Concentric/monopolar needle electrode modeling: Spatial recording territory and physiologic implications

Daniel Dumitru, John C. King, Sanjeev D. Nandedkar

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

Scaled 20:1 physical models of monopolar and standard concentric needle electrodes are investigated with a constant current bipolar generator to determine the amplitude versus radial distance characteristics of these two electrodes. Each model is examined at three scaled and simulated tissue penetration depths (4, 10 and 20 mm) with measurements documented from 20 to 9000 μm radially in front and behind the models. The monopolar compared to concentric electrode has a smaller response to a standardized stimuli but a flatter response curve at distances of less than 1500 μm. The cannula of the concentric needle also has a flatter response than that of its core. When compared to a remote reference such as that at scaled depths of tissue penetration approximating 4 mm or less the cannula-to-remote reference potential exceeds the amplitude of the core-to-remote reference, recording a net negative potential at 6500 μm in front and 3500 μm behind the core. This study offers an explanation for the clinically observed larger magnitude potentials detected with monopolar compared to concentric electrodes resulting from a larger recording cross-sectional area with more fibers contributing to the potential even though the magnitude of potential at any one location is comparatively smaller in magnitude than that for the concentric electrode. Additionally, the physiologic duration of a motor unit is anticipated to be considerably longer than presently measured clinically with automated methods because of the electrodes' ability to detect such small signals from a large region of the volume conductor.

Original languageEnglish (US)
Pages (from-to)370-378
Number of pages9
JournalElectroencephalography and Clinical Neurophysiology - Electromyography and Motor Control
Volume105
Issue number5
DOIs
StatePublished - Oct 1 1997

Keywords

  • Concentric needle electrode
  • Instrumentation
  • Monopolar needle electrode
  • Motor unit action potential
  • Volume conduction

ASJC Scopus subject areas

  • Neuroscience(all)
  • Clinical Neurology

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