近年國內外皆有不少文獻探討乳腺的重要性，由於乳腺緻密度與乳房攝影檢查準確性成反比，因此，乳腺緻 密度的測量有助傳達乳房攝影檢測乳癌的難度。本研究以回溯方式，收集各年齡層452 位女性接受過兩次乳房篩 檢，年齡範圍為27 歲至79 歲，得904 張乳房攝影影像。使用兩種方式測量乳腺，一為定性方法由專科醫師根據 BI-RADS 分級評估，二為定量方法使用電腦軟體ImageJ 推估乳腺比例，經由定性和定量方法進行乳腺分級，用 以了解不同年齡層其乳腺間隔兩年的退化程度。結果顯示，不同年齡層其兩年乳腺退化程度為：<40 歲為9.47%， 40 歲至49 歲為9.01%，50 歲至59 歲為8.95%，60 歲至69 歲6.83%，>70 歲為5.25，並使用SPSS 成對t 檢定進 行分析，本研究經由定性和定量方法發現其此分組年齡層中，不同年齡層對於兩年間乳腺退化程度並不明顯。

In recent years, many studies shows that the importance of the breast density, because mammographic sensitivity is inversely breast density, that the observed higher relative risk was solely due to mass obscuration by dense tissues at mammography. To retrospectively collect 452 women received two screenings had 904 digital mammography images, the age range of 27 years to 79 years old. There were two ways to measure the breast density, Qualitative estimates determined by a qualified breast radiologist using the BI-RADS Categorical Assessment scale. Quantitative analysis the percentage breast density use computer software ImageJ. The results showed that different age for its two-year breast degree of degradation: <40 years was 9.47%, 40 to 49 years old was 9.01%, 50 to 59 years was 8.95%, 6.83% 60 to 69 years,> 70 years was 5.25%. The student pair t-test was used for the statistics with the aids of SPSS. The qualitative and quantitative methods were for different age groups among its two-year limited degree of degradation breast.