Mawdsley Gordon E, Tyson Albert H, Peressotti Chris L, Jong Roberta A, Yaffe Martin J
Room S657, Imaging Research, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada.
Med Phys. 2009 Feb;36(2):577-86. doi: 10.1118/1.3065068.
The determination of volumetric breast density (VBD) from mammograms requires an accurate knowledge of the thickness of the compressed breast. Previously, the authors described a technique for measuring local thicknesses using optical stereoscopic photogrammetry [A. H. Tyson, G. E. Mawdsley, and M. J. Yaffe, "Measurement of compressed breast thickness by optical stereoscopic photogrammetry," Med. Phys. 36(2), 569-576 (2009)]. Here, the authors describe the use of this tool to guide the development of a simpler, more practical field technique for the estimation of breast thickness and test its accuracy. Phantoms were constructed having similar shapes and compression characteristics to breasts of different sizes. These phantoms were compressed at different forces on several types of mammography units and their thickness under compression was measured using optical stereoscopic photogrammetry at many points of contact with the compression plate. A prediction equation was developed that uses the readout of compressed thickness and compression force provided by the mammography system to estimate local breast thickness. Using this approach, systems can be calibrated to an accuracy of better than 5 mm in thickness using a simple test object compared to an error of up to 15 mm associated with using only the thickness readout of the mammography machine. On the systems tested, the estimated value of VBD obtained using this method is significantly reduced from that determined using the constant thickness reported by the mammography machine.
通过乳房X光片确定乳房体积密度（VBD）需要准确了解受压乳房的厚度。此前，作者描述了一种使用光学立体摄影测量局部厚度的技术[A. H. 泰森、G. E. 莫兹利和M. J. 亚菲，“通过光学立体摄影测量受压乳房厚度”，《医学物理》36(2)，569 - 576（2009年）]。在此，作者描述了如何使用该工具来指导开发一种更简单、更实用的现场技术，用于估计乳房厚度并测试其准确性。构建了具有与不同尺寸乳房相似形状和压缩特性的模型。这些模型在几种类型的乳房X光摄影设备上以不同的力进行压缩，并使用光学立体摄影在与压缩板的多个接触点测量其压缩状态下的厚度。开发了一个预测方程，该方程利用乳房X光摄影系统提供的压缩厚度和压缩力读数来估计局部乳房厚度。使用这种方法，与仅使用乳房X光机的厚度读数时高达15毫米的误差相比，通过一个简单的测试物体，系统可以校准到厚度精度优于5毫米。在所测试的系统上，使用此方法获得的VBD估计值与使用乳房X光机报告的恒定厚度确定的值相比显著降低。
