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Biomedical subjects

S Wilkinson

Publications and source records attributed to S Wilkinson.

At least 37 records · Page 2Linked to original sources
PubMed2001

Magnitude of microelectrode refinement in pallidotomy and thalamotomy.

The relative accuracy of starting point algorithms in microelectrode-guided stereotactic pallidotomy and thalamotomy was evaluated using postoperative magnetic resonance imaging (MRI) data. Multiplanar reformations were performed to align postoperative MRI in anterior-posterior, dorsal-ventral and mediolateral planes. Three-dimensional distance and direction from the pallidal and thalamic stereotactic starting points to the respective radiofrequency lesions were measured. Similar magnitude of microelectrode refinement in pallidotomy and thalamotomy suggested similar accuracy of algorithms used to set the stereotactic starting point. Fewer microelectrode-recording tracts were required to identify optimal lesioning sites in thalamotomy compared to pallidotomy. Lesions were consistently localized anterior and superior to the starting point and a refined starting point algorithm may reduce the number of microelectrode recording tracts.

Adult↗
PubMed2001

Comparisons between a pencil beam and two fan beam dual energy X-ray absorptiometers used for measuring total body bone and soft tissue.

A pencil beam Hologic QDR 1000W scanner (1000), a fan beam QDR 4500A scanner (4500) and a fan beam Lunar Expert scanner (Expert) were compared for bone mineral and body composition measurement accuracy. Phantoms were scanned with each instrument to assess magnification effects and to compare calibrations for bone mineral and fat proportion. 41 volunteers were scanned with both the 1000 and the 4500, and 21 patients with both the 4500 and the Expert. The height of a bone within the body affected the measured bone mineral content (BMC) and, to a lesser extent, the bone mineral density (BMD). There were differences in calibration against recognized standards for fat proportion between the three instruments. The 1000 underestimated low fat proportions and the 4500 underestimated high fat proportions. Fat results for the Expert were closer to nominal values. Comparisons on volunteers showed that measured mean total body BMD was 4% higher and BMC was 7% higher with the 1000 compared with the 4500; some regional differences were greater. Mean values of per cent fat were equal, but the total and regional regression coefficients were well above unity. Mean BMD was 3% higher and mean BMC was 10% higher with the Expert compared with the 4500, but most regression coefficients for these comparisons were less than unity. Mean values of per cent fat were equal, but regression coefficients were above unity. Errors due to magnification are acceptable. Differences between the instruments are appreciable, but can be accommodated by cross-calibration.

Absorptiometry, Photon↗
PubMed2000

Thinking differently about thinking positive: a discursive approach to cancer patients' talk.

There is an extensive social science and psycho-oncology literature on coping with cancer which claims that "thinking positive" is correlated with--and, by extension, causally implicated in--individuals' morbidity and mortality rates, and their overall level of mental health. Drawing on our own data, in which groups of women with breast cancer talk about "thinking positive", this paper interrogates the basis of such claims from a discursive perspective, by challenging the data analyses upon which they are based. We show that previous literature overwhelmingly relies on self-report data, which are taken as offering more or less accurate depictions of speakers' psychological states (i.e. their mental adjustment or coping style). A discursive approach, by contrast, explores talk as a form of action designed for its local interactional context, and pays detailed attention to what statements about "thinking positive" actually mean for speakers in the contexts in which they occur. We show that "thinking positive" functions not as an accurate report of a internal cognitive state, but rather as a conversational idiom, characterised by vagueness and generality, and summarising a socially normative moral requirement; we also show that even those breast cancer patients who report "thinking positive" can also actively resist its moral prescriptions. Finally, we sketch out the implications of our analysis for analyses of cancer patients' talk more generally and for future research on coping with cancer.

Breast Neoplasms↗
PubMed2000

Commodification arguments for the legal prohibition of organ sale.

The commercial trading of human organs, along with various related activities (for example, advertising) was criminalised throughout Great Britain under the Human Organ Transplants Act 1989. This paper critically assesses one type of argument for this, and similar, legal prohibitions: commodification arguments. Firstly, the term 'commodification' is analysed. This can be used to refer to either social practices or to attitudes. Commodification arguments rely on the second sense and are based on the idea that having a commodifying attitude to certain classes of thing (e.g. bodies or persons) is wrong. The commodifying attitude consists of three main elements: denial of subjectivity, instrumentality, and fungibility. Secondly, in the light of this analysis, the claim that organ sale involves commodifying the human body is examined. This claim is found to be plausible but insufficient to ground an argument against organ sale, because the very same commodifying attitude is likely to be present in cases of (unpaid) organ donation. It is also argued that commodifying bodies per se may not be wrong. Thirdly, the view that organ sale involves commodifying persons is examined. Although this and the claim that it is wrong to commodify persons are probably true, there is--it is argued--little reason to regard organ sale as worse in this respect than other widely accepted practices, such as the buying and selling of labour. The conclusion is that although commodification is a useful ethical concept and although commodification arguments may sometimes be successful, the commodification argument against organ sale is not persuasive. This is not to say, though, that there are no arguments for prohibition--simply that this particular justificatory strategy is flawed.

