Objective  To investigate the accuracy of a threshold-based segmentation method based on cone beam breast CT (CBBCT) images in breast density measurement, and its value for breast-type classification and breast cancer screening.

  Methods  A retrospective analysis of 195 patients who had undergone CBBCT examination at Tianjin Medical University Cancer Institute and Hospital between May 2012 and August 2014 was performed. A total of 64 breasts were analyzed. On the basis of the classification criteria for breast density in BI-RADS, they were classified into four types and the majority report was reported. Breast density was measured by the threshold-based segmentation method based on CBBCT images and corrected manually to obtain the corrected breast density. A month later, the procedure was repeated. Intra-class correlation coefficients (ICCs) were used to compare the intra-observer and interobserver consistencies of threshold-based segmentation and manually corrected breast density measurement results for non-dense and dense breasts.

  Results  For threshold-based segmentation measurements the intra-observer and inter-observer ICC values were 0.0.9624 (95% CI: 0.9388~0.9770) and 0.9666 (95% CI: 0.9500~0.9785). For manually corrected measurements, the intra-observer and inter-observer ICC values were 0.9750 (95% CI: 0.9592~0.9847) and 0.9775 (95% CI: 0.9661~0.9855). The ICC between the threshold-based segmentation method and manual correction was 0.9962 (95% CI: 0.9983~0.9977). The ICC values of thresholdbased and manually corrected measurement in non-dense and dense breasts were 0.9497 (95% CI:0.7072-0.9914) and 0.9983 (95% CI: 0.9971-0.9990), respectively.

  Conclusions  The threshold-based segmentation method based on CBBCT is a reliable and accurate computer-aided method of measuring breast density. It is expected to be applied in large-scale screening of breast cancer and to provide more information for predicting the risk of breast cancer