Performance Enhancement of an MTL Coil Loaded With High-Permittivity Dielectric Liner for 7 T Brain MRI
In a multi-element microstrip transmission line (MTL) transmit array coil, the transmit field (<inline-formula> <tex-math notation="LaTeX">$B_{1}^{+}$ </tex-math></inline-formula>) distribution is inhomogeneous due to its standing-wave nature, and the interference e...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IEEE
2021-01-01
|
| Series: | IEEE Access |
| Subjects: | |
| Online Access: | https://ieeexplore.ieee.org/document/9584839/ |
| _version_ | 1819041787141947392 |
|---|---|
| author | Sana Ullah Hyoungsuk Yoo |
| author_facet | Sana Ullah Hyoungsuk Yoo |
| author_sort | Sana Ullah |
| collection | DOAJ |
| description | In a multi-element microstrip transmission line (MTL) transmit array coil, the transmit field (<inline-formula> <tex-math notation="LaTeX">$B_{1}^{+}$ </tex-math></inline-formula>) distribution is inhomogeneous due to its standing-wave nature, and the interference effects can severely degrade the <inline-formula> <tex-math notation="LaTeX">$B_{1}^{+}$ </tex-math></inline-formula> and imaging. Therefore, to improve the homogeneity and strength of <inline-formula> <tex-math notation="LaTeX">$B_{1}^{+}$ </tex-math></inline-formula>, this study focuses on the development of a multi-element MTL transmit array coil integrated with a dielectric liner (DL) material. Furthermore, the transmission efficiency (<inline-formula> <tex-math notation="LaTeX">$T_{x,eff}$ </tex-math></inline-formula>) is improved in the head region. An eight-element MTL transmits array head coil is investigated using thinner DLs, and the optimized dimensions of the DL are found from its resonant mode at 7 Tesla (T). Simulations and measurements are performed with an MTL transmit array coil at 7 T, and the performance is analyzed for the DL positions and dimensions. Remarkably, the proposed DLs-integrated transmit array coil system offered significant improvements in the <inline-formula> <tex-math notation="LaTeX">$T_{x,eff}$ </tex-math></inline-formula> at different DLs positions. Compared to the case without the DL, the <inline-formula> <tex-math notation="LaTeX">$T_{x,eff}$ </tex-math></inline-formula> is improved by 9% (DL close to the head model), 15% (DL at center), and 39% (DL close to the RF coil). Interestingly, the DL acts as an efficiency tuner element exhibiting a 9% to 39% <inline-formula> <tex-math notation="LaTeX">$T_{x,eff}$ </tex-math></inline-formula> tuning range of improvement. In addition, the RF-shimming technique improves the <inline-formula> <tex-math notation="LaTeX">$B_{1}^{+}$ </tex-math></inline-formula> homogeneity and <inline-formula> <tex-math notation="LaTeX">$T_{x,eff}$ </tex-math></inline-formula> of the coil with DLs by 21% and 42%, respectively, compared to the case without the DL. Moreover, the specific absorption rate (SAR) analysis of the MTL transmit array coil with the DLs is performed. The peak 10g-averaged SAR is reduced from 3.1 W/kg to 2.13 W/kg in the head using DLs and RF-shimming technique. Finally, we used the bench measurement setup to obtain the measured magnetic field. The proposed work exhibits salient features with a smaller DL size and multi-element MTL transmit array coil than other proposed works. |
| first_indexed | 2024-12-21T09:30:32Z |
| format | Article |
| id | doaj.art-869e903d9e6141a6938fd113280fb78a |
| institution | Directory Open Access Journal |
| issn | 2169-3536 |
| language | English |
| last_indexed | 2024-12-21T09:30:32Z |
| publishDate | 2021-01-01 |
| publisher | IEEE |
| record_format | Article |
| series | IEEE Access |
