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目的探讨CT低剂量联合迭代算法在输尿管结石诊断中的应用价值。方法 90例输尿管结石患者在首次检查均应用常规剂量扫描(120 k V,400 m As),采用滤波反投影算法(FBP)薄层重组,保守治疗后结石未排出。复查CT应用低剂量扫描随机分为3组(A组:120 k V,200 m As;B组:120 k V,150 m As;C组:120 k V,100 m As)后分别行6级迭代算法薄层重组。由2名放射医师采用双盲法读片并对图像质量做主观评分,记录CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP),计算辐射有效剂量(ED);测量图像的客观噪声值,计算信噪比,测量结石CT值及最大长径,记录结石检出数。结果常规组:CTDIvol(23.51±0.79)m Gy,DLP(1166.38±52.78)m Gy·cm,ED(17.50±0.79)m Sv;A组:CTDIvol(11.78±0.38)m Gy,DLP(584.68±25.47)m Gy·cm,ED(8.77±0.38)m Sv;B组:CTDIvol(8.34±0.13)m Gy,DLP(462.87±24.76)m Gy·cm,ED(6.94±0.37)m Sv;C组:CTDIvol(5.47±0.21)m Gy,DLP(268.20±19.03)m Gy·cm,ED(4.02±0.29)m Sv;各组低剂量迭代算法重组的i Dose 1~6图像结石检出数、结石CT值及大小与常规剂量比较差异无统计学意义(P>0.05);A组低剂量迭代算法重组的i Dose4图像噪声(SD)、信噪比(SNR)及i Dose 4~6图像质量主观评分与常规剂量比较差异无统计学意义(P>0.05);B组低剂量迭代算法重建的i Dose6图像噪声、信噪比及图像质量主观评分与常规剂量比较差异无统计学意义(P>0.05);C组低剂量迭代算法重建的i Dose 1~6各组图像噪声、信噪比及图像质量主观评分与常规剂量比较差异有统计学意义(P<0.05)。结论 CT低剂量扫描联合迭代算法诊断输尿管结石是可行的,可以在不影响图像质量的前提下明显减低辐射剂量。管电压120 k V情况下,在i Dose6水平管电流150 m As为最低临界扫描参数。
Objective To explore the value of CT low-dose combined iterative algorithm in the diagnosis of ureteral calculi. Methods Totally 90 patients with ureteral calculi underwent routine dose scanning (120 kV, 400 m As) at the first examination and thin-layer recombination using FBP. After conservative treatment, the stones were not discharged. The low-dose CT scan was randomly divided into three groups (group A: 120 kV, 200 mAs; group B: 120 kV, 150 mAs; group C: 120 kV, 100 mAs) Iterative algorithm thin layer reorganization Two radiologists performed a double-blind reading and subjectively scored the image quality. CT volume dose index (CTDIvol) and dose length product (DLP) were recorded and the radiation effective dose (ED) was calculated. The objective noise value of the image was measured, Calculate the signal-to-noise ratio, measure the CT value of the stone and the maximum diameter, and record the number of stones detected. Results: The average volume of CTDIvol (23.51 ± 0.79) mGy, DLP (1166.38 ± 52.78) mGy · cm, ED (17.50 ± 0.79) mSv and A group: CTDIvol (11.78 ± 0.38) m Gy and DLP (584.68 ± 25.47 ); Group B: CTDIvol (8.34 ± 0.13) mGy, DLP (462.87 ± 24.76) m Gy · cm, ED (6.94 ± 0.37) m Sv; Group C: CTDIvol (5.47 ± 0.21) m Gy, DLP (268.20 ± 19.03) m Gy · cm and ED (4.02 ± 0.29) m Sv respectively. The detection numbers of i Dose 1 ~ 6 image stones reconstructed by low- (P> 0.05). Group A low dose iterative algorithm recombined i Dose4 image noise (SD), signal to noise ratio (SNR) and i Dose 4 ~ 6 image quality subjective score (P> 0.05). There was no significant difference between the subjective scores of i Dose6 images reconstructed by low-dose iterative algorithm in group B and the conventional dose (P> 0.05) ; Subjective scores of image noise, signal-to-noise ratio and image quality in i Dose 1 ~ 6 group reconstructed by low-dose iterative algorithm in C group were significantly different from conventional dose (P <0.05). Conclusions CT low-dose scanning combined with iterative algorithm to diagnose ureteral calculi is feasible, which can significantly reduce the radiation dose without affecting the image quality. At a tube voltage of 120 kV, the i Dose6 horizontal tube current of 150 mAs is the lowest critical scan parameter.