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A new high radial resolution 2D multichannel Charge eXchange Imaging (CXI) diagnostic is under development for deployment at DIII-D. The diagnostic system will measure low-to-intermediate radial wavenumber carbon density fluctuations by observing the n = 8 − 7 ( λ = 529.06 nm) C-VI emission line, resulting from charge exchange collisions between heating neutral beam atoms and the intrinsic carbon ion density. The new CXI diagnostic will provide measurements with Δ R ∼ 0.4 cm to access higher k r instabilities ( k r < 8 cm−1) predicted to arise in the steep-gradient region of the H-mode pedestal. The CXI system will feature 60 fiber bundles in a 12 × 5 arrangement, with each bundle consisting of four 1 mm fibers. A custom optical system has been designed to filter and image incoming signals onto an 8 × 8 avalanche photodiode array. Additionally, a novel electronics suite has been designed and commissioned to amplify and digitize the relatively low-intensity carbon signal at a 2 MHz bandwidth. Forward modeling results of the active C-VI emission suggest sufficient signal to noise ratios to resolve turbulent fluctuations. Prototype measurements demonstrate the ability to perform high frequency pedestal measurements.

Pudendal nerve evoked potentials were used in orthopaedic surgical procedures involving fixation below the S1 level. Pudendal nerve stimulation was used to monitor 154 patients. Eleven patients (7.14%) had responses that were either difficult or impossible to interpret in that they were not consistently replicable. In one case (0.65%), responses were lost during surgery, and there were no subsequent neurologic sequelae (false-positive response). No patients had postoperative deficit to the sacral roots or to the global cord. Although it is possible to obtain definitive dermatomal responses down to S1, the use of pudendal nerve stimulation was found to provide additional means of monitoring lower sacral roots. Since the pudendal nerve is intimately associated with bowel, bladder, and sexual dysfunction, easily obtainable routine monitoring of this nerve can provide significant safety that the conventional somatosensory and dermatomal responses give to higher spinal levels.

Dermatomal evoked potentials are being used to obtain accurate information concerning the viability of specific nerve root pathways and the quality and extent of nerve root decompression. Twelve patients with quantifiable weakness were selected and tested before, during, and after surgery. Nine patients showed dramatic intraoperative electrical improvement, including decreased latencies and/or increased amplitudes; all had postoperative relief of pain and motor return. Three patients showed variable intraoperative electrical responses with complete pain relief but no motor improvement. No patients had false-negative findings. Intraoperative monitoring of dermatomal evoked potentials appears to be of value in predicting the quality of spinal decompression. Similar monitoring of somatosensory evoked potentials alone cannot provide the specificity for individual root levels that is available by monitoring individual dermatomes.