Fischer Jonas Gabriel William, Maushart Claudia Irene, Becker Anton S, Müller Julian, Madoerin Philipp, Chirindel Alin, Wild Damian, Ter Voert Edwin E G W, Bieri Oliver, Burger Irene, Betz Matthias Johannes
Department of Endocrinology, Diabetes and Metabolism, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland, and University of Basel, Basel, Switzerland.
Institute of Diagnostic and Interventional Radiology, University Hospital Zürich, Rämistrasse 100, 8091, Zürich, Switzerland.
EJNMMI Res. 2020 Jul 22;10(1):85. doi: 10.1186/s13550-020-00665-7.
Brown adipose tissue (BAT) is a thermogenic tissue which can generate heat in response to mild cold exposure. As it constitutes a promising target in the fight against obesity, we need reliable techniques to quantify its activity in response to therapeutic interventions. The current standard for the quantification of BAT activity is [F]FDG PET/CT. Various sequences in magnetic resonance imaging (MRI), including those measuring its relative fat content (fat fraction), have been proposed and evaluated in small proof-of-principle studies, showing diverging results. Here, we systematically compare the predictive value of adipose tissue fat fraction measured by MRI to the results of [F]FDG PET/CT.
We analyzed the diagnostic reliability of MRI measured fat fraction (FF) for the estimation of human BAT activity in two cohorts of healthy volunteers participating in two prospective clinical trials (NCT03189511, NCT03269747). In both cohorts, BAT activity was stimulated by mild cold exposure. In cohort 1, we performed [F]FDG PET/MRI; in cohort 2, we used [F]FDG PET/CT followed by MRI. Fat fraction was determined by 2-point Dixon and 6-point Dixon measurement, respectively. Fat fraction values were compared to SUV in the corresponding tissue depot by simple linear regression.
In total, 33 male participants with a mean age of 23.9 years and a mean BMI of 22.8 kg/m were recruited. In 32 participants, active BAT was visible. On an intra-individual level, FF was significantly lower in high-SUV areas compared to low-SUV areas (cohort 1: p < 0.0001 and cohort 2: p = 0.0002). The FF of the supraclavicular adipose tissue depot was inversely related to its metabolic activity (SUVmean) in both cohorts (cohort 1: R = 0.18, p = 0.09 and cohort 2: R = 0.42, p = 0.009).
MRI FF explains only about 40% of the variation in BAT glucose uptake. Thus, it can currently not be used to substitute [F] FDG PET-based imaging for quantification of BAT activity.
ClinicalTrials.gov. NCT03189511 , registered on June 17, 2017, actual study start date was on May 31, 2017, retrospectively registered. NCT03269747 , registered on September 01, 2017.
棕色脂肪组织（BAT）是一种产热组织，可在轻度寒冷暴露时产生热量。由于它是对抗肥胖的一个有前景的靶点，我们需要可靠的技术来量化其在治疗干预后的活性。目前量化BAT活性的标准是[F]FDG PET/CT。磁共振成像（MRI）中的各种序列，包括那些测量其相对脂肪含量（脂肪分数）的序列，已在小型原理验证研究中被提出并评估，结果存在差异。在此，我们系统地比较了MRI测量的脂肪组织脂肪分数与[F]FDG PET/CT结果的预测价值。
我们在参与两项前瞻性临床试验（NCT03189511，NCT03269747）的两组健康志愿者中，分析了MRI测量的脂肪分数（FF）对估计人体BAT活性的诊断可靠性。在两组中，BAT活性均通过轻度寒冷暴露来刺激。在队列1中，我们进行了[F]FDG PET/MRI；在队列2中，我们先进行[F]FDG PET/CT，然后进行MRI。脂肪分数分别通过两点Dixon法和六点Dixon法测量。通过简单线性回归将脂肪分数值与相应组织库中的SUV进行比较。
总共招募了33名男性参与者，平均年龄23.9岁，平均BMI为22.8kg/m。在32名参与者中可见活跃的BAT。在个体水平上，高SUV区域的FF显著低于低SUV区域（队列1：p<0.0001，队列2：p = 0.0002）。在两个队列中，锁骨上脂肪组织库的FF与其代谢活性（SUVmean）呈负相关（队列1：R = 0.18，p = 0.09；队列2：R = 0.42，p = 0.009）。
MRI FF仅解释了BAT葡萄糖摄取变化的约40%。因此，目前它不能用于替代基于[F]FDG PET的成像来量化BAT活性。
ClinicalTrials.gov。NCT03189511，于2017年6月17日注册，实际研究开始日期为2017年5月31日，追溯注册。NCT03269747，于2017年9月1日注册。
