Tissue damage by pulsed electrical stimulation.
Repeated pulsed electrical stimulation is used in a multitude of neural interfaces; damage resulting from such stimulation was studied as a function of pulse duration, electrode size, and number of pulses using a fluorescent assay on chick chorioallontoic membrane (CAM) in vivo and chick retina in vitro. Data from the chick model were verified by repeating some measurements on porcine retina in-vitro. The electrode size varied from 100 microm to 1 mm, pulse duration from 6 micros to 6 ms, and the number of pulses from 1 to 7500. The threshold current density for damage was independent of electrode size for diameters greater than 300 microm, and scaled as 1/r2 for electrodes smaller than 200 microm. Damage threshold decreased with the number of pulses, dropping by a factor of 14 on the CAM and 7 on the retina as the number of pulses increased from 1 to 50, and remained constant for a higher numbers of pulses. The damage threshold current density on large electrodes scaled with pulse duration as approximately 1/t0.5, characteristic of electroporation. The threshold current density for repeated exposure on the retina varied between 0.061 A/cm2 at 6 ms to 1.3 A/cm2 at 6 micros. The highest ratio of the damage threshold to the stimulation threshold in retinal ganglion cells occurred at pulse durations near chronaxie-around 1.3 ms.
Butterwick
A
A
Department of Applied Physics, Stanford University, 445 Via Palou, Stanford, CA 94305, USA. butterwick@stanford.edu
Vankov
A
A
Huie
P
P
Freyvert
Y
Y
Palanker
D
D
D000818:Animals; D002462:Cell Membrane / Q000473:pathology / Q000528:radiation effects; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D049033:Chorioallantoic Membrane / Q000473:pathology / Q000503:physiopathology* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000009:adverse effects*; D005131:Eye Injuries / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology*; D012160:Retina / Q000293:injuries* / Q000503:physiopathology*