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Magnetic Induction Tomography (MIT) is a non-invasive imaging technique used for dynamic monitoring and early screening of cerebral hemorrhage. Currently, there is a significant challenge in cerebral hemorrhage MIT due to weak detection signals, which seriously affects the accuracy of the detection results. To address this issue, a dual-plane enhanced coil was proposed by combining the target field method with consideration of the spatial magnetic field attenuation pattern within the imaging target region. Simulated detection models were constructed using the proposed coil and cylindrical coil as excitation coils, respectively, and simulation imaging tests were conducted using the detection results. The simulation results indicate that compared to the cylindrical coil, the proposed coil enhances the linearity of the magnetic field within the imaging target region by 60.43%. Additionally, it effectively enhances the detection voltage and phase values. The simulation results of hemorrhage detection show that the proposed coil improves the accuracy of hemorrhage detection by 18.26%. It provides more precise detection results, offering a more reliable solution for cerebral hemorrhage localization and detection. [ABSTRACT FROM AUTHOR]

Magnetic Induction Tomography (MIT) is a non-invasive imaging technique used for dynamic monitoring and early screening of cerebral hemorrhage. Currently, there is a significant challenge in cerebral hemorrhage MIT due to weak detection signals, which seriously affects the accuracy of the detection results. To address this issue, a dual-plane enhanced coil was proposed by combining the target field method with consideration of the spatial magnetic field attenuation pattern within the imaging target region. Simulated detection models were constructed using the proposed coil and cylindrical coil as excitation coils, respectively, and simulation imaging tests were conducted using the detection results. The simulation results indicate that compared to the cylindrical coil, the proposed coil enhances the linearity of the magnetic field within the imaging target region by 60.43%. Additionally, it effectively enhances the detection voltage and phase values. The simulation results of hemorrhage detection show that the proposed coil improves the accuracy of hemorrhage detection by 18.26%. It provides more precise detection results, offering a more reliable solution for cerebral hemorrhage localization and detection.

The combination of high-permeability ferrite and coils is often used to nullify ambient magnetic fields and is widely used in applications such as magnetic resonance imaging and high-sensitivity magnetic sensors. We propose the design method of transverse gradient coils based on the target field method in a high-permeability shield considering sidewall apertures (TFM-HPSCSA), which are installed in the ferrite shield to zero the residual magnetic field gradient. TFM-HPSCSA coils enable an innovative combination of magnetic field gradient linearity and structural luminescence. The coil current density distribution is set to avoid the central sidewall apertures. As a result, the contour distribution of the stream function under the optimized weight coefficients is calculated to obtain the wire alignments of the dBy/dx, dBy/dy and dBy/dz gradient coils. The deviations of the experimentally measured values from the finite element simulations of the three types coils are 0.63%, 1.17% and 0.48%, respectively, which verified the validity and the accuracy of the proposed method. In comparison to the traditional saddle gradient coil designed under the free space condition, the proposed dBy/dx coil produces a 30.5% improvement in the percentage range of regions with 5% magnetic field gradient nonlinearity. The increased linear range of the gradient magnetic field contributes to the improvement of the residual field nulling range in magnetic sensors and magnetic shielding systems in practical applications.

• The uniform-field coils design parameters under ferromagnetic boundaries are optimized by swarm algorithms based on the target-field method. • The equipotential division equation of the flow function is given considering the actual needs of the magnetic shield with a through-hole. • The effect of the shield permeability and the endcap opening size on the magnetic field distribution at the center of the coils is analyzed. • The maximum relative errors between the measured field generated by the WOA-TFMUFY coil and the simulation results were no higher than 2.2 %. Combination systems of high permeability magnetic shields and coils are widely used in fields such as the magnetic field standard metrology and the zero magnetic room construction. To solve the problem that the magnetic field of uniform-field coils under the ferromagnetic boundary of magnetic shields is difficult to design precisely and the uniformity is difficult to improve, three-dimensional uniform field coils are designed based on the magnetic field model of coils under the ferromagnetic boundary using the target-field method (TFM), and the weight coefficient vectors determining the coils' structure are optimized using intelligent optimization algorithms, which improves the uniformity of the magnetic field in the target region by 2 orders of magnitude through whale optimization algorithm (WOA). Then, the radial WOA-TFMUFY coil and the axial WOA-TFMUFZ coil are designed considering sidewall optical holes, and their magnetic field distribution is analyzed and verified under different permeabilities and axial opening sizes of the shield. Compared to the traditional saddle coil and Lee-whiting coil, the maximum magnetic field non-uniformity in the target uniform field region is reduced by 82.2 % and 92.8 % for the WOA-TFMUFY coil and WOA-TFMUFZ coil. The maximum relative errors between the measured magnetic field generated by the designed coils and the finite element method (FEM) simulation results are no higher than 2.2%. This novel method can provide more precise and uniform magnetic field metrology standard elements. [ABSTRACT FROM AUTHOR]

