디지털구내방사선사진의 구리당량화상에 대한 평가
An Assesment on Cu-Equvalent Image of Digital Intraoral Radiography
김재덕,
소속 상세정보
김재덕 ( ) - 조선대학교 치과대학 구강악안면방사선학교실
KMID : 0353319980220020209
Abstract
Geometically standardaized dental radiographs were taken. We prepared Digital Cu-Equivalent Image Analyzing System for quantitative assessment of mandible bone. Images of radographs were digitized by means of Quick scanner and personal Mcquintosh computes. NIH image as software was used for analyzing images. A stepwedge composed of 10 steps of O.lmm copper foil in tickness was used for reference material.
This study evaluated the effects of step numbers of copper wedge adopted for calculating equation, kVp and exposure time on the coefficient of determination(r)of the equation for conversion to Cu-equivalent image and the coefficient of variation and Cu-Eq value(mm) measured at each copper step and alveolar bone of mandible.
The results were as follows:
1. The coefficients of determination(r) of 10 conversion equations ranged from 0.99% to 0.9973 (mean =0.9988) under 70kVp and 0.16 sec. exposure. The equation showed the highest r´` was Y=4.75614612-0.06300524x +0.00032367x´ -0.00000060x3.
2. The value of r` became lower when the equation was calculated from the copper stepwedge including 1.Omm step. In case of including Omm step for calculation, the value of r showed variability. ´
3. The coefficient of variation showed 0.11, 0.20 respectively at each copper step of 0.2. O.lmm in thickness. Those of the other steps to :0.9 mm ranged from 0.06 to 0.09 in mean value.
4. The mean Cu-Eq value of alveolar bone was 0.140.02mm under optimal exposure. The values were lower than the mean under the exposures over 0.20se~_. in 6OkVp and over 0.16sec. in 70kVp .
5. Under the exposure condition of 6OkVp 0.16sec., the coefficient of variation showed
0.03, 0.05 respectively at each copper-step of 0.3, 0.2mm in thickness. The value of r2
showed over 0.9991 from both 9 and 10 steps of copper. The Cu-Eq value and the
coefficient of variation was 0.14O.Olmm and 0.07 at alveolar bone respectively.
In summary, A clinical application of this system seemed to be useful for assessment of quantitative assessment of alveolar provided high coefficient of determination is obtained by the modified adoption of copper step numbers and the low coefficient of variation for the range of Cu-Equivalent value of alveolar bone from optimal kVp and exposure time for each x-rav machine.
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