Biomedical subjects

P Dunscombe

Publications and source records attributed to P Dunscombe.

24 records · Page 2Linked to original sources

PubMed1991

A simplified method for measuring cerebral blood flow with xenon-enhanced computed tomography.

The measurement of cerebral blood flow using the xenon-enhanced computed tomography (XECT) technique requires that the build-up of xenon in both brain tissue and end-tidal expired air be determined as a function of time. Monitoring of the former is carried out using CT scanning and the latter, most often, using a thermoconductivity analyser or mass spectrometer. This paper examines the possibility of greatly simplifying the XECT technique by eliminating the need for either thermoconductivity analyser or mass spectrometer. In the proposed approach, the patient's expired air is channelled through the scan field using a flexible plastic tube and sampled by the CT scanner in conjunction with the build-up of xenon in brain tissue. Phantom measurements have demonstrated the ability of the CT scanner to detect variations in the xenon concentration in expired air while computer simulations have shown that errors arising as a result of the proposed methodology are small compared to other inherent sources in the XECT technique.

Brain↗

PubMed1989

The teaching of physics and related courses to residents in radiation oncology.

A survey of physics and related teaching to radiation oncology residents in 21 Canadian cancer centres was undertaken in December 1987 and January 1988. This survey illustrates a very considerable variation in the formal teaching of physics to aspiring radiation oncologists with, for example, the number of hours offered ranging from 40 to 160 in those 10 centres which have a training program. It would appear to be of benefit to radiation oncology residents, those charged with teaching them, and the radiation oncology community as a whole, to develop specific guidelines for this aspect of resident education.

Canada↗

PubMedDate not supplied

Perturbation of the temperature distribution in microwave irradiated tissue due to the presence of metallic thermometers.

To date, satisfactory thermal dosimetry during the clinical application of localized hyperthermia can only be achieved using invasive thermometry. However the presence of commonly used metallic thermometers, such as thermocouples, may lead to the distortion of the temperature field due to self-heating of the probe under microwave irradiation. A computer simulation of the effect of this self-heating on the steady-state temperature distribution in plane-microwave irradiated homogeneous tissue has been undertaken and the significance of the effect for clinical hyperthermia dosimetry is assessed. The results indicate that a distortion of the temperature field in the neighborhood of the thermometer by several degrees can occur under adverse conditions.

Body Temperature↗

PubMedDate not supplied

Jaws 2: a description of in-air beam profiles for half blocked and dynamically wedged radiation fields.

In a recent paper [Med. Phys. 19, 1441 (1992)] it was shown that the field size dependence of on-axis relative output from a linear accelerator can be well described by a model comprising two components. One component represents radiation emanating from a point source and the other represents radiation from a field size dependent distributed source. In this communication the application of the model is extended to off-axis situations and demonstrates that a good description of the dependence of off-axis output on collimator configuration can be obtained. Of particular clinical relevance in this regard is the beam profile of half blocked fields which are adequately reproduced. The model has also been applied to the study of profiles generated by simulated dynamic wedging.

Humans↗

PubMedDate not supplied

A technique for the evaluation of a missing tissue compensator system.

A two dimensional approach to the evaluation of a missing tissue compensator system has been developed and implemented. Quantitative descriptors of the dose area histograms generated by scanning films irradiated under a variety of compensated and uncompensated conditions are proposed. The method has been found to be useful during the acceptance testing of a commercial compensator system and the results of this exercise are presented.

Evaluation Studies as Topic↗

PubMedDate not supplied

A policy for allocating off-site continuing education funds.

Providing support for travel to conferences, workshops and other off-site continuing education activities is an expensive component of a professional development program. The authors describe a policy addressing this issue which was implemented within the multidisciplinary environment of a comprehensive cancer centre. The policy is open, easily adapted to changes in overall funding and can be used to reflect the organization's expectations regarding employee performance in service, academic, management and leadership roles.

Budgets↗