Commerce↗
PubMed2000

Introduction and implementation of the basic treatment equivalent in a Varian-based department.

The increasing popularity of 3-D planning leads to procedural alterations as both workload and resource utilization increase. Although the complexity of the techniques has increased (as well as the set-up and treatment times), the workload statistics must still include the number of fields treated. It is commonly known that machine statistics of fields treated per day do not accurately represent workload because there are major differences between techniques. A mantle treatment technique and an opposed spine technique both have (statistically) two fields, although the set-up requirements and treatment times are very different. A basic treatment equivalent (BTE) formula was reported in early 1999 by Delaney et al. and incorporates a large number of variables inherent in patient treatment. The formula considers different factors that affect overall treatment time, and aims to represent a more accurate treatment time indicator. The aim of introducing the BTE into the Department of Radiation Oncology at Sir Charles Gairdner Hospital was to create a more accurate scheduling system and even out workloads on all treatment units. Therefore the BTE formula was used to assess accuracy of treatment times in order to determine if the values could be relied upon as accurate time indicators. Patients undergoing a variety of treatment techniques were timed for the duration of their treatment procedure, and their treatment times compared to the time estimated using the BTE formula. A few minor alterations were made to the equation for treatment units with multi-leaf collimation (MLC). A trial conducted at Sir Charles Gairdner Hospital found that, using the BTE formula (with a few modifications required for the MLC treatment units), of 60 patients timed for the duration of their set-up and treatment, 85% of values were in the range of +/- 3 min, and 95% were in the range of +/- 5 min of the estimated times. Through the routine use of the BTE equation a more sensitive indication of treatment machine workload can be found. Advantages such as: (i) a more accurate measure of treatment workload (for comparison with other departments) and (ii) increased scheduling accuracy will succeed over the currently accepted system of fields per hour.

Appointments and Schedules↗
PubMed2000

Evaluation of total volatile organic compound emissions from adhesives based on chamber tests.

In 1997, Homeswest in western Australia and Murdoch University developed a project to construct low-allergen houses (LAHs) in a newly developed suburb. Before the construction of LAHs, all potential volatile organic compound (VOC) emission materials used in LAHs are required to be measured to ensure that they are low total VOC (TVOC) emission materials. This program was developed based on this purpose. In recent times, the number of complaints about indoor air pollution caused by VOCs has increased. A number of surveys of indoor VOCs have indicated that many indoor materials contribute to indoor air pollution. Although some studies have been conducted on the characteristics of VOC emissions from adhesives, most of them were focused on VOC emissions from floor adhesives. Few measurements of VOC emissions from adhesives used for wood, fabrics, and leather are available. Furthermore, most research on VOC emissions from adhesives has been done in countries with cool climates, where ventilation rates in the indoor environment are lower than those in Mediterranean climates, due to energy conservation. VOCs emitted from adhesives have not been sufficiently researched to prepare an emission inventory to predict indoor air quality and to determine both exposure levels for the Australian population and the most appropriate strategies to reduce exposure. An environmental test chamber with controlled temperature, relative humidity, and airflow rate was used to evaluate emissions of TVOCs from three adhesives used frequently in Australia. The quantity of TVOC emissions was measured by a gas chromatography/flame ionization detector. The primary VOCs emitted from each adhesive were detected by gas chromatography/mass spectrometry. The temporal change of TVOC concentrations emitted from each adhesive was tested. A double-exponential equation was then developed to evaluate the characteristics of TVOC emissions from these three adhesives. With this double-exponential model, the physical processes of TVOC emissions can be explained, and a variety of emission parameters can be calculated. These emission parameters could be used to estimate real indoor TVOC concentrations in Mediterranean climates.

Adhesives↗
PubMed2000

Pallidotomy microelectrode targeting: neurophysiology-based target refinement.

