Calculation of absolute intensities from X-ray imaging plates

A numerical technique for deriving a conversion factor between the output pixel values from a scanned imaging plate and the actual incident X-ray photon flux is proposed. The technique requires no external calibration by independent detectors, but uses the statistical information inherent in the image. As a test case, this technique was applied to a Fuji BAS2000 imaging-plate scanner. The calculation showed that, at 1.2 Angstrom, 163 (8) photons pixel(-1) were required to give one output unit of pixel intensity on an image scanned 20 min after exposure. This conversion factor compared favourably with the independently measured conversion factor of 171.1 (5) photons pixel(-1) (output unit)(-1) obtained from a high-quantum-efficiency Ge detector.