Quantitative Evaluation of Image Quality using Automatic Exposure Control & Sensitivity in the Digital Chest Image

Abstract

The patient radiation dose is different depending on selection of Ion chamber when taking Chest PA which using AEC. In this paper, we studied acquiring the best diagnostic images according to selection of Ion chamber on AEC mode as well as minimizing patient radiation dose. Experimental methods were selection of Ion chamber and change of sensitivity under the same conditions as Chest PA projection. At AEC mode, two upper ion chambers sensors and one lower ion chamber sensor were divided into 7 cases according to selection of on/off. after measuring five times respectively, we obtained average value and calculated exposure dose. Image assessment was done with measured Modulation Transfer Function, Peak Signal to Noise Ratio, Root Mean Square, Signal to Noise Ratio, Contrast to Noise Ratio, Mean to Standard deviation Ratio respectively. In exposure assessment results, selection of two upper chambers was the lowest. In resolution assessment results, image of two upper chambers had the second high spatial frequency at sensitivity at 625(High) was 1.343 lp/mm. RMS value of image selecting two upper chambers was low secondly. SNR, CNR, MSR were the high value secondly. As the sensitivity was increased, radiation dose was decreased but better image could be obtained on image quality. In order to obtain the best medical images while minimizing the dose, usage of two upper ion chambers is considered to be clinically useful at sensitivity 625(High).

The Additional Filter and Ion Chamber Sensor Combination for Reducing Patient Dose in Digital Chest X-ray Projection

“…[10] . 실험은 사각파응 답함수(SWRF)의 구형파형 차트법(rectangular chart method)을 이용하여 공간주파수의 해상력 값을 측정하 였다 [11] . Table 6].…”

Evaluation of High Absorption Photoconductor for Application to Auto Exposure Control Sensor by Screen Printing Method

“…농도가 되도록 하는 장치이다 [4] . 이러한 AEC 장비는 영상수 용체 내부에 위치하여 선량에 비례한 전기적 신호를 발생시 키고, 미리 설정된 영상의 농도 기준 값과 비교기 회로를 통 하여 이상일 경우 X-ray 발생장치를 턴-오프 시키는 프로세 스로 구성된다.…”