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Use of magnetic particles for sensitizing MR images to blood flow
P A Hardy1, M J Bronskill, M J Belanger
1Department of Medical Biophysics, University of Toronto.
Abstract:
Magnetic resonance (MR) images made with the IVIM (intravoxel incoherent motion) technique for demonstrating tissue microcirculation are limited in sensitivity because of the small volume of blood involved. This limitation may be overcome by incorporating magnetic particles into the flow. The magnetic perturbation caused by the particles extends beyond the walls of the capillary and affects a much larger volume than that of the flowing material. Imaging experiments conducted with an artificial capillary system for renal dialysis, containing large magnetic particles, showed that signal intensity decreased with increasing flow rate through the dialysis bundle and with increasing particle concentration. Predictions of the effect based on a theoretical model of spin dephasing in the field of a magnetic dipole agreed with the experimental data. The results hold promise for development of the technique in vivo.
Insights
Incorporating magnetic particles into blood flow enhances magnetic resonance imaging (MRI) sensitivity for microcirculation. This technique improves visualization by extending the magnetic effect beyond capillaries, overcoming current limitations.
Area of Science:
- Biomedical Engineering
- Medical Imaging
- Physics
Background:
- Intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) is used for tissue microcirculation assessment.
- Current IVIM MRI techniques have limited sensitivity due to the small blood volume involved in microcirculation.
Purpose of the Study:
- To investigate a novel method for enhancing the sensitivity of IVIM MRI for microcirculation.
- To assess the feasibility of using magnetic particles to amplify the MR signal perturbation caused by blood flow.
Main Methods:
- Experiments were conducted using an artificial capillary system simulating renal dialysis.
- Large magnetic particles were introduced into the flow within the artificial capillaries.
- Magnetic resonance imaging was performed to observe signal intensity changes with varying flow rates and particle concentrations.
- A theoretical model based on spin dephasing in a magnetic dipole field was developed to predict the observed effects.
Main Results:
- Signal intensity in MR images decreased as the flow rate through the dialysis bundle increased.
- Higher concentrations of magnetic particles led to a greater decrease in signal intensity.
- The experimental data aligned well with predictions from the theoretical spin dephasing model.
Conclusions:
- Incorporating magnetic particles into blood flow can significantly enhance the sensitivity of IVIM MRI for microcirculation.
- The magnetic perturbation effect extends beyond the capillary volume, influencing a larger region.
- This approach shows promise for future in vivo applications of enhanced microcirculation imaging.