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Unformatted text preview: BME 552 Homework Set 3 Assigned Feb 6, 2009 Due Feb 13, 2009 1. Prove that stimulus pulse energy is minimized at chronaxie. 2. Consider the following strength duration data. A 800 micron diameter electrode is used to apply these pulses. Is the most energy efficient pulse safe with respect to neural damage limits? If not what pulse parameters that are effective also will be considered safe by Shannon’s rule for neural damage. How can you maximize dynamic range of stimulus, assuming linear response characteristics? pw pa 0.01 20 0.05 5 0.1 2.6 0.5 0.8 1 0.5 5 0.4 10 0.3 50 0.3 3. A spinal cord stimulator is being developed that is positioned directly on the dorsal column. The stimulating electrode is 1 mm in diameter (it is a disk). The maximum output specification is 1 uC/ph. Assume an electrochemical limit for platinum of 0.35 mC/cm2. a. What is the neural damage limit for this electrode, assuming Shannon’s model applies? Does the maximum output requirement violate the electrochemical safety limit or the neural damage limit? b. Assume the maximum output specification can be expressed in terms of charge density (this will have the same desired effect on the spinal cord). Given that the total charge will decrease as electrode size decreases, how much will charge/ph and electrode size decrease before the maximum output (expressed in charge density) no longer violates the neural damage limit? ...
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This note was uploaded on 06/08/2009 for the course BME 552 taught by Professor Berger,weiland during the Spring '09 term at USC.
- Spring '09