1997 Volume 53 Issue 11 Pages 1665-1672
We examined the relation between the frequency components of x-ray images of the chest and phalanges and their read sizes for digitizing. Images of the chest and phalanges were radiographed using three types of screens and films, and the noise images in background density were digitized with a drum scanner, changing the read sizes. The frequency components for these images were evaluated by converting them to the secondary Fourier to obtain the power spectrum and signal to noise ratio(SNR). After changing the cut-off frequency on the power spectrum to process a low pass filter, we also examined the frequency components of the images in relation to the normalized mean square error(NMSE)for the image converted to reverse Fourier and the original image. Results showed that the frequency components were 2.0 cycles/mm for the chest image and 6.0 cycles/mm for the phalanges. Therefore, it is necessary to collect data applying the read sizes of 200μm and 50μm for the chest and phalangeal iamges, respectively, in order to digitize these images without loss of their frequency components.
