Rapid MRI Measures of Absolute Fat Mass in Adipose Tissue and Organs

描述(申请人提供)：肥胖在美国是一种日益严重的流行病，影响儿童、青少年和成年人的多种健康结果。越来越多的数据表明，肥胖和不良健康结局之间的联系与特定区域的脂肪积聚(例如，腹腔内的内脏脂肪)和/或脂肪渗透到肝脏、胰腺和其他器官有关。体内内脏脂肪和器官脂肪的定量通常是通过磁共振成像(MRI)进行的。MRI非常适合于这一目的，因为它本身就是三维的，提供了一种分离水分和脂肪的敏感机制，并且不涉及电离辐射，导致了不确定的重复性和超低风险。虽然磁共振成像在肥胖研究中的应用越来越频繁，但其直接量化脂肪质量的能力尚未得到开发和验证。目前的测量要么是相对的(例如脂肪信号分数)，要么是间接的(例如脂肪组织体积)。此外，目前的磁共振成像方案受到磁化时间的高成本以及长时间和/或多次屏气的限制，这让人不舒服并降低了准确性。这项建议的目的是克服这些限制，开发并充分验证一种基于MRI的新方法，用于快速量化整个腹部的脂肪质量。具体地说，我们将(1)开发信号校准程序，允许在逐个体素的基础上量化脂肪质量，以及(2)通过将脂肪组织、整个器官和肌肉中脂肪质量的测量结果与死后化学分析(当前的金标准)进行比较，评估这种量化在猪身上的准确性。这项建议的意义在于开发了一种新的、有前途的、可能具有成本效益的评估脂肪质量和器官脂肪渗透的工具。该方法利用了在快速MRI脂肪-水分离、校准扫描和动物模型中严格验证方面的最新进展。创新之处在于应用了新的信号模型和校准方案来根据信号强度量化脂肪质量。调查人员包括两名在心血管疾病快速核磁共振技术开发方面有专长的磁共振物理学家，以及一名在身体成分技术验证方面有专长的知名肥胖症研究人员。南加州大学的环境为这项转译研究提供了大量专用于研究的成像设施、动物研究支持和基础设施。公共卫生相关性：腹型肥胖在美国人中是一个日益严重的问题，并与脂肪肝、心脏病和2型糖尿病等风险的增加有关。这项提议将开发一种基于磁共振成像的新的非侵入性测试，该测试可以确定腹部包括关键器官在内的脂肪的质量和位置，并可能成为肥胖研究中的有用工具。

DESCRIPTION (provided by applicant): Obesity is a growing epidemic in the United States, affecting multiple health outcomes in children, adolescents, and adults. Increasing data suggest that the link between obesity and poor health outcome is related to buildup of fat in specific areas (e.g. visceral fat inside the abdominal cavity) and/or infiltration of fat into the liver, pancreas, and other organs. Quantification of visceral fat and organ fat in vivo is generally performed by magnetic resonance imaging (MRI). MRI is well suited for this purpose because it is inherently three-dimensional, provides a sensitive mechanism for separating water and fat, and involves no ionizing radiation, leading to indefinite repeatability with ultra-low risk. Although MRI is becoming more frequently used in obesity research, its ability to directly quantify fat mass has not yet been developed and validated. Current measurements are either relative (e.g. fat signal fraction) or indirect (e.g. adipose tissue volume). Moreover, current MRI protocols are limited by the high-cost of magnet time, and the long and/or multiple breath-holds that are uncomfortable and reduce accuracy. The objective of this proposal is to overcome these limitations and develop and fully validate a novel MRI-based method for the rapid quantification of fat mass throughout the abdomen. Specifically, we will (1) develop signal calibration procedures that allow for the quantification of fat mass on a voxel-by-voxel basis, and (2) evaluate the accuracy of this quantification in swine, by comparing measurements of fat mass in adipose tissue, whole organs, and muscle, with post-mortem chemical analysis (the current gold standard). The SIGNIFICANCE of this proposal lies in the development of a new, promising, and potentially cost-effective tool for assessing fat mass and organ fat infiltration. The APPROACH utilizes recent advances in rapid MRI fat-water separation, calibration scans, and rigorous validation in an animal model. The INNOVATION lies in the application of novel signal models and calibration schemes for quantifying fat mass from signal intensity. The INVESTIGATORS include two MR physicists with expertise in the development of rapid MRI techniques for cardiovascular disease assessment and an established obesity researcher with expertise in the validation of body composition techniques. The ENVIRONMENT at USC provides generous access to research- dedicated imaging facilities, animal research support, and infrastructure for this translational research. PUBLIC HEALTH RELEVANCE: Abdominal obesity is a growing problem among Americans, and is linked with increased risks of fatty liver disease, heart disease, and type-2 diabetes, among other things. This proposal will develop a new non-invasive test based on magnetic resonance imaging that determines the mass and location of fat within the abdomen, including critical organs, and may potentially be a useful tool in obesity research.