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Biomedical subjects

M C Thorne

Publications and source records attributed to M C Thorne.

At least 19 recordsLinked to original sources
PubMed1992

Perineal proctectomy for rectal prolapse in elderly and debilitated patients.

This paper details the indications, operative technique and results of perineal proctectomy in the management of complete rectal prolapse in a high risk, elderly and debilitated group of patients. Eighteen procedures were performed by one surgeon (A.L.P.) on 16 consecutive patients over a 5 year period. Data collection was via: (i) retrospective analysis of hospital and office records; and (ii) response to a postal questionnaire by the patient, a relative or attending nursing staff. There were 14 females and two males with a mean age of 81 years. All patients had significant associated medical conditions. The interval from the time of a surgical procedure until review varied from 3 to 37 months with a mean follow-up period of 16 months. Total hospital stay varied between 6 and 20 days with a mean of 7 days. Eleven procedures were performed under general anaesthesia and seven under spinal anaesthesia. There was no postoperative mortality. One patient suffered an anastomotic haemorrhage that required operative intervention and another patient suffered a rectal stricture that necessitated dilatation. Two patients were re-operated for recurrent symptomatic prolapses at 34 and 36 months after the initial procedure. Continence improved in seven patients, worsened in one and was unchanged in the remaining patients. Fifteen of 16 patients were considered to have had a successful result from the operation with satisfactory control of the symptom of rectal prolapse. Perineal proctectomy is a low risk operative procedure for the elderly and debilitated group of patients in controlling complete rectal prolapse. If the condition recurs, the procedure can be repeated with equally low morbidity.

Aged↗
PubMed1989

Radiological protection and the lymphatic system: the induction of leukaemia consequent upon the internal irradiation of the tracheobronchial lymph nodes and the gastrointestinal tract wall.

The excess of leukaemia among young people living in the vicinity of the nuclear fuel reprocessing plant at Sellafield has focused attention on the possibility that irradiation of the lymphatic system from particulate alpha-emitting nuclides might be responsible. We discuss below two possible routes of such exposure; namely the inhalation and ingestion of particulates. We conclude that, in spite of the real possibility of substantial doses to tissues associated with the lymphatic system, there is little reason to expect that lymphatic leukaemia will be the dominant outcome of the exposure. However, the arguments presented are not, and cannot be, wholly conclusive.

Administration, Inhalation↗
PubMed1988

The potential for irradiation of the lens and cataract induction by incorporated alpha-emitting radionuclides.

Data on the uptake and retention of Ra and Pu in ocular tissues are reviewed. These data were used to calculate alpha radiation doses to the lens of the eye for patients injected with 224Ra and for individuals exposed to one annual limit on intake (ALI) per year of 224Ra, 226Ra, 228Ra and 239Pu for a period of 50 y. On the basis of this analysis, it is concluded that the induction of lens opacity should not be the factor limiting intake of any radioisotope of Pu or for 224Ra or 226Ra. However, for 228Ra the dose lies within the range of doses received by 224Ra patients who have developed cataracts.

Alpha Particles↗
PubMed1987

Principles of the International Commission on Radiological Protection system of dose limitation.

The current recommendations of the International Commission on Radiological Protection (ICRP), published in 1977, identify two types of effect against which protection is required. "Stochastic" effects are those for which the probability of an effect occurring, rather than its severity, is regarded as a function of dose without threshold, whereas "non-stochastic" effects are those for which the severity varies with the dose and for which a threshold may occur. The system of dose limitation recommended by the ICRP is based on the prevention of non-stochastic effects and limitation of the probability of stochastic effects to levels deemed to be acceptable. The prevention of non-stochastic effects is achieved by setting dose-equivalent limits at values such that no threshold dose would be reached, even following exposure for the whole of a lifetime or for the total period of a working life. The limitation of stochastic effects is achieved by keeping all justifiable exposures as low as is reasonably achievable, economic and social factors being taken into account, subject to the constraint that reductions in collective exposure do not cause unacceptably large individual exposures. The formulation of a quantitative system of dose limitation based on these principles requires that judgments be made on several factors including: relationships between radiation dose and the induction of deleterious effects for a variety of endpoints and radiation types; acceptable levels of risk for radiation workers and members of the public; and methods of assessing whether the cost of introducing protective measures is justified by the reduction in radiation detriment which they will provide. In the case of patients deliberately exposed to ionising radiations, the objectives of radiation protection differ somewhat from those applying to radiation workers and members of the public. For patients, risks and benefits relate to the same person and upper limits on acceptable risks may differ grossly from those appropriate to normal individuals. For these reasons, and because of its historical relationship with the International Congress of Radiology, the ICRP has given special consideration to radiation protection in medicine and has published reports on protection of the patient in diagnostic radiology and in radiation therapy.

