Serial periapical dental radiographs are produced using a constant exposure geometry made possible by a simple occlusal template. Selected radiograph pairs are placed in register with the aid of a micromanipulator and a closed-circuit video system. The same video system, interfaced with an A to D converter, is used to store the respective radiographs as 6 bit images in a frame buffer. A computer is then used to subtract the two images. Gamma correction is accomplished with special software to assure that any non-linear effects attributable to contrast differences between radiographs are minimized. Blurring of the difference image, in an area known to be unchanged, provides a means for thresholding out differences attributable to registration artifacts. Preliminary data on both patients and radiographic phantoms demonstrate that diagnostic accuracy from subtracted images is markedly improved when compared to that obtainable from the undigitized control radiographs displayed conventionally.

Date Published: 1 November 1982
PDF: 9 pages
Proc. SPIE 0372, Physics and Engineering in Medical Imaging, (1 November 1982); doi: 10.1117/12.934505

Published in SPIE Proceedings Vol. 0372:
Physics and Engineering in Medical Imaging
Orhan Nalcioglu, Editor(s)