Focal liver disease (1H MRS) The sensitivity and specificity of single-voxel 1H MRS in diagnosing malignant hepatic tumours (n= 53) were reported to be less than 50% and 20%, respectively [113], disappointing in view of ex vivo proton MRS results showing that normal liver and cirrhotic liver were distinguished from hepatocellular carcinoma (HCC) with accuracies of 100% and 98%, respectively [114]. In patients re-examined shortly after transcatheter arterial chemoembolisation (TACE), reduced Cho and reduced Cho/lipid ratios were observed in HCC [37, 114]. It may be concluded that single-voxel MRS, while of use in tumour follow-up, is not sufficiently robust for tumour character- isation. One of the advantages in the use of multivoxel MRS [67, 68] in tumour heterogeneity studies is the possibility of retrospective positioning of the spectral map over the tumour. Considering normal liver fat contents of up to 5% [58], about two orders of magnitude higher than Cho in malignant tumours, optimal multivoxel MRS of liver tumours includes suppression of both lipid and water signals. Previous single-voxel MRS studies lacked lipid suppression [37, 113, 114]. In order to get direct comparisons of voxels containing tumour and normal liver tissue multivoxel MRS should be used, preferably with fat suppression in order to improve the detection of the millimolar range of metabolite signals (i.e. Cho in liver and elevated Cho in tumour) in liver tissues containing at least 0.3% fat, even in healthy subjects [68]. Thus, with incorporation of multivoxel MRS methods as well as lipid suppression methods, MRS should soon develop into a more successful method for the characterisation of liver tumours than has been reported to date. The increasing availability of high-field MR systems (3 T, 7 T…) will enable future MRS studies to be performed faster and with References 1. Tian JL, Zhang JS (2006) Hepatic perfusion disorders: etiopathogenesis and related diseases. World J Gastroenterol 12:3265–3270 2. Lupescu IG, Grasu M, Capşa R, Pitrop A, Georgescu SA (2006) Hepatic perfusion disorders: computer- tomographic and magnetic resonance imaging. J Gastrointestin Liver Dis 15:273–279 3. Karabulut N, Elmas N (2006) Contrast agents used in MR imaging of the liver. Diagn Interv Radiol 12:22–30 2603 enhanced spatial resolution, the latter in particular of interest in the study of small malignancies and tumour heterogeneity. Future prospects In perfusion MRI a promising new application is thera- peutic monitoring of antiangiogenic drugs in liver tumours. The methods for quantifying liver iron content elevation, a measure of inflammation, liver disease and cancer, already appear to be optimised. It will be of interest to use the same methods for monitoring iron accumulations in other organs such as the heart. Because of the high perfusion fraction in liver, the apparent diffusion coefficients strongly depend on the gradient factors used in diffusion-weighted MRI. While complicating analysis, this offers the opportunity to study perfusion without contrast injection. Another novel method, MRE, has already been established as the only technique able to stage fibrosis or diagnose mild disease. Further studies are needed to validate the possible application of MRE in the diagnosis and monitoring of cancer. The MRS and MRI methods for determining liver fat content are already quite established and are expected to become a major instrument in epidemiological studies of populations increasingly suffering from overweight. 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