Deep brain stimulation (DBS) implants consist of long, electrically conductive leads which inject current into specific regions of the brain to treat various neurological disorders¹. MRI is important for surgical planning and post-procedure monitoring of patients that undergo DBS². However, DBS leads can cause local heating during MRI due to coupling of the long wires with the radiofrequency (RF) excitation, placing severe limits on imaging protocols³. Significant heating reductions have been obtained via parallel RF transmission (pTx) in a proof of concept study⁴. Here, we extend this pTx approach to improve computation time and investigate more realistic biophysical geometry, including a complex head model and bilateral curved implanted wires, as the next step towards a future clinical implementation at 3T.This work implements RF shimming, a type of pTx that reduces complexity and cost by implementing a constant amplitude and phase shift for each pTx channel instead of time-varying amplitude and phase shifts. In this case, RF shimming is performed to produce the minimum electric (E) field within a specified region and the maximum transmit RF magnetic field (B₁⁺) homogeneity in the imaging plane. To minimize computation time, an E-field and B₁⁺-field map was calculated via simulation using a commercially available electromagnetic solver, FEKO (Altair, Inc.). Optimization was then completed in Matlab (the MathWorks, Inc.), determining the RF shimming parameters using a simplex optimization algorithm. The cost function consisted of two terms: a B₁⁺-field homogeneity term in a plane of interest (POI), and an E-field minimization term, in a region of minimization (ROM), according to: $$\min\left(\sum_{\overrightarrow{r}\in ROM}|\overrightarrow{E}(\overrightarrow{r})|^{2}+\lambda\left\{\frac{\max|B_1^+(\overrightarrow{r})|-|B_1^+(\overrightarrow{r})|}{\max|B_1^+(\overrightarrow{r})|}\right\}_{POI}\right)$$ where the weighting factor, λ, was used to vary the importance of the two terms; $$$|\overrightarrow{E}(\overrightarrow{r})|$$$ is the magnitude of the E-field at position $$$\overrightarrow{r}$$$, $$$|B_1^+(\overrightarrow{r})|$$$ is the magnitude of the RF magnetic field at position $$$\overrightarrow{r}$$$ relative to the center of the imaged object. The POI was chosen to be perpendicular to the wires coinciding with the wire tips (where B₁⁺ distortion due to E-field minimization or coupling is expected to be highest). As multiple regions of E-field enhancement were anticipated with the presence of two curved wires, multiple ROMs were determined for E-field minimization. The weighting factor, λ, was varied to increase the degrees of freedom available during optimization. A 4-channel pTx configuration surrounding an asymmetric, complex head model was investigated with a single curved wire implant, and with bilateral implants (Figure 1). The head model included four tissue media: grey matter (ε_r=67.7, σ=0.619), white matter (ε_r=48.8, σ=0.364), cerebral spinal fluid (ε_r=79.1, σ=2.17) and bone (ε_r=41, σ=0.0067). The implants were modelled as perfectly conductive wires placed in the typical orientation of bilateral DBS leads. The chosen POI and ROMs are also shown in Figure 1. The 4-element pTx solution was compared with performance of a transmit/receive birdcage coil, the present standard of care for DBS patients.For the single, curved wire implant, the E-field at the tip of the wire was reduced by 98.5% when using optimized pTx compared to use of the birdcage coil. There was an associated improvement in B₁⁺-field homogeneity with a standard deviation of 28% obtained with optimized pTx versus 81% with the birdcage coil in the brain. The optimal RF shim was obtained with a λ value of 873. Results for bilateral wire implants are shown in Figures 2 and 3. The E-fields are shown in sagittal planes parallel to each wire in Figure 2, and B₁⁺-fields are shown in the axial imaging plane in Figure 3, with simulation results for optimized pTx and the birdcage coil comparison. The optimal value of the weighting factor, λ, = 943. The E-field was reduced by 31% at location 1 and 43% at location 2 in the first wire and 94% at location 1 and 91% at location 2 in the second wire. Locations were chosen as the regions of highest E-field in the birdcage coil excitation. Significant reductions in E-field are achieved along both wires in the bilateral phantom; however, the reduction is less in the first wire. This is due to the lower E-field surrounding the first wire in the birdcage coil excitation. The overall E-field in the optimized scenario is reduced by a factor of approximately 10 throughout the entire head. The B₁⁺-field homogeneity is 29.7%, which is improved when compared with the birdcage coil (73.4%). This work shows that optimized RF shimming can be used to reduce E-field near of bilateral, curved wires implanted in a complex, multimedia phantom while maintaining B₁⁺-field homogeneity.