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Featured researches published by Kim R. Fowler.


Pain | 1992

Automated 'pain drawing' analysis by computer-controlled, patient-interactive neurological stimulation system.

Richard B. North; Daniel J. Nigrin; Kim R. Fowler; Richard Szymanski; Steven Piantadosi

&NA; We have developed a new method for the collection and analysis of pain drawings, as part of a computer‐controlled, patient‐interactive system for use with implanted neurological stimulators. The system has been tested in 44 patients with permanently implanted spinal cord stimulators for the relief of chronic, intractable pain. Patients interact directly with the system, using a graphics tablet, to enter pain drawings and corresponding outlines of their perceptions of stimulation paresthesias, for different stimulating pulse parameters and electrode geometries. Image analysis software has been developed to examine these data quantitatively. This precludes the inter‐rater inconsistencies reported for manual pain drawing scoring techniques. A highly significant correlation has been observed between patients analog ratings of the overlap of pain by paresthesias and the results of our automated analysis of graphic data. This in turn has been found to correlate with clinical observations of pain relief. The contemporary implantable stimulation devices supported by our system permit non‐invasive selection of stimulating anodes and cathodes from a linear array of 4 electrodes. The 50 possible electrode combinations have certain geometric features, which we have entered into a multivariate statistical analysis, to determine their relationship with the overlap of pain by paresthesias. One particular configuration (cathode(s) flanked by anode(s) above and below) is significantly better, by this measure, than all the alternatives. This is consistent with prior clinical observations that this configuration is favored by patients whose systems have been adjusted by conventional, manual methods. ‘Pain drawing’ entry and analysis by a computerized, patient‐interactive system has been useful in this specialized setting and may have broader applications.


Stereotactic and Functional Neurosurgery | 1987

Computer-Controlled, Patient-Interactive, Multichannel, Implanted Neurological Stimulators

Richard B. North; Kim R. Fowler

Programmable implantable neurological stimulation systems with multiple electrodes have many advantages in clinical use, but time-consuming postoperative adjustment of stimulation parameters is a distinct disadvantage. A personal computer interface to standard commercial radiofrequency-coupled devices has been developed, permitting direct patient interaction to expedite this process. In addition, the system permits simulated multichannel operation and implementation of various modulation schemes.


instrumentation and measurement technology conference | 2003

Automatic gain control for image-intensified camera

Kim R. Fowler

Stability of a nonlinear, sampled-data automatic gain control (AGC) for image-intensified cameras is described. The AGC increases the intensifier gain if the video scene is too dim and decreases the gain if the video scene is too bright. Otherwise, the AGC does not alter the gain. The gain of the system is stable, i.e., the gain does not oscillate between two values, for all possible static video scenes if the thresholds for defining both dim and bright scenes and the gain factor are chosen properly. This paper derives the regions for gain stability and provides the criteria for choosing the thresholds and the gain factor.


Brain Research | 1984

Recovery of function following injections of kainic acid: Behavioral, electrophysiological and neuroanatomical correlates

Kim R. Fowler; David S. Olton

This research examined the electrophysiological, behavioral and neuroanatomical changes following an injection of kainic acid (KA) which destroyed most of the CA3 pyramidal cells in the hippocampus. For 5 days following the injection of KA, the evoked potential (EP) in the CA1 pyramidal cells produced by stimulation of the perforant path (PP), dentate gyrus (DG), or remaining CA3 cells was markedly altered. These rats also had an impairment of choice accuracy in a discrimination task that required working memory. Within 30 days, however, all EPs had become more normal. Choice accuracy had either returned to criterion levels, or improved substantially above that immediately following the KA injection. Analysis of the EPs indicated that the normal trisynaptic pathway through the hippocampus had been re-established. Neuroanatomical examination of the remaining CA3 pyramidal cells showed a marked increase in cross-sectional area. These data provide an electrophysiological description of the effects of KA on neuronal transmission in the hippocampus, and suggest that the behavioral recovery following these injections was due to sprouting of the remaining CA3 cells which re-established the trisynaptic pathway in the hippocampus.