OBJECTIVE: Microelectrode recording can refine targeting for stereotactic radiofrequency lesioning of the globus pallidus to treat Parkinson's disease. Multiple intraoperative microelectrode recording/stimulating tracks are searched and assessed for neuronal activity, presence of tremor cells, visual responses, and responses to kinesthetic input. These physiological data are then correlated with atlas-based anatomic data to approximate electrode location. On the basis of these physiological properties, one or more tracks are selected for lesioning. This study analyzes the track physiological factors that seem most significant in determining the microelectrode recording track(s) that will be chosen for pallidal lesioning. METHODS: Thirty-six patients with Parkinson's disease underwent microelectrode-guided pallidotomy. Between one and five microelectrode recording tracks were made per patient. Usually, one (n = 23) or two (n = 12) of these tracks were lesioned. Electrode positions in the x (mediolateral) and y (anteroposterior) axes were recorded and related to track neurophysiological findings and final lesion location. The stereotactic location and sequence of microelectrode tracks were recorded and plotted to illustrate individual search patterns. These patterns were then compared with those noted in other patients. Neurophysiological data obtained from recording tracks were analyzed. A retrospective analysis of track electrophysiology was performed to determine the track characteristics that seemed most important in the surgeon's choice of the track to lesion. Track physiological properties included general cell spike amplitude, tremor synchronous neuronal firing, kinesthetically responsive neuronal firing, and optic track responses (either phosphenes reported by the patient during track microstimulation or neuronal firing in response to light stimulus into the patient's eyes). Orthogonally corrected postoperative magnetic resonance images were used to confirm the anatomic lesion locations. RESULTS: In patients who had a single mapped track lesioned, specific track electrophysiological characteristics identified the track that would be lesioned most of the time (20 of 24 patients). Tracks that exhibited a combination of tremor synchronous firing, joint kinesthesia, and visual responsivity were lesioned 17 (85%) of 20 times. Analysis of intraoperative electrode movement in the x and y axes indicated a significant subset of moves but did not result in microelectrode positioning closer to the subsequently lesioned track. Accuracy of initial electrode movement in the x and y axes was most highly correlated with a measure of first-track electrophysiological activity. The number of microelectrode recording tracks did not correlate with clinical outcome. Anatomic analysis, using postoperative magnetic resonance imaging, revealed that all lesions were placed in the globus pallidus. Most patients (35 of 36) improved after surgery. CONCLUSION: The level of electrophysiological activity in the first track was the best predictive factor in determining whether the next microelectrode move would be closer to the ultimately lesioned track. The analysis of electrode track location and neurophysiological properties yields useful information regarding the effectiveness of microelectrode searching in the x and y axes. Within an institution, the application of this modeling method may increase the efficiency of the microelectrode refinement process.

Aged↗
PubMed1999

Educational campaign to improve the prevention of postoperative venous thromboembolism.

BACKGROUND: Recent studies have revealed considerable scope for improvement in preventing postoperative venous thromboembolism. This project comprised a baseline assessment of the use of preventive measures within the Royal Hobart Hospital, followed by the implementation and evaluation of an educational program directed at hospital staff. AIM: To determine whether the Royal Hobart Hospital's guidelines for the prophylaxis of postoperative venous thromboembolism were being utilized effectively and, if necessary, attempt to improve use of the guidelines through an educational programme. METHODS: Data were collected retrospectively from the medical records of 250 surgical patients undergoing a procedure during February 1997. Patients were classified as being at a low, medium or high risk of venous thromboembolism using two sets of criteria. The percentage of patients receiving the appropriate prophylaxis was determined. An educational programme to promote the hospital's guidelines for the prophylaxis of postoperative venous thromboembolism was then implemented. Included were presentations to staff, posters placed throughout the hospital and the wide distribution of the results and a glossy card showing the hospital's guidelines. Follow-up data were subsequently collected from another 250 surgical patients. RESULTS: Only 59% of patients received appropriate prophylaxis according to the hospital's approved guidelines, with little change when those patients with possible contraindications to thromboprophylaxis were excluded. When those patients at a high risk of venous thromboembolism were examined, only 25% were prescribed the recommended preventive measures. There was no difference between elective versus emergency surgery and the use of appropriate prophylaxis. Following the implementation of the educational programme, data collection from another 250 surgical patients revealed a significant increase (P < 0.05 by chi-square test) in the level of appropriate thromboprophylaxis to 70% of patients, with 77% of the high-risk patients being prescribed the recommended preventive measures. CONCLUSIONS: A pharmacy-based educational intervention significantly improved adherence to the hospital's guidelines for the prophylaxis of postoperative venous thromboembolism.

Australia↗