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Liver perfusion imaging is a quantitative functional investigation. Liver perfusion imaging is complicated because of the liver's dual vascular supply, artefacts due to respiratory movements and the fenestrated sinusoidal capillaries which allow the contrast medium to diffuse out. Liver perfusion can be examined by ultrasound, CT or MRI: each technique has its limitations and specific features. The major indications in hepatology are oncology (detection, characterization and tumor response) and non-invasive investigation of patients with chronic liver disease. Work is needed to standardize acquisition and modeling methods to allow wider use of results and more widespread use of the technique.

Diffusion-weighted MR imaging of the liver Diffusion-weighted imaging studies the motion of water molecules within a given tissue. Initially used for neuroradiological applications, it is now routinely used for abdominal imaging, especially liver imaging. The diffusion pulse sequence is a T2 echo-planar sequence where diffusion gradients are applied. In this article, we will review the sequence itself and the parameters used to optimize the sequence, quantitative and qualitative image evaluation, and the main applications for liver imaging: characterization of focal lesions, detection of focal lesions, evaluation of response to therapy and quantification of liver fibrosis.

The purpose of our study was to assess the effects of intravenous administration of ferumoxides on normal and abnormal vertebral bone marrow T1 and T2 relaxation times. Changes in bulk T1 and T2 relaxation times induced by intravenous administration of ferumoxides were determined in the normal vertebral marrow of two healthy subjects and four patients. In the four patients, changes in bulk T1 and T2 values induced by furomoxides injection were also determined in 12 vertebral metastases. Relative to precontrast relaxation time values, bulk T1 and T2 values of normal bone marrow had declined by a mean of 24% and 19%, respectively, in the two subjects and the four patients 45 minutes after ferumoxides administration. Relative to precontrast values, bulk T1 and T2 values of abnormal bone marrow had decreased by a mean of 16% and 2%, respectively. Decreases in bulk T1 and T2 values in normal bone marrow and in bulk T1 values in metastases were statistically significant (P

Magnetic resonance (MR) elastography is an emerging method for measuring the viscoelastic properties of tissues. Hepatic fibrosis, which increases the elasticity or stiffness of the liver, can be detected and staged by MR elastography. The technique has several advantages compared with transient ultrasound elastography (FibroScan): it can evaluate much larger liver volumes; it can be performed in obese patients and in those with ascites; and it can assess the full three-dimensional displacement vector, allowing a more precise analysis of viscoelastic parameters. These technical advantages mean that MR elastography is more accurate forstaging liver fibrosis than is transient ultrasound elastography. Moreover, it has been shown in animal studies using MR elastography that parameters other than fibrosis can also increase liver elasticity, including inflammation and myofibroblast activation before extracellular matrix deposition. Because of its greater accuracy-but also its higher cost-MR elastography will probably have a complementary role alongside ultrasound elastography. Nevertheless, this role should be further studied, especially in terms of response to treatment and the early detection of chronic liver diseases such as steatohepatitis.

Bile duct calculi can be classified into primary or secondary stones, depending on their site of origin. The majority of bile duct stones are secondary stones formed in the gallbladder, which then migrate into the extrahepatic biliary tree. These stones reflect the composition of gallbladder stones, i.e. predominantly cholesterol in 80% and black pigment in 20% (Hawes and Sherman 1995) The frequency of common bile duct stones increases with increasing age of the patient. Cystic duct diameter appears to be an important factor in the migration of gallbladder stones into the common bile duct. Primary stones form de novo in the bile ducts. These pigmented stones are brown or black and are often friable. Their pathogenesis depends on two main factors, which are biliary stasis and bacterial or parasitic infection.

The aim of our study was to assess the feasibility of using Doppler sonography for the detection of acute intestinal ischemia due to occlusion of the superior mesenteric artery. Between September 1993 and March 1995, abdominal sonography with Doppler imaging of the mesenteric vessels was performed in 770 patients with emergency admissions for acute abdominal pain. In six cases, the diagnosis, based on surgery or arteriography and computed tomography, was acute intestinal ischemia due to complete or localized occlusion of the superior mesenteric artery. Five cases of occlusion of the superior mesenteric artery were correctly detected by Doppler sonography. These results suggest that Doppler sonography may be a feasible method for detecting acute intestinal ischemia due to proximal superior mesenteric artery occlusion.