Contrast-enhanced magnetic resonance imaging of the abdomen and pelvis

Contrast media in magnetic resonance imaging (MRI) of the abdomen and pelvis are applied for various purposes; different substances and forms of application must be distinguished. Oral contrast agents are primarily used to enhance the discrimination of the intestine from the other organs and from pathological lesions. Clinical studies of i.v. contrast agents focus on two substances: gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) and superparamagnetic iron oxide. Whereas dynamic Gd-DTPA-enhanced MRI improves the differential diagnosis of focal hepatic lesions, iron oxide is a promising agent for increasing the sensitivity of MRI in the detection of hepatic and splenic tumors. Dynamic Gd-DTPA-enhanced MRI of the kidney allows functional assessment of this organ; good demarcation of kidney tumors is only achieved during the early phase of a dynamic examination. In the assessment of adrenal lesions, dynamic Gd-DTPA-enhanced MRI permits better differentiation of adenoma from malignancy. Intravenous Gd-DTPA also appears to be useful in the staging of urinary bladder tumors to distinguish between superficial and infiltrating tumors. Although offering no major diagnostic advantage in the staging of cervical carcinomas, Gd-DTPA-enhanced MRI improves the discrimination of necrotic tumor portions of endometrial carcinoma and allows good differentiation of this lesion from fluid retained in the uterine cavity. Studies of new contrast agents for MRI of the abdomen, which have so far only been investigated in animal experiments, focus on liver imaging. These substance include hepatobiliary agents, Gd-DTPA-containing liposomes, and paramagnetic macromolecules.