| spelling | doaj.art-869e903d9e6141a6938fd113280fb78a2022-12-21T19:08:45ZengIEEEIEEE Access2169-35362021-01-01914441714442510.1109/ACCESS.2021.31221229584839Performance Enhancement of an MTL Coil Loaded With High-Permittivity Dielectric Liner for 7 T Brain MRISana Ullah0https://orcid.org/0000-0001-5671-6989Hyoungsuk Yoo1https://orcid.org/0000-0001-5567-2566Department of Electronics Engineering, Hanyang University, Seoul, Republic of KoreaDepartment of Electronics Engineering, Hanyang University, Seoul, Republic of KoreaIn a multi-element microstrip transmission line (MTL) transmit array coil, the transmit field (<inline-formula> <tex-math notation="LaTeX">$B_{1}^{+}$ </tex-math></inline-formula>) distribution is inhomogeneous due to its standing-wave nature, and the interference effects can severely degrade the <inline-formula> <tex-math notation="LaTeX">$B_{1}^{+}$ </tex-math></inline-formula> and imaging. Therefore, to improve the homogeneity and strength of <inline-formula> <tex-math notation="LaTeX">$B_{1}^{+}$ </tex-math></inline-formula>, this study focuses on the development of a multi-element MTL transmit array coil integrated with a dielectric liner (DL) material. Furthermore, the transmission efficiency (<inline-formula> <tex-math notation="LaTeX">$T_{x,eff}$ </tex-math></inline-formula>) is improved in the head region. An eight-element MTL transmits array head coil is investigated using thinner DLs, and the optimized dimensions of the DL are found from its resonant mode at 7 Tesla (T). Simulations and measurements are performed with an MTL transmit array coil at 7 T, and the performance is analyzed for the DL positions and dimensions. Remarkably, the proposed DLs-integrated transmit array coil system offered significant improvements in the <inline-formula> <tex-math notation="LaTeX">$T_{x,eff}$ </tex-math></inline-formula> at different DLs positions. Compared to the case without the DL, the <inline-formula> <tex-math notation="LaTeX">$T_{x,eff}$ </tex-math></inline-formula> is improved by 9% (DL close to the head model), 15% (DL at center), and 39% (DL close to the RF coil). Interestingly, the DL acts as an efficiency tuner element exhibiting a 9% to 39% <inline-formula> <tex-math notation="LaTeX">$T_{x,eff}$ </tex-math></inline-formula> tuning range of improvement. In addition, the RF-shimming technique improves the <inline-formula> <tex-math notation="LaTeX">$B_{1}^{+}$ </tex-math></inline-formula> homogeneity and <inline-formula> <tex-math notation="LaTeX">$T_{x,eff}$ </tex-math></inline-formula> of the coil with DLs by 21% and 42%, respectively, compared to the case without the DL. Moreover, the specific absorption rate (SAR) analysis of the MTL transmit array coil with the DLs is performed. The peak 10g-averaged SAR is reduced from 3.1 W/kg to 2.13 W/kg in the head using DLs and RF-shimming technique. Finally, we used the bench measurement setup to obtain the measured magnetic field. The proposed work exhibits salient features with a smaller DL size and multi-element MTL transmit array coil than other proposed works.https://ieeexplore.ieee.org/document/9584839/7 Tdielectric padeight-elementMTL transmit arrayradio frequency (RF) coilRF shimming |
| spellingShingle | Sana Ullah Hyoungsuk Yoo Performance Enhancement of an MTL Coil Loaded With High-Permittivity Dielectric Liner for 7 T Brain MRI IEEE Access 7 T dielectric pad eight-element MTL transmit array radio frequency (RF) coil RF shimming |
| title | Performance Enhancement of an MTL Coil Loaded With High-Permittivity Dielectric Liner for 7 T Brain MRI |
| title_full | Performance Enhancement of an MTL Coil Loaded With High-Permittivity Dielectric Liner for 7 T Brain MRI |
| title_fullStr | Performance Enhancement of an MTL Coil Loaded With High-Permittivity Dielectric Liner for 7 T Brain MRI |
| title_full_unstemmed | Performance Enhancement of an MTL Coil Loaded With High-Permittivity Dielectric Liner for 7 T Brain MRI |
| title_short | Performance Enhancement of an MTL Coil Loaded With High-Permittivity Dielectric Liner for 7 T Brain MRI |
| title_sort | performance enhancement of an mtl coil loaded with high permittivity dielectric liner for 7 t brain mri |
| topic | 7 T dielectric pad eight-element MTL transmit array radio frequency (RF) coil RF shimming |
| url | https://ieeexplore.ieee.org/document/9584839/ |
| work_keys_str_mv | AT sanaullah performanceenhancementofanmtlcoilloadedwithhighpermittivitydielectriclinerfor7tbrainmri AT hyoungsukyoo performanceenhancementofanmtlcoilloadedwithhighpermittivitydielectriclinerfor7tbrainmri |