• developed specifically for the head shape and sensitive skin of preterm infants
• no face straps, simplifying application, minimizing stress for infants, and making it less likely to interfere with other medical devices
• Available in 32, 64, and 128 channel counts
• Available in small (28–30 cm), medium (30–32 cm) and large (32–34 cm) sizes

• 

  Very low profile for use in EEG-TMS or EEG-MEG
• No sponges or saline; use with gel or paste
• Ideal for larger head sizes, which often are difficult to fit into the MEG
• Available in 32, 64, 128, and 256 channel counts
• Available in adult sizes from small to extra large

Benefits

Comfort
EGI's Geodesic Sensor Nets (GSN) do not require any scalp preparation or abrasion, making them a perfect choice for your research participants. Suitable for all ages and hair types (with the exception of corn rows and dreadlocks, where hair density prevents seating of electrodes), Geodesic Sensor Nets have been used successfully with difficult-to-record populations such as autistic children, elderly patients with dementia, and ADHD teens.

Application and Fit
Application times for the sponge-based HydroCel Geodesic Sensor Nets range between 5 minutes for 32 channels to 15 minutes for 256 channels. EGI's support engineers teach proper Net application during EEG system installation and training visits. With just a few practice sessions you will be ready to collect data. Training DVDs are also available. 

With sizes ranging from neonate through adult and configurations for 32, 64, 128, and 256-channels, researchers can find the right fit for their budget and their participants.

Uses
The GSN is available for standard EEG/ERP recordings (1-2 hours) and for extended/sleep recordings (up to 24 hours)

EGI customers use the Geodesic Sensor Nets with our Geodesic EEG System 300 in a variety of environmental settings including: EEG/ERP laboratories, instrumented aircraft and autos, flight and driving simulators, sleep laboratories, Neonatal Intensive Care Units, epilepsy centers, classrooms, clinics, and hospitals.

Design
Geodesic Sensor Nets' complete head coverage ensures that all relevant data is captured. Guaranteeing complete head coverage requires attention to both appropriate intersensor distance and coverage of the underside of the head.

The first aspect of complete head coverage refers to the intersensor distance (that is, how far apart one sensor is from another sensor). Smaller intersensor distances translate to a more accurate measurement of the voltage field.

The second aspect refers to coverage of the underside of the head (for example, below the ears, including the face). It is common to believe that electrodes on the inferior surface of the head do not pick up EEG. However, voltage fields generated by the brain are volume conducted throughout the entire head. Moreover, certain brain regions, such as the inferior temporal lobes and ventral aspects of the frontal lobe, are oriented such that the voltage fields generated by these brain regions are best detected by electrodes on the inferior surface of the head.

The consequence of incomplete head coverage is that clinically significant EEG signals can be missed by sparse electrode placement and by lack of electrode placement on the underside of the head. For detailed information, see:

Luu, P., Tucker, D. M., Englander, R., Lockfeld, A., Lutsep, H., & Oken, B. (2001). Localizing acute stroke-related EEG changes: Assessing the effects of spatial undersampling. Journal of Clinical Neurophysiology, 18, 302-317.

Sperli, F., Spinelli, L., Seeck, M., Kurian, M., Michel, C. M., & Lantz, G. (2006). EEG source imaging in pediatric epilepsy surgery: A new perspective in presurgical workup. Epilepsia, 47, 1-10.

Srinivasan, R., Tucker, D. M., & Murias, M. (1998). Estimating the spatial Nyquest of the human EEG. Behavior Research Methods, Instruments, & Computers, 30, 8-19. 

Safety
Geodesic Sensor Nets use abrasion-free application methods and the electrodes themselves are held in place by gentle radial compression afforded by the unique geodesic tension structure. Because no abrasion is required, the scalp is not compromised, reducing infection risk. Often, it is argued that mild abrasion during the course of skin preparation does not compromise the integrity of the skin. However, studies have shown that this is not an accurate assumption. For further information, see:

Bild, S. (1997). Detection of occult blood on EEG surface electrodes. American Journal of Electroneurodiagnostic Technology, 38, 251-257.

More Information
Geodesic Sensor Nets are compatible with EGI's Geodesic EEG systems only. Contact us for more information on purchasing Geodesic EEG systems or purchasing Nets for your current Geodesic EEG system.