title: Biomedical signal acquisition with streaming wireless communication for recording evoked potentials.
abstract: BACKGROUND
  Commercial electrophysiology systems for recording evoked potentials always connect patients to the acquisition unit via long wires. Wires guarantee timely transfer of signals for synchronization with the stimuli, but they are susceptible to electromagnetic and electrostatic interferences. Though wireless solutions are readily available (e.g. Bluetooth), they introduce high delay variability that will distort the evoked potential traces. We developed a complete wireless acquisition system with a fixed delay.
  
  
  METHODS
  The system supports up to 4 bipolar channels; each is amplified by 20,000× and digitized to 24 bits. The system incorporates the "driven-right-leg" circuit to lower the common noise. Data are continuously streamed using radio-frequency transmission operating at 915 MHz and then tagged with the stimulus SYNC signal at the receiver. The delay, noise level and transmission error rate were measured. Flash visual evoked potentials were recorded monocularly from both eyes of six adults with normal vision. The signals were acquired via wireless and wired transmissions simultaneously. The recording was repeated on some participants within 2 weeks.
  
  
  RESULTS
  The delay was constant at 20 ms. The system noise was white and Gaussian (2 microvolts RMS). The transmission error rate was about one per million packets. The VEPs recorded with wireless transmission were consistent with those with wired transmission. The VEP amplitudes and shapes showed good intra-session and inter-session reproducibility and were consistent across eyes.
  
  
  CONCLUSIONS
  The wireless acquisition system can reliably record visual evoked potentials. It has a constant delay of 20 ms and very low error rate.
authors: Australian School of Advanced Medicine, Macquarie University, 2 Technology Place, Building F10A, Sydney, NSW 2109, Australia. johnson.thie@gmail.com
authors: Johnson
authors: J
authors: Thie
authors: Alexander
authors: A
authors: Klistorner
authors: Stuart L
authors: SL
authors: Graham
mesh_terms: D000328:Adult; D004569:Electroencephalography / Q000379:methods*; D004867:Equipment Design; D005074:Evoked Potentials, Visual / Q000502:physiology*; D006801:Humans; D012016:Reference Values; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013686:Telemetry / Q000295:instrumentation*; D014795:Visual Pathways / Q000502:physiology*