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Biomedical subjects

J S Orr

Publications and source records attributed to J S Orr.

At least 19 recordsLinked to original sources
PubMed1979

Image formation by back-projection: a reappraisal.

The theory of image formation by simple summation of an object's projections, without further processing, is considered. Calculations are presented of the resultant image from a point, a rectangle, an annulus, and three rotationally symmetric objects. The general features of these images are discussed and it is postulated that for many objects of interest a limited compensation for edge unsharpening would suffice to produce recognition of the objects.

Tomography↗
PubMed1978

Carcinoma of the larynx - results of primary radiotherapy.

Results for 180 patients with carcinoma of the larynx treated by radiotherapy at Belvidere Hospital in Glasgow between 1958 and 1968 are presented. The policy of treatment was primary radiotherapy with surgery for recurrences. All the patients have been followed up for more than five years. Overall crude five-year survival is 57%. For stages I and II it is 70%. Surgical rescue was successful in 50% of fit patients.

Adult↗
PubMed1977

The assessment of red cell survival in normal subjects and in patients with haemolytic disorders and ineffective erythropoiesis using the radioiron occupancy method.

A direct method for measuring red cell lifespan in vivo using the radioiron occupancy method (Dagg et al, 1972) has been applied to eight normal subjects. The mean red cell lifespan was 116 d with a range of 104-124 d. To establish the method clinically in the presence of haemolysis and ineffective erythropoiesis, 22 patients with haemolytic disease and six patients with megaloblastic and sideroblastic anaemia were studied. All 22 patients with haemolytic anaemia had shortening of the red cell lifespan, with a range from 62 to 10 d; the results were compared with red cell lifespan derived from simultaneous radiochromium studies (Bentley et al, 1974). A close agreement between the two methods was obtained (r = 0.87; P less than 0.001). To assess the validity of the method in the presence of ineffective erythropoiesis, double isotope studies were also carried out in three patients with megaloblastic anaemia and three with sideroblastic anaemia. Close agreement was again obtained between lifespan measurements obtained from radioiron occupancy data and those derived from radiochromium studies, suggesting that the presence of significant ineffective erythropoiesis does not invalidate the method. The theoretical considerations involved in the application of the radioiron occupancy method to haemolytic states are discussed.

Anemia, Hemolytic↗
PubMed1977

Interaction of hyperthermia and radiation: the survival surface.

The interaction of hyperthermia and radiation on cell survival is illustrated by the increase in sensitivity to radiation caused by hyperthermia and the increase in sensitivity to hyperthermia caused by radiation. A method of expressing the total response to a combination of these two agents by means of a survival surface in three dimensions is explained and discussed. A simple mathematical model of the suface is formulated in which is a first order interaction term is separated from the two terms representing unperturbed radiation survival and unperturbed hyperthermia survival. An experiment is described in which survival data points were obtained for 77 combinations of radiation and hypertermia doses in the form of a matrix. These data points are plotted as 11 radiation survival curves and seven hyperthermia survival curves. The results are also analysed to give the parameters of the survival surface model. The model with its three components is shown to be a good approximation to the experimental results.

Cell Survival↗
PubMed1977

Interaction of hyperthermia and radiation: temperature coefficient of interaction.

Cell survival data were collected to determine the survival surface for asynchronous CHO cells X-irradiated at room temperature 100 min prior to a hyperthermic exposure. The survival surface could be approximately described by a survival model comprising three components of cell killing; the unperturbed radiation component, the unperturbed hyperthermia component and the interaction component. The temperature sensitivities of the hyperthermia component and of the interaction component were investigated by using different hyperthermic temperatures, revealing that the interacting component is significantly less sensitive to a change in temperature than the unperturbed hyperthermia component.

Cell Survival↗