g.HIamp is a multi-channel biosignal amplifier with 256 channels for invasive and non-invasive measurements of the brain that is FDA cleared and CE approved. g.HIamp provides excellent signal resolution and a wide input sensitivity to record EEG, ECoG, ECG, EMG, and EOG without any saturation. External body sensors can also be connected. Internally, signal processing is performed with the fastest floating-point DSP and a sophisticated real-time Kernel. The amplifier relies on a very high oversampling to reduce the noise as much as possible by averaging samples.
256 channels can be analyzed in real-time with g.HIsys Highspeed Processing for Simulink software. This provides faster and more accurate control of BCI systems that use Common Spatial Patterns (CSP). g.HIamp is equipped with 16 digital trigger channels and a HOLD input for artifact suppression (e.g. during electrical or magnetic stimulation).
g.HIamp multi-channel amplifier has 16, 32, 80, 144 or 256 channels and can be used with passive or active EEG, ECoG, ECG, EMG and EOG electrodes. The difference between these options is just the electrode connector box. Each block of 64 channels is connected via a multi-pole medical safety connector to the electrode box. For ECoG grids and strips, special interface connectors are available too.
|Fully integrated into g.tec software environment for real-time analysis|
|Supports active and passive EEG electrodes and ECoG grids|
|16/32/80/144/256 DC coupled wide-range input channels, able to record any type of signal (EEG, ECoG, EMG, EOG/spikes, connected various sensors)|
|256 channels perfectly synchronized with 24 Bit resolution|
|Integrated impedance measurement for active and passive electrodes|
|simultaneous TMS possible|
|simultaneos tDCS possible|
|Easy configuration and setup with g.HIsys High-speed Online Data Processing for Simulink|
|Driver package/API available|
|FDA cleared and CE certified medical product|
|Size||197 (L) × 197 (W) × 90 (H) mm|
|Digital inputs||2 x 8 digital trigger inputs 1 x HOLD input (for artifact suppression)|
|Supply||5V DC, medical mains power supply|
|Sensitivity||85,7 nV / +/- 340 mV|
|Noise level||<0,5 µV rms 1-30 Hz|
|Amplifier type||real DC coupled|
|256 × ADC||24 Bit (38.4 kHz internal sampling per channel)|
|Input channels||256 mono-polar / 128 bi-polar (per device, software selectable)|
|Input impedance||>100 MOhm|
|Input connectors||standard safety connectors for passive electrodes, 2-pin connectors for active electrodes|
|Certification and Standards||FDA cleared and CE certified medical product EN60601-1, EN60601-1-2, EN60601-2-26, EN ISO 14971|
BRAIN MAPPING AND EPILEPSY MONITORING
A passive brain mapping procedure based on electrocorticographic (ECoG) signals is a fast and precise mapping technique without the risk of causing pain or seizures. They can accurately identify cortical regions related to receptive and expressive language functions, motor functions and the somatosensory system in the brain.
g.HIamp multi-channel amplifier can be used to realize brain mappings in the operating room or neuro monitoring unit.
RECORD EEG, TMS AND tDCS SIMULTANEOUSLY
There is a strong DC component in the raw data with tDCS, but it can be removed with a proper filter. As a result of the strong electromagnetic field, transcranial magnetic stimulation (TMS) can cause large discharge artifacts in the EEG due to amplifier characteristics and skin/electrode capacitance/impedance. Therefore, the dedicated 64 Channel Electrode Connector Box TMS for g.HIamp minimizes the amplifier-related artifact, and a post-processing artifact removal algorithm is integrated in g.BSanalyze software that robustly eliminates discharge artifacts in already contaminated data within seconds.
STUDY MUSIC AND THE MIND
The LIVELAB at McMaster Institute for Music and the Mind (MIMM) is engaged in neuroscientific research that aims to understand the positive role of music training, movement and performance. Researchers study music in a live setting using g.HIamp multi-channel amplifier and g.HIsys software to learn how performers interact, how audiences move during a performance and the social and emotional impact of these experiences.
RECORD ECOG AND SPIKES
ECoG electrodes from Ad-Tech, PMT, Unique Medical and Cortec can be used with g.HIamp for ECoG recordings. Furthermore, g.HEADstage amplifier can be connected to g.HIamp and used for neural spike recordings. Cortec grids can be connected with a direct interface cable which allows a very quick and error-free recording.
RECORD HIGH-FREQUENCY OSCILLATIONS
High-frequency oscillations (HFOs) can be recorded with the Electrocorticogram (ECoG) with implanted electrode grids in epilepsy patients. The HFOs occur in frequencies between 80-500 Hz. Hence, recording HFOs requires a high-performance biosignal amplifier such as g.HIamp with a high sampling frequency and a very good signal-to-noise ratio and resolution.
