Fig 1.
(a) Circuit schematic of a high-impedance coil (b) Surface electric field distribution over the single high-impedance coil element. Higher electric fields are observed over the low-value lumped capacitor placed opposite the port.
Fig 2.
(a) Simulation setup for high-impedance coil without HDC material: 3D view with resonators near phantom, top view of components, side view. (b) Simulation setup for coils with 30 × 11.5 cm2 HDC sheet: 3D view with resonators and HDC sheet, top view of components, side view. (c) Simulation setup for coils with 30 × 23 cm2 HDC sheet: 3D view with resonators and HDC sheet, top view of components, side view.
Table 1.
Lumped element values of the high-impedance coil as a function of the 30 × 11.5 cm2 HDC material distance and permittivity.
Table 2.
Lumped element values of the high-impedance coil as a function of the 30 × 23 cm2 HDC material distance and permittivity.
Fig 3.
Bench test measurement setup and the identical simulation setup used for verification.
(a) The high-impedance coil without any high dielectric constant material placed on top is kept on the low loss platform on the 3D positioning system and field measuring probe. (b)The high-impedance coil and the 3D printed tray containing the water + gelatin solution mimic one of the high relative permittivity values partially covering the high-impedance coil below. The partially covering 3D printed tray had the dimensions of 11×28 cm2 and the distance between the high dielectric constant material from the high-impedance coil was approximately 10cm. (c)The high impedance coil and 22×28 cm2 3D printed tray with water + gelatin solution added on top. The distance between the high dielectric constant material and the high-impedance coil was approximately 10cm.
Fig 4.
3D perspective and 2D top view of the voxel simulation setup used for evaluating the 8-channel array configuration, with and without High-Dielectric Constant (HDC) material.
The human head voxel bio-model serves as the phantom: (a) Array without HDC material and (b) Array with HDC material.
Fig 5.
(a) Scattering parameters demonstrate reflection and transmission coefficients of high-impedance coils without HDC material. (b) Scattering parameters for experimental cases with 30 × 11.5 cm2 HDC material partially covering high-impedance coils: (i) HDC material placed 3mm away, (ii) HDC material placed 5mm away, (iii) HDC material placed 8mm away, (iv) HDC material placed 10mm away. (c) Scattering parameters for experimental cases with 30 × 23 cm2 HDC material completely covering high-impedance coils: (i) HDC material placed 3mm away, (ii) HDC material placed 5mm away, (iii) HDC material placed 8mm away, (iv) HDC material placed 10mm away.
Fig 6.
(a) Electric field distribution on cylindrical phantom with 30×11.5 cm2 HDC material: (i) 3D setup with coils and HDC material overlay; (ii) HDC material-free coil; (iii)-(vi) E-field distribution for HDC material 3mm, 5mm, 8mm, and 10mm from coils. (b) Electric field distribution on cylindrical phantom with 30×23 cm2 HDC material: (i) 3D setup with coils and HDC material overlay; (ii) HDC material-free coil; (iii)-(vi) E-field distribution for HDC material 3mm, 5mm, 8mm, and 10mm from coils.
Fig 7.
The 1D profiles of the peak electric field strengths evaluated for various cases involving different topologies of the HDC material, its distance from the high-impedance coils, its relative permittivity, and various human tissue properties assigned to the cylindrical phantom.
(a) 30× 11.5 cm2 HDC material: Brain Phantom (b) 30× 11.5 cm2 HDC material: Kidney Phantom (c) 30× 11.5 cm2 HDC material: Breast Fat Phantom (d) 30× 11.5 cm2 HDC material: Tendon/ligament Phantom (e) 30× 23 cm2 HDC material: Brain Phantom (f) 30× 23 cm2 HDC material: Kidney Phantom (g) 30× 23 cm2 HDC material: Breast Fat Phantom (h) 30× 23 cm2 HDC material: Tendon/ligament Phantom.
Fig 8.
(a) Specific Absorption Rate (SAR) distribution on cylindrical phantom with 30×11.5 cm2 HDC material: (i) Simulation setup for SAR evaluation; (ii) HDC material-free coil SAR distribution; (iii)-(vi) SAR distribution for HDC material 3mm, 5mm, 8mm, and 10mm from coils. (b) Specific Absorption Rate (SAR) distribution on cylindrical phantom with 30×23 cm2 HDC material: (i) Simulation setup for SAR evaluation; (ii) HDC material-free coil SAR distribution; (iii)-(vi) SAR distribution for HDC material 3mm, 5mm, 8mm, and 10mm from coils.
Fig 9.
The 1D profiles of the peak SAR values evaluated for various cases involving different topologies of the HDC material, its distance from the high-impedance coils, its relative permittivity, and various human tissue properties assigned to the cylindrical phantom.
(a) 30× 11.5 cm2 HDC material: Brain Phantom (b) 30× 11.5 cm2 HDC material: Kidney Phantom (c) 30× 11.5 cm2 HDC material: Breast Fat Phantom (d) 30× 11.5 cm2 HDC material: Tendon/ligament Phantom (e) 30× 23 cm2 HDC material: Brain Phantom (f) 30× 23 cm2 HDC material: Kidney Phantom (g) 30× 23 cm2 HDC material: Breast Fat Phantom (h) 30× 23 cm2 HDC material: Tendon/ligament Phantom.
Fig 10.
(a) B1 field distribution on central sagittal cross-section of cylindrical phantom with 30×11.5 cm2 HDC material: (i) 3D and 2D perspectives of central sagittal cut plane, illustrating B1 field distribution within phantom; (ii) HDC material-free coil B1-field distribution; (iii)-(vi) B1-field distribution for HDC material 3mm, 5mm, 8mm, and 10mm from coils. (b) B1 field distribution on central sagittal cross-section of cylindrical phantom with 30×23 cm2 HDC material: (i) 3D and 2D perspectives of central sagittal cut plane, illustrating B1 field distribution within phantom; (ii) HDC material-free coil B1-field distribution; (iii)-(vi) B1-field distribution for HDC material 3mm, 5mm, 8mm, and 10mm from coils.
Fig 11.
(a) Comparison of Electric Field Distributions: Measured and simulated electric fields within a 104mm x 104mm Field of View (FOV) for direct comparison. (b) Comparative Analysis of B1 Field Distributions: Measured and simulated B1 field distributions in an identical setup for each case.
Fig 12.
B1 field distribution evaluation in the voxel bio model for 8-channel array setups with and without the High Dielectric Constant (HDC) material sheet.
The figure shows the B1 field distribution in coronal and sagittal planes at the center of the human model, highlighting the improved performance with HDC material.
Fig 13.
Effect of multiple phase combinations on SAR distribution and performance.
SAR distributions in sagittal planes, with analysis. Peak SAR is reduced with HDC εr: 50 and 200. Mean SAR values show reductions of 6.26% and 20.14%, respectively, when compared to no HDC material.