Induced Current Magnetic Resonance Electrical Conductivity Imaging With Oscillating Gradients

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Electrical Engineering

Background:

• Electrical impedance tomography (EIT) provides functional imaging of conductivity distributions.
• Integrating EIT with MRI offers potential for enhanced spatial resolution and multimodal data acquisition.
• Existing methods face challenges in sensitivity, accuracy, and integration with MRI systems.

Purpose of the Study:

• To propose and evaluate induced current magnetic resonance electrical impedance tomography (ICMREIT) using MRI gradient fields.
• To establish a relationship between secondary magnetic flux density and low-frequency (LF) MR phase.
• To assess the feasibility, safety, and limitations of ICMREIT for conductivity imaging.

Main Methods:

• Development of ICMREIT by inducing eddy currents via time-varying MRI gradient fields.
• Numerical modeling of eddy current and magnetic flux density distributions.
• Experimental evaluation on a 3T MRI scanner using a developed pulse sequence.
• Formulation of the relationship between secondary magnetic flux density and LF MR phase.
• Comparison of simulated and physical measurements of LF phase, eddy currents, and reconstructed conductivity.

Main Results:

• Simulated and measured characteristics of LF phase, eddy currents, and conductivity distributions showed agreement.
• MR magnitude images confirmed the absence of geometric shifts affecting LF phase measurements.
• Reconstructed conductivity images provided rough estimates of phantom conductivity distributions.
• Low sensitivity of LF phase measurements was identified as a key limitation.

Conclusions:

• ICMREIT is a safe and potentially applicable technique for conductivity imaging.
• The technique shows promise for integration with MRI systems.
• Further optimization of measurement sensitivity and reconstruction accuracy is crucial for clinical translation.