Al-Mrabeh Ahmad, Hollingsworth Kieren G, Steven Sarah, Tiniakos Dina, Taylor Roy
Magnetic Resonance Centre, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.
Department of Cellular Pathology, Royal Victoria Infirmary, Newcastle upon Tyne Hospitals and Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.
PLoS One. 2017 Apr 3;12(4):e0174660. doi: 10.1371/journal.pone.0174660. eCollection 2017.
Accumulation of intrapancreatic fat may be important in type 2 diabetes, but widely varying data have been reported. The standard quantification by MRI in vivo is time consuming and dependent upon a high level of experience. We aimed to develop a new method which would minimise inter-observer variation and to compare this against previously published datasets.
A technique of 'biopsying' the image to minimise inclusion of non-parenchymal tissues was developed. Additionally, thresholding was applied to exclude both pancreatic ducts and intrusions of visceral fat, with pixels of fat values of <1% or >20% being excluded. The new MR image 'biopsy' (MR-opsy) was compared to the standard method by 6 independent observers with wide experience of image analysis but no experience of pancreas imaging. The effect of the new method was examined on datasets from two studies of weight loss in type 2 diabetes.
At low levels of intrapancreatic fat neither the result nor the inter-observer CV was changed by MR-opsy, thresholding or a combination of the methods. However, at higher levels the conventional method exhibited poor inter-observer agreement (coefficient of variation 26.9%) and the new combined method improved the CV to 4.3% (p<0.03). Using either MR-opsy alone or with thresholding, the new methods indicated a closer relationship between decrease in intrapancreatic fat and fall in blood glucose.
The inter-observer variation for quantifying intrapancreatic fat was substantially improved by the new method when pancreas fat levels were moderately high. The method will improve comparability of pancreas fat measurement between research groups.
胰腺内脂肪堆积在2型糖尿病中可能具有重要意义，但所报告的数据差异很大。磁共振成像（MRI）在体内进行标准定量既耗时又依赖于高水平的经验。我们旨在开发一种新方法，以尽量减少观察者间的差异，并将其与先前发表的数据集进行比较。
开发了一种对图像进行“活检”的技术，以尽量减少非实质组织的纳入。此外，应用阈值排除胰管和内脏脂肪的侵入，脂肪值<1%或>20%的像素被排除。6名具有丰富图像分析经验但无胰腺成像经验的独立观察者将新的磁共振图像“活检”（MR活检）与标准方法进行了比较。在两项2型糖尿病体重减轻研究的数据集上检验了新方法的效果。
在胰腺内脂肪含量较低时，MR活检、阈值法或两种方法结合使用，结果和观察者间变异系数（CV）均未改变。然而，在较高水平时，传统方法的观察者间一致性较差（变异系数为26.9%），新的联合方法将CV提高到4.3%（p<0.03）。单独使用MR活检或与阈值法结合使用，新方法表明胰腺内脂肪减少与血糖下降之间的关系更为密切。
当胰腺脂肪水平中等偏高时，新方法显著改善了胰腺内脂肪定量的观察者间变异。该方法将提高研究组之间胰腺脂肪测量的可比性。