international conference of the ieee engineering in medicine and biology society | 1991

Computer-optimized Neurological Stimulation

Kim R. Fowler; Richard B. North

COMPUTER INTERFACE Neurological stimulation alleviates chronic pain by delivering elechid pulses to the nervous system of a pa ti en^ We have developed a compum intexface that optimizes stimulation with commercially avaihble nwostimulatars. For research purposes. the computer and intexfax can deliver arbilrary and uniqw paradigms of stimulation far beyond the current capabiities of neuroStimulators. In clinical practice, the computer and interface provides for patient interaction. optimizes stimulation automatically. and reduces the time spent by health care professionals.


international conference of the ieee engineering in medicine and biology society | 1988

A programmable, arbitrary waveform electrosurgical device

Kim R. Fowler

The programmable electrosurgical device is an arbitrary waveform generator that provides feedback control of selected output variables. A desktop computer provides the human interface and controls the operation of the electrosurgical device. The generated waveform drives an RF amplifier. The electrosurgical device samples the instantaneous voltage and current of the amplifiers output. Any one of several variables-voltage, current, power, or impedance-may be selected for feedback control.<<ETX>>


instrumentation and measurement technology conference | 2004

System design that minimizes both missed detections and false alarms: a case study in arc fault detection

Kim R. Fowler; H.B. Land

This paper considers several components in the architecture and design of systems to discriminate conditions and fuse the data. It focuses on the problems of missing detections and reducing the possibility of generating false positive alarms. It uses a case study of a protective system that detects arcing faults in power switchboards on board ships. The results in this paper can be used in many systems that must monitor and detect hazardous events both accurately and consistently while minimizing false positive alarms that can cause harmful results. Examples include power plants, hospitals, computer installations, web servers, military sensors that detect enemy vehicles, aircraft engine monitoring, and telecommunications.


instrumentation and measurement technology conference | 1998

Instrumentation for ballistic missile defense: lessons learned from the LEAP experiment

Kim R. Fowler

Integrating instrumentation into complex systems demands careful planning, execution, and testing. Ballistic missile defense is a complex system with many distributed components: radar and imaging sensors, wireless and satellite communications, digital signal processing nodes, interceptor fire control, and command centers. The U.S. Navy has investigated the feasibility of missile defense through the Light Exo-Atmospheric Projectile (LEAP) experiment. This paper explains the lessons learned by The Johns Hopkins University Applied Physics Laboratory from building, integrating, and testing instrumentation in the LEAP experiment and gives insights for designing complex systems. The biggest challenge in the LEAP experiment involved people: communications between the large number of contractors and their understanding of the interactions between the various instruments. Other concerns included verifying software and system operation, robust data and satellite communications, time and coordinate conversions, and electromagnetic interference. LEAP demonstrated that complex systems and missile defense system in particular, can only work through careful design, dedicated teamwork, clear and continuous communications, and extensive testing.


instrumentation and measurement technology conference | 2003

Space environment testbed (set): adaptable system for piggybacked satellite experiments

Kim R. Fowler; Laurence J. Frank; Robert L. Williams

This paper introduces the concept of a flexible, adaptable subsystem for satellites that provides a platform for space-based experiments. The subsystem, called a carrier, comprises mechanical, electrical/electronic, thermal, data, and software components. We have performed a number of tradeoff studies and recommend a general type of architecture for the carrier that will satisfy many requirements and accommodate the constraints of space-based experimentation.


instrumentation and measurement technology conference | 2004

Transient response for automatic gain control with multiple intensity thresholds for image-intensified camera

Kim R. Fowler

This paper describes the transient response of an automatic gain control (AGC) with multiple thresholds for intensity in an image-intensified camera. Similar examples have flown in intensified-video systems used in satellites. The paper develops a stable AGC with an improved transient response over the system described in previous work. The improved transient response uses the integrated scene brightness at various intensity thresholds.

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David S. Olton

Johns Hopkins University

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H.B. Land

Johns Hopkins University

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Daniel J. Nigrin

Boston Children's Hospital

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Steven Piantadosi

Cedars-Sinai Medical Center

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