目的:利用噪声功率谱(NPS)评价不同重建方法的CT图像噪声特征,并与主观视觉噪声评价进行相关性分析.方法:对CT设备自带的水模进行扫描,采用8种常见的重建算法处理图像,将NPS曲线峰值、峰值对应频率和标准差(SD)与主观评价指标噪声的颗粒度、对比度、锐利度和整体噪声水平进行相关性分析.结果:8种重建算法在频段和峰值上均各有侧重,阅片者的颗粒度评分与峰值频率呈负相关;对比度与峰值呈正相关;锐利度同时与峰值和峰值频率呈正相关.所有的主观评价指标均与SD相关.结论:NPS较传统的SD评价方法能够更为全面地反映噪声的强弱和形态特征,且具有潜在的应用价值.%Objective: To evaluate the noise characteristic of different reconstruction type CT image by using the noise power spectrum (NPS), and analyze the correlation between this results and subjective vision noise evaluation. Methods: QA water phantom of CT equipment was scanned and 8 common reconstruction algorithms were applied to dispose image. NPS peak value, the peak frequency and standard deviation (SD) were compared with the subjective evaluation measurements, such as granularity, contrast, sharpness and optical noise level, by using the correlation analysis. Results: Each reconstruction algorithm owned different peak value and peak frequency. Granularity negatively correlated with the peak frequency. A positive correlation was found between contrast and peak value. Sharpness was positively correlated with both peak value and peak frequency. All of the subjective evaluation measurements were correlated with SD. Conclusion: Comparing with SD, NPS can reflect both intensity and morphological feature of the noise and possess applicative potential as a more comprehensive evaluation index.
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