Water equivalent thickness analysis of immobilization devices for clinical implementation in proton therapy.

Immobilization devices can impact not only the inter- and intra-fraction motion of the patient, but also the range uncertainty of the treatment beam in proton therapy. In order to limit additional range uncertainty, the water equivalent thickness (WET) of the immobilization device needs to be well known and accurately reflected in the calculations by the treatment planning system (TPS). The method presented here focusses on the use of a nozzle-mounted variable range shifter and precision-machined polystyrene blocks of known WET to evaluate commercial immobilization devices prior to clinical implementation. CT studies were also completed to evaluate the internal uniformity of the immobilization devices under study. Mul- tiple inserts of the kVue platform (Qfix Systems, Avondale, PA) were evaluated as part of this study. The results indicate that the inserts are largely interchangeable across a given design type and that the measured WET values agree with those generated by the TPS with a maxi- mum difference less than 1 mm. The WET of the devices, as determined by the TPS, was not impacted by CT beam hardening normally experienced during clinical use. The reproduc- ibility of the WET method was also determined to be better than ±0.02 mm. In conclusion, the testing of immobilization prior to implementation in proton therapy is essential in order to ascertain their impact on the proton treatment and the methodology described here can also be applied to other immobilization systems.

A classification and regression tree to assist clinical decision making in airway management for patients with cervical spinal cord injury.

STUDY DESIGN: This was a prospective observational study. OBJECTIVES: To review airway management of patients with acute cervical spinal cord injury (CSCI) who are admitted to the intensive care unit (ICU) and to develop a classification and regression tree (CART) to direct clinical decision making in airway management. SETTING: This study was carried out in Australia. METHODS: All patients with CSCI who required intubation and mechanical ventilation and who were admitted to ICU in three tertiary hospitals in Melbourne between October 2004 and May 2009 and two other interstate hospitals between December 2004 and December 2005 were included. Airway management was recorded. RESULTS: A total of 114 patients were included. Tracheostomy insertion occurred in 68 patients (59.7%). Using CART analysis, it was found that the variables forced vital capacity, the volume of pulmonary secretion and gas exchange were predictive of airway management on 82.3% occasions with an 8.7% extubation failure rate. CONCLUSION: A CART can be useful in clinical decision making regarding airway management in CSCI.

A comparison of statistical methods for meta-analysis.

Meta-analysis may be used to estimate an overall effect across a number of similar studies. A number of statistical techniques are currently used to combine individual study results. The simplest of these is based on a fixed effects model, which assumes the true effect is the same for all studies. A random effects model, however, allows the true effect to vary across studies, with the mean true effect the parameter of interest. We consider three methods currently used for estimation within the framework of a random effects model, and illustrate them by applying each method to a collection of six studies on the effect of aspirin after myocardial infarction. These methods are compared using estimated coverage probabilities of confidence intervals for the overall effect. The techniques considered all generally have coverages below the nominal level, and in particular it is shown that the commonly used DerSimonian and Laird method does not adequately reflect the error associated with parameter estimation, especially when the number of studies is small.

Effect of casemix funding on outcomes in patients admitted to hospital with suspected unstable angina.

OBJECTIVES: To determine the effect of the introduction of casemix funding on resource utilisation and clinical outcomes in patients admitted to hospital with suspected unstable angina. DESIGN: A prospective cohort study with a 6-month follow-up. SETTING: A suburban community hospital in Melbourne, Victoria. PATIENTS: 336 consecutive patients admitted to the coronary care unit with suspected unstable angina before (156) and after (180) the introduction of casemix funding. INTERVENTION: Introduction of casemix funding in July 1993. MAIN OUTCOME MEASURES: Indices of resource utilisation: length of stay in hospital, length of stay in the coronary care unit, and total cost of investigations (pathology and radiology). Rates of serious cardiac events during hospital stay and after discharge. Readmissions within 28 days and 6 months of discharge. RESULTS: After the introduction of casemix funding there was a 1% increase in duration of hospital stay and a 5% increase in time spent in the coronary care unit, but neither of these increases was statistically significant. However, there was a significant reduction in total cost of investigations (39% decrease; 95% confidence interval, 14%-70%; P < 0.001). The rate of serious cardiac events after discharge did not increase, and neither did readmission rates, either within 28 days or over the 6 months' follow-up. CONCLUSION: Casemix funding had no effect on short term clinical outcomes but resulted in significantly reduced investigation costs.

A multi-stream analysis of the changing pattern of interregional migration in Great Britain, 1960-1991.

PIP: "This paper uses a combination of spatial and econometric modelling techniques to investigate longer term patterns and processes of change in British interregional migration.... The two major influences on the longer distance flows are found to be relative rates of employment growth and perceived environmental quality, but while the former induces marked fluctuations within the observation period, the influence of the latter factors shows little variation, with no sign of a clean break. There is, however, evidence of a sharply reduced responsiveness of migration to unemployment differentials since the mid-1970s." (EXCERPT)^ieng

Cancer incidence and mortality and proximity to TV towers.