HFOs can be found in normal brain structures, but also in pathological networks, and mapping these neural networks is important for pre-surgical planning in epilepsy patients. Therefore, brain surgeons need to distinguish physiological from pathological HFOs. Recently, this was realized by the University of Houston with unsupervised machine learning techniques.
This technology can detect the repetitive waveforms of pathological HFOs within a few minutes, what is an important step for a valid clinical biomarker.
INPUT CHANNEL PROPERTIES
g.HIamp uses wide-range DC-coupled amplifier technology in combination with 24-bit sampling. The result is an input voltage of +/- 340 mV with a resolution of 85,7 nV! This means that every electrophysiological signal can be recorded directly, without additional hardware.
Neither high electrode offset voltage nor large artifacts resulting from electrical or magnetic stimulation will saturate the amplifier inputs. This feature is important for various artifact treatment and correction algorithms.
The use of digital filters avoids hardware related variations between channels.
g.HIamp uses a new principle for impedance measurement that can determine the skin-electrode impedance for both passive and active electrodes. It works for both gel or dry electrodes provided by g.tec, and even for ECoG grids.
The impedance values are color coded, and all 256 channels are shown in one window, which is updated every few seconds! The impedance check can also beep if an electrode was successfully mounted. This allows very fast assembly of electrodes during real-time impedance control.
g.HIamp can be ordered with 16, 32, 64+16, 128+16 or 256 channels. The 64+16 channel version comes with one 64 and one 16 channel connector box. The 128+16 version comes with two 64 channels and one 16 channel connector box, and the 256 channel version comes with four 64 channel boxes.
If the multi-device toolbox from g.HIsys is used up to 1024 channels can be recorded.
ACTIVE/PASSIVE ELECTRODE CONNECTOR BOX
A useful feature of the g.HIamp is that the main amplifier unit can be used with different electrode connector boxes. Therefore, the main amplifier unit must be purchased only once, and can be used for many different applications:
- 64 Channel Passive Electrode Connector Box
The box can be connected to one of the 4 groups of the g.HIamp. It can be used with standard 1.5 mm safety connectors, which are standard for EEG and ECoG electrodes.
- 16 Channel Passive Electrode Connector Box
The box can be connected to one of the 4 groups of the g.HIamp. This connector box can provide additional inputs for external sensors.
- 64 Channel Active Electrode Connector Box
The Box can be connected to one of the 4 groups of the g.HIamp. It has 2-pin connectors to support all g.tec active electrodes, such as g.LADYbird or g.SCARABEO (not for medical use).
- 64 Channel Active Electrode Connector Box TMS
The box allows EEG recordings with Transcranial Magnetic Stimulation (TMS) and can be connected to one of the 4 groups of the g.HIamp. It can be used with standard 1.5 mm safety connectors, which are standard for EEG and ECoG electrodes. The box contains additional filters to suppress artifacts.
- 64 Channel Passive Electrode Connector Splitter Box
ACCURACY AND DATA QUALITY
The amplifier drives each ADC at 614,4 kHz, which is much higher than the required sampling frequency. Then, the floating-point DSP internally performs the oversampling and averages samples to increase the signal-to-noise ratio. The floating-point DSP also performs real-time bandpass filtering and notch filtering of the data. Several hundred different bandpass filters are predefined.
Bipolar derivations can be calculated by the DSP to work with a very high CMRR. g.HIamp uses two additional co-processors for a steep anti-aliasing filter that guarantees a superior signal-to-noise ratio.
All these features together make it possible to record even high-gamma activity in the kHz range! The amplifier uses 256 ADC for the 256 channels, and hence all signals are sampled exactly at the same time point to avoid any time delay between channels. This is especially important for brain mapping procedures.
SOFTWARE OPTIONS AND PLUGINS
g.tec provides a broad spectrum of software solutions for different groups of users (e.g. engineers, researchers & scientists, physiologists, and medical staff, along with software developers & programmers). g.HIamp is integrated into the main core of BCI2000 and OpenVIBE and supports the LSL (lab streaming layer) as well as a plugin for Dewesoft X that allows you to acquire data with g.HIamp inside the Dewesoft data acquisition system for automotive applications.
g.HIAMP RESEARCH EDITION
g.HIamp RESEARCH is the non-certified version of g.HIamp and offers 16/32/80/144/256 channels. Therefore, it is less expensive, and intended for research applications only. The device has freely accessible and configurable features, although any kind of ECoG experiments are excluded.
“g.HIamp allows us to perform robust intraoperative recordings to ensure cortical and subcortical electrodes are placed in the correct functional regions, which is critical various clinical applications and research directions at the University of Florida Hospital.”Aysegul Gunduz, PhD - University of Florida, USA
“Fused with a variety of rapid prototyping and research software tools, g.HIamp serves as a unique tool in our clinical research applications to record electrocorticogram and local field potentials. The oversampling process executed by the internal DSP provides exceptional SNR and enables capturing higher frequency brain rhythms with superior quality.”Nuri Firat Ince, PhD - University of Houston, USA