Adjacent stimulation and measurement patterns considered harmful

Abstract. We characterize the ability of electrical impedance tomography (EIT) to distinguish changes in internal conductivity distributions, and analyze it as a function of stimulation and measurement patterns. A distinguishability measure, z, is proposed which is related to the signal to noise ratio of a medium and to the probability of detection of conductivity changes in a region of interest. z is a function of the number of electrodes, the EIT stimulation and measurement protocol, the stimulation amplitude, the measurement noise, and the size and location of the contrasts. Using this measure we analyze various choices of stimulation and measurement patterns under the constraint of medical electrical safety limits (maximum current into the body). Analysis is performed for a planar placement of 16 electrodes for simulated 3D tank and chest shapes, and measurements in a saline tank. Results show that the traditional (and still most common) adjacent stimulation and measurement patterns have by far the poorest performance (by 6.9×). Good results are obtained for trigonometric patterns and for pair drive and measurement patterns separated by over 90 ◦. Since the possible improvement over adjacent patterns is so large, we present this result as a call to action: adjacent patterns are harmful, and should be abandoned. We recommend using pair drive and measurement patterns separated by one electrode less than 180 ◦. We describe an approach to modify an adjacent pattern EIT system by adjusting electrode placement

Adler “A phantom based system to evaluate EIT performance

Abstract: This work is motivated by the requirement to generate stable and accurate phantoms on which EIT systems can be calibrated and tested. Such testing is required in order to quantitatively and reproducibly validate EIT system performance. We proposed a phantom system design based on reproducible procedures with completely characterized and traceable test objects. A robotic system was used to reproduce predefined positions of targets in a saline filled tank, and a data analysis system was implemented to evaluate the image reconstruction accuracy and performance. Using this methodology, three EIT hardware systems were tested and compared

Development of a performance calibration system for X-26 Tasers

Conducted Energy Weapons (specifically the Taser) are being increasingly used by police in several countries, and have also been subject to significant media concern over the level of emissions and applicable safety standards. One issue has been the variability in electrical output between weapons, and of individual weapons over time. In order to address this issue, we present work to: 1) establish consensus on the appropriate electrical parameters to characterize a weapon's biomedical effects, and 2) the development and design of a portable test system to measure these parameters. A weapon is electrically connected to a calibrated dummy resistive load of 600 ohms and fired for 5s while the output voltage is measured and the parameters are subsequently calculated. This test system has been used to characterize 256 shots from 84 weapons over 8 test episodes spanning 16 months