Various liver diseases lead to significant alterations of the hepatic microcirculation. Therefore, quantification of hepatic perfusion has the potential to improve the assessment and management of liver diseases. Most methods used to quantify liver perfusion are invasive or controversial. This paper describes and validates a non-invasive method for the quantification of liver perfusion using computed tomography (CT). Dynamic single-section CT of the liver was performed after intravenous bolus administration of a low-molecular-mass iodinated contrast agent. Hepatic, aortic and portal-venous time-density curves were fitted with a dual-input one-compartmental model to calculate liver perfusion. Validation studies consisted of simultaneous measurements of hepatic perfusion with CT and with radiolabelled microspheres in rabbits at rest and after adenosine infusion. The feasibility and reproducibility of the CT method in humans was assessed by three observers in 10 patients without liver disease. In rabbits, significant correlations were observed between perfusion measurements obtained with CT and with microspheres (r=0.92 for total liver perfusion, r=0.81 for arterial perfusion and r=0.85 for portal perfusion). In patients, total liver plasma perfusion measured with CT was 112+/-28 ml.min(-1).100 ml(-1), arterial plasma perfusion was 18+/-12 ml.min(-1).100 ml(-1) and portal plasma perfusion was 93+/-31 ml.min(-1).100 ml(-1). The measurements obtained by the three observers were not significantly different from each other (P>0.1). Our results indicate that dynamic CT combined with a dual-input one-compartmental model provides a valid and reliable method for the non-invasive quantification of perfusion in the normal liver.

Hepatic epithelioid haemangioendotheliomas (HEHEs) are rare, low-grade vascular tumours. transplantation Five adults with HEHEs and one adult with a vascular tumour showing combined features of haemangioma and haemangioendothelioma underwent liver transplantation. Two HEHE patients had extrahepatic metastases at the time of transplantation. Median survival time following diagnosis was 10.7 years (range 40 months to 195 months). One patient needed resection of a HEHE in the breast 13 years post-transplantation. All six patients are surviving free from disease 22 to 166 months after transplantation (median 77 months). One HEHE-patient who had been treated for 8 years for vertebral and cerebral localisations is free of disease without immunosuppression 56 months after transplantation. We can conclude that liver transplantation is a valuable treatment for hepatic haemangioendothelioma, even in cases of extrahepatic localisation of the disease.

Elasticity imaging is a rather recent non-invasive imaging modality which provides in-vivo data about the viscoelastic properties of tissue. With manual palpation being an integral part of many diagnostic procedures, it is obvious that elasticity imaging has many interesting and promising potentials in medical imaging, i.e. from tissue/lesion characterization over therapy follow-up to guidance during interventions which involve ablation. The general concept of this method is to displace the material mechanically and infer from displacement measurements the intrinsic local viscoelastic properties. Many different technical realizations exist (static, dynamic, transient) utilizing different imaging modalities (MRI, ultrasound) which all probe different frequency domains. Since viscoelastic properties of tissue change strongly with frequency, care must be taken when interpreting the data in terms of elastic and viscous component. In this review we will focus on the dynamic 3D approach via MRI, i.e. a mono-frequent mechanical excitation and a volumetric assessment of the displacement field. This allows overcoming several physical difficulties: firstly compressional waves can be properly suppressed via the application of the curl-operator, secondly waveguide effects are eliminated and finally the calculation of the complex shear modulus does not necessitate any assumption of the underlying rheological model. Clinical results on a large patient collective show that mechanical parameters are very pertinent for the differentiation between low-grade and mid/high-grade liver fibrosis. They outperform the well establish classical APRI blood test as well as a 1D ultrasound-based approach for elasticity imaging.