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Biomedical subjects

T D Hawkins

Publications and source records attributed to T D Hawkins.

At least 19 recordsLinked to original sources
PubMed1989

The accuracy of volumetric measurement of high-grade gliomas.

To assess the accuracy of volumetric measurement of high-grade intracranial gliomas by computed tomography (CT), the scans of 26 patients were studied retrospectively. Twenty patients had only pre-treatment scans while six had scans both before and after chemotherapeutic treatment. Tumour volumes were measured separately by two observers, each on two occasions. A significant intraobserver variation in volumetric measurement was encountered, as well as a systematic variation between the observers; one radiologist consistently reading higher than the other. The after treatment readings were more variable than the pre-treatment readings, and most changes in tumour volume following treatment were obscured by the intra-observer variation. This study provides further evidence of the limitations of volumetric measurement as a means of assessing the response of high-grade gliomas to treatment.

Brain Neoplasms↗
PubMed1989

Subarachnoid haemorrhage of unknown cause: a long term follow-up.

Three hundred and sixteen patients who suffered a subarachnoid haemorrhage of unknown cause were followed up by questionnaire after 2 to 23 years, the average interval being 10 years. Two hundred and fifty one (79.5%) are known to be alive, 49 (15.5%) had died, and 16 (5%) patients were untraceable. The cumulative survival for the whole group after 22 years was 69%, the expected survival being 89%. The certified cause of death of 30 patients was from diseases of the circulatory system, mainly myocardial infarction and cerebrovascular disease, the expected number being 21.8. The results of this survey show a reduced life expectancy for both males and females and suggest that a more guarded view should be taken than is presently the case about the long term prognosis of these patients.

Adult↗
PubMed1987

The permeability of detachable latex rubber balloons. An in vitro study.

Previous studies have shown that a silicone rubber balloon filled with a hyperosmolar solution of contrast medium expands and may rupture because the wall acts as a semipermeable membrane. The deflation of latex rubber balloons in vivo has been attributed to the same cause. The authors investigated the behavior of latex rubber balloons filled with metrizamide solutions ranging from hyperosmolar to hypo-osmolar relative to plasma. When balloons were immersed in plasma, tritiated water passed bidirectionally through the wall at a rate unrelated to the concentration or volume of the contrast medium in the balloon. There was no exchange of sodium ions across the wall, and the osmolality of the metrizamide did not change over a period of up to six weeks. The authors conclude that deflation of a latex rubber balloon during the first few hours or days is not due to osmosis.

Animals↗
PubMed1986

Extracranial/intracranial anastomosis in therapeutic balloon occlusion of the internal carotid artery.

Occlusion of the internal carotid artery with a detachable balloon was attempted or achieved in 19 patients suffering from a carotid aneurysm or dural arteriovenous malformation. An extracranial/intracranial anastomosis was performed prior to the occlusion in 11 patients, 4 of whom developed complications as did one of the 8 patients without an anastomosis. Although the morbidity of the procedure might have been greater without an arterial bypass a comparison of the two groups of patients lends no support for this view.

Adult↗
PubMed1979

Changes in brain levels of cyclic nucleotides and gamma-aminobutyric acid in barbiturate dependence and withdrawal.

Rats exposed to chronic intake of sodium barbital maintained high circulating levels of barbital in blood and brain and exhibited increased sensitivity ot audiogenic convulsions during the withdrawal period. Levels of gamma-aminobutyric acid (GABA), glutamate, guanosine 3',5'-monophosphate (cyclic GMP) and adenosine 3',5'-monophosphate (cyclic AMP) were measured in selected brain regions after sacrifice with high power microwave inactivation. Cyclic GMP during chronic barbital administration was significantly lower than controls in most brain regions, especially the hindbrain. During the withdrawal period cyclic GMP in the cerebellum was significantly increased, while returning at least to control levels in all other regions. GABA throughout the brain tended to be reduced during barbital dependence, while cyclic AMP and glutamate levels remained unchanged in all groups. These results indicate a possible role for cyclic GMP in the mediation of the central nervous system response during barbiturate dependence and withdrawal.

Acoustic Stimulation↗
PubMed1979

Role of lacrimal scintigraphy and subtraction macrodacryocystography in the management of epiphora.

