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OMR, a positive bowel contrast agent for abdominal and pelvic MR imaging: safety and imaging characteristics
R M Patten1, A A Moss, T A Fenton
1Department of Radiology, University of Washington School of Medicine, Seattle.
Abstract:
To determine the safety and imaging characteristics of OMR--an effervescent solution of ferric ammonium citrate--as a bowel contrast agent, magnetic resonance (MR) imaging at 1.5 T was performed in 29 volunteers. T1- and T2-weighted images of the upper abdomen and pelvis were obtained before and after oral administration of OMR at doses of 100-400 mg of iron in 300-600 mL of water. Respiratory-ordered phase encoding and presaturation pulses were used routinely for artifact suppression. All dose levels of OMR provided marking of the bowel by increasing intraluminal signal intensity; however, the degree and percentage of small bowel opacification appeared more prominent at higher dose levels of iron. Semisolid or watery bowel movements were noted in 31% of subjects, but no clinically important laboratory abnormalities were seen. OMR improved delineation of the head of the pancreas on T1-weighted images in 72% of subjects but was less useful in defining the body and tail. OMR is a safe and effective bowel contrast agent for MR imaging. Because artifacts due to movement of hyperintense bowel may degrade the images, OMR may be most useful on short TR/TE or fast imaging pulse sequences or when combined with antiperistaltic agents.
Insights
Ferric ammonium citrate (OMR) is a safe and effective oral contrast agent for MR imaging, enhancing bowel visualization. While generally well-tolerated, image artifacts may necessitate specific imaging techniques.
Area of Science:
- Radiology
- Medical Imaging
- Gastrointestinal Imaging
Background:
- Magnetic resonance (MR) imaging requires effective bowel contrast agents for optimal visualization.
- Ferric ammonium citrate (OMR) is an effervescent solution investigated for its potential as an MR bowel contrast agent.
Purpose of the Study:
- To evaluate the safety and imaging characteristics of OMR as a bowel contrast agent in MR imaging.
- To assess the effect of OMR dosage on small bowel opacification and image quality.
Main Methods:
- Twenty-nine healthy volunteers underwent 1.5 T MR imaging of the abdomen and pelvis.
- Oral administration of OMR (100-400 mg iron in 300-600 mL water) before T1- and T2-weighted imaging.
- Utilized respiratory-ordered phase encoding and presaturation pulses for artifact reduction.
Main Results:
- OMR effectively opacified the bowel, increasing intraluminal signal intensity, with enhanced opacification at higher iron doses.
- Mild gastrointestinal side effects (31% incidence) were observed, with no clinically significant laboratory abnormalities.
- OMR improved pancreatic head delineation on T1-weighted images in 72% of subjects.
Conclusions:
- OMR is a safe and effective bowel contrast agent for MR imaging.
- Higher OMR doses yield more prominent small bowel opacification.
- Image quality may be optimized using fast imaging sequences or antiperistaltic agents to mitigate motion artifacts.