Paramagnetic substances, for example Gd-DTPA solutions, are used as MRI oral contrast agents in gastrointestinal imaging to depict the lumen of the digestive organs. Different Gd-DTPA solutions or zeolites containing gadolinium can be used e.g., for diagnosis of delayed gastric emptying, diagnosis of Crohn's disease etc.
Low concentrations of gastrointestinal paramagnetic contrast agents cause a reduction in T1 relaxation time; consequently, these agents act on T1 weighted images by increasing the signal intensity of the bowel lumen. High concentrations cause T2 shortening by decreasing the signal, similar to superparamagnetic iron oxide. Gd-DTPA chelates are unstable at the low pH in the stomach, therefore buffering is necessary for oral use.

See also Gadopentetate Gastrointestinal, Gadolinium Zeolite, Negative Oral Contrast Agents, Gastrointestinal Superparamagnetic Contrast Agents, and Ferric ammonium citrate.

Magnevist® is a paramagnetic ionic contrast agent for use in magnetic resonance imaging. Contrast enhanced MRI with Magnevist® allows additional diagnostic information of tumors, inflammation and vascular lesions and the determination or differentiation of such lesions.
The contrast enhancing effect is produced by the di-N-methylglucamine salt of gadopentetate (Gd-DTPA), the gadolinium complex of diethylenetriamine pentaacetic acid. Magnevist® has the strongest effect on T1 weighted images, by increasing T1 signal intensity in tissues where Magnevist® has accumulated.

WARNING: NEPHROGENIC SYSTEMIC FIBROSIS Gadolinium-based contrast agents increase the risk for nephrogenic systemic fibrosis (NSF) in patients with acute or chronic severe renal insufficiency (glomerular filtration rate less than 30 mL/min/1.73m²), or acute renal insufficiency of any severity due to the hepato-renal syndrome or in the perioperative liver transplantation period.

See also Ionic Intravenous Contrast Agents and Gadopentetate Dimeglumine.

Magnevist® enteral (Gadopentetate) is a Gd-DTPA solution for use as a gastrointestinal contrast agent to visualize the bowel in MRI scans.

See also Positive Oral Contrast Agents and Gadopentetate Gastrointestinal.

Omniscan® is a nonionic chelate complex with low osmolality used as a paramagnetic MRI contrast agent. The efficacy of Omniscan® is similar to that of Gd-DTPA. Omniscan® is given intravenously to enhance images of intracranial and spinal lesions where there is abnormal vascularity or an abnormal blood brain barrier. The complex does not cross an intact blood brain barrier so Omniscan® only accumulates in lesions such as neoplasm's and abscesses.

WARNING: NEPHROGENIC SYSTEMIC FIBROSIS Gadolinium-based contrast agents increase the risk for nephrogenic systemic fibrosis (NSF) in patients with acute or chronic severe renal insufficiency (glomerular filtration rate less than 30 mL/min/1.73m²), or acute renal insufficiency of any severity due to the hepato-renal syndrome or in the perioperative liver transplantation period.

See also Gadodiamide, and Classifications, Characteristics, etc.

ABLAVAR™ (formerly named Vasovist™) is a blood pool agent for magnetic resonance angiography (MRA), which opens new medical imaging possibilities in the evaluation of aortoiliac occlusive disease (AIOD) in patients with suspected peripheral vascular disease.
ABLAVAR™ binds reversibly to blood albumin, providing imaging with high spatial resolution up to 1 hour after injection, due to its high relaxivity and to the long lasting increased signal intensity of blood.
As with other contrast media: the possibility of serious or life-threatening anaphylactic or anaphylactoid reactions, including cardiovascular, respiratory and/or cutaneous manifestations, should always be considered.

WARNING:
NEPHROGENIC SYSTEMIC FIBROSIS Gadolinium-based contrast agents increase the risk for nephrogenic systemic fibrosis (NSF) in patients with acute or chronic severe renal insufficiency (glomerular filtration rate less than 30 mL/min/1.73m²), or acute renal insufficiency of any severity due to the hepato-renal syndrome or in the perioperative liver transplantation period.

See also Cardiovascular Imaging, Adverse Reaction, Molecular Imaging, and MRI Safety.