The effects of aliasing error on computed radiography in medical imaging

Abstract

In computed radiography in medical imaging, the quality of the image made on the imaging plate (IP) is changed by the digitizing and printing processes. According to the sampring theorem, aliasing errors will occur when the image is sparsely sampled. We simulated these processes and measured the modulation transfer function (MTF) and aliasing error. Both an X-ray film and an IP were packed in a cassette so that X-ray film was exposed by instantaneous luminescence of the IP. Analog and digital images on clinical radiographs, such as of the chest and the foot, were obtained by this method. Both images were compared by radiologists under the usual viewing condition and with optical magnification. Results showed that the digital images were degraded with poor sharpness and had aliasing error produced by the digitizing process, but the aliasing error could not be observed on the clinical image. Therefore, a system producing sharper images will be required, although aliasing errors could increase.