Liver imaging can be performed with sonography, computed tomography (CT) and magnetic resonance imaging (MRI). Ultrasound is, caused by the easy access, still the first-line imaging method of choice; CT and MRI are applied whenever ultrasound imaging yields vague results. Indications are the characterization of metastases and primary liver tumors e.g., benign lesions such as focal nodular hyperplasia (FNH), adenoma, hemangioma and malignant lesions (cancer) such as hepatocellular carcinomas (HCC). The decision, which medical imaging modality is more suitable, MRI or CT, is dependent on the different factors. CT is less costly and more widely available; modern multislice scanners provide high spatial resolution and short scan times but has the disadvantage of radiation exposure.
With the introduction of high performance MR systems and advanced sequences the image quality of MRI for the liver has gained substantially. Fast spin echo or single shot techniques, often combined with fat suppression, are the most common T2 weighted sequences used in liver MRI procedures. Spoiled gradient echo sequences are used as ideal T1 weighted sequences for evaluating of the liver. The repetition time (TR) can be sufficiently long to acquire enough sections covering the entire liver in one pass, and to provide good signal to noise. The TE should be the shortest in phase echo time (TE), which provides strong T1 weighting, minimizes magnetic susceptibility effects, and permits acquisition within one breath hold to cover the whole liver. A flip angle of 80° provides good T1 weighting and less of power deposition and tissue saturation than a larger flip angle that would provide comparable T1 weighting.
Liver MRI is very dependent on the administration of contrast agents, especially when detection and characterization of focal lesions are the issues. Liver MRI combined with MRCP is useful to evaluate patients with hepatic and biliary disease.
Gadolinium chelates are typical non-specific extracellular agents diffusing rapidly to the extravascular space of tissues being cleared by glomerular filtration at the kidney. These characteristics are somewhat problematic when a large organ with a huge interstitial space like the liver is imaged. These agents provide a small temporal imaging window (seconds), after which they begin to diffuse to the interstitial space not only of healthy liver cells but also of lesions, reducing the contrast gradient necessary for easy lesion detection. Dynamic MRI with multiple phases after i.v. contrast media (Gd chelates), with arterial, portal and late phase images (similar to CT) provides additional information.
An additional advantage of MRI is the availability of liver-specific contrast agents (see also Hepatobiliary Contrast Agents). Gd-EOB-DTPA (gadoxetate disodium, Gadolinium ethoxybenzyl dimeglumine, EOVIST Injection, brand name in other countries is Primovist) is a gadolinium-based MRI contrast agent approved by the FDA for the detection and characterization of known or suspected focal liver lesions.
Gd-EOB-DTPA provides dynamic phases after intravenous injection, similarly to non-specific gadolinium chelates, and distributes into the hepatocytes and bile ducts during the hepatobiliary phase. It has up to 50% hepatobiliary excretion in the normal liver.
Since ferumoxides are not eliminated by the kidney, they possess long plasmatic half-lives, allowing circulation for several minutes in the vascular space. The uptake process is dependent on the total size of the particle being quicker for larger particles with a size of the range of 150 nm (called superparamagnetic iron oxide). The smaller ones, possessing a total particle size in the order of 30 nm, are called ultrasmall superparamagnetic iron oxide particles and they suffer a slower uptake by RES cells. Intracellular contrast agents used in liver MRI are primarily targeted to the normal liver parenchyma and not to pathological cells. Currently, iron oxide based MRI contrast agents are not marketed.
Beyond contrast enhanced MRI, the detection of fatty liver disease and iron overload has clinical significance due to the potential for evolution into cirrhosis and hepatocellular carcinoma. Imaging-based liver fat quantification (see also Dixon) provides noninvasively information about fat metabolism; chemical shift imaging or T2*-weighted imaging allow the quantification of hepatic iron concentration.

See also Abdominal Imaging, Primovistâ„¢, Liver Acquisition with Volume Acquisition (LAVA), T1W High Resolution Isotropic Volume Examination (THRIVE) and Bolus Injection.

For Ultrasound Imaging (USI) see Liver Sonography at Medical-Ultrasound-Imaging.com.

Short name: NC100150, PEG-feron, generic name: Feruglose, preliminary trade name: Clariscanâ„¢
NC100150 injection is the code name for an USPIO (ultrasmall superparamagnetic iron oxide) MRI contrast agent under development. Microvessel permeability depends on functional and morphologic characteristics of cancer vessels and on physicochemical properties of the injected contrast medium molecule.
USPIO particles have a favorable pharmacological and tolerance profile and are being tested clinically of the potential for the quantitative characterization of tumor microvasculature and specifically for measures of the microvessel permeability. Iron-based products take advantage of their large molecular size, which prevents diffusion into body tissues. These agents are disposed of by the liver and spleen as particulate matter.
NC100150 Injection (Nycomed Amersham, Amersham Health ) consists of USPIO particles that are composed of single crystals (4- to 7-nm diameter) and stabilized with a carbohydrate polyethylene glycol (PEG) coat. The iron oxide particles have to be suspended in an isotonic glucose solution. The final diameter of an USPIO particle is approximately 20 nm. Blood pool half-life is more than two hours in humans; the particles are taken up by the mononuclear phagocyte system and distributed mainly to the liver and spleen.
NC100150 would compete with the contrast agents Ferumoxytol from AMAG Pharmaceuticals, Inc. and Vasovistâ„¢ from EPIX Pharmaceuticals, Inc., but at this time the development of NC100150 Injection/Clariscan™ is discontinued.

Short name: NC100150, PEG-feron, generic name: Feruglose, preliminary trade name: Clariscan™, central moiety: Fe
An ultrasmall superparamagnetic iron oxide under development as a blood pool agent (MRI contrast agent).

See Clariscan™ and NC100150 Injection.

Sinerem® is the brand name (same as Combidex®) for an ultrasmall superparamagnetic iron oxide (USPIO) to detect metastatic disease in lymph nodes. Metastatic nodes show less uptake of this MRI contrast agent, which results in less signal decrease and allows the differentiation of normal lymph nodes from normal-sized, metastatic nodes.
Lymph node imaging with Sinerem® is performed 24 to 36 hours after slow infusion. Normal lymph nodes turn black post contrast, namely on T2* weighted images. Metastatic lymph nodes remain unchanged in signal intensity.
Indication and Diseases: Cancer, Imaging for diagnosis, Lymphatic disorders.
See Ferumoxtran, and Classifications, Characteristics, etc.

Guerbet decided in 2007 to withdraw its Marketing Authorisation Application (MAA) for Sinerem.

Small particles of ferrite are used as superparamagnetic contrast medium in MR imaging (appearing predominantly dark on MRI). These agents exhibit strong T1 relaxation properties, and due to susceptibility differences to their surroundings also produce a strongly varying local magnetic field, which enhances T2 relaxation to darken the contrast media containing structures.
Superparamagnetic contrast agents are also known by the abbreviation SPIO's (small particle iron oxide or superparamagnetic iron oxide) and USPIO's (ultrasmall particle iron oxide or ultrasmall superparamagnetic iron oxide).
Two types of USPIO will be available on the market as blood pool agents, while SPIO's have been used as darkening contrast agents for liver imaging. As particulate matter they are taken up by the RES. Very small particles of less than 300 nanometers also remain intravascular for a prolonged period of time and thus can serve as blood pool agents.

See also the related poll result: 'The development of contrast agents in MRI is'