[논문]시간에 따르는 CR장비의 영상의 질평가

손순룡; 최관우; 김정민; 정회원; 권경태; 황선광; 이익표; 김기원; 정재용; 이영아; 손진현; 민정환

doi:10.17946/jrst.2015.38.4.05

[국내논문] 시간에 따르는 CR장비의 영상의 질평가
Measurement of Image Quality According to the Time of Computed Radiography System 원문보기

방사선기술과학 = Journal of radiological science and technology, v.38 no.4, 2015년, pp.365 - 374

손순룡 (서울아산병원 영상의학과) , 최관우 (서울아산병원 영상의학과) , 김정민 (고려대학교 방사선학과) , 정회원 (백석문화대학교 방사선과) , 권경태 (동남보건대학교 방사선과) , 황선광 (강동경희대병원 영상의학과) , 이익표 (강동경희대병원 영상의학과) , 김기원 (강동경희대병원 영상의학과) , 정재용 (상계백병원 종양학과) , 이영아 (신구대학교 바이오 동물학과) , 손진현 (신구대학교 방사선과) , 민정환 (신구대학교 방사선과)

초록
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진단의 높은 정확성을 유지하기 위하여 영상 품질의 정기적인 quality assurance (QA) 검사는 필수적이다. 이 연구의 목적은 2006년부터 2015년까지 시간에 따른 (2006, 2009, 2012, 2015) computed radiography (CR) system의 modulation transfer function (MTF: 변조전달함수), the noise power spectrum (NPS: 잡음전력스펙트럼) and the detective quantum efficiency (DQE: 양자검출효율)를 측정하여 평가 하는 것이다. 우리는 edge method를 이용하여 pre-sampled MTF를 구하였고 international electrotechnical commission standard IEC: 62220-1의 RQA5가 측정에 적용되었으며, X선관 초점으로부터 CR 표면까지의 거리는 150 cm이며, 부가필터 21 mmAl을 사용하였다. 관전압은 $72{\pm}2kVp$였으며 관전압을 1~2 kVp조절하여 HVL이 $7.1{\pm}1mmAl$되도록 하였다. 연구결과는 MTF의 공간주파수 50% ($mm^{-1}$)에서 사용 기간 별로 2006년은 1.54, 2009년은 1.14, 2012년은 1.12, 2015년은 1.38 이었고 공간주파수 10% ($mm^{-1}$)에서 사용 기간 별로 2006년은 2.68, 2009년은 2.44, 2012년은 2.44, 2015년은 2.46 이었다. 각각의 노이즈 분포는 2006년이 가장 낮은 노이즈 분포를 보였으며 2015, 2009, 2012 순으로 낮은 노이즈 분포를 나타내었다. Peak DQE와 $1mm^{-1}$에서도 2006년이 가장 우수한 DQE를 보였으며 2015년, 2009년, 2012년 순으로 DQE값을 나타내었다. 정확한 진단을 위하여 주기적인 CR 시스템의 유지보수가 필요하며 본 연구는 CR 시스템의 QA 및 수행성능 평가에 기초가 될 것으로 생각된다.

Abstract ▼ AI-Helper

The regular quality assurance (RQA) of X-ray images is essential for maintaining a high accuracy of diagnosis. This study was to evaluate the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE) of a computed radiography (CR) system for various periods of use from 2006 to 2015. We measured the pre-sampling MTF using the edge method and RQA 5 based on commission standard international electro-technical commission (IEC). The spatial frequencies corresponding to the 50% MTF for the CR systems in 2006, 2009, 2012 and 2015 were 1.54, 1.14, 1.12, and $1.38mm^{-1}$, respectively and the10% MTF for 2006, 2009, 2012, and 2015 were 2.68, 2.44, 2.44, and $2.46mm^{-1}$, respectively. In the NPS results, the CR systems showed the best noise distribution in 2006, and with the quality of distributions in the order of 2015, 2009, and 2012. At peak DQE and DQE at $1mm^{-1}$, the CR systems showed the best efficiency in 2006, and showed better efficiency in order of 2015, 2009, and 2012. Because the eraser lamp in the CR systems was replaced, the image quality in 2015 was superior to those in 2009 and 2012. This study can be incorporated into used in clinical QA requiring performance and evaluation of the performance of the CR systems.

주제어

AI 본문요약
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문제 정의

In Figure 2, the R² value close to 1 shows stabilized linearity of the system. The results also showed linearity for the MTF measurements in our experiments.

제안 방법

Thus, maintaining the CR systems, including the replacement of the erasing lamp, has an important role and is essential for accurate diagnosis. The purpose of this study is to evaluate the MTF, the NPS and the DQE of CR systems during various periods of use, from 2006 to 2015 (specifically, during 2006, 2009, 2012 and 2015).
The MTF was computed by performing a fast Fourier transfer (FFT) of the LSF and normalizing its value to unity at a zero spatial frequency. The one-dimensional NPS was expressed by averaging the axis direction from the bandwidth of the two dimensional NPS space, and the accumulation correction was calculated by extracted the ROI from the whole image size. The DQE was evaluated from the measured MTF and NPS
For evaluating the NPS, white images are obtained by projecting onto detectors without imaging an object. We applied two-dimensional FFTs in order to obtain region of interest (ROI) images and performed a scale revision by using the average ROI extracted from the whole image. The matrix was 1024 × 1024 pixels, the pixel size was 0.
This study was undertaken to evaluate the MTF, the NPS and the DQE of the CR systems for various periods of use, from 2006 to 2015 (2006, 2009, 2012, and 2015), in order to maintain a high accuracy of diagnosis. The remaining latent image resulting in better MTF at high emission rates than at low.

이론/모형

The MTF measurement was performed using the pre-sampled MTF method described by Fujita et al.^{6, 15-18)}. Fujita et al.

성능/효과

In our results, the spatial frequencies corresponding to the 50% MTF for the CR systems in 2006, 2009, 2012 and 2015 were 1.54, 1.14, 1.12, and 1.38 mm^-1, respectively. The spatial frequencies corresponding to the 10% MTF for 2006, 2009, 2012 and 2015 were 2.
In Figure. 3, the MTFs at 0 ~ 2.5 mm^-1 in 2009 and 2012 were superior to the MTF at 0 ~ 2.5 mm^-1 in 2015. However, the MTF at 2.
In this study, the DQE results in 2006 are superior to those in 2009, 2012, and 2015, and these results indicate that maintaining the CR systems is important as recommended by the AAPM, and R² value close to 1 shows stabilized linearity of the system. The results also showed linearity and reproducibility for the MTF measurements in our experiments.

후속연구

With the progress of time, the deterioration in image quality and changes in general image quality were caused by practices in maintaining the CR systems. This study could be incorporated into used in clinical QA requiring performance and evaluation of the performance of the CR systems.

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