A STUDY ON EVALUATION OF DENTAL FILMS BY DIGITAL IMAGE PROCESSING

-ANALYSIS OF ALVEOLAR TRABECULA BY MEANS OF TWO DIMENSIONAL FFT-

Abstract

The purpose of this paper is to evaluate the newly composed Image Processing System as a method for analyzing radiographic trabecular pattern of dental films objectively by use of First Fourier Transform (FFT).
In this Image Processing System, TV-camera was used for data sampling of radiographic images of alveolar trabecula of dental films. These sampling data were digitized and memorized in IMAGE MEMORY UNIT (IMU-6008). These digitized data were prepared by Low Cutoff Filter to remove TREND and by HANNING WINDOW FUNCTION for reproduction. Then the two dimensional Power Spectra which reflected the information of trabecular pattern were selected by image reconstruction used Band Pass Filter.
The following results were obtained.
1) In this Image Processing System, the optical resolving power of TV-camera was less than 8.0LP/mm in spatial frequency. The linearity of the film density and the brightness were obtained in the range of density from 0.68 to 1.80.
2) Pretreatment by TREND and HANNING was useful for analzing of the data.
3) The radiographic information of alveolar trabecular pattern of dental films could be expressed as the sum of Power Spectrum between 0.5 and 3.0LP/mm in spatial frequency.
4) Clinical application of this Image Processing System were used for analyzing radiographic alveolar trabecular pattern of the patients with renal osteodystrophy. Radiological changes of trabecular pattern were classified into 5 groups based on the value of Power Spectra.