利用乳房磁振造影與乳房X光影像評估非均質乳房組織的乳腺劑量值

Evaluation of the normalized absorbed dose for inho-mogeneous breast tissue in MRI and mammography

黃美蘭(Mei-lan Huang)

指導教授 ： 林政勳

中臺科技大學/健康科學院/醫學影像暨放射科學系暨研究所/碩士(2012年)

https://doi.org/10.6822/CTUST.2012.00054

摘要

臨床運用平均乳腺劑量轉換因子(Normalized average glandular dose，DgN)評估乳房X光攝影所造成的能量沉積，會導致乳腺劑量被高估或低估。主要是因為乳房組織屬非均質性，易造成轉換因子之錯誤評估。本研究針對同時執行三維(three dimensional，3D)乳房磁振造影(magnetic resonance，MR)與乳房X光攝影之受檢者，計算其3D乳房磁振造影影像上非均質性乳房腺體分佈的組織型態與比例值，將腺體-脂肪比例以多層乳房和全乳房方式評估乳房X光攝影的輻射劑量。結果顯示71組影像中，3D乳房磁振造影影像將多層乳房均分三層後，其乳腺比例分別為25.33%、37.36%、17.61%，而全乳房則為26.77%，印證了乳腺比例為非均質性。經獨立成對樣本t檢定比較多層與全乳房之轉換因子與評估乳腺劑量值，其多層和全乳房的轉換因子數據分別為0.239±0.039(mGy/mGy)和0.219±0.042(mGy/mGy)。而評估乳腺劑量值部分則為1.286±0.293 (mGy)與1.176±0.286 (mGy)，其結果具有顯著性(p<0.05)。因此，乳房X光攝影劑量需嚴謹考慮到非均質性乳腺之分佈，避免單一全乳房方式計算平均乳腺劑量，造成低估病人實際接受的乳腺劑量值。

關鍵字

平均乳腺劑量 ； 轉換因子 ； 非均質性 ； 三維乳房磁振造影 ； 乳房X光攝影

並列摘要

The Normalized average glandular dose (DgN) is possible to overestimate or underestimate in the assessment of radiation dose to the breast during mammography. The reason is that the inhomogeneous breast density is ape to the incorrect transfer factor. In the research , the authors compared 3D MRI and X-ray mammography in each patient and calculate the ratio of fibrogland distribution and tissue pattern. In addition, we used multilayer breast images slices to predict the X-ray mammography dosage. The results suggested that the ratio of fibrogland in each of 3 layer MRI images were 25.33%, 37.36%, and 17.61%. 26.77% is in whole layer image slices. As a result, inhomogeneous fibrogland tissue breast is verified. The conversion factors in multilayer MRI slices and whole layer MRI images were 0.239±0.039 (mGy/mGy) and 0.219±0.042 (mGy/mGy) by using paired sample analysis of comprise of transfer factors and prediction of breast mammography dosage. It is a significant result between two groups in prediction of mammography dosage (1.286±0.293 mGy vs. 1.176±0.286 mGy, p=0.000). In conclusion, it is important to consider the inhomogeneous fibrogland distribution for predicting the dosage. In avoid using single one layer whole breast to calculate the normalized overage glandular dose. That could result in underestimate the radiation dose to the breast.

並列關鍵字

Transfer factors ； Mammography ； Three dimensional breast magnetic resonance ； Average Glandular Dose ； Heterogeneity

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