Investigation of Magnetoelectric Sensor Requirements for Deep Brain Stimulation Electrode Localization and Rotational Orientation Detection

Abstract

Correct position and orientation of a directional deep brain stimulation (DBS) electrode in the patient’s brain must be known to fully exploit its benefit in guiding stimulation programming. Magnetoelectric (ME) sensors can play a critical role here. The aim of this study was to determine the minimum required limit of detection (LOD) of a ME sensor that can be used for this application by measuring the magnetic field induced by DBS. For this experiment, a commercial DBS system was integrated into a head phantom and placed inside of a state-of-the-art Superconducting Quantum Interference Device (SQUID)-based magnetoencephalography system. Measurements were performed and analyzed with digital signal processing. Investigations have shown that the minimum required detection limit depends on various factors such as: measurement distance to electrode, bandwidth of magnetic sensor, stimulation amplitude, stimulation pulse width, and measurement duration. For a sensor that detects only a single DBS frequency (stimulation frequency or its harmonics), a LOD of at least 0.04 pT/Hz0.5 is required for 3 mA stimulation amplitude and 60 μμs pulse width. This LOD value increases by an order of magnitude to 0.4 pT/Hz0.5 for a 1 kHz, and by approximately two orders to 3 pT/Hz0.5 for a 10 kHz sensor bandwidth. By averaging, the LOD can be reduced by at least another 2 orders of magnitude with a measurement duration of a few minutes.

MaDoPO: Magnetic Detection of Positions and Orientations of Segmented Deep Brain Stimulation Electrodes: A Radiation-Free Method Based on Magnetoencephalography

“…Increasing the resolution can increase the detection accuracy, but drastically increases the computational complexity. Further investigation in this study has shown that the cap-shaped MEG system must have the following characteristics: (1) suitable magnetic field sensors that have the sensitivity and bandwidth required for this application [ 21 ]; (2) at least 40 and 60 sensors with concentrated distribution of sensors near the electrode for electrode localization and electrode orientation detection, respectively; (3) alignment of the sensors to the expected direction of the magnetic field (tangential component), with the direction of the magnetic field rotated 90° between directional and non-directional stimulation; (4) a pure measurement duration for a single recording of 50 and 77 s for localization and orientation detection, respectively; and (5) a minimum of three measurements with non-directional electrode configuration and a minimum of six measurements with directional configuration to achieve decent accuracy, although additional measurements may be considered to improve accuracy.…”

“…The feasibility of DBS electrode localization based on scalp EEG has already been demonstrated, but localization errors of more than 10 mm have been reported [ 17 ]. The potential of MEG recordings to detect electrode position and orientation has been demonstrated in our previous research [ 18 , 19 , 20 , 21 , 22 ]. In this study, we present an improved and patient-oriented method for the radiation-free detection of electrode positions and orientations using a series of measurements with a conventional SQUID-based MEG.…”

Determining the rotational orientation of directional deep brain stimulation electrodes using magnetoencephalography

“…Although these sensors still have too low a bandwidth for use in DBS applications due to the presence of much higher frequencies (stimulation frequency and its harmonics), the IPG allows a lower stimulation frequency to be set and, according to our physicians, poses no problem in reducing the stimulation frequency in patients for the duration of the measurement in order to perform multiple recordings required for the detection of electrode position and orientation. In our recent work [34], we investigated the minimum requirements that magnetic field sensors must meet in order to be used for electrode localization and electrode orientation detection. A high sensor sensitivity, as provided by a SQUID sensor, is not required.…”

A Wide-Band Magnetoelectric Sensor Based on a Negative-Feedback Compensated Readout Circuit

“…The deep brain stimulation (DBS) therapy system is crucial for the treatment of Parkinson’s disease. The precise positioning of its stimulation tool—the DBS electrode—at the location of the brain can effectively improve the treatment effect; it has been found that ME sensors could potentially be used for the localization of DBS electrodes, with a required bandwidth of 10 kHz–85 kHz for the localization signal [ 18 ]. Geophysical measurements using transient electromagnetics (TEM) methods require the extension of the readout bandwidth of the sensor to 5 MHz [ 19 ].…”