Graeme Clark Collection

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Author: TYKOCINSKI, MICHAEL × End date: 2002 × Start date: 2000 × Subject: otolaryngology ×

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    X-ray phase-contrast imaging
    XU, JIN ; Lawrence, D. ; Tykocinski, Michael. ; Duan, Y. Y. ; Saunders, E. ; Clark, Graeme M. ( 2001)
    Foreign language abstract
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    Application of advanced radiographic technology in cochlear implant research
    XU, JIN ; TYKOCINSKI, MICHAEL ; Saunders, E. ; Clark, Graeme M. ; Cowan, R. ( 2001)
    The effective development of peri-modiolar or other advanced electrode arrays for cochlear implants requires detailed analysis of the insertion procedure and electrode positioning in the cochlea. Routine x-ray techniques cannot provide sufficient detail to meet this need. A new micro-focus x-ray imaging system has been built for our research. The system consists of a x-ray tube with a sub 10-micron focal spot mounted below an adjustable work surface and an image intensifier placed approximately 100 cm above the x-ray aperture. A variety of intracochlear electrode arrays and human temporal bones were studied using this system. The micro-focus x-ray imaging system allows for micro-fluoroscopy to visualise the real time implantation procedure. It also enables capturing of images onto reusable phosphor imaging plates or films for subsequent viewing or analysis. Images are produced at up to 95 times magnification with superior resolution and enhanced contrast. This new radiographic technology plays an important role in development of safe and effective advanced intracochlear electrode arrays.
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    Chronic monopolar high rate simulation of the auditory nerve: physiological and histopathological effects
    TYKOCINSKI, MICHAEL ; Linahan, Neil ; Shepherd, R. K. ; Clark, Graeme M. (Kugler Publications, 2001)
    There is clinical interest in the development of high rate speech processing strategies, since there are indications that these might enhance speech perception due to an improved representation of the rapid variations in amplitude of speech. Significant improvement in speech perception using high rate stimulation has been demonstrated in cochlear implant recipients. However, it is important that the long-term safety of high rate stimulation is clearly established prior to its general clinical application. This is especially important, since acute animal studies have shown that high rate stimulation can induce a reduction in the excitability of the auditory nerve. This was also associated with an increase in both threshold and latency of the electrically evoked auditory brainstem response (EABR). However, while a chronic stimulation study indicated that monopolar electrical stimulation of the auditory nerve at rates of 1000 pulses per second (pps)/channel (three channels) had no adverse effects on the spiral ganglion cell density (SGCO),5 there is limited data concerning higher rates. In the present study, we evaluated the electrophysiological and histopathological effects of chronic monopolar electrical stimulation of the auditory nerve using considerably higher stimulus rates than have been used in previous studies.