Digital image processing and clinical application of video densitometer

The purpose of this study was to propose the utility which was evaluated the digital image processing and clinical application of the video densitometry. The experiments were performed with IBM-PC/16 bit-AT compatible, video camera (CCdtr55, Sony Co., Japan), an colormonitor (MultiSync 3D, NEC, Japan) providing the resolution of 512 X 480 and 64 levels of gray. Sylvia Image Capture Board for the ADC (analog to digital converter) was used, composed of digitized image from digital signal and the radiographic density was measured by 256 level of grey. The periapical radiograph (Ektaspeed EP-21, Kodak Co., U. S. A.) which was radiographed dried human mandible by exposure condition of 70 kVp and 48 impulses, was used for primary X-ray detector. And them evaluated for digitized image by low and high pass filtering, between aluminum equivalent values and the thickness of aluminum step wedge, aluminum equivalent values of sound enamel, dentin, and alveolar bone, the range of diffuse density for gray level ranging from 0 to 255. The obtained results were as follows: 1. The edge between aluminum steps of digitized image were somewhat blurred by low pass filtering, but edge enhancement could be resulted by high pass filtering. Especially, edge enhancement between digital root of lower left 2nd molar and alveolar lamina dura was observed. 2. The correlation between aluminum equivalent values and the thickness of aluminum step wedge was intimated, yielding the coefficient of correlation r=0.9997 (p<0.001), the regression line was described by y=0.9699X + 0.456, and coefficient of variation amounting to 1.5%. 3. The aluminum equivalent values of sound enamel, dentin, and alveolar bone were 15.41 mm, 12.48 mm, 10.35 mm, respectively. 4. The range of diffuse density for gray level ranging from 0 to 255 was enough than that of photodensitometer to be within the range of 1-4.9.