title: Reliability of the percent density in digital mammography with a semi-automated thresholding method.
abstract: OBJECTIVE
  The reliability of the quantitative measurement of breast density with a semi-automated thresholding method (Cumulus™) has mainly been investigated with film mammograms. This study aimed to evaluate the intrarater reproducibility of percent density (PD) by Cumulus™ with digital mammograms.
  
  
  METHODS
  This study included 1,496 craniocaudal digital mammograms from the unaffected breast of breast cancer patients. One rater reviewed each mammogram and estimated the PD using the Cumulus™ method. All images were reassessed by the same rater 1 month later without reference to the previously assigned values. The repeatability of the PD was evaluated by an intraclass correlation coefficient (ICC). All patients were grouped based on their body mass index (BMI), age, family history of breast cancer, breastfeeding history and breast area (calculated with Cumulus™), and subgroup analysis for the ICC of each group was performed. All patients were categorized by their Breast Imaging Reporting and Data System (BI-RADS) density pattern, and the mean and standard deviation of the PD by each BI-RADS categories were compared.
  
  
  RESULTS
  The ICC for the PD was 0.94, indicating excellent repeatability. The discrepancy between the paired PD values ranged from 0 to 23.93, with an average of 3.90 (standard deviation=3.39). The subgroup ICCs for the PD ranged from 0.88 to 0.96, indicating excellent reliability in all subgroups regardless of patient variables. The ICCs of the PD for the high-risk (BI-RADS 3 and 4) and low-risk (BI-RADS 1 and 2) groups were 0.90 and 0.88, respectively.
  
  
  CONCLUSIONS
  This study suggests that PD calculated with digital mammograms has an acceptable reliability regardless of patient age, BMI, family history of breast cancer, breastfeeding history, breast size, and BI-RADS density pattern.
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Guiyun
authors.initials: G
authors.lastname: Sohn
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jong Won
authors.initials: JW
authors.lastname: Lee
authors.affiliation: Department of Radiology, Health Promotion Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Sung Won
authors.initials: SW
authors.lastname: Park
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jihoon
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jiyoung
authors.initials: J
authors.lastname: Woo
authors.affiliation: Department of Biostatistics and Clinical Epidemiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Hwa Jung
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Hee Jung
authors.initials: HJ
authors.lastname: Shin
authors.affiliation: Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Hak Hee
authors.initials: HH
authors.lastname: Kim
authors.affiliation: Department of Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Kyung Hae
authors.initials: KH
authors.lastname: Jung
authors.affiliation: Department of Epidemiology, School of Public Health and Institution of Health and Environment, Seoul National University, Seoul, Korea.
authors.forename: Joohon
authors.initials: J
authors.lastname: Sung
authors.affiliation: Graduate School of Public Health, Seoul National University, Seoul, Korea.
authors.forename: Seung Wook
authors.initials: SW
authors.lastname: Lee
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Byung Ho
authors.initials: BH
authors.lastname: Son
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Sei-Hyun
authors.initials: SH
authors.lastname: Ahn
keywords: Breast; Mammography; Observer variation