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A Study on the Dynamic Range Performance Evaluation Method of Detector with Variation of Tube Voltage and Automatic Exposure Control (AEC) in Digital Radiography (DR) -Focused on the Dynamic Step Wedge and Histogram Evaluation

DR(Digital Radiography)에서 관전압 및 자동노출제어장치의 감도 변화에 따른 검출기의 동적 범위 성능평가 방법연구 -Dynamic Step Wedge와 히스토그램 평가를 중심으로

  • 황준호 (경희대학교병원 영상의학과) ;
  • 최지안 (경희대학교병원 영상의학과) ;
  • 김현수 (신구대학교 방사선과) ;
  • 이경배 (경희대학교병원 영상의학과)
  • Received : 2019.01.29
  • Accepted : 2019.02.20
  • Published : 2019.04.28

Abstract

This study proposes a method to evaluate the performance of a detector by analyzing the dynamic step wedge and histogram according to the change of the tube voltage and sensitivity when using the Automatic Exposure Control (AEC). The performance of a detector was evaluated by measuring X-ray quality, Entrance Surface Dose (ESD), tube current, dynamic range corresponding to detector sensitivities of S200, S400, S800, S1000 per tube voltage of 60, 70, 81, 90 kVp. As a results, all of the qualities satisfied the acceptance criteria, and the Entrance Surface Dose and tube current were decreased stage by stage as sensitivity was set higher. In the dynamic step wedge, the observable dynamic range has also increased as tube voltage became higher. The histogram showed the quantization separation phenomena as the tube voltage was set higher. The higher the sensitivity, the more the underflow and overflow occurred in which the amount of information on both ends of the histogram was lost. In conclusion, the deterioration in the performance of the detector was found to be insufficient to realize the change of the tube voltage and sensitivity when using the Automatic Exposure Control, and it is useful to use dynamic step wedge and histogram in evaluating detector performance evaluation.

Keywords

Automatic Exposure Control (AEC);Sensitivity;Detector;Dynamic Range;Histogram

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그림 1. Primus A phantom

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그림 2. 다목적 선량계 MagicMax Universal과 Unfors Raysafe ThinX

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그림 3. Philips DIGITAL DIAGNOST VR(A)와 Philips DIGITAL DIAGNOST VR(B)의 dynamic step wedge 영상

CCTHCV_2019_v19n4_368_f0004.png 이미지

그림 4. 관전압 및 감도 변화에 따른 히스토그램

표 1. 방사선 발생장치와 관련된 특성

CCTHCV_2019_v19n4_368_t0001.png 이미지

표 2. 방사선 발생장치의 검사조건

CCTHCV_2019_v19n4_368_t0002.png 이미지

표 3. Philips DIGITAL DIAGNOST VR(A)의 백분율 평균 오차와 반가층

CCTHCV_2019_v19n4_368_t0003.png 이미지

표 4. Philips DIGITAL DIAGNOST VR(B)의 백분율 평균 오차와 반가층

CCTHCV_2019_v19n4_368_t0004.png 이미지

표 5. Philips DIGITAL DIAGNOST VR(A)의 입사표면선량의 평균과 표준편차

CCTHCV_2019_v19n4_368_t0005.png 이미지

표 6. Philips DIGITAL DIAGNOST VR(B)의 입사표면선량의 평균과 표준편차

CCTHCV_2019_v19n4_368_t0006.png 이미지

표 7. Philips DIGITAL DIAGNOST VR(A)와 Philips DIGITAL DIAGNOST VR(B)의 관전류량

CCTHCV_2019_v19n4_368_t0007.png 이미지

표 8. Philips DIGITAL DIAGNOST VR(A)와 Philips DIGITAL DIAGNOST VR(B)의 동적 범위의 정성적 평가

CCTHCV_2019_v19n4_368_t0008.png 이미지

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