Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2003-05-22
2004-05-04
Hoang, Tu Ba (Department: 3742)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S059000
Reexamination Certificate
active
06731986
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to implantable stimulators, e.g., an implantable neural stimulator, and more particularly to a system and method for programming the magnitude (e.g., amplitude) of the stimulation pulses that are generated by such neural stimulator. The invention may be used with a wide variety of neural stimulators, e.g., spinal cord stimulators, brain stimulators, urinary incontinence stimulators, cochlear stimulators, and the like.
Neural stimulation systems of the type with which the present invention may be used are described in the art, e.g., in U.S. Pat. No. 5,603,726. Such stimulator systems typically include: (1) an implantable pulse generator; (2) an electrode array connected to the implantable pulse generator; and (3) some means, e.g., an external programmer, for controlling or programming the implantable pulse generator. In operation, the implantable pulse generator generates an electrical stimulation pulse, or pulse sequence, in accordance with a prescribed pattern or stimulation strategy. Each pulse may be programmed or set to a desired magnitude (amplitude and/or pulse width), and applied at a set or programmed rate (or frequency) to surrounding body tissue through a selected pair or grouping of electrode contacts of a multiple electrode array.
U.S. Pat. No. 5,895,416 teaches one type of method and apparatus for controlling and steering an electric field. The '416 patent steers the size and location of the electric field in order to recruit only target nerve tissue and exclude unwanted nerve tissue. Such steering is done by changing the voltage amplitude at each anode in response to changes in electrode impedance of an electrode array in order to maintain a constant anodic current.
Unfortunately, programming implantable stimulators that have multi-electrode contacts can be a very time consuming task. This is particularly true for a spinal cord stimulation system, or similar system, where there are typically 8 to 16 electrode contacts on the electrode array through which the stimulation pulses are applied to the spinal nerves. With 8 to 16 electrode contacts there are thousands and thousands of possible electrode combinations. The goal of programming a spinal cord stimulator, or similar neural stimulator, is to figure out which electrode combinations of the thousands that are possible should be used to apply electrical stimulus pulses (each of which can theoretically be programmed to have a wide range of amplitudes, pulse widths, and repetition rates) so as to best serve the patient's needs. More particularly, the goal of programming a spinal cord stimulator, or other neural stimulator, is to optimize the electrode combination of anodes and cathodes, as well as the amplitude, pulse width and rate of the applied stimulation pulses, so as to allow the stimulator to best perform its intended function, e.g., in the case of a spinal cord stimulator, to relieve pain felt by the patient. The manual selection of each electrode combination and the stimulus parameters that are used with such electrode combination (where the “stimulus parameters” include amplitude, pulse width, and repetition rate or frequency) is an unmanageable task. What is needed is a system and method for programming a neural stimulator, such as a spinal cord stimulator, that automates much of the programming process using interactive programs, and in particular wherein the amplitude of the applied stimulus may be programmed in a way that facilitates the use of automated and interactive programs safely and effectively.
A disadvantage associated with many existing neural stimulators is that such systems cannot independently control the amplitude for every electrode in a stimulating group of electrodes, or “channel”. Thus, stimulation fields cannot be highly controlled with multiple stimulating electrodes. Instead, a constant voltage is applied to all electrodes assigned to stimulate a target site at any given time (wherein the electrodes thus assigned are referred to as a “channel”). While such approach may make programming such stimulator a much more manageable task (because the number of possible electrodes and parameter choices are severely limited), such limitations may prevent the stimulator from providing the patient with an optimal stimulation regimen. What is needed, therefore, is a neural stimulator wherein all of the possible electrode combinations and parameter settings can be used, and wherein a programming technique exists for use with such neural stimulator whereby an optimum selection of electrode combinations and parameters settings may be quickly and safely identified and used.
To illustrate the problem that a clinician or other medical personnel faces when programming a typical neural stimulator wherein each electrode on an electrode array may be tested, consider the following example. The clinician typically performs an electrode test in terms of the patient's response, e.g., by selecting a set of electrodes (assigning anodes and cathodes), setting a pulse width and rate, and by then increasing the amplitude until the patient begins to feel stimulation. The clinician continues to increase the stimulation amplitude until the stimulation is strongly felt, and then the patient is asked the location where the stimulation is felt. The stimulation is then turned off and the steps are repeated for the next electrode set, until the clinician has a good map of the stimulation coverage by an electrode array. Disadvantageously, however, the clinician cannot simply jump from one set of electrodes within the array to a next set of electrodes within the array and back again while the stimulation is turned on because the perception thresholds vary. What is needed is a system or apparatus that does not require that the clinician turn off the stimulation and start over, increasing the amplitude for each electrode set, but rather allows the clinician to compare back and forth between electrode sets while continuously obtaining patient feedback. What is further needed is a system or apparatus wherein the clinician does not have to start over every time he or she repeats a formerly-tested electrode set. Unfortunately, with current programming approaches, because there is no means to automatically adjust the magnitude of stimulation, the clinician must start over every time another electrode set is selected.
The threshold ranges derived from such clinician tests usually vary from one electrode to the next. That is, at a given pulse width the perception threshold at a first electrode may be 2 milliamps (mA), (or 2 volts (V) at 1000 ohms), with a maximum tolerable threshold of 7 mA (or 7 V at 1000 ohms). At that same pulse width, the perception threshold at a second electrode may be 3 mA (or 3 V at 1000 ohms), with a maximum tolerable threshold of 6 mA (or 6 V at 1000 ohms). Thus, switching from one electrode to the next at a constant current or voltage level may not be done without the patient feeling perceptual intensity differences. Moreover, automatically switching between electrodes at constant parameter outputs could result in unintentionally exceeding the maximum tolerable threshold associated with a particular electrode where the maximum tolerable threshold of the electrode is less than the maximum tolerable threshold of another electrode. As a result, the typical method for testing electrode combinations, as described above, is to start with the output at zero for every combination of electrodes (including combinations which result in too many combinations to test), and gradually increase the amplitude to a comfortable level, and then have the patient respond to paresthesia or other coverage. No quick or rapid electrode switching can be done. It is thus evident that what is needed is a system and method of equalizing the perceived amplitude, and to thereby enable quick, automated, and/or interactive (i.e., directional programming) methods.
SUMMARY OF THE INVENTION
The present invention addresses the above and other needs by providing a system
Advanced Bionics Corporation
Gold Bryant R.
Hoang Tu Ba
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