Eur Radiol (2012) 22:891–899 DOI 10.1007/s00330-011-2313-1 MAGNETIC RESONANCE Effects of microperfusion in hepatic diffusion weighted imaging Hildebrand Dijkstra & Paul Baron & Peter Kappert & Matthijs Oudkerk & Paul E. Sijens Received: 5 July 2011 / Revised: 30 August 2011 / Accepted: 9 September 2011 / Published online: 12 November 2011 # The Author(s) 2011. This article is published with open access at Springerlink.com Abstract Objective Clinical hepatic diffusion weighted imaging (DWI) generally relies on mono-exponential diffusion. The aim was to demonstrate that mono-exponential diffusion in the liver is contaminated by microperfusion and that the bi-exponential model is required. Methods Nineteen fasting healthy volunteers were exam- ined with DWI (seven b-values) using fat suppression and respiratory triggering (1.5 T). Five different regions in the liver were analysed regarding the mono-exponentially fitted apparent diffusion coefficient (ADC), and the bi- exponential model: molecular diffusion (Dslow), micro- perfusion (Dfast) and the respective fractions (fslow/fast). Data were compared using ANOVA and Kruskal–Wallis tests. Simulations were performed by repeating our data analyses, using just the DWI series acquired with b-values approx- imating those of previous studies. Results Median mono-exponentially fitted ADCs varied sig- nificantly (P<0.001) between 1.107 and 1.423×10−3 mm2/s for the five regions. Bi-exponential fitted Dslow varied between 0.923 and 1.062×10−3 mm2/s without significant differences (P=0.140). Dfast varied significantly, between 17.8 and 46.8× 10−3 mm2/s (P<0.001). F-tests showed that the diffusion data fitted the bi-exponential model significantly better than the mono-exponential model (F>21.4, P<0.010). These results were confirmed by the simulations. H. Dijkstra (*) : M. Oudkerk Center for Medical Imaging - North East Netherlands, Department of Radiology, University of Groningen, University Medical Center Groningen, EB44, PO Box 30001, 9700 RB Groningen, The Netherlands e-mail: h.dijkstra01@umcg.nl P. Baron : P. Kappert : P. E. Sijens Department of Radiology, University of Groningen, University Medical Center Groningen, EB44, PO Box 30001, 9700 RB Groningen, The Netherlands Conclusion ADCs of normal liver tissue are significantly dependent on the measurement location because of sub- stantial microperfusion contamination; therefore the bi- exponential model should be used. Key Points & Diffusion weighted MR imaging helps clinicians to differentiate tumours by diffusion properties & Fast moving water molecules experience microperfusion, slow molecules diffusion & Hepatic diffusion should be measured by bi-exponential models to avoid microperfusion contamination & Mono-exponential models are contaminated with micro- perfusion, resulting in apparent regional diffusion differences & Bi-exponential models are necessary to measure diffusion and microperfusion in the liver Keywords Diffusion weighted imaging . IVIM . Liver parenchyma . Microperfusion . ADC variability Introduction Diffusion weighted imaging (DWI) started with the introduction of intravoxel incoherent motion (IVIM) imag- ing by Le Bihan et al. in the late 1980s [1]. IVIM was developed to quantify microscopic translational motions in a voxel by defining the apparent diffusion coefficient (ADC), which integrates the effects of both molecular diffusion and microperfusion of blood in the capillary network [2]. The ADC is sensitive to all intravoxel incoherent motions and equals the diffusion coefficient Dslow if only molecular diffusion is present. However, ADCs of brain tissue were often higher than expected because of microperfusion contamination. Therefore, the IVIM theory was extended to a bi-exponential model that was used to obtain pure and separate images of molecular diffusion Dslow and microperfusion Dfast [3]. DWI was introduced in the abdominal organs from the early 1990s