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Biomedical subjects

A H Beddoe

Publications and source records attributed to A H Beddoe.

49 records · Page 3Linked to original sources
PubMed1977

'Radial' scanning of trabecular bone: consideration of the probability distributions of path lengths through cavities and trabeculae.

Previous methods of dosimetry for radionuclides deposited in trabecular bone have been based on probability distributions of random path lengths through the trabeculae and marrow cavities. These distributions have been measured by a technique in which thin bone sections are effectively scanned along sets of parallel grid lines. A new technique is described in this paper, in which all scan lines pass through a selected point in the section scanned, so that they effectively radiate from the point (or focus) in the manner in which particles emerge isotropically from a radioactive atom. By scanning from a number of foci a 'radial-random' distribution can be obtained for a whole bone, and this distribution compared with that obtained from 'parallel' scanning. Differences between the two types of distribution have been observed, especially where the bone exhibits structural anisotropy, the effect on the lengths being up to 13% longer for the radial scanning mode. The effect on the calculated dose factors is not great; based on radial scanning, the factors for a lumbar vertebra are from 5 to 12% less than those for parallel scanning, depending on particle energy. The differences are very small for bones with more uniform trabecular structures, so that for the skeleton as a whole the differences will be smaller than those quoted.

Bone and Bones↗
PubMed1977

Measurements of endosteal surface areas in human long bones: relationship to sites of occurrence of osteosarcoma.

Using techniques of bone scanning and ashing, the areas of the endosteal surfaces in cortical and trabecular bone have been determined for the proximal, mid and distal thirds of each of the six long bones of an adult human subject. The relative frequency of occurrence of bone sarcomas, scored as to site, has been analysed in relation to these measured areas. Data on tumour occurrence have been drawn from three sources: radium-case data from Rowland and Keane (33 cases), naturally-occurring cases from series by Sissons (139 cases) and by Dahlin (473 cases). A strong correlation is demonstrated between tumour frequency and trabecular area, but correlation with cortical area is poor. By comparing the tumour frequency in the mid thirds of the bones with the total recorded it has been possible to show that the probability of tumour occurrence per unit area of cortical bone, relative to that of trabecular bone, is 0.16 +/- 0.06. Analysis of the available dose data for the radium cases shows that in this instance dose has not contributed to the observed correlations. The results lend support to the thesis that tumour occurrence depends on surface area, i.e. on the number of cells at risk.

Anthropometry↗
PubMed1976

Measurements of trabecular bone structure in man.

A quantitative analysis of trabecular bone structure is presented, based on omnidirectional distributions of paths across (a) trabeculation and (b) marrow cavities. The omnidirectional distributions, which take into account structural anisotropy, are generated from measured distributions of paths. Representative examples are given, together with values of two commonly quoted structural parameters, the ratio of endosteal surface to bone volume and percentage bone volume. Data on the biological and age variations in the third lumbar vertebra are also presented and an index of trabecular anisotropy suggested. Finally, the results are compared with those of other workers and estimates of useful skeletal parameters given.

Adult↗
PubMed1976

The absorbed dose to bone marrow in the treatment of polycythaemia by 32P.

This paper reports the determination of absorbed dose to bone marrow in the treatment of polycythaemia by 32P, based on the measurement of activities in bone and marrow biopsies taken at various times from 1 to 27 days after injection of the radionuclide. Activities were measured in the cortex, trabeculation and marrow of biopsies taken from the iliac crest, and slso in sternal marrow. The biological half-life of 32P in marrow from the iliac crest was found to be nine days; that derived for sternal marrow was lower, but the difference was not statistically significant; the value for trabecular bone was 27 days. The biological half life for 32P in the body, as measured by whole-body counting, was 39 days. Calculations of the dose-rate to trabecular marrow have been made by a method based on that of Whitwell and Spiers (1971), but modified to allow for the presence of32P in the marrow as well as in trabecular bone. The dose-rates follow a single exponetial decay with a half-life of 6.7 days. The intergrated dose including that during the first day is 24 rad per mCi injected.

Aged↗
PubMedDate not supplied

Body fat: estimation or guesstimation?

Skinfold anthropometry is performed world-wide with little appreciation of its limitations. This paper shows that it is important to appreciate the magnitude of the biological component of the residual error in any regression of body density against sums of skinfolds; for example, for young adult males a biological error of around 21% (s.d.) is observed. Such 'errors' simply express nature's refusal to conform to imposed regression relationships, reflecting the inherent variability in the ratio of subcutaneous to total body fat.

Absorptiometry, Photon↗
PubMedDate not supplied

Measurement and prediction of total body fat.

Though it has been established that skinfold anthropometry has severe limitations as a method of deriving total body fat (TBF), the possibility that the problem might be related more to the assumptions implicit in densitometry has to be addressed. This paper suggests that smaller residual errors might be obtained if sums of skinfolds are regressed against TBF measured by a difference technique (IVNAA + 3H2O dilution), suggesting that the latter may perhaps be a better standard than densitometry.

Adipose Tissue↗