inference engine and a blackboard. Edges associated with the lung boundary are automatically identified and abnormal features are reported. In preliminary testing on 14 images for a set of 18 detectable abnormalities, the system showed a sensitivity of 88% and a specificity of 95% when compared with assessment by an experienced radiologist.

Algorithms↗