hypervascular tumours, inflammatory changes, aberrant blood supply and hepatic parenchymal compression [1, 2]. MRI contrast agents are intended to improve lesion detection and characterisation by increasing liver–lesion contrast. These agents include nonspecific extracellular gadolinium (Gd) chelates, reticuloendothelial system- specific (RES) iron oxides and hepatocyte-selective agents [3]. All contrast agents used in MRI of the liver display their effect by decreasing T1 relaxation times (Gd and manganese [Mn]) and T2 relaxation times of liver paren- chyma (superparamagnetic iron oxides). After extracellular contrast agent has been injected, the liver is imaged in the hepatic artery (18–20 s delay), portal vein (45–60 s) and interstitial (1.5–5 min) phases, and it can be characterised by the enhancement pattern during these phases and the differences between the degree and duration of enhance- ment and washout [3]. During the hepatic arterial dominant phase haemangiomas, metastases and hepatocellular carci- nomas show heterogeneous enhancement, while adenomas and focal nodular hyperplasia are enhanced uniformly. In the portal vein phase the liver signals are very intense, whereas the other structures show delayed enhancement and washout phenomena. Reticuloendothelial system- specific contrast agents contain iron oxide particles and they affect RES cells, receptors in cell walls or the blood pool, leading to signal loss in normal liver parenchyma as observed in T2*- and T2-weighted sequences. RES- specific contrast is frequently used in MR angiography. Hepatocyte-selective, Mn-containing contrast agents, taken up by hepatocytes and eliminated through bile, reveal nonenhancing lesions such as haemangiomas, metastases, cholangiocarcinomas and lymphomas. Up to now quantitative perfusion MRI studies of the liver have mainly focused on tissue characterisation with Gd contrast, using the hepatic perfusion index (HPI), mean transit time (MTT), distribution volume (DV), total blood flow (Ft), arterial blood flow (Fa) and portal blood flow (Fp) as parameters. It was reported that the values of Ft, Fa, Fp and DV are significantly higher in hepatocellular carcinoma than in liver metastases of colorectal cancer, whereas MTT is higher in the metastases [4]. The largest and most significant difference between hepatocellular carcinoma and colorectal metastatic cancer was that in Fp: 8.1 vs. 0.03 mL/min/g (median values; p= 0.0001). The example in Fig. 1 illustrates that in hepatocellular carcino- ma and in colorectal metastases total blood flow is, respectively, higher and lower than in normal liver tissue [4]. In hepatic metastases the HPI, initially elevated compared with the whole liver (0.75 ± 14 vs. 0.66 ± 0.16; p < 0.01), was shown to decrease by 15% (P < 0.05) after treatment with an antiangiogenic compound [5]. This opens up the therapeutic monitoring of antiangiogenic drugs in liver tumours as a promising new application of perfusion-weighted MRI. In patients with advanced liver fibrosis Fa and MTT were about three times as large as in controls (p < 0.01, in both cases) [6]. It is concluded that the a b 140 120 100 y t isn80 e itn60 l an40 g i S20 0 -20 140 120 y100 t isn80 e itn60 l an40 g i S20 0 -20 1 7 13 19 25 31 37 43 49 Time/S 2595 Aorta Vein Liver HCC Aorta Vein Liver CMC 1 7 13 19 25 31 37 43 49 Time/S Fig. 1 Signal intensity vs. time curves of the liver, aorta, portal vein and nodule a in a man with hepatocellular carcinoma (the total blood flow is higher in the hypervascular tumour than in the liver parenchyma) and b in a woman with colorectal metastatic cancer (the total blood flow is lower in the hypovascular metastasis than in normal liver) (reproduced with permission from Abdullah et al. [4]) use of contrast-enhanced MRI for the noninvasive diagno- sis of hepatocellular carcinoma can make an important contribution to patient prognosis, and in the identification and characterisation of liver lesions such as distinguishing between malignant and benign lesions. Although, cur- rently, combined use of contrast-enhanced spiral CT in arterial phase and portal phase is considered the most sensitive imaging technique [2] and contrast-enhanced ultrasonography also remains a good alternative to con- trast-enhanced MRI [7], MRI with specific contrast enhancement may offer more relevant information on hepatic perfusion abnormalities. Iron content Ferritin concentration in plasma reflects the amount of ferritin, the iron storage molecule in the human body, within body cells and has thus been used for decades as a diagnostic indicator of the iron concentration in the liver [8]. This measure of the size of iron stores in the liver is a key parameter in the management of haemochromatosis and other diseases associated with iron overload and an important cofactor in the morbidity attributed to many