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D J Watmough

Publications and source records attributed to D J Watmough.

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

Ultrasound-induced damage of veins in pig ears, as revealed by scanning electron microscopy.

Pig ear veins have been treated in situ with ultrasound at a frequency of 750 kHz and intensity of 1.5 W cm-2 (spatial average) during which the temperature in the surrounding tissues rose to 52-54 degrees C. The veins were examined by scanning electron microscopy. Gaps developed between the endothelial cells, which showed many fine perforations in their membranes. Extensive blood clots were observed in which erythrocytes had become more spherical and showed damaged membranes. Effects on membranes were also found with HeLa cells heated to 50 degrees C, and have been previously described by others in heat-treated blood vessels.

Animals↗
PubMed1989

Applicators for generating ultrasound-induced hyperthermia in neoplastic tumours and for use in ultrasound physiotherapy.

Ultrasound in the low megahertz frequency range is used by physiotherapists to treat a variety of conditions. The treatments reduce swelling, reduce pain and increase movement at joints. Ultrasound is now also beginning to be used to treat malignant tumours. The tumours are heated to temperatures between 42 degrees and 45 degrees C, producing cellular damage, the extent of which is determined by the duration and number of treatments and 'concurrent' treatments by chemo and x-ray therapy. In the light of the results of computer simulation, we discuss in this paper: (a) The properties of a five-element divergent transducer array to treat large superficial neoplastic tumours. The field distribution measured by the Sarvazyan method will be described and also compared with that of computer simulation. The benefits of frequency wobbling will also be discussed. (b) The possibility of employing a multiple field applicator for use by physiotherapists to obviate the need for continuous movement of a small transducer of area approximately 5 cm2 over the affected area.

Humans↗
PubMed1988

'Son et lumière': a new combined optical and Doppler ultrasound approach to the detection of breast cancer.

X-ray mammography is the gold standard for diagnosis of lesions within the female breast. It is also recognized as the technique of choice for breast cancer screening in women over 50-years-old. Notwithstanding these important roles it has shortcomings in terms of limited sensitivity and specificity, especially in younger women. This paper describes the concept of a combined optical density and Doppler ultrasound method proposed initially as a supplement to mammography. A specially devised tissue compressor is also described. Results obtained using test phantoms and initial clinical studies are presented. Neovascularization at the advancing front of neoplastic lesions is believed to underlie detection of lesions by both telediaphanography and Doppler ultrasound.

Adult↗
PubMed1987

Preliminary results using computerized telediaphanography for investigating breast disease.

An instrument (telediaphanograph) for examination of the female breast has been developed which is optically based and carries no risk to the patient. Malignant lesions, which are strongly light absorbing, can be visualized by dark shadows cast on the superior aspect of the breast. The discriminating ability of telediaphanography for carcinoma has been investigated in relation to 129 patients with suspected breast disease. The sensitivity was found to be 0.94 and the specificity 0.89.

Breast Diseases↗
PubMed1986

A new motor-driven surgical probe and its in vitro comparison with the Cavitron Ultrasonic Surgical Aspirator.

The Cavitron Ultrasonic Surgical Aspirator (CUSA) has been applied in neurosurgery for several years, but its mode of action is not yet clear and its efficiency at removing soft tissue has not been quantified. We describe here how we have measured the rate of removing soft tissue per unit time, taking ox-liver tissue as the test material. A motor-driven vibrator/aspirator has been developed in our laboratory. It has permitted us to examine the effect of varying independently frequency, amplitude of the vibration, and suction pressure on the removal rate. The results of this investigation show that beyond a certain tip acceleration amplitude (about 100 g) the removal rate does not increase significantly. Also the removal rate is more or less independent of vibration amplitude within the range between 300 micron and 1 mm. Our in vitro experiments with the new probe show that a tip acceleration of about 100 g is enough to remove ox-liver tissue and then the rate of removal is comparable to that obtained with the CUSA operating at maximum vibration amplitude. Analysis of the particle size of the debris collected from CUSA and from our motor-driven device shows that the particle size distribution is similar over the range of 0.5 micron less than d less than 250 micron.

Animals↗
PubMed1983

Transillumination of breast tissues: factors governing optimal imaging of lesions.

Lesions within the female breast may be observed in a darkened room when the tissues are transilluminated by white light. Telediaphanography is a method of recording that can reproduce images of lesions in monochrome or pseudocolor in real time. A model system is described that permits measurement of spatial resolution.

Breast Neoplasms↗
PubMed1982

A light torch for the transillumination of female breast tissues.

The breast can be examined by transillumination with white light. The tissues transmit more light in te red and infrared part of the spectrum than in the blue. Images of the breast are normally recorded on colour infrared film. An alternative to photography is the use of a television camera sensitive to the near infrared, which can demonstrate lesions on a monitor in real time. This paper examines the limitations of the type of light torch used in recent investigations and describes a new version which should permit detection and imaging of smaller lesions.

Breast Diseases↗
PubMed1982

Diaphanography: mechanism responsible for the images.

Preliminary measurements showed that spectrophotometry of samples of tissue taken at operation from the female breast demonstrated no obvious correlation between transmission coefficient and pathology, except that thicker samples tended to transmit less light than thinner samples. However all the samples had absorption minima corresponding to the bands of oxyhaemoglobin. This simple fact led to the speculation that the density of blood in the tissues, (number of red cells per unit volume) was the factor giving rise to different colours of breast tissues and of breast pathology observed upon transillumination with white light in vivo. Examination by infrared colour photography and by spectrophotometry of transilluminated samples of blood diluted with normal saline confirms that the observed colour is dependent on red cell concentration.

Breast Neoplasms↗
PubMed1982

A study of ultrasound-induced microstreaming in blood vessels of tropical fish.

Tails of the tropical fish Xiphophorous maculatus have been studied by light microscopy during irradiation with continuous wave 780 kHz ultrasound. Acoustically-induced microstreaming was observed in blood vessels during irradiation with peak intensities above 1 Wcm-2. The microstreaming took the form of rotation of single blood cells and clusters of a few cells and occurred at positions close to the edges of cartilage rods supporting the tail. Streaming was detected initially in vessels 5-10 micrometers across where it impeded blood flow, and as the blood velocity fell it was also observed in larger vessels 15-30 micrometers across. Measurements of rotation speed showed that streaming velocity increased with intensity. The microstreaming is thought to result from radiation torque created by the complex standing wave field produced by reflection from the irradiation tank window and the cartilage rods, or by vibration of the rods in the sound field.

Animals↗
PubMed1981

The effects of some physical factors on the production of hyperthermia by ultrasound in neoplastic tissues.

A one-dimensional and a three-dimensional computer model have been built in order to study the importance of blood flow and ultrasonic absorption in tissues during local hyperthermia. The decreased blood flow in the interior of certain tumours and possibly the increased ultrasonic absorption of the malignant tissue in some cases may cause selectively higher temperatures inside the tumours though the heat input is the same as in the surrounding tissues. Also, the vasodilation of blood vessels in normal tissues as a response to heat causes a therapeutically useful temperature difference. These blood flow differences can lead to enhanced effects during sonication to produce hyperthermia in the tumour. The inhomogeneity of blood flow in the tumour causes a non-uniform temperature distribution leaving the well-perfused cells in the advancing front at a much lower temperature than the cells in the necrotic centre. Thus, the combination of local hyperthermia with radio-and chemotherapy seems to offer the most attractive means of destroying malignant tissue.

Fever↗