High-pitch Dual-source Computed Tomography Coupled with Sinogram-affirmed Iterative Reconstruction: Image Quality and Radiation Dose in Children
JCY Lee, KS Tse, HY Lau, WS Fok, KK Chan, WH Chat, WK Yung, TM Mui
Hong Kong J Radiol 2018;21:40-7
DOI: 10.12809/hkjr1616427
Objectives: High-pitch imaging in computed tomography (CT) reduces scan time and radiation dose at the expense of increased noise. Recent advances in iterative reconstruction techniques allow for noise reduction without a significant increase in processing time, by using Sinogram-Affirmed Iterative Reconstruction (SAFIRE). We evaluated the combined effects of high-pitch imaging with SAFIRE in CT of the thorax and abdomen on image quality, diagnostic confidence, and radiation dose in children.
Methods: Consecutive CT examinations of the thorax and abdomen performed in young children (age <12 years) on a dual-source CT scanner using standard-pitch, filtered back-projection (group A) between January 2012 and February 2013 were compared retrospectively with those using high-pitch dual-source imaging with SAFIRE between March 2013 and December 2014 (group B). Radiation dose, objective image quality (noise and signal-to-noise ratio), subjective image quality (sharpness, noise, and beam-hardening artifacts), and diagnostic confidence for the two groups were compared by two independent blinded operators.
Results: Noise and signal-to-noise ratios of lung parenchyma were similar in the two groups, whereas those of the trachea were better in group B (p < 0.001). In the abdomen, both noise and signal-to-noise ratios of the liver and aorta were similar. Sharpness (p = 0.011) and noise (p = 0.005) were improved in the thorax for group B, but beam hardening worsened (p = 0.001). Both independent readers had excellent diagnostic confidence on all CT examinations in both groups. The combination of high-pitch imaging, iterative reconstruction, and reduction of tube current in group B allowed the radiation dose to be significantly lowered in the thorax (1.70 vs 2.71 mGy; p = 0.012), and slightly lowered in the abdomen (1.93 vs 3.26 mGy; p = 0.08).
Conclusion: The combination of high-pitch imaging with an iterative reconstruction algorithm allows the radiation dose to be lowered while offering preserved or even improved diagnostic image quality in paediatric patients.
中文摘要
兒童雙源大螺距電腦斷層掃描加上正弦圖確定迭代重建：圖像質量和輻射劑量
李俊賢、謝健燊、劉顯宇、霍泳珊、陳敬光、翟永康、翁偉強、梅大明
目的：電腦斷層掃描（CT）的大螺距成像以增加噪聲為代價縮短掃描時間和輻射劑量。迭代重建技 術的最新進展透過正弦圖確定迭代重建（SAFIRE）容許在不顯著增加處理時間的情況下降低噪聲。 本研究評估兒童CT胸腔和腹部造影檢查中的大螺距成像與SAFIRE對圖像質量、診斷可信度和輻射 劑量帶來的綜合效果。
方法：回顧性分析兩組數據。A組為2012年1月至2013年2月期間以標準螺距濾波反投影的雙源CT掃 瞄進行CT胸腔和腹部檢查的12歲以下兒童，B組為2013年3月至2014年12月期間接受雙源大螺距影 像結合SAFIRE CT的12歲以下兒童。由兩名兒科放射學專家以獨立盲性法比較兩組的輻射劑量、客 觀圖像質量（噪聲和信噪比）、主觀圖像質量（清晰度、噪聲和射束硬化偽影）和診斷可信度。
結果：兩組的肺實質噪聲和信噪比相當，但在氣管方面B組表現較佳（p < 0.001）。在腹部，兩組 的肝臟和主動脈噪聲和信噪比亦相當。B組的胸部清晰度（p = 0.011）和噪聲（p = 0.005）得到改 善，但射束硬化則變差（p = 0.001）。兩名獨立讀片人均認為兩組的所有CT檢查有良好的診斷可 信度。B組使用大螺距成像、迭代重建和減低管電流的結合減低CT胸腔造影的放射劑量（1.70比 2.71 mGy，p = 0.012），而CT腹部造影的放射劑量則呈下降趨勢（1.93比3.26 mGy，p = 0.08）。
結論：大螺距成像結合迭代重建可降低輻射劑量，且為兒童患者維持甚至提高診斷圖像質量。