Quantification of breast density using dual energy mammography

描述(申请人提供)：在美国女性中，乳腺癌是最常见的癌症，也是第二大致死癌症。乳腺密度定义为纤维腺组织与总纤维腺组织和脂肪组织的比率，是乳腺癌发生的重要危险因素。乳房X光摄影致密乳房是指由于纤维腺组织相对于脂肪组织体积分数较大而使X射线光子衰减较大的乳房。目前还没有公认的标准来可靠地测量乳房密度。仅凭主观视觉评估不足以量化乳房密度。其他更定量的尝试也受到了一些限制，比如只提供一个面积，而不是乳房密度的体积测量，或者假设乳房厚度不变。此前的研究表明，乳房X光检查密度每增加1%，患乳腺癌的相对风险就会增加2%，这表明需要一种准确的方法来测量乳房密度。这项建议的目标是开发一种使用双能量乳房X光照相技术客观和定量测量女性乳房密度的方法。双能量成像利用了纤维腺和脂肪组织之间X射线光子衰减的差值能量依赖性。图像像素被分解成两个主要乳房组织中每一个的单独的厚度测量。具体目标是：(1)开发一个分析模拟模型，以研究使用双能量乳房X光摄影术准确测量乳房密度的可行性。(2)探讨双能量乳房X光摄影可准确测量乳房密度的假说。(3)应用磁共振成像(MRI)和锥束计算机断层扫描(CT)对双能技术进行乳腺密度量化的验证。(4)对双能X线乳腺摄影测量的人体乳房密度与MRI测量的乳房密度相关系数大于0.95的假设进行检验。提出的方法提供了一个像素的基础上的乳腺密度的体积测量，它有可能纳入常规筛查乳房X光检查。这些优势应该转化为对乳腺癌风险的更准确评估。该项目的长期计划是开发一种临床上可行的方法，用双能X射线乳房X光照相术测量女性的乳房密度。与公众健康相关：乳房密度已被确定为乳腺癌发展过程中一个重要但未得到充分利用的风险因素。仅凭主观视觉评估不足以量化乳房密度。这项建议的目标是开发一种使用双能量乳房X光照相技术客观和定量测量女性乳房密度的方法。提出的方法提供了一种测量乳腺密度的体积测量方法，并有可能被纳入常规筛查乳腺X光检查。

DESCRIPTION (provided by applicant): Among American women breast cancer is the most common cancer and the 2nd leading cause of death from cancer. Breast density, which is defined as the ratio of fibroglandular tissue to the total fibroglandular and adipose tissue, is an important risk factor in the development of breast cancer. A mammographically dense breast refers to a breast which attenuates a greater proportion of x-ray photons due to its significant volume fraction of fibroglandular tissue relative to adipose tissue. There are currently no accepted standards to reliably measure breast density. Subjective visual assessment alone is inadequate to quantify breast density. Other more quantitative attempts have suffered from a number of limitations such as providing only an area as opposed to volumetric measure of breast density or assuming a constant breast thickness. Previous studies have shown that the relative risk for developing breast cancer increases by 2% for every 1% increase in mammographic density, indicating the need for an accurate method to measure breast density. The goal of this proposal is to develop a method to objectively and quantitatively measure the density of a woman's breast using dual energy mammography. Dual energy imaging exploits the differential energy dependence in x-ray photon attenuation between fibroglandular and adipose tissue. Image pixels are decomposed into separate thickness measurements for each of the two primary breast tissues. The specific aims are: (1) Development of an analytical simulation model to investigate the feasibility of accurate breast density measurements using dual energy mammography. (2) Investigation of the hypothesis that breast density can be accurately measured in breast phantoms using dual energy mammography. (3) Validation of the dual energy technique for breast density quantification with magnetic resonance imaging (MRI) and cone-beam computed tomography in postmortem breast tissue. (4) To test the hypothesis that breast density measured in human volunteers with dual energy mammography and breast density measured with MRI have a correlation coefficient higher than 0.95. The proposed method provides a volumetric measure of breast density on a pixel by pixel basis and it has the potential to be incorporated into routine screening mammography. These advantages should translate into a more accurate assessment of breast cancer risk. The long-range plan for this project is to develop a clinically feasible method to measure the density of a woman's breast with dual energy x-ray mammography. PUBLIC HEALTH RELEVANCE: Breast density has been identified as an important yet underutilized risk factor in the development of breast cancer. Subjective visual assessment alone is inadequate to quantify breast density. The goal of this proposal is to develop a method to objectively and quantitatively measure the density of a woman's breast using dual energy mammography. The proposed method provides a volumetric measure of breast density and it has the potential to be incorporated into routine screening mammography.