Reference-Based Integral MR-EPT:Simulation and Experiment Studies on the 9.4T MRI.

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Electromagnetics

Background:

• Current integral-equation (IE) based MR electrical properties tomography (EPT) methods rely on simulated incident radio-frequency (RF) fields, leading to inaccuracies and reconstruction errors.
• Accurate incident RF field estimation is crucial for precise EPs reconstruction in MR-EPT.

Purpose of the Study:

• To develop and validate a novel approach for MR-EPT that improves the accuracy and practicality of IE-based methods.
• To obtain accurate incident RF fields using reference subjects and RF field mapping techniques, thereby reducing reconstruction errors.

Main Methods:

• Introduced the Incident Field Approximation (IFA), assuming similar incident RF fields for subjects with comparable coil/subject interactions.
• Measured total RF fields in a reference subject with known EPs using field mapping.
• Rearranged Ampere's Law and integral equations to calculate incident RF fields, then used these for 3D EPs reconstruction.

Main Results:

• Numerical simulations showed the proposed method achieved <16% RMSE in noise-free conditions, significantly outperforming conventional IE methods (>28% RMSE).
• Phantom experiments at 9.4T MRI demonstrated robustness against noise, with <21% RMSE compared to conventional differential equation-based methods (>37% RMSE).

Conclusions:

• The proposed IFA method enhances the accuracy and robustness of IE-based MR-EPT.
• This technique offers a more practical and reliable approach for EPs reconstruction in MR imaging.