PubMed Health⌕ Search

Biomedical subjects

Donald McLean

Publications and source records attributed to Donald McLean.

5 recordsLinked to original sources
PubMed2006

Thyroid dose measurements for staff involved in modified barium swallow exams.

Following a successful claim for damages by a speech pathologist, who was diagnosed with thyroid cancer after a period of employment including involvement in modified barium swallow procedures, a detailed study on occupational dose was commissioned. In this study radiation doses were measured routinely over 8 clinical periods using TLD100H dosimeters for staff involved with modified barium swallow radiological studies at three hospitals. The regions monitored included the unshielded thyroid, waist under apron, and axilla. Average unshielded thyroid doses for the speech pathologists were measured as 0.017, 0.003, and nil mGy per procedure over the hospitals surveyed, with dose measurements also found for the unshielded thyroid of the radiologist and nurse. This compares to thyroid doses of 0.200 and 0.055 mGy per procedure typically for cardiologists and orthopedic surgeons involved in radiological work, respectively. The use of a thyroid collar will substantially reduce this dose by a factor of about 40. While the worst-case doses are very small, attention should be given to education for staff involved in radiological procedures as well as ensuring that sound procedure protocols are in place and used.

Barium Sulfate↗
PubMed2004

Mammographic breast glandularity in Malaysian women: data derived from radiography.

OBJECTIVE: This study was undertaken to estimate mammographic breast glandularity in Malaysian women from radiographic data. MATERIALS AND METHODS: A mammography X-ray unit was used to expose different thicknesses of phantom material of varying glandular and adipose composition at 27 kV. A least squares method was then used to fit the combined data of phantom glandularity, thickness, and milliampere-seconds. The subsequent fitted equation was then applied to calculate breast glandularity for 705 women who underwent diagnostic mammography, who were drawn equally from the three major ethnic groups of Malaysia: Malay, Chinese, and Indian. The difference in breast glandularity among ethnic groups was tested for significance using the nonparametric Kruskal-Wallis test. RESULTS: The fitted equation gave an absolute error of less than or equal to +/- 8% when applied to the data from phantom exposure. The average breast glandularity of the study sample was 48.9% +/- 18.7%. Breast glandularity was found to decrease with breast thickness and age. CONCLUSION: No significant difference was seen in breast glandularity among the ethnic groups (p > 0.05, Kruskal-Wallis test).

Adipose Tissue↗
PubMed2003

Breast compression in mammography: how much is enough?

The amount of breast compression that is applied during mammography potentially influences image quality and the discomfort experienced. The aim of this study was to determine the relationship between applied compression force, breast thickness, reported discomfort and image quality. Participants were women attending routine breast screening by mammography at BreastScreen New South Wales Central and Eastern Sydney. During the mammographic procedure, an 'extra' craniocaudal (CC) film was taken at a reduced level of compression ranging from 10 to 30 Newtons. Breast thickness measurements were recorded for both the normal and the extra CC film. Details of discomfort experienced, cup size, menstrual status, existing breast pain and breast problems were also recorded. Radiologists were asked to compare the image quality of the normal and manipulated film. The results indicated that 24% of women did not experience a difference in thickness when the compression was reduced. This is an important new finding because the aim of breast compression is to reduce breast thickness. If breast thickness is not reduced when compression force is applied then discomfort is increased with no benefit in image quality. This has implications for mammographic practice when determining how much breast compression is sufficient. Radiologists found a decrease in contrast resolution within the fatty area of the breast between the normal and the extra CC film, confirming a decrease in image quality due to insufficient applied compression force.

Adult↗
PubMed2003

Survey of effective dose levels from typical paediatric CT protocols.

Concern over reported large radiation doses leading to a high cancer risk for paediatric CT patients has prompted considerable investigation in paediatric CT. The recent release of software from Germany has allowed effective doses to be calculated from CT protocol information and radiation measurement for standard paediatric patient sizes for both sexes. An initial study has been undertaken in nine radiology departments, four of which were dedicated paediatric departments, for routine chest and abdominal CT procedures. The dose calculation software is based on Monte Carlo simulation of X-ray conditions during a CT procedure and utilized a 'tomographic' phantom model of a 7-year-old child and an 8-week-old baby to allow calculation of organ dose and hence effective dose. Results of the survey indicate that effective doses were higher for females than males, and higher for abdominal procedures. Slightly higher effective doses were calculated for the child compared to the baby. All centres but one recorded lower effective doses with their current protocols than if they had used recommended CT protocols found in the literature. Analysis of the survey data indicates that scan parameters are the main cause of dose variations, although the type of scanner can affect dose by a factor of 2 (when comparing different units) as well as variation in anatomy scanned in protocols. Dose reduction appears to be most closely linked with reduced mAs and increased pitch as expected. The calculation of effective dose appears to be a key factor in assessing CT protocols, particularly for paediatric patients.

Child↗