The use of an oblique transformation to obtain physiological factors from a factor analysis of dynamic studies has recently been suggested. The technique involves using an apex-seeking routine to enable these factors and their contribution images to be formed. This paper investigates the effects of errors in apex-finding on these factor images. In particular it is shown that, apart from scaling, the factor image obtained from a given apex is independent of the position of that apex (and hence is independent of its own factor).

Spatial reproducibility in ROI drawing does not necessarily relate directly to the associated quantitative reproducibility.

Boxers who had fought fewer bouts had a tendency to perform better at psychometric tests than those boxers who had fought more bouts. Tc-99m HMPAO SPECT cerebral perfusion scanning showed that controls had less aberrations in cerebral perfusion than the boxers.In conclusion, significant differences were shown in two neurophysiological variables between young amateur sportsmen who box and those who do not. The long term effects of these findings remain unknown.(7 Neurol Neurosurg Psychiatry 1 995;59:368-374)

Results were received from 63 nuclear medicine centres using 77 computer systems. The vast majority of participants (57) carried out fewer than 10 scans per month. Only two centres performed more than 30 scans per month. Sixteen centres did not quote a minimum normal value for left ventricular ejection fraction (LVEF) and 36 did not record a maximum value. The remainder recorded between 0.40 and 0.60 for the minimum of normal range and 0.60-0.90 for the maximum of normal range. Analysis of returns showed that LVEF estimates for the data sets were highly variable between centres and computer systems. The overall standard deviation of results compared to the mean for each study was 0.076. Approximately half this variation was due to systematic variation between centres. The overall precision taking into consideration this systematic variation, was 0.055. Lower variability was found between studies with higher overall counts and this was highly significant.