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    Analyzing Spinal Cord Stimulation With Different Electrode Configurations: A Numerical Study
    (Wiley, 2024) Aydin, Elif Feyza; Zengln, Reyhan
    Spinal cord stimulation (SCS) represents a therapeutic approach for chronic pain management in patients refractory to conventional treatments. By implanting electrodes in the epidural space, SCS aims to mitigate pain transmission to the brain through electrical stimulation, often resulting in sensory perceptions such as paresthesia. This study investigates the influence of electrode configurations on electrical parameters, including current density and electric potential, within the spinal cord environment. Utilizing computational models of the spinal canal incorporating components such as epidural fat, cerebrospinal fluid (CSF), gray matter, and white matter, our analysis explores the distribution of electric potential and current density. Specifically, configurations employing four and nine electrodes are evaluated under both direct current (DC) and alternating current (AC) stimulations. For DC stimulations at currents of 1, 5, and 10 mA, our findings indicate that the four-electrode model generated current density values in epidural fat ranging from 107.90 to 130.98 mA/cm2 and electric potential values ranging from 3.51 to 4.78 V. Similarly, the nine-electrode model produced current density values ranging from 92.51 to 223.61 mA/cm2 and electric potential values ranging from 1.27 to 7.83 V under the same conditions. The results demonstrate a proportional relationship between applied current, current density, and electric potential. Furthermore, our investigation reveals a gradual decrease in electrical potential and current density from the epidural space to the gray matter. Discussions encompass the safety implications of these findings, examining whether the observed electrical parameters remain within tolerable limits for patient well-being. Additionally, the study explores the effects of AC stimulation across frequencies ranging from 250 Hz to 10 kHz, revealing an inverse correlation between frequency and charge parameters. Specifically, higher frequencies corresponded to reduced charge per phase and charge density, underscoring the frequency-dependent nature of these electrical properties.
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    Investigation of Lorentz field effects on wound healing: theoretical, computational, and experimental analysis
    (Iop Publishing Ltd, 2026) Gurcan, Aliye; Acikgoz, Merve; Tutuk, Rabia; Aydin, Elif Feyza; Yuksel, Furkan; Korkmaz, Engin; Tekin, Cigdem
    Objective. This study introduces a novel non-invasive wound healing method that generates Lorentz fields (LFs) in the wound area using ultrasonic transducers under a static magnetic field, enabling localized stimulation without direct electrode contact. Approach. Theoretical derivations of the governing equations, supported by numerical simulations, demonstrate the feasibility and potential effectiveness of this technique. The model includes the two-dimensional geometry of the wound, skin layers, gel, a single-element ultrasonic probe, or a 16-element linear phased array (LPA) transducer. The pressure and velocity current density distributions in the wound area were analyzed under three different excitation configurations: (i) excitation using a single-element ultrasonic probe, (ii) beam steering of the LPA transducer at 5 degrees intervals between -30 degrees and +30 degrees at 13 different angles, and (iii) focusing of the LPA transducer at 0 degrees. In each configuration, distinct pressure distributions and velocity current density patterns were obtained in the wound region. In addition, in vivo animal experiments were conducted using the single-element ultrasonic probe to evaluate the biological effects of LF-based stimulation on wound healing. The study included four experimental groups: a static magnetic field (SMF) group, an ultrasound (US) group, a combined LF group, and a control group without any stimulation. Main results. In the single-element probe configuration, the simulated velocity current density reached approximately 4.51 mu Acm-2, corresponding to a pressure of 0.17 MPa. These values remained within the established safety limits while being sufficient to promote wound healing. For the LPA transducer, electronic beam steering enabled a uniform distribution of acoustic pressure and induced current density over a wider wound area. The pressure ranged between +/-(0.118-0.203) MPa, and the corresponding velocity current density varied between +/-(2.33-2.69) mu Acm-2. In the focusing configuration (0 degrees), the maximum pressure in the wound region reached 0.285 MPa, while the peak absolute velocity current density was 6.72 mu Acm-2, both remaining within safe limits. Animal experiments were conducted for 14 d, with each group receiving a 5 min daily treatment. The Lorentz-field group exhibited the fastest wound closure, followed by the US and magnetic-field groups, whereas the control group showed the least improvement. Significance. The proposed method offers an innovative and safe alternative for accelerating wound healing by combining US and SMFs to generate Lorentz-induced current densities in the wound, providing localized and non-invasive therapeutic stimulation.
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    Numerical Analysis of Spinal Cord Stimulation with an Eight-Shape Electrode Model
    (Ieee, 2022) Aydin, Elif Feyza; Zengin, Reyhan
    Spinal Cord Stimulation is used for drug-free treatment in indications of chronic pain of the spinal cord. As a result of sending current from the electrodes placed in the epidural region of the spinal cord with laminectomy, pain information is prevented from reaching the brain and the patient only feels paresthesia. Today, different shapes of electrode designs are available. In this study, the current density distribution resulting from the application of 0.0417 mA to the anode and -0.0417 mA to the cathode from the eight-shaped electrodes were examined. The maximum current density is 36 mA/cm(2), and this value is within the safety limits that the patient can feel.