The `Seed-Skewness' Method for Integration of Peaks on Imaging Plates

A new method of area-detector peak integration based on the statistical analysis of pixel intensities is described. The presence of the peak in the integration box causes the skewness of the pixel intensity distribution to increase compared to the skewness of the noise distribution. After the pixel intensities have been smoothed, the peak mask, assumed to be contiguous, grows from a `seed' until the skewness of the pixel intensity distribution outside the seed area reaches a minimum. The new method has been successfully applied to the processing of imaging-plate data from a buckminsterfullerene derivative and from sodium nitroprusside collected by the oscillation method at a synchrotron source. In both cases, the seed-skewness procedure proved to be superior to the standard-box and dynamic mask methods, especially for weaker reflections. Similar results were obtained with rotating-anode data.