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.

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.

Objective:To evaluate the application value of the histogram features of quantitative parameters from synthetic MRI in predicting the expression of human epidermal growth factor receptor 2 (HER2) in breast invasive ductal carcinoma (IDC) and to compare the prediction efficiency with that of ADC histogram parameters.Methods:A total of 195 patients with breast lesions were prospectively enrolled in the Fudan University Cancer Hospital, from January 2020 to September 2020. All patients underwent preoperative synthetic MRI, DWI and dynamic contrast-enhanced MRI (DCE-MRI). All surgical specimens were confirmed by pathology. The histogram features of the quantitative parameters [T 1, T 2, and proton density (PD)] and ADC values were extracted by PyRadiomics software. Student t test or Mann-Whitney U test were used to compare the histogram characteristics of quantitative parameters (T 1, T 2, and PD) and ADC values between HER2-positive and HER2-negative breast cancers. The diagnostic efficacy of the variables in predicting HER2 expression state was evaluated using the area under curve (AUC) value of ROC. Results:A total of 122 patients with breast IDC were included into analysis, with 31 of HER2-positive and 91 of HER2-negative. There was no significant difference in the clinicopathological characteristics between HER2-positive and HER2-negative breast IDC patients. Univariate analysis showed that there was statistically significant difference in PD-median [79.80 (75.90, 83.90)ms vs. 76.56 (72.59, 79.09) ms, Z=-3.46, P<0.01], PD-mean [78.89 (74.80, 84.01) ms vs. 75.99 (71.70, 78.63) ms, Z=-2.61, P=0.01], PD-Kurtosis [6.45(3.45, 7.54) vs. 5.04 (3.55, 5.58), Z=-2.21, P=0.03], T 1-10 th percentile [731.52 (668.50, 975.39) ms vs. 726.51 (588.38, 852.19) ms, Z=-2.54, P=0.01], T 1-mean [1 161.97 (1 063.56, 1 253.78) ms vs. 1 072.75 (989.39, 1 154.04)ms, Z=-2.21, P=0.03] and ADC-Kurtosis [4.75 (2.72, 5.91) vs. 3.82 (2.69, 4.39), Z=-2.43, P=0.02] between HER2 positive and negative breast IDC patients. Multivariate analysis showed that PD-median ( P=0.004) and T 1-mean ( P=0.004) were independent risk factors for HER2 expression. The ROC curve of HER2 expression predicted by this model showed an AUC was 0.853(95%CI 0.779-0.926), with a sensitivity of 71% and a specificity of 81%. The ROC curve of ADC-Kurtosis for predicting the expression of HER2 showed that the AUC was 0.714 (95%CI 0.611-0.817), with the sensitivity of 45%, and the specificity of 85%. DeLong test showed that the diagnostic efficacy of quantitative parameters from synthetic MRI in predicting the status of HER2 was higher than that of ADC histogram parameters ( Z=2.18, P=0.04). Conclusion:Histogram features of synthetic MRI quantitative parameters contribute to the prediction of HER2 expression status in IDC and may therefore contribute to the determination of individualized anti-HER2 targeted therapy strategies.