Journal of the Korean Society of Radiology (한국방사선학회논문지)

The Korean Society of Radiology (한국방사선학회)
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Analysis of the Relationships according to the Frame (f/s) Change of Cine Imaging in Coronary Angiographic System: With Focus on FOV Enlargement and Live Zoom

심장 혈관 조영장치에서의 프레임 레이트(f/s) 변화에 따른 상관 관계 분석 : FOV 확대와 Live Zoom을 중점으로

  • Received : 2018.11.27
  • Accepted : 2018.12.31
  • Published : 2018.12.30
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Abstract

This study aimed to investigate the difference of X-ray exposure by comparing and analyzing absorbed dose according to changes in the number of frames in coronary angiography, also depending whether the zoom mode is FOV enlargement or Zoom Live. Moreover, for appropriate frame selection measures for examination, including the effect of frame change on the image quality, were sought by measuring the noise strength expressed by the standard deviation (SD), the signal to noise ratio (SNR) and contrast to noise ratio (CNR). The study was conducted with an anthropomorphic phantom on an angio-system. The linear relationship between the frame rate and the radiation dose was evident. On the contrary, the indices of image quality (SD, SNR, and CNR) were almost constant irrespective of the number of frames. The difference depending on the zoom mode was not statistically significant for DAP, air kerma, and SD (p > 0.05). However, SNR and CNR were statistically different between FOV enlargement and Zoom Live. In conclusion, since the image quality was not degraded significantly with the decreasing frame rate from 30, 15, to 7.5 f/s and the radiation dose evidently decreases in almost exactly linear proportion to the decreasing frame rate, the number of frames per second needs to be maintained as low as reasonably achievable. As for the dependence on the zooming mode, the Live Zoom mode showed statistically significant improvement in the image quality indices of SNR and CNR and it justifies active use of the Live Zoom mode which enables real-time image enlargment without additional radiation dose.

본 연구는 심장 혈관 조영술의 투시 영상과 씨네 영상을 획득하는 데 있어서 초당 프레임 횟수를 변화함에 따라 흡수선량과 획득 영상의 화질의 추이를 살펴보는 것을 목적으로 한다. 또, FOV 확대와 Live Zoom이라는 두 가지 확대 모드에 따른 변화도 고찰 대상으로 한다. 인체모형 팬텀을 심장 혈관 조영장치 위에서 초당 프레임 횟수를 7.5, 15, 30 f/s로 설정하고 두 가지 확대 모드에 대하여 각각 5회씩 촬영하였다. 선량의 척도로서는 흡수선량과 에어 커머가 사용되었고, 화질 평가의 척도로는 잡음의 세기로서의 표준 편차(SD), 신호 대 잡음비(SNR)와 대조도 대 잡음비(CNR) 등을 활용하였다. 초당 프레임 횟수가 30부터 15, 7.5 f/s로 감소되었을 때, DAP와 에어 커머는 동일한 비율로 감소하였으나, 화질의 척도인 SD, SNR과 CNR은 거의 변화가 없었다. 확대 모드에의 의존도에 관해서는, Live Zoom이 FOV 확대와 비교하였을 때, DAP, 에어 커머와 SD에 대해서는 통계적 의미 있는 차이를 보이지 않았으나, SNR과 CNR에 있어서는 통계적 유의미한 개선을 보였다. 이러한 실험 결과에 의하여, 초당 프레임 횟수는 화질의 열화 없이 되도록 낮게 설정하는 것이 가능하며, 확대 모드도 추가적인 선량 없이 실시간 확대가 가능한 Live Zoom 모드를 적극적으로 활용 가능하며 이는 화질의 여러 척도의 저하를 가져오지 않음을 알 수 있었다.

Keywords

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Fig. 1. Chest model phantom (LungMan, Kyoto Kagaku): (Left) Imaging of Radiography (Right) Photographs taken in this study.

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Fig. 2. Pulsatile coronary artery phantom (Mocomo, Fuyo Corporation): (Left) Coronary angiography device and phantom, (Right) Coronary anastomosis.

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Fig. 3. ROI setting for image quality evaluation in chest simulated phantom images.

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Fig. 4. Setting the region of interest for image quality assessment in pulsed coronary phantom projection.

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Fig. 5. Magnification mode and change in frame rate per second: (top) 7.5 f/s, (middle) 15 f/s (bottom) 30 f/s.

Table 1. DAP and reference air kerma according to varying frame rate and zooming modes of Cine acquisition

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Table 2. DAP and reference air kerma according to varying frame rate and zooming modes of Cine acquisition of pulsatile coronary phantom

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Table 3. Signal intensity, standard deviation, SNR, and CNR according to varying frame rate and zooming modes of Cine acquisition

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Table 4. Signal intensity, standard deviation, SNR, and CNR according to varying frame rate and zooming modes of Cine acquisition

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