• Proposed a method to design transverse gradient coils considering sidewall apertures in a ferrite shield. • The designed gradient coils achieve both high gradient linearity and structural luminescence. • In comparison to the traditional saddle gradient coil designed under the free space condition, the proposed d B y /d x coil and d B y /d z coil produce 30.5% and 5.8% improvement in the percentage range of regions with 5% magnetic field gradient nonlinearity, respectively. • The experimental values match well with the simulations, confirming the validity and accuracy of the method. The combination of high-permeability ferrite and coils is often used to nullify ambient magnetic fields and is widely used in applications such as magnetic resonance imaging and high-sensitivity magnetic sensors. We propose the design method of transverse gradient coils based on the target field method in a high-permeability shield considering sidewall apertures (TFM-HPSCSA), which are installed in the ferrite shield to zero the residual magnetic field gradient. TFM-HPSCSA coils enable an innovative combination of magnetic field gradient linearity and structural luminescence. The coil current density distribution is set to avoid the central sidewall apertures. As a result, the contour distribution of the stream function under the optimized weight coefficients is calculated to obtain the wire alignments of the d B y /d x , d B y /d y and d B y /d z gradient coils. The deviations of the experimentally measured values from the finite element simulations of the three types coils are 0.63%, 1.17% and 0.48%, respectively, which verified the validity and the accuracy of the proposed method. In comparison to the traditional saddle gradient coil designed under the free space condition, the proposed d B y /d x coil produces a 30.5% improvement in the percentage range of regions with 5% magnetic field gradient nonlinearity. The increased linear range of the gradient magnetic field contributes to the improvement of the residual field nulling range in magnetic sensors and magnetic shielding systems in practical applications. [ABSTRACT FROM AUTHOR]

A novel strategy for designing uniform magnetic field and gradient magnetic field coils considering the boundary effect of magnetic shielding is proposed in this study. This strategy uses intelligent optimization algorithm to skillfully transform the complex coil design problem into the spatial optimization problem of individual population. The mirror method is combined with Green's function to accurately calculate the magnetic field, and the target field method (TFM) is combined with the whale optimization algorithm to optimize the stream functions using adaptive ridge regression. The minimum fitness function is defined as the real-time magnetic field relative error, and the optimal ridge coefficient is continuously obtained by determining the current density coefficient. The proposed method significantly reduces the magnetic field deviation in the target area compared to the conventional TFM, with reductions ranging from 12.2 % to 0.11 % (B x coil), 0.3 % to 0.02 % (B z coil), 20 % to 10 % (d B x / d z coil) and 2.9 % to 2.4 % (d B z / d z coil). The strategy has been effectively validated by analytical simulations and experimental results, and is expected to be applied to the design of uniform field coils and gradient coils for ultra-high precision atomic sensors. [Display omitted] • The coupling problem between the magnetic shielding system and the designed magnetic field coil is greatly reduced. • This method determines the fitness evaluation function according to the real-time actual current density. • The magnetic field coil designed by the hybrid optimization method proposed in this paper reduces the magnetic field deviation by nearly one to two orders of magnitude compared to the conventional TFM. • The proposed method significantly reduces the magnetic field deviation in the target area compared to the conventional TFM. [ABSTRACT FROM AUTHOR]

A novel approach of asymmetrical gradient coil design for head imaging in MRI (magnetic resonance imaging) is presented in this paper. The design is based on a modified target field method in which the stream function is introduced to replace lams scheme for the length control. The transverse head coil calculated by this method has a high performance. The coil efficiency is 0.41 mT/ m/A and the inductance is 512 μH. The coil has an inner diameter of 32 cm and a length of 45.8 cm. The size of the ROU (region of uniformity) is 20 cm along the transverse direction and 17 cm along the axial direction and it is close to one end of the coil. The ROU of the coil matches the ROU (region of interest) of human head very well. Compared with previous designs, our design has relatively high performance and the overlap between the ROU and the ROI is larger (the overlap percent is 95 %). [ABSTRACT FROM AUTHOR]

Shim coils used in magnetic resonance imaging and NMR to produce magnetic fields are commonly designed to generate spherical harmonics, and thus achieve accuracy over a spherical region. Herein a cylindrical basis set is presented as an alternative to spherical harmonics, so as to better suit the cylindrical coil geometry and, in cases where it more closely matches a cylinder, the imaging region of interest. Example coil winding patterns for a selection of functions in this new set are derived using the target field method. A computational approach is taken to determine their accuracy, and it is found the basis functions are generated with high accuracy over cylindrical imaging regions within the coil. The basis set is also applied to a double‐coil configuration with active shielding, which results in slightly reduced accuracy within the coil but highly effective field nullification beyond the coil radius. [ABSTRACT FROM AUTHOR]