| 张永县,牛延涛,郭森林,刘丹丹,虞滨滨,康天良,鲜军舫.CT扫描方式对表浅器官辐射剂量测量值变异性的影响[J].中华放射医学与防护杂志,2021,41(12):956-960 |
| CT扫描方式对表浅器官辐射剂量测量值变异性的影响 |
| Influence of CT scanning mode on the variability of radiation dose measurements of superficial organs |
| 投稿时间：2021-05-05 |
| DOI：10.3760/cma.j.issn.0254-5098.2021.12.014 |
| 中文关键词: 辐射剂量 图像质量 表浅器官剂量 |
| 英文关键词:Radiation dose Image quality Superficial organ dose |
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| 中文摘要: |
| 目的 探讨CT扫描中表浅器官剂量测量值和图像噪声的不确定性。方法 使用GE Revolution CT对离体头颅标本分别行逐层和螺旋两种模式20次重复扫描。取GE Revolution CT和Philips Brilliance iCT准直宽度80 mm，Siemens Somatom Definition Flash CT准直宽度40 mm，螺距均为1，对胸部模体进行45次重复扫描。以上扫描中各序列均保持容积CT剂量指数（volume CT dose index，CTDIvol）不变。用剂量计测量头颅标本右眼晶状体位置和胸部模体右乳腺中心位置剂量，剂量计传感器位置保持不变。重组传感器中心所在层面的5 mm层厚肺/软组织算法横断面图像，测量空气区CT值的标准偏差（图像噪声）。分别计算扫描3、5、10、20、30、45次剂量测量值及CT值标准偏差的平均值（Av）、标准差（SD）、变异系数（CV）和相对极差（RR）。采用Pearson和Spearman相关分析评估CT值标准偏差与剂量测量值之间的相关性。结果 头颅标本逐层扫描时剂量测量值几乎不变，螺旋扫描时测量值变化较大，20次测量RR达到10.67%。3台CT扫描仪重复扫描45次的剂量测量值RR分别达到43.83%、25.31%、14.32%。肺/软组织算法图像空气区CT值标准偏差变化幅度亦较大，但差异与剂量测量值不完全相关。结论 逐层扫描模式时，表浅器官剂量测量值稳定。螺旋扫描时，表浅器官剂量测量值和图像噪声均有较大变化。 |
| 英文摘要: |
| Objective To investigate the uncertainty of the dose measurements of superficial organs and the image noise in CT scanning. Methods GE Revolution CT was used to perform 20 repeated scans on the isolated skull specimen in sequential and helical mode. The chest phantom was scanned for 45 times with the pitch 1.0 and the collimation 80 mm for two scanners (GE Revolution CT, Philips Brilliance iCT) and 40 mm for the Siemens Somatom Definition Flash CT. The volume CT dose index (CTDIvol) was maintained during the above scannings. A dosimeter was used to measure the dose at the position of the right eye lens of the specimen and the center of right breast of the chest phantom. The position of dosimeter sensor remained unchanged. The standard deviation of CT values (image noise) in the air region of cross-sectional images at the center of the sensor reconstructed with lung/soft tissue algorithms were measured. The mean values (Av), standard deviations (SD), coefficients of variation (CV) and relative ranges (RR) of the dosimetric values and the standard deviations of CT values of 3, 5, 10, 20, 30 and 45 scans were calculated. Pearson and Spearman correlation analysis were used to evaluate the correlation between the dosimetric values and the standard deviations of CT values. Results The measured dosimetric values of the skull specimen were almost unchanged in the sequential scannings. The relative range of dose in helical mode was 10.67%. The relative ranges of the measured values of the three CT scanners for 45 scans reached 43.83%, 25.31%, and 14.32%. The standard deviations of CT values of the lung/soft tissue images varied greatly and the differences were not completely related to the dosimetric values. Conclusions The dosimetric values of superficial organs were stable in the sequential scanning mode. The dose measurements of superficial organs and the image noise changed greatly in helical scanning mode. |
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