Animals↗
PubMed1982

Relationship between blood flow, bone structure, and 239Pu deposition in the mouse skeleton.

The rate at which blood is supplied to several bones in female CBA mice was calculated from 18F measurements in bone and blood. Blood flow measurements were compared with plutonium uptake in whole bone and on endosteal and periosteal bone surfaces. The results showed that: (a) the rate at which blood is supplied to bone determines the rate of deposition of plutonium; (b) there is a threshold rate of blood supply below which plutonium is not deposited; and (c) the rate of blood supply determines the density of plutonium deposition on endosteal but not no periosteal bone surfaces. These results are discussed in the light of the current bone blood supply hypotheses.

Animals↗
PubMed1981

A semi-automated technique for assessing the microdistribution of 239 Pu deposited in bone.

A semi-automated analytical procedure is described for the localisation of 239 Pu in bone. The method is based on the use of a Quantimet 720B Image Analyser for the analysis of neutron-induced autoradiographs, and may be applied to most tissues with fissionable radionuclides. Compared with former methods the present technique offers improvements in accuracy and a considerable saving on time and manpower. These savings arise mainly from the ability of the Quantimet to be used for the automatic detection of the fission-fragment tracks and to operate directly on the neutron-induced autoradiograph without recourse to photography. Results are presented for the distribution of 239 Pu in the ilia of CBA mice at 24 h post-injection.

Animals↗
PubMed1981

Morphometric studies on mouse bone using a computer-based image-analysis system.

The morphological structure of the ilium, femur, third lumbar vertebra and a central caudal vertebra of the female CBA mouse has been studied using 5 micrometer thick, plastic embedded, transverse and longitudinal sections. The sections were analysed on a Quantimet 720, system 30, image analyser connected on-line to a PDP11 computer. Separate endosteal and periosteal surface to volume ratios were calculated for each position of sampling in each bone. For this calculation the anisotrophy of the bone was estimated from measurements of mean chord lengths in longitudinal sections of the bone using a new analytical technique. Chord length distributions in transverse sections of bone were also measured and the relevance of such measurements to the study of morphological changes in the bone and its included marrow are briefly discussed.

Animals↗
PubMed1979

Quantitative microscopic studies of the distribution and retention of 239Pu in the ilium of the female CBA mouse.

Three month old female CBA mice were injected with 50 nCi kg-1 body mass of minimally polymeric 239Pu-citrate and killed at 24 hours, 10 days, 1 month and 3 months after injection. The distribution of 239Pu in the ilia of these mice was analysed using neutron-induced autoradiography of bone sections together with computer-based methods of data reduction. Results of these investigations demonstrate that while 239Pu is initially localized on bone surfaces, by 3 months after injection it is fairly uniformly distributed throughout mineral bone and its included marrow.

Animals↗
PubMed1978

Plutonium-239 deposition in the skeleton of the mouse.

Using the technique of neutron-induced autoradiography, together with computer-based methods of data reduction, the distribution of intravenously injected plutonium-239 in the skeleton of the female CBA mouse, 24 hours after injection, has been investigated. With these techniques, it is possible to measure the localization of 239Pu on the endosteal and periosteal surfaces of the bone to an accuracy of approximately +/- 2 x 5 micrometer. Results are reported for the distribution of 239Pu in the third lumbar vertebra, a central caudal vertebra, the right ilium and the right femur. Radiochemical analyses of the 239Pu in other comparable bones of the skeleton are also reported.

Animals↗
PubMed1977

The measurement of blood flow in mouse femur and its correlation with 239Pu deposition.

The concentration of 18F was measured in three parts of the femur and in the blood of 36 mice killed at intervals of from 1 min to 2 h after intravenous injection. Blood supply to the bone sections, calculated by dividing the increase in 18F concentration in bone by the integral of 18F concentration in blood between selected time intervals, was shown to be unaffected by the return of 18F from bone to blood at times earlier than 90 min following injection. The supply of blood per unit mass of bone was greatest in distal end of the femur, less in proximal end and least in shaft. In whole femur average blood flow was 230 mm3 per gram fresh bone per min. The deposition of 239Pu in three parts of the mouse femur was shown to be linearly related to blood flow and the nature of the relationship is discussed.

Animals↗
PubMed1977

Aspects of the dosimetry of alpha-emitting radionuclides in bone with particular emphasis on 226Ra and 239Pu.

The dosimetry of alpha-emitting radionuclides in bone is discussed. Results are presented for average dose rates to tissues close to endosteal surfaces and to haematopoietic bone marrow from thin plane sources of radionuclides buried to different depths in bone and emitting alpha-particles with energies in the range 3-8 MeV. These results are used to demonstrate that on an activity basis 239Pu is unlikely to be more than fifteen times as toxic as 226Ra with respect to osteosarcoma and leukaemia induction in man.

Animals↗