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Biomedical subjects

S C Lillicrap

Publications and source records attributed to S C Lillicrap.

9 recordsLinked to original sources
PubMed1985

Coherent-Compton scattering for the assessment of bone mineral content using heavily filtered x-ray beams.

The feasibility of using heavily filtered x-ray beams to assess trabecular bone mineral content has been investigated by measuring the ratio of coherent to incoherent scattered x-rays with a high purity Ge detector. The technique uses the strong dependence of coherent scattering on the effective atomic number of the scattering medium. With an x-ray beam filtered with a high-atomic-number filter, a spectrum characterised by a sharp discontinuity at the K-absorption edge is produced. Analysis of the spectral shape after scattering allows the coherent to Compton scattering ratio to be obtained. Theoretical and experimental results from phantom studies are presented and a comparison made between the results obtained with x-ray beams and radionuclide sources respectively. The influence of overlying tissue thickness on the sensitivity of the measurements is demonstrated.

Biophysical Phenomena↗
PubMed1979

The recovery of iron uptake in erythropoietic bone marrow following large field radiotherapy.

Large X-ray fields, such as those used to irradiate major lymph-node areas in the treatment of lymphomas, often irradiate large areas of haemopoietic bone marrow. The absorbed doses received by the marrow are close to the tolerance level. Quantitative scanning of the bone marrow, using 52Fe and a digital whole-body scanner, has been carried out in a series of 22 patients treated by radiotherapy up to nine years previously in order to assess the extent and recovery of their erythropoietic marrow. The results showed large variations from patient to patient; in some patients the iron uptake in the marrow returned to near normal levels in two to three years, while in others the uptake remained suppressed after seven to eight years. The tolerance dose for the bone marrow appeared to be about 1100 ret. There was some evidence of a more rapid recovery of erythropoietic function in males than females, but no evidence to show that age of patient, type of disease or whether chemotherapy had been used influenced the results. Patients who showed a decreased iron uptake in an irradiated region of marrow generally showed a compensating increased uptake in unirradiated regions, which in some cases was associated with anaemia.

Adolescent↗
PubMed1975

Dose distributions in high energy electron beams: production of broad beam distributions from narrow beam data.

In a high energy electron beam the spatial distribution of absorbed energy is dominated by multiple scattering of the electrons. The dose distribution in a broad parallel electron beam entering a uniform phantom can be resolved into a series of narrow beams overlapping one another, in each of which the scattering conditions are identical. It is therefore possible to build up a broad beam dose distribution from a knowledge of the axial and radial dose distribution in a narrow beam. Measurements have been made of such narrow beam distributions using finely collimated electron beams in the energy range 4-10 MeV, and the resulting data added by computer to give broad beam distributions which are compared with measured isodose curves. The method has been extended also to construct isodose distributions in heterogeneous phantoms. The advantages of storing electron beam data in the form of narrow beam distributions are described with particular reference to the problem of irradiating heterogeneous tissue volumes.

Electrons↗