Short name: AMI-25, generic name: Ferumoxide (SPIO)
Ferumoxides are superparamagnetic (T2*) MRI contrast agents, so the largest signal change is on T2 and T2* weighted images.
The agent distributes relatively rapidly to organs with reticuloendothelial cells primarily the liver, spleen and bone marrow. The liver shows decreased signal intensity, as does the spleen and marrow. The agent is taken up by the normal liver, resulting in increased CNR between tumor and normal liver. Hepatocellular lesions, such as adenoma or focal nodular hyperplasia, contain reticuloendothelial cells, so they will behave similar to the liver, with decreased signal on T2 weighted images. On T1 images, there is typically some circulating contrast agent, and blood vessels show increased signal intensity.
Current MRI protocols involve T1 weighted breath-hold gradient echo images of the liver, and fast spin echo T2 weighted pictures. This requires about 15 minutes. The patient is then removed from the scanner, and the contrast agent administered. After contrast administration, the same pulse sequences are again repeated.

The characteristics of a hepatobiliary contrast agent are specific liver uptake and excretion via the biliary system. The paramagnetic substance (e.g. manganese, gadolinium) is taken up by normal hepatocytes. Diseased liver tissue did not include hepatocytes or their function is disturbed. Therefore, the signal of healthy liver tissue increases on T1 weighted sequences, but not in the liver lesions.
Another type of liver imaging contrast agent is superparamagnetic iron oxide. These particles accumulate in the reticuloendothelial system (RES) of the liver, and darken the healthy liver tissue in T2 weighted images. RES cells (including Kupffer cells) are existing in healthy liver tissue, in altered tissue with reduced RES activity or without RES cells the contrast agent concentration is also low or not existing, which improves the liver to lesion contrast.
Benefits of hepatobiliary contrast agents:
Differences of a hepatobiliary contrast agent compared with a targeted contrast agent for Kupffer cells:
See also Superparamagnetic Contrast Agents, Hepatobiliary Chelates, Liver Imaging, Endoremâ„¢, Primovistâ„¢, and Classifications, Characteristics, etc.

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

MRI of the lumbar spine, with its multiplanar 3 dimensional imaging capability, is currently the preferred modality for establishing a diagnosis. MRI scans and magnetic resonance myelography have many advantages compared with computed tomography and/or X-ray myelography in evaluating the lumbar spine. MR imaging scans large areas of the spine without ionizing radiation, is noninvasive, not affected by bone artifacts, provides vascular imaging capability, and makes use of safer contrast agents (gadolinium chelate).
Due to the high level of tissue contrast resolution, nerves and discs are clearly visible. MRI is excellent for detecting degenerative disease in the spine. Lumbar spine MRI accurately shows disc disease (prolapsed disc or slipped disc), the level at which disc disease occurs, and if a disc is compressing spinal nerves. Lumbar spine MRI depicts soft tissues, including the cauda equina, spinal cord, ligaments, epidural fat, subarachnoid space, and intervertebral discs. Loss of epidural fat on T1 weighted images, loss of cerebrospinal fluid signal around the dural sac on T2 weighted images and degenerative disc disease are common features of lumbar stenosis.

Common indications for MRI of the lumbar spine:
Lumbar spine imaging requires a special spine coil. often used whole spine array coils have the advantage that patients do not need other positioning if also upper parts of the spine should be scanned. Sagittal T1 and T2 weighted FSE sequences are the standard views. With multi angle oblique techniques individually oriented transverse images of each intervertebral disc at different angles can be obtained.

See also the related poll result: 'MRI will have replaced 50% of x-ray exams by'

(MRCP) This MR imaging technique takes advantage of the high signal intensity of body fluids and acquires heavy T2 weighted images of the gall bladder, the pancreas and parts of the liver. Due to the T2 weighting, the liver and other solid parenchyma are signal suppressed and only fluid-filled structures in addition to the gall bladder, the bile and pancreatic ducts retain important signal intensity. Hepatobiliary contrast agents (e.g. Gadoxetic Acid, CMC 001) can be useful for enhancement of the bile ducts and better imaging of the biliary tract.
A 2D cholangiogram, often only one thick slice (a volume with a thickness of 4 - 8 cm, mostly coronal planned) or 5 - 6 radial placed slices, shows a view like single slices. If a 3D acquisition is used, the postprocessing function maximum intensity projection (MIP) can show reconstructions from multiple sides.

(MTC) This MRI method increases the contrast by removing a portion of the total signal in tissue. An off resonance radio frequency (RF) pulse saturates macromolecular protons to make them invisible (caused by their ultra-short T2* relaxation times). The MRI signal from semi-solid tissue like brain parenchyma is reduced, and the signal from a more fluid component like blood is retained.
E.g., saturation of broad spectral lines may produce decreases in intensity of lines not directly saturated, through exchange of magnetization between the corresponding states; more closely coupled states will show a greater resulting intensity change. Magnetization transfer techniques make demyelinated brain or spine lesions (as seen e.g. in multiple sclerosis) better visible on T2 weighted images as well as on gadolinium contrast enhanced T1 weighted images.
Off resonance makes use of a selection gradient during an off resonance MTC pulse. The gradient has a negative offset frequency on the arterial side of the imaging volume (caudally more off resonant and cranially less off resonant). The net effect of this type of pulse is that the arterial blood outside the imaging volume will retain more of its longitudinal magnetization, with more vascular signal when it enters the imaging volume. Off resonance MTC saturates the venous blood, leaving the arterial blood untouched.
On resonance has no effect on the free water pool but will saturate the bound water pool and is the difference in T2 between the pools. Special binomial pulses are transmitted causing the magnetization of the free protons to remain unchanged. The z-magnetization returns to its original value. The spins of the bound pool with a short T2 experience decay, resulting in a destroyed magnetization after the on resonance pulse.

See also Magnetization Transfer.