Intravoxel Incoherent Motion Diffusion-weighted MR Imaging of Hepatocellular Carcinoma: Correlation with Enhancement Degree and Histologic Grade

Abstract

Purpose To compare the association of intravoxel incoherent motion (IVIM)–derived parameters and apparent diffusion coefficient (ADC) with the histologic grade of hepatocellular carcinoma (HCC) and evaluate the relationship between IVIM-derived parameters and arterial enhancement degree. Materials and Methods This retrospective study was institutional review board–approved, and informed consent was waived. Forty patients with 42 surgically confirmed HCCs underwent diffusion-weighted magnetic resonance (MR) imaging with eight b values (0–800 sec/mm²). ADC, diffusion coefficient (D), pseudodiffusion coefficient, and perfusion fraction (f) were calculated. Two radiologists determined the enhancement degree in consensus, as well as the percentage of arterial enhancement of HCC. The relationship between the parameters and histologic grade, as well as arterial enhancement, was assessed by using the Spearman or Pearson correlation test. Receiver operating characteristic (ROC) analysis of discrimination between low-grade (grades 1 and 2) and high-grade (grades 3 and 4) HCC was performed for D and ADC values. Results D and ADC values were both significantly correlated with histologic grade: r = −0.604 (P < .0001) and r = −0.448 (P = .002), respectively. D and ADC values were both significantly lower in high-grade HCC (D = [0.99 ± 0.13] × 10⁻³mm²/sec, ADC = [1.13 ± 0.14] × 10⁻³mm²/sec) than in low-grade HCC (D = [1.18 ± 0.16] × 10⁻³mm²/sec, ADC = [1.25 ± 0.17] × 10−³mm²/sec) (P < .0001 and P = .029, respectively). However, ROC analysis demonstrated a higher area under the ROC curve value for D than for ADC for differentiating high-grade HCC from low-grade HCC (0.838 vs 0.728; P = .026). The percentage of arterial enhancement was correlated with f (r = 0.621, P < .0001). Conclusion IVIM-derived D values of HCC showed significantly better diagnostic performance than ADC values in differentiating high-grade HCC from low-grade HCC, and significant correlation was observed between f and the percentage of arterial enhancement. © RSNA, 2013 Online supplemental material is available for this article.