基于体质量指数的个性化噪声指数设定在腹部CT成像中的应用研究

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Abstract Objective: To explore the value of personalized noise index(NI) setting based on body mass index(BMI) in abdominal CT imaging. Methods: Group A contained 211 patients who underwent abdominal ATCM-CT at a fixed NI(10 HU), while group B contained 109 patients who underwent abdominal ATCM-CT at different NIs(10~14 HU, interval: 2 HU). Either group A or B was further divided into three subgroups based on BMI(BMI≤23, ＞23~26, >26): A1(n=47), A2(n=93) and A3(n=71); B1(n=42), B2(n=35) and B3(n=32). The examinations of all the cases were completed on GE Discovery HD CT. The following scan parameters were used in group A: 120 kVp, 3D Auto mA, NI=10 HU, scan time=0.8 s, slice thickness=5 mm, reconstruction interval=5 mm, pitch=1.375∶1, image processing mode: 40% ASIR, and reconstruction mode: Stnd. The individualized scan plan was used in group B: B1: NI=10 HU, B2: NI=12 HU, B3: NI=14 HU; the remaining parameters were the same as group A. Three levels adjacent to hepatic hilum were selected for each group of images. The SD of liver with a uniform density was measured and the results were averaged as the final image SD, and the volume-dose index(CTDIvol) was recorded. The inter-group and intra-group comparisons of SD and CTDIvol of groups A and B were performed with t test. The image quality was subjectively evaluated by two senior radiologists(working experience more than 5 years) with a 5-point scale, and the inter-observer consistency was analyzed by Kappa test. Results: The SD of subgroups A1, A2 and A3 was (11.01±0.88) HU, (9.44±1.24) HU and (8.30±1.40) HU, respectively, and that of subgroups B1, B2 and B3 was (10.90±0.82) HU, (10.79±0.52) HU and (10.96±0.68) HU, respectively. The results showed a significant difference within group A(A1>A2>A3)(P<0.05), but not within group B(P>0.05). There was no significant difference between subgroups A1 and B1(P>0.05), but A2<B2 and A3<B3 with significant differences(P<0.05). The CTDIvol of subgroups A1, A2 and A3 was (7.82±1.48) mGy, (15.00±4.21) mGy and (23.42±5.31) mGy, respectively, and that of subgroups B1, B2 and B3 was (7.33±1.49) mGy, (8.45±2.35) mGy and (9.54±2.84) mGy, respectively. The results showed no significant difference between subgroups A1 and B1, but B2<A2(a decrease by 43.67%) and B3<A3(a decrease by 59.26%) significantly. The image score of subgroups A1, A2 and A3 was 4.57±0.62, 4.58±0.61 and 4.59±0.62, respectively, and that of subgroups B1, B2 and B3 was 4.57±0.50, 4.80±0.65 and 4.56±0.67, respectively. The inter-group and intra-group comparisons of group A and B showed no significant difference in image quality(P>0.05). The results of Kappa test for the consistency of image quality score between two senior radiologists were 0.835, 0.711, 0.734, 0.742, 0.809 and 0.761. Conclusion: Using abdominal ATCM-CT based on BMI-dependent NI adjustment, there is a great reduction of radiation dose for patients with a bigger BMI, without influencing the diagnostic quality of images.

Key words： Abdomen Noise Radiation dosage Tomography, spiral computed

Received: 24 September 2015

PACS:	Ｒ656
	Ｒ814.42

Corresponding Authors: LIU Yi-jun

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	PU Ren-wang
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	LU Xu-lun
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	WANG Shi-yu
	LIU Ai-lian
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Cite this article:

PU Ren-wang,LIU Yi-jun,LU Xu-lun, et al. Clinical study of personalized noise index setting based on body mass index in abdominal CT imaging[J]. JOURNAL OF CHINA MEDICAL IMAGING, 2016, 27(7): 487-490.

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http://www.jccmi.com.cn/EN/ OR http://www.jccmi.com.cn/EN/Y2016/V27/I7/487