成人标准BMI双低剂量CTE图像质量控制研究

Study on image quality control of double low dose CTE for adult standard BMI

关键词:  体层摄影术  CT小肠造影  辐射剂量  图像质量  噪声

Key words:  tomography  CT enterography(CTE)  radiation dose  image quality  noise

摘要:

目的 探讨成人标准BMI低辐射剂量和低碘对比剂使用量下CT小肠造影（CT enterography，CTE）图像质量控制的可行性。方法 将60例CTE患者随机分为双低剂量扫描组（A组，n=30）和常规扫描组（B组，n=30），A组扫描采用100 kV管电压，注射65 mL碘对比剂实现双低剂量扫描，B组采用120 kV管电压，注射85 mL碘对比剂。比较图像噪声、信噪比（SNR）和对比噪声比（CNR）组间差异。两名腹部亚专科医师独立对三期图像进行主观评分（1~5分），Kappa检验操作者间的一致性，并采用Wilcoxon秩和检验评估图像质量主观评分。小肠肿瘤性病变、炎症性病变检出率比较采用χ²检验。结果 图像噪声：A组>B组（P<0.05）；图像质量客观指标中，平扫（SNR_十二指肠、SNR_空肠）、动脉期（SNR_小肠、CNR_十二指肠、CNR_空肠）及静脉期（SNR_小肠、SNR_{肠系膜上静脉}、CNR_小肠及CNR_{肠系膜上静脉}）A组低于B组，差异有统计学意义（P<0.05）。图像质量主观评分均≥3分，操作者间呈中高度一致，三期图像A、B两组间主观评分结果均无显著性差异（P>0.05）。对小肠肿瘤性病变、炎症性病变检出率两组间亦无统计学差异（P>0.05）。结论 成人标准BMI双低剂量CTE扫描不仅降低了辐射剂量还减少了碘对比剂使用量，虽然图像噪声有所增加，部分图像质量有所下降，但均不影响做出诊断。

Abstract:

Objective To investigate the feasibility of image quality control of CT enterography (CTE) in adults with BMI standard under the condition of low radiation dose and low iodine contrast agent. Methods Totally 60 patients with CTE were divided into two groups randomly, including Double low dose scanning group (group A, n=30) and Routine group (group B, n=30). In group A, the scanning tube voltage was set as 100 kV and we use 65 mL iodine contrast agent for each patient to fulfill double low-dose. In group B, the scanning tube voltage was set as 120 kV and we use 85 mL iodine contrast agent for each patient. The image noise, Signal-to-noise ratio (SNR) and contrast noise ratio (CNR) were compared between the groups. Two abdominal subspecialists scored the three-stage images independently and subjectively (1-5 points). Kappa test was used to check the consistency among operators, and Wilcoxon rank sum test was used to evaluate the subjective image quality score. χ²-test was used in the diagnosis of small intestinal tumor and inflammatory lesions. Results The image noise of group A was significantly higher than that of group B (P<0.05). In the objective evaluation of image quality, there were statistically significant differences between groups A and B (P<0.05) for plain scan (SNR duodenum, SNR jejunum), arterial phase (SNR small intestine, CNR duodenum, CNR jejunum) and venous phase (SNR small intestine, SNR superior mesenteric vein, CNR small intestine and CNR superior mesenteric vein). The subjective scores of all images were≥3, and the operators were consistent in a medium to high degree. There was no significant difference in subjective scores between two groups (P>0.05). There was no detection rate difference between two group diagnosis of small intestinal tumor and inflammatory lesions (P>0.05). Conclusion The double low dose CTE scan of adult standard BMI can not only reduce the radiation dose, but also the iodine contrast agent. Although the image noise has increased and some image quality has decreased, it does not affect the diagnosis.