Romu Thobias, Elander Louise, Leinhard Olof Dahlqvist, Lidell Martin E, Betz Matthias J, Persson Anders, Enerbäck Sven, Borga Magnus
Department of Biomedical Engineering, Linköping University, Linköping, Sweden.
Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.
J Magn Reson Imaging. 2015 Dec;42(6):1639-45. doi: 10.1002/jmri.24931. Epub 2015 Apr 25.
To evaluate the possibility of quantifying brown adipose tissue (BAT) volume and fat concentration with a high resolution, long echo time, dual-echo Dixon imaging protocol.
A 0.42 mm isotropic resolution water-fat separated MRI protocol was implemented by using the second opposite-phase echo and third in-phase echo. Fat images were calibrated with regard to the intensity of nearby white adipose tissue (WAT) to form relative fat content (RFC) images. To evaluate the ability to measure BAT volume and RFC contrast dynamics, rats were divided into two groups that were kept at 4° or 22°C for 5 days. The rats were then scanned in a 70 cm bore 3.0 Tesla MRI scanner and a human dual energy CT. Interscapular, paraaortal, and perirenal BAT (i/pa/pr-BAT) depots as well as WAT and muscle were segmented in the MRI and CT images. Biopsies were collected from the identified BAT depots.
The biopsies confirmed that the three depots identified with the RFC images consisted of BAT. There was a significant linear correlation (P < 0.001) between the measured RFC and the Hounsfield units from DECT. Significantly lower iBAT RFC (P = 0.0064) and significantly larger iBAT and prBAT volumes (P = 0.0017) were observed in the cold stimulated rats.
The calibrated Dixon images with RFC scaling can depict BAT and be used to measure differences in volume, and fat concentration, induced by cold stimulation. The high correlation between RFC and HU suggests that the fat concentration is the main RFC image contrast mechanism.
评估采用高分辨率、长回波时间双回波狄克逊成像协议量化棕色脂肪组织（BAT）体积和脂肪浓度的可能性。
通过使用第二个反相位回波和第三个同相位回波实施0.42毫米各向同性分辨率的水脂分离MRI协议。脂肪图像根据附近白色脂肪组织（WAT）的强度进行校准，以形成相对脂肪含量（RFC）图像。为评估测量BAT体积和RFC对比动态变化的能力，将大鼠分为两组，分别在4℃或22℃饲养5天。然后在70厘米孔径的3.0特斯拉MRI扫描仪和一台人体双能CT中对大鼠进行扫描。在MRI和CT图像中对肩胛间、主动脉旁和肾周BAT（i/pa/pr-BAT）储存库以及WAT和肌肉进行分割。从确定的BAT储存库中采集活检样本。
活检证实，通过RFC图像识别出的三个储存库均由BAT组成。测量的RFC与双能CT的亨氏单位之间存在显著的线性相关性（P < 0.001）。在冷刺激大鼠中观察到iBAT的RFC显著降低（P = 0.0064），iBAT和prBAT的体积显著增大（P = 0.0017）。
经RFC标度校准的狄克逊图像能够描绘BAT，并可用于测量冷刺激引起的体积和脂肪浓度差异。RFC与HU之间的高度相关性表明，脂肪浓度是RFC图像的主要对比机制。
