Tunnicliffe Elizabeth M, Banerjee Rajarshi, Pavlides Michael, Neubauer Stefan, Robson Matthew D
University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK.
Translational Gastroenterology Unit, University of Oxford, Oxford, UK.
J Magn Reson Imaging. 2017 Feb;45(2):450-462. doi: 10.1002/jmri.25392. Epub 2016 Jul 23.
To propose a simple multicompartment model of the liver and use Bloch-McConnell simulations to demonstrate the effects of iron and fibrosis on shortened-MOLLI (shMOLLI) T measurements. Liver T values have shown sensitivity to inflammation and fibrosis, but are also affected by hepatic iron content. Modified Look-Locker inversion recovery (MOLLI) T measurements are biased by the lower T associated with high iron.
A tissue model was generated consisting of liver cells and extracellular fluid (ECF), with iron-dependent relaxation rates. Fibrosis was imitated by increasing the ECF proportion. Simulations of the shMOLLI sequence produced a look-up table (LUT) of shMOLLI-T for a given ECF fraction and iron content. The LUT was used to calculate ECF(shMOLLI-T ), assuming normal hepatic iron content (HIC), and ECF(shMOLLI- T1,T2*), accounting for HIC determined by T2*, for 77 patients and compared to fibrosis assessed by liver biopsy.
Simulations showed that increasing HIC decreases shMOLLI-T , with an increase in HIC from 1.0 to 2.5 mg/g at normal ECF fraction decreasing shMOLLI-T by 160 msec, while increasing ECF increased ShMOLLI-T , with an increase of 20% ECF at normal iron increasing shMOLLI-T by 200 msec. Calculated patient ECF(shMOLLI-T ) showed a strong dependence on Ishak score (3.3 ± 0.8 %ECF/Ishak stage) and 1/T2* (-0.23 ± 0.04 %ECF/Hz). However, when iron was accounted for to produce ECF(shMOLLI- T1,T2*), it was independent of HIC but retained sensitivity to Ishak score.
Use of this multicompartment model of the liver with Bloch-McConnell simulation should enable compensation of iron effects when using shMOLLI-T to assess fibrosis.
1 J. Magn. Reson. Imaging 2017;45:450-462.
提出一种简单的肝脏多室模型，并使用Bloch-McConnell模拟来证明铁和纤维化对缩短MOLLI（shMOLLI）T测量值的影响。肝脏T值已显示出对炎症和纤维化的敏感性，但也受肝铁含量的影响。改良的Look-Locker反转恢复（MOLLI）T测量值会因与高铁相关的较低T值而产生偏差。
生成一个由肝细胞和细胞外液（ECF）组成的组织模型，其具有铁依赖性弛豫率。通过增加ECF比例来模拟纤维化。shMOLLI序列的模拟产生了给定ECF分数和铁含量下的shMOLLI-T查找表（LUT）。该LUT用于计算77例患者的ECF（shMOLLI-T）（假设肝铁含量正常）和ECF（shMOLLI-T1，T2*）（考虑由T2*确定的肝铁含量），并与肝活检评估的纤维化进行比较。
模拟显示，增加肝铁含量会降低shMOLLI-T，在正常ECF分数下，肝铁含量从1.0增加到2.5mg/g时，shMOLLI-T降低160毫秒，而增加ECF会增加ShMOLLI-T，在正常铁含量下ECF增加20%时，shMOLLI-T增加200毫秒。计算得出的患者ECF（shMOLLI-T）显示出对Ishak评分（3.3±0.8%ECF/Ishak分期）和1/T2*（-0.23±0.04%ECF/Hz）有很强的依赖性。然而，当考虑铁来产生ECF（shMOLLI-T1，T2*）时，它与肝铁含量无关，但对Ishak评分仍保持敏感性。
使用这种带有Bloch-McConnell模拟的肝脏多室模型，在使用shMOLLI-T评估纤维化时应能够补偿铁的影响。
1 J.Magn.Reson.Imaging 2017;45:450 - 462。