Fifty-one patients were investigated by subtraction macrodacryocystography (SMDCG, 103 systems) and by lacrimal scintigraphy (LS, 105 systems). It was found that these investigations complemented each other and between them the precise site of obstruction in the lacrimal drainage apparatus could be determined in 80%. The radiation dosage to the lens in SMDCG significant, and it is therefore recommended that the patients with lacrimal obstruction should: (1) have lacrimal puncta dilated with a probe to No. 1 diameter and be forbstruction is still uncertain, then and only then should SMDCG be performed.

Child, Preschool↗
PubMed1978

Sustained tumour opacification in infants during cerebral angiography.

Total body opacification in infants following the intravenous injection of a large dose of water soluble contrast medium has long been recognised, but no example of increased radiodensity of abdominal or intracranial tumours has been reported using this technique. This paper reports the sustained opacification of intracranial tumours in three infants during cerebral angiography. Two of the tumours were papillomas of the choroid plexus of the lateral ventricle and the third a medulloblastoma of the fourth ventricle. Three possible explanations of this phenomenon are briefly considered: 1. That the amount of contrast medium was sufficient to cause total body opacification and the visibility of the tumours was due to a combination of their vascularity and the iodine concentration in the circulation blood. 2. That the observed phenomenon is peculiar to these tumours. 3. That the sustained opacity of these these tumours is due to the same cause or causes as the density enhancement of some intracranial tumours demonstrated by computerised tomography after intravenous injection of contrast medium.

Cerebral Angiography↗
PubMed1977

Microwave alteration of the blood-brain barrier system of rats.

Rats were exposed to 1.3 gHz microwave energy to assess the uptake of several neutral polar substances in certain areas of the brain. A quantitative, radioactive isotope method, which uses an internal standard, was employed to measure the loss of test substances to brain tissue. Single, 20 min exposure, to either pulsed or continuous wave (CW) microwave energy induced an increase in the uptake of D-mannitol at average power densities of less than 3.0 mW/sp. cm. The permeability change was greatest in the medulla, followed, in decreasing order, by the cerebellum and hypothalamus, with small or negligible changes in the hippocampus and cortex. Permeability increases were observed for mannitol and inulin but not for dextran. Increased permeability was observed both immediately and 4 h after exposure, but not 24 h after exposure. After an initial rise, the permeability of cerebral vessels to saccharides decreased with increasing microwave power. Differences in the level of uptake occurred between CW energy and pulsed energy of the same average power. Microwaves of the same average power but different pulse characteristics also produced different uptake levels. Our findings suggest that microwaves induce a temporary change in the permeability for small molecular weight saccharides in the blood-brain barrier system of rats.

Animals↗
PubMed1977

Distribution of calcification within the pineal gland.

The distribution of calcification in the normal pineal gland was investigated by a macroradiographic in vitro technique. The centre of calcification in 72 out of 73 glands studied was within 2 mm of the mid-line of the gland. In one gland it lay 2.6 mm from the mid-line. These findings explain the accepted normal limits for pineal calcification on the standard semi-axial projection of the skull of up to 2 mm to either side of the mid-line and the occasional measurement in excess of this in normal subjects.

Adult↗
PubMed1976

Ventricular size following head injury: a clinico-radiological study.

A retrospective study of the records of 93 patients who had sustained a severe closed head injury was carried out to determine the relationship, if any, between the severity of the injury, the size of the cerebral ventricles and the residual disability. Ventricular size was expressed as a ventricular index. The callosal angle was also measured to see whether this was of value in the recognition of post-traumatic external obstructive hydrocephalus. A normal range of ventricular indices and callosal angles was obtained from a review of the air encephalograms of 56 patients matched for age and sex with the head injury group, and whose air studies were considered to be normal. The findings on the head injury group were subjected to detailed statistical analysis. The study showed that there was no statistically significant relationship between severity of injury, measured by duration of unconsciousness, and ventricular size expressed as a ventricular index. There was a relationship between ventricular size and residual disability as graded in this study. If age was taken into consideration, the relationship between ventricular size and disability was closer. It was not possible to predict residual disability of individual patients from ventricular size alone due to the wide range of values in any disability grade. Failure of air to pass from the basal cisterns over the cerebral convexities is a widely accepted sign of extraventricular obstruction. The shapes of the ventricles, the ventricular index and a callosal angle of 110 degrees or less provided supporting evidence of obstruction in this study. Recognition of an obstructive element in ventricular dilatation following head injury is important, since in a small carefully selected group of patients a ventricular shunting operation may favourably affect recovery.

Adolescent↗