Intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) allows for simultaneous assessment of tissue diffusion and pseudodiffusion due to capillary blood flow (1). IVIM-DWI may serve as a surrogate for contrast-enhanced MRI measurements and thereby allow for assessment of tissue perfusion without contrast injection. The correlation between IVIM-DWI and contrast-enhanced MRI has been assessed in different organs and tissues, including liver cirrhosis (2). However, no correlative studies between these two techniques have been performed in hepatocellular carcinoma (HCC), while both techniques have been studied extensively in HCC (3-5). The aim of our study was to quantify IVIM-DWI and DCE-MRI parameters in HCC lesions and liver parenchyma and to assess the correlation between these quantitative techniques.Twenty-five patients with HCC (M/F 23/2, mean age 58y) underwent abdominal MRI at 1.5 or 3.0T, including IVIM-DWI (respiratory-triggered single-shot SE-EPI, bipolar diffusion gradient, b-values 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 175, 200, 400, 600, 800 s/mm², TR one respiratory cycle, TE 78-81 ms, FOV 340-450 x 220-305 mm², reconstruction matrix 320 x 100-256, slice thickness 7 mm, 20-30 slices covering the entire liver) and DCE-MRI (3D FLASH, TR 2.7 ms, TE 0.97-1.07 ms, FA 9.5-11.5°, reconstruction matrix 384x264-312, FOV 370-401x254-325 mm², 40 slices, slice thickness 4-5 mm, mean temporal resolution 2.3 s, 100 dynamics, contrast agent 0.05 mmol/kg Gd-BOPTA). 8 patients underwent the MRI examination twice to assess test-retest reproducibility. Regions-of-interest (ROIs) were placed on the IVIM-DWI and DCE-MRI images in the entire HCC lesion and in the liver parenchyma and were matched as closely as possible between the acquisitions. Additional ROIs were drawn in the portal vein and aorta in the DCE-MRI images. IVIM-DWI parameters (pseudodiffusion coefficient D*, diffusion coefficient D and perfusion fraction PF) in the ROIs were quantified by a Bayesian fitting algorithm. DCE-MRI parameters (arterial flow F_a, portal flow F_p, total flow F_t, mean transit time MTT, distribution volume DV and arterial fraction ART) were determined by fitting a dual-input single compartment model to the dynamic data in HCC and liver, using pre-contrast T₁ data acquired in a separate Look-Locker acquisition. Differences in IVIM-DWI and DCE parameters between liver and HCC tissue were tested for significance using a Mann-Whitney U test. Spearman correlation coefficients between all IVIM-DWI and DCE-MRI parameters were determined, both for liver and HCC. IVIM-DWI and DCE-MRI data of 34 HCC lesions (mean size 4.9±3.5 cm) and 25 livers were analyzed. D, D*, PF and F_p were all significantly lower in HCC vs. liver, while Fa and ART were significantly higher in HCC (Table 1). Significant moderate to strong negative correlations were observed between ART and D*, ART and PF, ART and PFxD*, F_a and PF and between F_a and PFxD* in the liver (Figure 1 a-e). There were no significant correlations between IVIM-DWI and DCE-MRI in HCC lesions [highest P-value of 0.086 found for correlation between Fa and PF (Figure 1 f)]. The observed negative correlations between ART and PF, D* and PF x D* and between Fa and PF and PF x D* in the liver may be associated with incomplete compensation of loss of portal venous flow by the arterial buffer response (6) in cirrhotic patients, leading to hampered liver perfusion. The lack of correlations between IVIM-DWI and DCE-MRI in HCC lesions suggests that IVIM-DWI is more sensitive to portal capillary flow than to arterial flow, given the predominant arterial perfusion of HCC lesions. In addition, the drastically altered hemodynamics, including tortuous vasculature, in tumors make it considerably challenging to estimate capillary properties in cancerous tissue.IVIM-DWI and DCE-MRI provide non-redundant information in HCC, while they correlate in liver parenchyma.