OBJECTIVE: To determine whether there is an increased cancer incidence and mortality in populations exposed to radiofrequency radiations from TV towers. DESIGN: An ecological study comparing cancer incidence and mortality, 1972-1990, in nine municipalities, three of which surround the TV towers and six of which are further away from the towers. (TV radiofrequency radiation decreases with the square of the distance from the source.) Cancer incidence and mortality data were obtained from the then Commonwealth Department of Human Services and Health. Data on frequency, power, and period of broadcasting for the three TV towers were obtained from the Commonwealth Department of Communications and the Arts. The calculated power density of the radiofrequency radiation in the exposed area ranged from 8.0 microW/cm2 near the towers to 0.2 microW/cm2 at a radius of 4km and 0.02 microW/cm2 at 12 km. SETTING: Northern Sydney, where three TV towers have been broadcasting since 1956. OUTCOME MEASURES: Rate ratios for leukaemia and brain tumour incidence and mortality, comparing the inner with the outer areas. RESULTS: For all ages, the rate ratio for total leukaemia incidence was 1.24 (95% confidence interval [CI], 1.09-1.40). Among children, the rate ratio for leukaemia incidence was 1.58 (95% CI, 1.07-2.34) and for mortality it was 2.32 (95% CI, 1.35-4.01). The rate ratio for childhood lymphatic leukaemia (the most common type) was 1.55 (95% CI, 1.00-2.41) for incidence and 2.74 (95% CI, 1.42-5.27) for mortality. Brain cancer incidence and mortality were not increased. CONCLUSION: We found an association between increased childhood leukaemia incidence and mortality and proximity to TV towers.

Duration dependence in migration behaviour: cumulative inertia versus stochastic change.

"In this paper a new theoretical framework and supporting empirical evidence on the relationship between movement probabilities and length of stay are presented. Individuals' evaluations of the relative value of alternative locations are assumed to evolve stochastically, with a possible tendency either to cumulative inertia or to cumulative stress. In general this yields a nonmonotonic duration function, with probabilities of movement starting at zero, rising and then falling--a pattern consistent with either cumulative tendency, or neither. A version of the model fitted to data on household movement intentions, from the U.K. General Household Survey, confirms the hypothesised form of this function and indicates a dominance of cumulative stress over cumulative inertia."

Suicide and related deaths in Victorian doctors.

A cohort of University of Melbourne medical graduates (1950-1959 graduates inclusive) was followed up until December 31, 1986. Vital status at the end of the study period was ascertained and, for those who had died, cause of death was determined. The cohort consisted of 1453 members (1279 men and 174 women). One hundred and twenty-six of the group had died (115 men and 11 women) and 68 (4.7%; 57 men and 11 women) were lost to follow-up. The major causes of death were cardiovascular disease and malignant neoplasms. The standardised mortality ratios (SMRs) for all-cause mortality were low (59 for the male doctors and 84 for the female doctors) indicating that male doctors experience a "force of mortality" 59% that of the general population and female doctors 84%. For the male doctors, the SMR for suicide was 113 (95% confidence interval [CI], 54-207) (10 of 115 deaths in male doctors) about double the SMR for mortality from all causes. For the female doctors, the SMR for suicide was 501 (95% CI, 103-1500) (3 of 11 deaths in female doctors). For deaths resulting from all accidents the SMR was low for the males (29) and higher for the females (126). The SMR for mental disorders for the male doctors was marginally raised (132). This study reveals some indication of a problem in doctors in regard to deaths by suicide, other violent deaths and mental disorders. A larger study involving a control group of equivalent social class is required to confirm the findings of this study.

The bristol registry of bone dysplasias: the first 10 years.

The Bristol Bone Dysplasia Registry was established in 1969. The panel included radiologists, paediatricians, orthopaedic surgeons, pathologists, a paediatric biochemist, an anatomist/anthropologist, a veterinary surgeon, dentists and oral surgeons, and a psychiatrist. The panel met every two months. Cases either entered the Registry directly if they were straightforward or after discussion by the panel if there was doubt about the diagnosis or a point of special interest. A total of 468 cases was collected, including 81 cases with miscellaneous bony disorders and 34 cases where the diagnosis was uncertain. The Registry provided a useful regional diagnostic service and promoted interest in body dysplasias. Some of the research aims have not yet been fully achieved. This paper explains how the Registry is run to help those whom it is hoped will set up similar registries elsewhere.

The Patterson syndrome, leprechaunism, and pseudoleprechaunism.

