The development of high-efficiency cathode converters for a multiwire proportional chamber positron camera

A high-efficiency cathode converter for 511-keV photons has been developed for incorporation into a multiwire proportional chamber (MWPC) positron camera. The converter consists of a honeycomb pattern produced in a 1-mm-thick lead sheet to leave lead walls with a thickness of approximately 60 micron. The converter also serves as the cathode of an MWPC, the gap between the converter and the anode wire plane being 2.5 mm. This small gap results in a high secondary electron extraction efficiency without the need for additional drift voltages. Measurements of the efficiencies of a plane converter and of two types of structured converters in a single section MWPC are described and the efficiency is found to increase in proportion to the converter surface area. This result justifies the use of a simple theoretical model whereby an extrapolation to the efficiency of a detector consisting of a stack of 20 MWPC sections, each section having two converters, is made. The efficiency of this proposed system is calculated to be 17% for 511-keV photons.     

Vertical saccades in superior oblique palsy

Vertical saccadic velocities in 10 patients who had unilateral superior oblique muscle palsy and 14 normal subjects were measured with the magnetic scleral search coil. The authors sought to determine whether downward saccades in patients who had superior oblique palsy are slow. Peak velocities of 10 degrees and 20 degrees saccades performed in the superior and inferior fields of the orbit, and 10 degrees, 20 degrees, and 30 degrees saccades performed across the center of the orbit were recorded with the eye in center gaze, 30 degrees of adduction, and 30 degrees of abduction. Paired t-tests did not show statistically significant differences between upward and downward saccades in patients with superior oblique palsy; no effects of orbital field or position of horizontal gaze were found (P greater than 0.01). Comparison of similar saccades between normal subjects and patients with superior oblique palsy by two-sample t-tests did not show significant differences between the two groups (P greater than 0.01).     

Accident prevention in the A&E department

Accident and Emergency units are often regarded as the 'shop window' of a health service. While the priority is to attend to those in need of emergency services, there may also be opportunities for health education amongst a 'captive audience', particularly in relation to accident prevention. This report illustrates how the influence of one A&E department was used amongst primary school children to increase their awareness of cycle safety. Educational materials were developed, a series of visits to schools was planned, which over 600 children attended, and a competition organised. Initial responses from the children were very positive, and an analysis of subsequent cycle injury levels is now under way. The project formed part of a wide ranging practice development programme within a large district general hospital in Whitehaven in collaboration with St Martin's College Department of Nursing. It combined the need to develop quality services and staff in tandem. The outreach educational approach is now being examined for adoption in other areas of the Trust.     

Severe malaria in children in Papua New Guinea

The clinical features of severe falciparum malaria and risk factors for mortality were studied in 489 children admitted with malaria to Madang Hospital, Papua New Guinea. The most common severe manifestations of malaria were severe anaemia (22%) and coma (16%). Children with severe anaemia were younger than those with coma (median age 2.2 vs. 3.7 years) and had been ill for longer before admission (median 7 vs. 4 days, respectively). Although the clinical features of coma in Madang children with malaria resembled closely those reported in African children, mortality was lower (8% vs. 17-25%, respectively). Overall, 17 (3.5%) children died, most within 12 h of admission. A high level of plasma lactate (> or = 5 mmol/l) was common (20%) and was the major predictor of death in multiple regression analysis. Raised plasma creatinine and decreased plasma bicarbonate were also independent predictors of mortality. Coma was not predictive of death, although a high proportion of children with profound coma died. Investigation of the causes of acidosis in children with malaria is a high research priority. In view of the short time interval between admission and death in many children, emphasis must be placed on the prevention or early recognition and treatment of acidosis in the district health clinic as well as the central hospital.