利用雙能數位乳房攝影消除及量化乳房組織

Cancellation and quantification of breast tissue using dual energy digital mammography

張傑鈞(Chieh-Chun Chang)

指導教授 ： 李尚熾 ； 吳杰

中山醫學大學/醫學科技學院/生物醫學科學學系碩士班/碩士(2014年)

摘要

數位乳房攝影（digital mammography, DM）為目前臨床最主要的乳癌篩檢及診斷工具，然而，病灶發生在乳房中不同位置將因組織相互重疊而被掩蓋，造成病灶的偵測效率降低，另一方面，高密度乳房的女性較容易罹患癌症，且會造成乳癌的偵測率大幅降低。本研究利用雙能數位乳房攝影（dual energy digital mammography, DEDM）搭配雙能組織消除法（tissue cancellation algorithm）將乳房中背景結構抑制，以增加病灶的偵測效率，並以此方法評估乳房密度。
　　於實驗中，我們先利用期望值最大化方法搭配穿透量測資訊求得乳房攝影機之高、低能量X光能譜資訊，並將能譜資訊及雙能影像代入組織除法中，改變向量空間投影角度，以消除不同物質間的對比度及評估乳腺比例。在對比消除上，我們利用球型假體模擬不同情況之乳房結構，並消除背景雜訊，結果顯示此方法可有效的抑制背景雜訊，並保留病灶資訊；在乳腺比例評估上，我們利用乳房組織等校假體驗正，在乳腺比例為61.1%、54.4%、50%、45.5%及38.8%時，以組織消除法評估之乳腺比例為66.4%、58.2%、52.6%、47.3%及37.6%，平均百分誤差為5.5%，此方法可有效評估乳腺比例。

關鍵字

乳房攝影 ； 乳房密度 ； 雙能 ； X光能譜

並列摘要

X-ray digital mammography (DM) is a primary imaging modality for breast cancer screening and diagnosis. However, mammography projection of 3-D anatomical information onto a 2-D image plane is superimposed. This overlapping structure reduces the cancer detection rate. On the other hand, the high breast density has been strongly associated with the increasing risk of breast cancer. In this study, we used dual energy digital mammography (DEDM) with a tissue cancellation method to suppress the background structure of breast and quantify the density of breast.
In the experiments, we estimated the high and low energy x-ray spectra of DM using the expectation maximization (EM) algorithm with transmission measurement data. We substituted the spectra data and dual energy images into the tissue cancellation algorithm. Then, we used this method to cancel the contrast of different materials and estimate breast density by changing the projection angle in the vector space. In the experiment of contrast cancellation, a ball phantom was designed to simulate different situations of breast. The results showed that the background structure can effective suppress and retain the signal of lesions. In the experiment of breast density estimation, a tissue-equivalent phantom was used to verification the quantification method, and the mean percentage error of glandular density was 5.5%. This method is an effective technique to estimate the breast density.

並列關鍵字

mammography ； breast density ； dual energy ； x-ray spectrum

參考文獻

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