Rat Head Phantom for Testing of Electroencephalogram Source Localization Techniques

Abstract

In this paper we report a new rat head phantom developed for testing electroencephalogram source localization techniques. The phantom is composed of an agar based mixture mimicking the rat brain, six dipoles and fourteen electrodes for modeling and monitoring of neural activity of the brain, respectively, and a 3D printed skull based on a computed tomography scan of a rat skull. In order to fabricate the phantom with currently available conventional techniques, the phantom is 1.8 times enlarged. To allow scaling, we performed an extensive study of electric properties of the agar based mixture, including electric conductivity, permittivity, and applied voltage, to ensure a linear operating regime. The new phantom facilitates testing of existing and the development of new cortical electrode implants as well as studying the quality of various source localization techniques.

Electrical Source Imaging in Freely Moving Rats: Evaluation of a 12-Electrode Cortical Electroencephalography System

“…To evaluate inverse solutions, a realistic homogeneous phantom of the rat's head was created (Lacik et al, 2020 ). It consisted of the following main parts: skull, brain, excitation dipoles, and sensing electrodes.…”

“…Small holes were removed, a low-profile brick was added to have a stable support for the excitation dipoles, and it was split into two parts. Both parts were scaled by 1.8 (the scaling is allowed by a linear operating regime of the phantom, Lacik et al, 2020 ) and printed. For printing, a 3D printer based on stereolithography technology and a Formlabs standard resin (Formlabs, USA) was used.…”

“…Then, both parts of the skull were glued together. Finally, an agar-based mixture mimicking the gray matter was prepared with respect to the procedure described in Lacik et al ( 2020 ), poured into the skull, and cooled to room temperature.…”

“…After each test procedure, post-processing was applied to the electrode voltages obtained (Lacik et al, 2020 ). The first procedure was performed to test the localization algorithms and the second one to verify the operation of the phantom measurements in the linear regime at a test frequency of excitation of 1 kHz.…”

“…The first procedure was performed to test the localization algorithms and the second one to verify the operation of the phantom measurements in the linear regime at a test frequency of excitation of 1 kHz. Detailed information about the phantom fabrication and testing may be found in Lacik et al ( 2020 ).…”