Digital Fluoroscopy System에서 촬영조건의 변화에 따른 DICOM Image의 Histogram 변화와 JPEG 압축률의 변화 분석

Comparison of Change of Histogram and JPEG Compression Rate of DICOM Image by Exposure Condition in Digital Fluoroscopy

To find the proper exposure condition in digital fluoroscopic system, it is compared the change of histogram and JPEG compression rate of DICOM Image according to exposure condition. Digital fluoroscopic system was Philips easy diagnost with under table tube. BaSO4 of 220% w/v phantom to the size 18×22.5 ×0.2㎝ and two polyethylene phantom to 35.5×35.6×7㎝ were used for this study. A standard value (90㎸, 1.93mAs, 9.55㎳, 202㎃) was obtained by Automatic exposure Controler (AEC) for comparing with manual exposure condition. The test were done by changing 40, 50, 60, 70, 81, 90, 102, 109, 117㎸ with mAs fixed, and 63, 80, 100, 125, 160, 200, 250, 320, 400㎃ with ㎸ fixed, and 3.2, 4, 5, 6.2, 8, 10, 12.5 16, 20㎳ with mA and ㎸ fixed. Distribution of histogram of DICOM Image in the case of mAs fixed shifted from left toward right according to ㎸ increment gradually. Distribution of histogram in the case of ㎸ fixed also shifted from left toward right according to mAs increment gradually. When mA and ㎸ was fixed, the histogram was not a significant change according to change ㎳. JPEG compression rate was the lowest at standard value including 90㎸, 1.93mAs, 9.55㎳,and 202㎃ obtained by AEC. The exposure condition is better by AEC than by manual setting up. Analysis of histogram of DICOM Image can be used as a method for quality control of AEC.