Quantification of Brown Adipose Tissue by MRI in Children and Teenagers

通过 MRI 对儿童和青少年棕色脂肪组织进行定量

• 批准号: 8044608
• 负责人: VICENTE GILSANZ
• 金额: $ 22.3万
• 依托单位: CHILDREN'S HOSPITAL OF LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-30 至 2012-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8044608
• 关键词: Quantification; Brown; Adipose; Tissue; MRI

DESCRIPTION (provided by applicant): The objective of this proposal is to develop and validate chemical-shift fat-water MRI methods for the detection and quantification of both metabolically active and inactive brown adipose tissue (BAT) in humans. While the current gold-standard modality for BAT imaging is fusion positron emission and computed tomography (PET/CT), the approach has several limitations. PET/CT can only identify metabolically active BAT through the uptake of exogenous radionuclide tracers, limiting its applicability. Additionally, PET/CT is expensive, not widely available, and is imprecise since the uptake of a tracer is highly dependent on environmental factors. In contrast, MRI is non-ionizing and non-invasive, making it applicable to a larger proportion of the population even for prospective longitudinal studies in healthy subjects. Furthermore, chemical-shift fat-water MRI is capable of yielding very sensitive measures of a tissue's fat fraction on a voxel- wise basis in the imaging volume. Due to BAT's cytological structure differences from white adipose tissue (WAT), we hypothesized that the fat fraction of BAT is uniquely represented by chemical-shift MRI, and that it is significantly lower than that of lipid-rich WAT. In addition to MRI, we will also determine whether standalone CT, which measures X-ray attenuation in Hounsefield Units (HUs), is also capable of differentiating BAT and WAT. It is hypothesized that since BAT contains more intracellular water, its HUs are significantly more positive than that of WAT. The proposed work will be implemented at Childrens Hospital of Los Angeles. Two studies are proposed. First, a cross-sectional study involving 90 patients will be used to validate standalone CT and MRI in the assessment of metabolically active BAT. These patients will undergo routine PET/CT imaging as part of their medical care, and PET/CT values for active BAT will be compared to standalone CT and MRI. A validation study will be conducted in 20 cadavers to assess the specificity and reproducibility of MRI and CT measurements to locate and quantify BAT. To this end, volume, HUs, and fat fraction measurements will be compared and correlated to histological analysis. Another aim of this study is to examine the relationships between BAT and age, weight, body mass, body adiposity, and musculature in children and teenagers. The development of MRI techniques to quantify BAT will provide simpler, more accessible approaches to longitudinally study the genetic and environmental factors (e.g. diet, temperature, exercise, etc.) that influence BAT in different populations. PUBLIC HEALTH RELEVANCE: Brown adipose tissue is of great research interest since by increasing energy expenditure through thermogenesis, it can potentially counteract weight gain and development of obesity. This proposal investigates the utilization of advanced imaging methods in computed tomography and more importantly, magnetic resonance imaging to safely and non-invasively measure brown adipose tissue in humans. In addition, the proposal will study how brown adipose tissue quantity varies with age, gender, and body composition, particularly in children and adolescents.

描述（由申请人提供）：本提案的目的是开发和验证化学位移脂肪-水 MRI 方法，用于检测和定量人体代谢活跃和非活跃的棕色脂肪组织 (BAT)。虽然目前 BAT 成像的黄金标准方式是融合正电子发射和计算机断层扫描 (PET/CT)，但该方法有一些局限性。 PET/CT只能通过摄取外源放射性核素示踪剂来识别代谢活跃的BAT，限制了其适用性。此外，PET/CT 价格昂贵，无法广泛使用，并且不精确，因为示踪剂的吸收高度依赖于环境因素。相比之下，MRI 是非电离和非侵入性的，使其适用于更大比例的人群，甚至适用于健康受试者的前瞻性纵向研究。此外，化学位移脂肪-水 MRI 能够在成像体积中以体素为基础对组织的脂肪分数进行非常灵敏的测量。由于 BAT 的细胞学结构与白色脂肪组织 (WAT) 不同，我们假设化学位移 MRI 独特地代表了 BAT 的脂肪分数，并且其明显低于富含脂质的 WAT。除了 MRI 之外，我们还将确定测量 Hounsefield 单位 (HU) 中 X 射线衰减的独立 CT 是否也能够区分 BAT 和 WAT。据推测，由于 BAT 含有更多的细胞内水，因此其 HU 的阳性率明显高于 WAT。 拟议的工作将在洛杉矶儿童医院实施。提出了两项​​研究。首先，一项涉及 90 名患者的横断面研究将用于验证独立 CT 和 MRI 评估代谢活性 BAT 的效果。作为医疗护理的一部分，这些患者将接受常规 PET/CT 成像，并且活性 BAT 的 PET/CT 值将与独立 CT 和 MRI 进行比较。将在 20 具尸体上进行验证研究，以评估 MRI 和 CT 测量的特异性和可重复性，以定位和量化 BAT。为此，将比较体积、HU 和脂肪分数测量值并将其与组织学分析相关联。这项研究的另一个目的是检查儿童和青少年的 BAT 与年龄、体重、体重、身体肥胖和肌肉组织之间的关系。 用于量化 BAT 的 MRI 技术的发展将为纵向研究影响不同人群 BAT 的遗传和环境因素（例如饮食、温度、运动等）提供更简单、更容易的方法。 公共健康相关性：棕色脂肪组织具有很大的研究兴趣，因为它通过生热作用增加能量消耗，有可能抵消体重增加和肥胖的发展。该提案研究了先进成像方法在计算机断层扫描中的应用，更重要的是，利用磁共振成像来安全、非侵入性地测量人体棕色脂肪组织。此外，该提案还将研究棕色脂肪组织的数量如何随年龄、性别和身体成分变化，特别是在儿童和青少年中。