J Breast Cancer.  2014 Jun;17(2):174-179.

Reliability of the Percent Density in Digital Mammography with a Semi-Automated Thresholding Method

• Sohn G
• Lee JW
• Park SW
• Park J
• Woo J
• Kim HJ
• Shin HJ
• Kim HH
• Jung KH
• Sung J
• Lee SW
• Son BH
• Ahn SH

Abstract

PURPOSE
The reliability of the quantitative measurement of breast density with a semi-automated thresholding method (Cumulus(TM)) has mainly been investigated with film mammograms. This study aimed to evaluate the intrarater reproducibility of percent density (PD) by Cumulus(TM) 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(TM) 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(TM)), 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.
CONCLUSION
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.

Keyword

Breast; Mammography; Observer variation

MeSH Terms

Body Mass Index
Breast
Breast Feeding
Breast Neoplasms
Humans
Information Systems
Mammography*
Observer Variation

Figure

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  Figure 1 Computer assisted semi-automated thresholding method, Cumulus™. The green area indicates dense area, and the red line indicates total breast area.

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  Figure 2 Intrarater reproducibility for two percent density value by one rater calculated with Cumulus™. Intraclass correlation coefficient between two PD values was 0.94, which indicates excellent agreement between two values.

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  Figure 3 This histogram represents the distribution of the difference between two percent density (PD) values by one rater. 70.9% fell in within difference of 5, and 94.4% within difference of 10 between two paired PD values.

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  Figure 4 This distribution plot represents the distribution of first measured percent density (PD) value in each Breast Imaging Reporting and Data System (BI-RADS) density pattern group. The attached table indicates intraclass correlation coefficient (ICC) between two PD values by one rater in fatty breast group (BI-RADS 1 and 2), and in dense breast group (BI-RADS 3 and 4) separately.

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  Figure 5 Bland-Altman plot of discrepancy between the two pared percent density (PD) values. X-axis indicates the average of two PD values and Y-axis indicates the discrepancy between two PD values, and in overall this plot represents the distribution of the discrepancy between two PD values, and it doesn't show any specific pattern in its distribution. SD=standard deviation.

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