A bizarre syndrome has hitherto masqueraded as leprechaunism, and although it is a quite different disorder it has been used as the prototype of leprechaunism in some birth defects atlases. It is proposed that this condition is designated the Patterson syndrome and details of a second case are reported. The features of this connective tissue and neuroendocrine disorder include bronzed hyperpigmentation, cutis laxa of the hands and feet, bodily disproportion, severe mental retardation, and major bony deformities. Radiographs revealed a unique and gross generalised skeletal dysplasia, unlikely to be confused with any other disorder. This endocrine abnormality comprised hyperadrenocorticism, cushingoid features, and diabetes mellitus in the first case, and premature adrenarche in the second case. The pathogenesis and aetiology of the Patterson syndrome are unknown, although quantitative and qualitative abnormalities of mucopolysaccharide excretion were found in the second case.

Height and skeletal maturity in children with newly-diagnosed juvenile-onset diabetes.

Height and skeletal maturity scores (TW 2) were determined in 77 diabetic children at diagnosis and again in 48 of them after 1 to 4 years on insulin treatment. Boys, especially those of prepubertal age, were tall at onset. Girls had normal stature, but showed significant growth retardation after treatment. Skeletal maturity was appreciably advanced in both sexes at diagnosis, and on treatment returned to normal only in boys. Girls maintained their advanced skeletal maturity, resulting in an increased disparity between height and skeletal maturity. The results of this study suggest that a prediabetic metabolic abnormality may enhance skeletal maturity in children with diabetes and continues to operate in girls after treatment, despite a reduced growth rate.

Keratan sulphate excretion in a patient with Kniest dysplasia.

The clinical and radiological features of a patient with Kniest dysplasia, a form of metatropic dwarfism, are described. The patient excreted glycosaminoglycans (mucopolysaccharides) in normal amounts during infancy but subsequently showed abnormal keratan sulphate excretion. The significance of these findings and the possibility that Kniest dysplasia represent another mucopolysaccharidosis are discussed.

Cystic fibrosis, atopy, and airways lability.

In a survey of cystic fibrosis (CF) in the Avon area, 48 children with CF from 40 families together with 71 of their parents were studied by spirometry, exercise tests, and pinch tests. A control group of 42 young adults was similarly tested; control data for children were taken from previously published work. The prevalence of atopy (any positive prick test) in children with CF was 48%. Sensitivity to grass pollens and house dust mite was no more common in these children (29%) than in a normal population (34%). Hypersensitivity to Aspergillus fumigatus was found in 35% of children with CF and was associated with severe lung disease. The parents had a normal pattern and prevalence of atopy. Exercise-induced airways obstruction was present in only 22% of children with CF; its association with severe lung disease rendered interpretation difficult. The parents had a normal response to exercise. Both hypersensitivity to A. fumigatus and exercise-induced airways lability had the features of acquired characteristics. There was nothing in the present study to support the hypothesis that the possession of a CF gene predisposed to atopy.

Clinical and biochemical studies in Engelmann's disease (progressive diaphyseal dysplasia).

The clinical and biochemical features of four adults with Engelmann's disease (Camurati-Engelmann disease; progressive diaphyseal dysplasia) are presented. One young patient, with a particularly severe form of the disease, is discussed in detail. Biochemical abnormalities were found in three of the patients. In two of them, one with localized hyperostosis and one with generalized bone disease, the only changes were an increase in the plasma alkaline phosphatase and urinary total hydroxyproline excretion. The most severely affected patients, who had had progressive and generalized bone disease from age two and a half years, also had persistent hypocalcaemia and hyperphosphataemia, a positive calcium balance, and a very low urine calcium excretion. It is suggested that some patients with Engelmann's disease may have a previously unrecognized metabolic disorder associated with increased retention of calcium and excessive bone formation. The possible role of abnormal phosphate metabolism in this increased formation of bone, and the relationship of Engelmann's disease to other hyperostoses, are discussed.

Urinary lithiasis in childhood in the Bristol clinical area.

A series of 59 consecutive cases of urinary calculi in childhood is presented, being acquired from one local area (Bristol). These children were treated from 1950 to 1973. The peak presentation was in the 2nd and 3rd year of life, with a secondary peak in the 10th year. Anatomical (39%), metabolic (8.5%) or primary infective abnormalities (29%) were demonstrable, but 22% had to be left in an unsatisfactory "idiopathic classification''. The overall recurrence rate of 7% was reduced to 3.5% when those patients with cystinuria were excluded. The local water supply areas have been studied and a tentative association is suggested between patients and their environment when they live in an area where the water is not only hard but also alkaline (pHgreater than 8).

Urinary lithiasis in childhood in the Bristol clinical area.

A series of 59 consecutive cases of urinary calculi in childhood is presented, being acquired from one local area (Bristol). These children were treated from 1950 to 1973. The peak presentation was in the 2nd and 3rd year of life, with a secondary peak in the 10th year. Anatomical (39%), metabolic (8.5%) or primary infective abnormalities (29%) were demonstrable, but 22% had to be left in an unsatisfactory "idiopathic classification". The overall recurrence rate of 7% was reduced to 3.5% when those patients with cystinuria were excluded. The local water supply areas have been studied and a tentative association is suggested between patients and their environment when they live in an area where the water is not only hard but also alkaline (pH greater than 8).