Imaging Department, Centro Hospitalar do Porto, Largo Prof Abel Salazar, 4099-001, Porto, Portugal.
Radiology Department, Hospital Universitario y Politécnico La Fe and Biomedical Imaging Research Group (GIBI230), Valencia, Spain.
Abdom Radiol (NY). 2017 Feb;42(2):468-477. doi: 10.1007/s00261-016-0899-0.
The purpose of the study was to evaluate the role of intravoxel incoherent motion (IVIM) diffusion model for the assessment of liver fibrosis and inflammation in diffuse liver disorders, also considering the presence of liver steatosis and iron deposits.
Seventy-four patients were included, with liver biopsy and a 3 Tesla abdominal magnetic resonance imaging examination, with an IVIM diffusion-weighted sequence (single-shot spin-echo echo-planar sequence, with gradient reversal fat suppression; 6 b-values: 0, 50, 200, 400, 600, and 800 s/mm). Histological evaluation comprised the Ishak modified scale, for grading inflammation and fibrosis, plus steatosis and iron loading classification. The liver apparent diffusion coefficient (ADC) and IVIM parameters (D, D*, f) were calculated from the IVIM images. The relationship between IVIM parameters and histopathological scores were evaluated by ANOVA and Spearman correlation tests. A test-retest experiment assessed reproducibility and repeatability in 10 healthy volunteers and 10 randomly selected patient studies.
ADC and f values were lower with higher fibrosis stages (p = 0.009, p = 0.006, respectively) and also with higher necro-inflammatory activity grades (p = 0.02, p = 0.017, respectively). Considered together, only fibrosis presented a significant effect on ADC and f measurements (p < 0.05), whereas inflammation had no significant effect (p > 0.05). A mild correlation was found between ADC and f with fibrosis (R = -0.32 and R = -0.38; p < 0.05) and inflammation (R = -0.31 and R = -0.32, p < 0.05; respectively). The AUROC for ADC and f measurements with the different dichotomizations between fibrosis or inflammation grades were only fair (0.670 to 0.749, p < 0.05). Neither D nor D* values were significantly different between liver fibrosis or inflammation grades. D measurements were significantly different across histologic grades of steatosis (p < 0.001) and iron overload (p < 0.001), whereas f measurements showed significant differences across histologic steatosis grades (p = 0.005). There was an excellent agreement between the different readers for ADC, f, and D.
Although fibrosis presented a significant effect on ADC and f, IVIM measurements are not accurate enough to stage liver fibrosis or necro-inflammatory activity in diffuse liver diseases. D values were influenced by steatosis and iron overload.
本研究旨在评估体素内不相干运动（IVIM）扩散模型在弥漫性肝脏疾病中评估肝纤维化和炎症的作用，同时考虑到肝脂肪变性和铁沉积的存在。
共纳入 74 例患者，均行肝脏活检和 3T 腹部磁共振成像检查，采用 IVIM 扩散加权序列（单次激发自旋回波回波平面序列，带梯度反转脂肪抑制；6 个 b 值：0、50、200、400、600 和 800 s/mm）。组织学评估包括 Ishak 改良分级，用于评估炎症和纤维化，以及脂肪变性和铁负荷分类。从 IVIM 图像中计算肝脏表观扩散系数（ADC）和 IVIM 参数（D、D*、f）。通过方差分析和 Spearman 相关检验评估 IVIM 参数与组织病理学评分之间的关系。在 10 名健康志愿者和 10 名随机选择的患者研究中进行了测试-再测试实验，以评估可重复性和可重复性。
随着纤维化程度的增加（p=0.009，p=0.006），ADC 和 f 值降低，随着坏死性炎症活动程度的增加（p=0.02，p=0.017），ADC 和 f 值也降低。综合考虑，只有纤维化对 ADC 和 f 的测量有显著影响（p<0.05），而炎症无显著影响（p>0.05）。ADC 和 f 与纤维化（R=-0.32 和 R=-0.38；p<0.05）和炎症（R=-0.31 和 R=-0.32；p<0.05）均呈轻度相关性。ADC 和 f 测量值在纤维化或炎症分级的不同二分类之间的 AUROC 仅为中等（0.670 至 0.749，p<0.05）。D 或 D*值在肝纤维化或炎症分级之间无显著差异。D 测量值在组织学脂肪变性（p<0.001）和铁过载（p<0.001）的不同分级之间有显著差异，而 f 测量值在组织学脂肪变性分级之间有显著差异（p=0.005）。不同读者之间在 ADC、f 和 D 的测量值上有很好的一致性。
尽管纤维化对 ADC 和 f 有显著影响，但 IVIM 测量值不足以准确分期弥漫性肝脏疾病中的肝纤维化或坏死性炎症活动。D 值受脂肪变性和铁过载的影响。
