Lee N A, Rusinek H, Weinreb J, Chandra R, Toth H, Singer C, Newstead G
Department of Radiology, New York University Medical Center, NY 10016, USA.
AJR Am J Roentgenol. 1997 Feb;168(2):501-6. doi: 10.2214/ajr.168.2.9016235.
A method for segmenting MR images of the breast was applied to determine fatty and fibroglandular tissue volumes in breasts of women in different age groups. The results were compared with subjective assessments of breast density from X-ray mammograms in the same patients.
Two experienced mammographers assessed the percentage of fat in the breasts of 40 women who were 20-83 years old. MR images were obtained on a 1.0-T scanner equipped with a bilateral receive-only breast coil. Images were acquired using a three-dimensional T1-weighted gradient-echo sequence with a 1.25 x 1.4 x 2.5 mm resolution. On average, breast parenchyma appeared in 30 images in each breast. Image segmentation was based on a semiautomated, two-compartmental (fatty and fibroglandular tissue) model that accounts for partial volume effects. To validate the accuracy of the MR imaging segmentation technique, we performed a phantom study using an identical imaging sequence.
The accuracy of the MR imaging segmentation of the phantom was of the order of 2%. In our subjects, fat content was 42.5% +/- 30.3% (mean +/- SD) on mammography versus 66.5% +/- 18% on MR images. Although we found a significant correlation (r = .63) between the two techniques, mammography poorly differentiated breasts containing less than 45% fat. When our analysis included only dense breasts (i.e., those containing less than 75% fat on MR images), the correlation coefficient decreased to .34. The largest discrepancies between mammography and MR imaging occurred in breasts that had 60-80% fat as measured on MR imaging.
Fatty and fibroglandular tissue can be differentiated on MR images of the breast with high precision and accuracy, therefore allowing assessment of breast density. The conclusions of researchers who used mammographic density patterns should be reassessed.
应用一种乳腺磁共振成像（MR）图像分割方法，测定不同年龄组女性乳房中脂肪组织和纤维腺体组织的体积。将结果与同一患者乳腺X线摄影对乳房密度的主观评估结果进行比较。
两名经验丰富的乳腺造影师评估了40名年龄在20 - 83岁女性乳房中的脂肪百分比。在配备双侧仅接收乳腺线圈的1.0-T扫描仪上获取MR图像。使用分辨率为1.25×1.4×2.5 mm的三维T1加权梯度回波序列采集图像。每个乳房平均有30幅图像显示乳腺实质。图像分割基于一个考虑部分容积效应的半自动双腔室（脂肪和纤维腺体组织）模型。为验证MR成像分割技术的准确性，我们使用相同的成像序列进行了体模研究。
体模MR成像分割的准确性约为2%。在我们的研究对象中，乳腺X线摄影显示脂肪含量为42.5%±30.3%（均值±标准差），而MR图像上为66.5%±18%。尽管我们发现两种技术之间存在显著相关性（r = 0.63），但乳腺X线摄影对脂肪含量低于45%的乳房区分能力较差。当我们的分析仅包括致密型乳房（即MR图像上脂肪含量低于75%的乳房）时，相关系数降至0.34。乳腺X线摄影与MR成像之间的最大差异出现在MR成像测量脂肪含量为60 - 80%的乳房中。
乳腺MR图像能够高精度、准确地区分脂肪组织和纤维腺体组织，从而实现对乳房密度的评估。使用乳腺X线摄影密度模式的研究人员得出的结论应重新评估。
