Clinical deep brain stimulation (DBS) uses 4 cylindrical electrodes driven in monopolar or bipolar configurations. This yields a spherical stimulation field around the electrode modulating both targeted and untargeted areas. This paper presents an approach in which activation field spread beyond targeted areas can be mitigated using dynamic current steering. Dynamic current steering uses segmented electrodes together with dynamic current sources in order to accurately stimulate intended neural tissue. This paper will focus on the output stage of the dynamic current steering system. The output stage uses dynamic current sources (DCS) in implementing 8 push-pull current sources that are interfaced to 16 electrodes so as to enable current steering. The dynamic current sources operate in two phases - programming and stimulation. This technique was adopted because it reduces power consumption and output current mismatch. The 16 electrodes can be driven both as anodes and cathodes. As a proof of concept the stimulator uses a supply of 3.3 V to drive biphasic current pulses of up to 0.5 mA through its electrodes. The circuit was implemented in a 0.18 μm CMOS technology.

@en

Clinical deep brain stimulation (DBS) is based on the use of cylindrical electrodes driven in monopolar or bipolar configurations. The simulation field spreads symmetrically around the electrode modulating both targeted and non-targeted neural structures. Recent advances have focused on novel stimulation techniques based on the use of high-density segmented electrodes, which allow current-steering and field-shaping capability. This paper presents the architecture of a multi-channel current-steering stimulator output stage that allows for monopolar, bipolar, tripolar and quadripolar multi-site stimulation. The core of the output stage comprises N independent high-compliance current drivers (HCCDs), capable of delivering up to 1.5 mA complementary currents in 10 different current ranges. Each of the N HCCDs can drive up to 8 adjacent electrode contacts thanks to a 2-32 multiplexer controlled by a 5-32 decoder. The HCCD was designed in a HV 0.18μm CMOS process. The circuits were simulated in Cadence Spectre and simulated results are presented in the paper.@en

A significant problem with clinical deep brain stimulation (DBS) is the high variability of its efficacy and the frequency of side effects, related to the spreading of current beyond the anatomical target area. This is the result of the lack of control that current DBS systems offer on the shaping of the electric potential distribution around the electrode. This paper presents a stimulator ASIC with a tripolar current-steering output stage, aiming at achieving more selectivity and field shaping than current DBS systems. The ASIC was fabricated in a 0.35-μm CMOS technology occupying a core area of 0.71 mm ². It consists of three current sourcing/sinking channels. It is capable of generating square and exponential-decay biphasic current pulses with five different time constants up to 28 ms and delivering up to 1.85 mA of cathodic current, in steps of 4 μA, from a 12 V power supply. Field shaping was validated by mapping the potential distribution when injecting current pulses through a multicontact DBS electrode in saline.

@en

This paper presents an investigation into the use of a leaky wave antenna for deep brain stimulation. The proposed design could replace the currently used electrode array which provides a periodic pulse train to stimulate a region of brain tissue within the subthalamic nucleus or globus pallidus, pars interna to minimize the effects of tremor in a human subject. We demonstrate that it is possible to apply a simple-structured Leaky Wave Antenna in human tissue to steer the field of activation. It is the first time a leaky wave antenna is employed in biomedical context. The preliminary design operates between 70 to 120 GHz. Its main beam can cover 72 degree of angular range with an average 13 dBi directivity within the operating frequency band.@en

Active control over the electric field distribution during deep brain stimulation (DBS) can provide better focus of the stimulation field on target regions, beneficial to improve neural selectivity and reduce side effects arising from simulation of non-target regions. A current-steering tripolar electrode configuration can be adopted to achieve better selectivity in DBS. The tripole consists of a central cathode and two lateral anodes. The currents through the anodes are set by two complementary current sources. By varying the ratio between the amplitude of the anodic currents, the current can be steered toward one anode, while keeping the cathodic current constant. In this paper we present the design of a current-steering tripolar current source in 0.35μm CMOS technology. The current source is capable of delivering cathodic currents up to 1.5mA and generate exponential and quasi-trapezoidal pulses needed for anodal blocking. The average mismatch between sourcing and sinking currents is in the order of 0.4% and the output compliance ranges between 6.1V and 11.15V for a 12V supply, when the maximum and minimum anodic currents are supplied, respectively.@en

Deep brain stimulation (DBS) is a widely accepted clinical tool adopted for the treatment of a number of motor disorders. Despite its clinical efficacy, its underlying mechanisms have not been yet fully understood. One major issue that we identify as partly responsible for this lack of understanding is related to the poor control over the size, shape and location of the distribution of the depolarizing field around the electrode. With this and a parallel work the authors are proposing to develop and implement techniques that would allow for some degree of control over the distribution of the potential fields. This paper presents the application to DBS of a technique based on a tripolar current source configuration, with adjustable current flow through the lateral (anodic) branches of the tripole. The behavior of potential fields in the tissue were simulated by adopting FEM models of DBS electrode implanted in brain tissue. The profiles of simulated and measured fields were in agreement and they have shown how a dynamic tripolar current source can be adopted to obtain increase the focus and control the location of distribution of the fields around the electrode.@en

Deep brain stimulation (DBS) is a clinical tool adopted to treat various neurological disorders, including chronic pain, incontinence and movement disorders. One major limitation of commercial DBS systems i. The inability to controy the distribution oy the electric field aroun. The target region, resulting i. The activation of both target and non-target neural clusters. The authors have previously proposed a method to provide controlled stimulation by the adoption of phased array technology. A model was developed to stud. The behavior of wavefronts, generated by phased arrays, in tissue. This study represents an improvement to this model, wher. The frequency-dependence oy the dielectric properties of brain tissue is taken into account. Results have shown that the applicability of phased array stimulation depends oy the frequency of stimulation, with frequencies i. The region of GHz providin. The best trade-off between field steering, focusing and tissue penetration.@en

Deep brain stimulation (DBS) is a clinical technique adopted for the treatment of various neurological disorders. One major limitation of today's DBS systems is the inability to focus the electric field in the desired direction and provide a more efficient stimulation. This study adopted 2D and 3D FEM tools to explore the the application of phased array (PA) techniques to control the direction of the stimulation pattern delivered during DBS. Results illustrate that a PA DBS system can be used to steer the stimulation pattern from broadside to endfire, by driving the electrode contacts with high frequency sinusoids with phase delays varying from 0° to 90°. This study can provide a framework for future investigation in the development of more efficient DBS systems based on PA technology.@en