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Optimization of an oral magnetic particle formulation as a gastrointestinal contrast agent for magnetic resonance
D L Rubin1, H H Muller, S W Young
1Department of Diagnostic Radiology, Stanford University School of Medicine, CA 94305.
Rationale And Objectives:
Magnetically susceptible iron oxide (MSIO) contrast agents for magnetic resonance imaging (MRI) of the gastrointestinal (GI) tract are limited because they produce magnetic susceptibility artifacts. To determine whether oral magnetic particles (WIN 39996) can be an effective MRI contrast agent without producing induced image artifacts, we optimized a liquid formulation of WIN 39996.
Methods:
A range of concentrations (25-250 micrograms iron/mL) and viscosities (1-600 cP) was imaged in a phantom at 1.5 T using conventional spin-echo and gradient-recalled echo pulse sequences. Some formulations also contained titanium.
Results:
All concentrations of WIN 39996 at 1 cP produced susceptibility artifacts. For formulations in the 150 to 600 cP range, the 125 to 150 micrograms/mL concentrations produced signal blackening and magnetic susceptibility image distortion comparable to an air control. Concentrations greater than 150 micrograms/mL were unacceptable because they produced significant susceptibility artifacts, while concentrations less than 125 micrograms/mL were undesirable because they produced insufficient signal blackening.
Conclusions:
These preliminary in-vitro studies suggest that an optimized liquid formulation of WIN 39996 can be produced that yields excellent negative contrast without producing image artifacts.
Insights
Optimized oral magnetic particles (WIN 39996) provide effective gastrointestinal MRI contrast. This formulation achieves excellent negative contrast without causing image artifacts, overcoming limitations of previous agents.
Area of Science:
- Medical Imaging
- Biomaterials Science
- Gastroenterology
Background:
- Magnetically susceptible iron oxide (MSIO) contrast agents for gastrointestinal (GI) magnetic resonance imaging (MRI) are limited by magnetic susceptibility artifacts.
- Developing effective GI MRI contrast agents requires overcoming artifact generation.
Purpose of the Study:
- To determine if oral magnetic particles (WIN 39996) can serve as an effective MRI contrast agent for the GI tract.
- To optimize a liquid formulation of WIN 39996 to prevent induced image artifacts.
Main Methods:
- A phantom study was conducted at 1.5 T using spin-echo and gradient-recalled echo pulse sequences.
- Various concentrations (25-250 µg Fe/mL) and viscosities (1-600 cP) of WIN 39996 were evaluated.
- Some formulations included titanium.
Main Results:
- Low viscosity (1 cP) WIN 39996 formulations produced susceptibility artifacts at all concentrations.
- Optimal contrast was achieved with 125-150 µg Fe/mL concentrations in the 150-600 cP viscosity range, yielding signal blackening comparable to an air control.
- Higher concentrations (>150 µg Fe/mL) caused significant artifacts, while lower concentrations (<125 µg Fe/mL) provided insufficient contrast.
Conclusions:
- Preliminary in-vitro studies demonstrate the feasibility of an optimized liquid formulation of WIN 39996.
- The optimized formulation provides excellent negative contrast for GI MRI.
- This approach successfully avoids the generation of image artifacts.