基于模体的乳腺X线摄影质量控制中SNR变异系数的分析

doi:10.19401/j.cnki.1007-3639.2025.08.007

摘要/Abstract

摘要：

背景与目的：在乳腺X线摄影质量控制中，信噪比（signal-to-noise ratio，SNR）是指图像中有用的信号强度与背景噪声的比值，是衡量图像质量好坏的重要指标之一。变异系数是描述SNR一致性和可重复性的常用指标。本研究通过分析不同厂家的3台乳腺X线摄影设备在不同曝光模式下的二维图像和X线断层摄影（tomography，Tomo）图像（简称断层图像）中SNR变异系数的变化情况，旨在评估乳腺X线摄影设备性能的稳定性和可重复性。方法： 选用乳腺X线摄影质量控制专用的聚甲基丙烯酸甲酯模体（polymethylmethacrylate phantom，PMMA），分别在全数字化乳腺X线摄影（full-field digital mammography，FFDM）、低剂量乳腺X线摄影和数字乳腺断层摄影（digital breast tomosynthesis，DBT）3种曝光模式下行PMMA厚度从20~80 mm，实际压迫厚度等效于乳腺平均密度的压迫厚度21~103 mm的自动曝光检测。计算不同乳腺X线摄影设备在不同曝光模式、不同压迫厚度时二维图像和断层图像中SNR的变异系数变化情况。结果： 在FFDM、低剂量乳腺X线摄影、DBT曝光模式下，等效于乳腺平均密度的压迫厚度21~103 mm时，分析乳腺X线摄影设备1、2、3在不同曝光模式下二维图像的SNR变异系数间的差异，仅DBT曝光模式下不同设备间的二维图像差异有统计学意义（P=0.003），设备1、2、3中二维图像的SNR变异系数分别为0.188%~0.720%、0.368%~1.073%和0.402%~1.662%。FFDM和低剂量曝光模式下设备1、2、3中二维图像的SNR变异系数差异均无统计学意义（P=0.060）。在DBT曝光模式时不同乳腺X线摄影设备的断层第一张投影图和0°投影图的SNR变异系数变化范围在设备1（2种角度）、2、3中差异均无统计学意义（P=0.373，P=0.742，P=0.225，P=0.693）。结论： 不同乳腺X线摄影设备、不同曝光模式时二维图像和断层图像的SNR变异系数变化范围各不相同，没有固定和标准的数值，但都在乳腺X线摄影设备质量控制要求范围内。在FFDM和低剂量曝光模式时乳腺X线摄影设备二维图像的稳定性、可重复性更好；在DBT曝光模式时断层第一张投影图和0°投影图的变异系数值差异无统计学意义，均显示设备的稳定性良好。

关键词: 乳腺X线摄影, 信噪比, 变异系数, 质量控制

Abstract:

Background and purpose: In the quality control of mammography, the signal-to-noise ratio (SNR) refers to the ratio of the useful signal intensity to the background noise in the image, which is one of the important indicators for measuring the quality of the image. The coefficient of variation (CoV) is a commonly used indicator to describe the consistency and repeatability of SNR. This study aimed to assess the stability and repeatability of mammographic device performance by analyzing the changes in SNR CoV in two-dimensional (2D) images and tomosynthesis images (referred to as Tomo images) under different exposure modes using three mammographic devices from different manufacturers. Methods: A polymethylmethacrylate (PMMA) phantom designed for mammography quality control was used to perform automatic exposure detection at PMMA thicknesses ranging from 20-80 mm, with actual compression thickness equivalent to the average density of the breast compressed to 21-103 mm under full-field digital mammography (FFDM), low-dose mammography and digital breast tomosynthesis (DBT) exposure modes. The CoV of SNR in 2D images and tomosynthesis images was calculated for different mammographic devices under different exposure modes and compression thicknesses. Results: Between the compression thicknesses equivalent to the average density of the breast from 21 mm to 103 mm under FFDM, low-dose mammography, and DBT exposure modes, the differences in SNR CoV of 2D images under different exposure modes among mammographic devices 1, 2, and 3 were statistically significant only in the DBT exposure mode (P=0.003), with SNR CoV ranging from 0.188% to 0.720%, 0.368% to 1.073% and 0.402% to 1.662%, respectively. There were no statistically significant differences in SNR CoV of 2D images among devices 1, 2, and 3 under FFDM and low-dose exposure modes (P=0.060). Under the DBT exposure mode, there were no statistically significant differences in the SNR CoV of the first projection image and the 0° projection image of tomosynthesis among devices 1 (2 angles), 2, and 3 (P=0.373, P=0.742, P=0.225, P=0.693, respectively). Conclusion: The SNR CoV in 2D images and tomosynthesis images varies under different mammographic devices and exposure modes, with no fixed or standard values, but all within the required range for mammographic device quality control. The stability and repeatability of 2D images of mammographic devices are better under FFDM and low-dose exposure modes; the SNR CoV values of the first projection image and the 0° projection image of tomosynthesis under the DBT exposure mode show no statistical differences, indicating good stability of the devices.

Key words: Mammography, Signal-to-noise ratio, Coefficient of variation, Quality control

中图分类号:

R737.9

沈茜刚, 柴青焕, 姜婷婷, 沈悦, 肖勤, 顾雅佳. 基于模体的乳腺X线摄影质量控制中SNR变异系数的分析[J]. 中国癌症杂志, 2025, 35(8): 784-791.

SHEN Xigang, CHAI Qinghuan, JIANG Tingting, SHEN Yue, XIAO Qin, GU Yajia. Analysis of variation coefficient of SNR in phantom-based mammography quality control[J]. China Oncology, 2025, 35(8): 784-791.

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Device		M1/%			M2/%			M3/%			P value
Phantom thickness/mm	Equivalent breast thickness/mm	FFDM	Low-dose	Combo	FFDM	Low-dose	Combo	FFDM	Low-dose	Combo	P₁	P₂	P₃
20	21	0.807	0.489	0.428	0.437	0.637	0.368	0.480	0.570	0.777	0.370	0.003	0.060
30	32	0.538	0.431	0.471	0.656	1.814	1.073	0.238	1.192	0.942
40	45	0.500	1.404	0.580	0.634	1.598	0.920	1.001	0.899	1.662
50	60	0.552	0.764	0.188	0.606	0.905	0.844	0.325	0.518	0.884
60	75	0.257	0.792	0.720	1.279	1.298	1.010	0.570	1.183	0.886
70	90	0.330	0.477	0.407	0.831	0.555	0.756	0.450	0.544	0.402
80	103	0.768	0.274	0.562	0.437	1.577	1.024	-	0.620	-

Device		The CoV value of SNR for the first image of projection on different devices/%				The CoV values of SNR for the projection 0° position images from different devices/%				P value
Phantom thickness/mm	Equivalent breast thickness/mm	M1-N	M1-W	M2	M3	M1-N	M1-W	M2	M3	P₁	P₂	P₃	P₄
20	21	1.542	0.551	0.423	1.240	1.201	0.442	0.760	1.244	0.373	0.742	0.225	0.693
30	32	0.422	0.237	0.414	0.893	1.047	0.545	0.559	1.298
40	45	1.369	0.600	0.149	1.194	1.869	0.802	1.010	1.089
50	60	1.043	0.677	0.370	0.935	0.958	0.563	0.604	1.108
60	75	2.277	1.814	0.206	1.329	1.338	1.474	0.539	0.799
70	90	1.392	0.596	0.976	0.113	1.017	1.089	0.790	0.673
80	103	1.553	0.513	1.187	-	0.432	0.630	0.936	-