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Biomedical subjects

C S Hamilton

Publications and source records attributed to C S Hamilton.

54 records · Page 3Linked to original sources
PubMed1991

Breast conservation, the problem of treating the excision site effectively: physical criteria for the choice of technique used.

This paper examines how physical factors such as the depth of the excision cavity below the skin surface and its distance from the underlying lung may impact upon the choice between the use of an electron field (from a Varian Clinac 1800) or an implant (using a double plane of iridium-192 wires). Data have been derived from a phantom dosimetry experiment simulating different permutations of breast size and depth of excision cavity. An anthropomorphic female phantom with two different-sized wax breast phantoms has been used to simulate the clinical circumstances envisaged and isodose distributions have been estimated from an array of TLD readings. The biological significance of doses measured in skin and lung have been examined using the linear-quadratic (LQ) model. Both on physical and biological grounds, the results favour the implant under the experimental conditions adopted. The use of the electron beam to definitively treat the excision cavity (omitting breast tangents) to 60 Gy would result in unacceptable late effects in the skin and an observable incidence of pneumonitis if the excision cavity were near the chest wall. Small carcinogenic risks, particularly to the lung, are apparent with each modality, but may be moderated for the iridium-192 implant by a reduced carcinogenic potential associated with low-dose rate radiation. The use of the newer radionuclides iodine-125 and samarium-145, with less penetrating gamma ray emissions, might be preferred to iridium-192 from the point of view of bronchial carcinogenesis if definitive treatment of the excision cavity became widespread practice.

Brachytherapy↗
PubMed1991

Clinical utility of high-resolution portal films.

We have evaluated the film quality and overall clinical utility of a unique high-resolution portal film system which utilizes high contrast graphics art film. A total of 127 unselected patients had their conventional portal films and high-resolution films of the same site, compared and graded subjectively for a variety of parameters by an independent panel of radiotherapists and radiographers. Although consistent improvements in most aspects of image quality were noted, improved overall clinical usefulness of the high-resolution portal film system in comparison to the conventional films, when subjected to multiple regression analysis, was confined to lateral neck views only. High-resolution portal film utility was also found to depend significantly on field size with areas less than 110 cm2 having a markedly worse clinical utility score.

Humans↗
PubMed1990

Low dose rate teletherapy using a telecaesium 137 unit radiobiological, physical and clinical considerations.

Low dose rate teletherapy aims to combine the supposedly superior results obtained with low dose rate implants with the convenience and staff protection characteristics of external beam therapy. Previous investigators have used telecobalt units to produce dose rates of 1.1 to 1.8 Gy/hr to treat in daily sessions lasting 6-10 hours to total doses of 60-70 Gy. These studies have not discounted the possibility that much of the advantage of interstitial implants results from the low dose rates used per se, and from the fact that the total dose is delivered in a short overall time. The relationship between total dose, dose rate and volume giving normal tissue and anit-tumour effects, however, remains ill-defined. At the Newcastle Mater Misericordiae Hospital a Caesium teletherapy unit has been modified to treat at low dose rates and a study has been designed with a view to establish which permutations of total dose and dose rate are isoeffective for acute mucosal and acute skin reactions in the dose rate range between 0.8 and 9.6 Gy/hr (1.3 and 16 cGy/min).

Cesium Radioisotopes↗
PubMed1990

CT scanning for definitive radiotherapy planning of prostate cancer: necessity or nicety? Results from survey of radiation oncologists working at different institutions in Australasia.

Interactive computerised tomographic (CT) planning techniques offer the prospect of better anatomical localisation, more consistent tumour coverage, and limiting normal tissue dose. However, its value in the management of prostate cancer remains undefined. The present study addresses the impact of planning CT on the designated target volumes for localised carcinoma of the prostate at a multi-institution national level. Nine radiation oncologists from different centres in Australia and New Zealand were asked to designate a target volume on five sample patients with different disease stages (A2-C2) using both conventional cystogram films and planning CT scans. Target volumes estimated by CT means in this study differed by more than 10% from those estimated by conventional means in 75.6% of instances, being smaller in 55.6%. Volumes varied widely between individual radiation oncologists, both using conventional planning and CT information. These variations were found to exceed any differences in the volume caused by the planning technique itself. Results from this survey suggest that volumes appear to change more according to the individual radiation oncologist rather than to any other factor. In most or all of the sample cases six of nine radiation oncologists defined the borders of their CT volumes to be either consistently smaller (5 out of 9) or greater (1 out of 9) than their conventionally defined borders. The results of this survey are potentially important and warrant repetition with larger sample numbers in other countries where interactive CT planning facilities exist, both with and without diagnostic radiological input, to exclude similar variation and to define causes for any variations that do become apparent.

Data Collection↗
PubMed1990

Breast appearance and function after breast conserving surgery and radiotherapy.

Between 1978 and 1985, 247 breast cancer patients were treated with breast conserving surgery and radiotherapy. One hundred and twenty of these patients form the basis of this report, having replied to an 11-point structured questionnaire evaluating breast appearance and breast, shoulder and arm function. Good to perfect cosmetic, functional and overall scores are shown to be in the range 61-89%. The extent of primary surgery and axillary irradiation are the major factors affecting the cosmetic appearance. Other problems with cosmetic and functional assessment from subjective and objective view points are also discussed.

Adult↗
PubMed1990

Results of breast conserving treatment of breast cancer.

Between 1978 and 1985, 247 patients with primary breast cancer have been treated with breast conserving surgery and external beam radiotherapy. Median follow-up is 3 years and 9 months. Actuarial 5-year disease-free survival for the whole group is 72%; 16 patients (6.8%) have relapsed in the breast to date. Of these, 6 (38%) have died from breast cancer. Patients who have experienced a local recurrence have significantly worse survival than those who remain locally recurrence-free (p less than 0.001). Complication data are presented and shown to be almost entirely mild to moderate and in the range 1-19%. This series shows the breast conserving approach to be effective and at least equivalent to breast ablative procedures in early follow-up.

Adult↗
PubMed1987

ACUPS (adenocarcinoma of unknown primary site): a clinical and cost benefit analysis.

A retrospective review of 287 patients with a diagnosis of adenocarcinoma unknown primary site was performed. These patients represented 2.9% of the new referrals to the Westmead Department of Radiation Oncology between the years 1979 and 1985. Age, sex, and survival characteristics of the study population are presented. Tissue biopsy procedures are reviewed and the uniform necessity of open biopsy is questioned in the light of recent advances in FNA (fine needle aspirate) techniques. A semi-quantitative analysis of the monetary cost of the investigation of these patients has been performed. This has been correlated with the objective and symptomatic benefit accrued by the patient population. A higher incidence of speculative, low-yield investigations has been demonstrated for those patients referred from general medical and surgical units. Ante-mortem identification of the primary site remains the exception rather than the rule in this and other series. This fact, coupled with an inability of therapeutic intervention to alter the natural history of the disease means the cost and toxicity of investigation and treatment of these patients must influence approaches to their management.

Adenocarcinoma↗
PubMed1984

Enhancing supervision of psychotherapy.

This paper reports the efforts of a psychiatry training faculty to explicitly study the supervisory process and enhance the faculty's supervisory skills. To accomplish this, a psychiatry resident permitted the videotaping of her supervision. These videotapes were then reviewed and presented in an ongoing conference to members of the training faculty. Through these conferences, the faculty was able to learn methods of elucidating issues within the supervisory process. Techniques for assisting residents in the development of their psychotherapeutic skills were elaborated.

Adult↗