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目的探讨螺旋CT颈椎低剂量扫描参数的优化。方法 50例患者,随机分为常规剂量组25例和低剂量组25例,并选择同期进行的椎间盘扫描患者25例作为对照组,记录辐射剂量、有效剂量,原始图像及重建图像均传输至PACS系统,由两位经验丰富的放射科医生对图像质量进行评分;测量椎体周围肌肉及背景(空气)的CT值。采用F检验进行统计分析。结果低剂量组的剂量指数6.5 mGy,剂量长度积(98.21±2.47)mGy·cm,有效剂量(0.53±0.01)mSv;常规剂量组的剂量指数19.1 mGy,剂量长度积(287.84±27.94)mGy·cm,有效剂量(1.63±0.24)mSv;对照组的有效剂量26.5 mGy,剂量长度积106 mGy·cm,有效剂量0.57mSv。统计分析发现,常规剂量组与低剂量组、常规剂量组与对照组的剂量长度积差异有统计学意义(P<0.01);低剂量组与对照组的剂量长度积差异无统计学意义(P=0.326)。常规剂量组与低剂量组、常规剂量组与对照组的有效剂量差异有统计学意义(P<0.01);低剂量组与对照组的有效剂量差异无统计学意义(P=0.326)。椎体扫描低剂量组的辐射剂量少于常规剂量组。常规剂量组、低剂量组、对照组患者原始图像得分为(4.58±0.23)分、(4.47±0.24)分、(4.50±0.19)分。组间比较椎间盘的图像评分差异无有统计学意义(P>0.05),低剂量组的图像得分均高于4分。低剂量组的肌肉组织及背景(空气)CT值的标准差(SD肌肉=6.1;SD背景=20.5)均大于对照组(SD肌肉=3.2;SD背景=13.9)和常规剂量组(SD肌肉=5.8;SD背景=2.3)。结论优化参数可以明显减少辐射剂量,降低管电压和管电流,加大螺距是降低辐射的有效途径,与单纯椎间盘扫描相比,该检查方法并没有增加患者的辐射剂量。
Objective To explore the optimization of low-dose scanning parameters of cervical spine by spiral CT. Methods Totally 50 patients were randomly divided into conventional dose group (25 cases) and low dose group (25 cases). 25 cases of intervertebral disc scan in the same period were selected as control group. The radiation dose, effective dose, original image and reconstructed image were all transferred to PACS System, two experienced radiologists rated the image quality; measured CT values of the muscles and background (air) around the vertebral body. F test for statistical analysis. Results The dose index of the low-dose group was 6.5 mGy, the dose-length product was (98.21 ± 2.47) mGy · cm and the effective dose was 0.53 ± 0.01 mSv. The dose index of the conventional dose group was 19.1 mGy and the dose length product was 287.84 ± 27.94 mGy · cm, effective dose (1.63 ± 0.24) mSv; control group, the effective dose of 26.5 mGy, the dose length product of 106 mGy · cm, the effective dose of 0.57mSv. Statistical analysis showed that there was a significant difference in dose length product between conventional dose group and low dose group, conventional dose group and control group (P <0.01), and there was no significant difference in dose length product between low dose group and control group (P = 0.326). The effective dose of conventional dose group and low dose group, conventional dose group and control group were statistically significant (P <0.01). The effective dose of low dose group and control group had no significant difference (P = 0.326). Radiotherapy dose was lower in low-dose vertebral body scan group than in conventional dose group. The scores of original images in the routine dose group, low dose group and control group were (4.58 ± 0.23) points, (4.47 ± 0.24) points and (4.50 ± 0.19) points respectively. There was no significant difference in image score between groups (P> 0.05). The image score of low dose group was higher than 4 points. The standard deviation (SD muscle = 6.1; SD background = 20.5) of the CT value of muscle tissue and background (air) in the low dose group was greater than that of the control group (SD muscle = 3.2; SD background = 13.9) and the conventional dose group 5.8; SD background = 2.3). Conclusion The optimized parameters can significantly reduce the radiation dose, reduce the tube voltage and tube current, increase the pitch is an effective way to reduce radiation, compared with the simple disc scan, the test did not increase the patient’s radiation dose.