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Dilute oral iron solutions as gastrointestinal contrast agents for magnetic resonance imaging; initial clinical
Abstract:
Delineation of the gastrointestinal tract in magnetic resonance imaging (MRI) remains a problem. Ferric ammonium citrate is paramagnetic, producing a high MRI signal intensity by virtue of its spin-lattice (T1) relaxation rate enhancement properties. Water is diamagnetic, producing a low MRI signal intensity, especially with short TR and TE times. To compare efficacy for gastrointestinal contrast alteration, ferric ammonium citrate was administered to 18 patients and water was given to 10 patients. Spin-echo imaging at 0.35T was performed after administration of these agents. Ferric ammonium citrate produced high signal intensity within the esophagus, stomach, duodenum, and small intestine that aided in the differentiation of the gastrointestinal tract from adjacent tumors, vessels, and viscera. Delineation of the gut wall was superior using ferric ammonium citrate compared to that produced by water. Delineation of the margins of the pancreas, liver, and kidney from adjacent gastrointestinal tract was also better with ferric ammonium citrate. Optimal distinction between bowel and fat was better with water. Longer TE times (75 to 200 ms) may allow improved contrast between gut and intrabdominal fat using ferric ammonium citrate.
Insights
Ferric ammonium citrate enhances gastrointestinal tract visualization in magnetic resonance imaging (MRI) by increasing signal intensity. This paramagnetic agent improves delineation of the gut wall and adjacent organs compared to water.
Area of Science:
- Medical Imaging
- Radiology
- Gastroenterology
Background:
- Gastrointestinal tract delineation in MRI is challenging.
- Paramagnetic agents can alter MRI signal intensity.
- Water provides low signal intensity, especially with short imaging parameters.
Purpose of the Study:
- To compare the efficacy of ferric ammonium citrate versus water for gastrointestinal contrast enhancement in MRI.
- To evaluate the impact of these agents on the differentiation of gastrointestinal structures from surrounding tissues.
Main Methods:
- Ferric ammonium citrate administered to 18 patients; water to 10 patients.
- Spin-echo MRI performed at 0.35T after oral administration.
- Comparison of signal intensity and delineation of gastrointestinal tract and adjacent organs.
Main Results:
- Ferric ammonium citrate produced high signal intensity in the esophagus, stomach, duodenum, and small intestine.
- Superior delineation of the gut wall and margins of adjacent organs (pancreas, liver, kidney) with ferric ammonium citrate.
- Water provided better distinction between bowel and fat, especially with longer echo times (TE).
Conclusions:
- Ferric ammonium citrate is an effective MRI contrast agent for improving gastrointestinal tract visualization and differentiation from adjacent structures.
- Water remains optimal for distinguishing bowel from intra-abdominal fat.
- Further optimization of MRI parameters, like longer TE, may enhance contrast with ferric ammonium citrate.