Fig. 4.

Identification of safe radiant exposures for stimulation human dorsal roots. Results from the safety and efficacy study from seven patients (102 stimulation sites) graded on a three-point scale. Laser radiant exposure used for each stimulation (20 pulses at 2 Hz recorded for 10 s) is graphed as a function of the thermal damage score assigned to each site based on histopathology from optical stimulation over a range of laser energies (0.46 to $2.05\mathrm{J}/{\mathrm{cm}}^2$). Probability of damage is given by cumulative distribution function from statistical analysis of binary damage data. Successful stimulations are indicated by blue diamonds, no stimulation is indicated by red dots, and stimulation sites with no EMG recordings are indicated by black triangles. Compound muscle action potentials are first observed at $0.53\mathrm{J}/{\mathrm{cm}}^2$. Stimulation range is identified as 0.53 to $1.28\mathrm{J}/{\mathrm{cm}}^2$. Safe stimulation range is identified as 0.53 to $1.00\mathrm{J}/{\mathrm{cm}}^2$.