Use of dielectric padding to eliminate low convective field artifact in cr-MREPT conductivity images

Gulsah Yildiz, Yusuf Ziya Ider*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Purpose: Convection–reaction equation-based magnetic resonance electrical properties tomography (cr-MREPT) provides conductivity images that are boundary artifact-free and robust against noise. However, these images suffer from the low convective field (LCF) artifact. We propose to use dielectric pads to alter the transmit magnetic field (B1+), shift the LCF region, and eliminate the LCF artifact. Methods: Computer simulations were conducted to analyze the effects of pad electrical properties, pad thickness, pad height, arc angle, and thickness of the pad–object gap. In 3T MR experiments, water pads and BaTiO3 pads were used with agar–saline phantoms. Two data sets (e.g., with the pad located on the left or on the right of the object [phantom]) were acquired, and the corresponding linear systems were simultaneously solved to get LCF artifact-free conductivity images. Results: A pad needed to have 180° arc angle and the same height with the phantom for maximum benefit. Increasing the pad thickness and/or the relative permittivity of the pad increased the LCF shift, whereas excessive amounts of these parameters caused errors in conductivity reconstructions because the effect of neglected Bz terms became noticeable. Conductivity of the pad, on the other hand, had minimal effect on elimination of the LCF artifact. Combining 2 data sets (i.e., with 2 different dielectric pad positions) resulted in more accurate conductivity maps (low L2-errors) as opposed to no pad or single pad cases in experiments and simulations. Conclusions: Using the proposed technique, LCF artifact is significantly removed, and the reconstructed conductivity values are improved.

Original languageEnglish
Pages (from-to)3168-3184
Number of pages17
JournalMagnetic Resonance in Medicine
Volume81
Issue number5
DOIs
Publication statusPublished - May 2019
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2019 International Society for Magnetic Resonance in Medicine

Funding

This study was supported by TUBITAK 114E522 research grant. Experimental data were acquired using the facilities of UMRAM, Bilkent University, Ankara.

FundersFunder number
TUBITAK114E522

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