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Nonclercq A.,Roosevelt University | Lonys L.,Roosevelt University | Vanhoestenberghe A.,Implanted Devices Group | Demosthenous A.,Malet Place Engineering Building | Donaldson N.,Implanted Devices Group
Medical and Biological Engineering and Computing | Year: 2012

One reason given for placing capacitors in series with stimulation electrodes is that they prevent direct current flow and therefore tissue damage under fault conditions. We show that this is not true for multiplexed multi-channel stimulators with one capacitor per channel. A test bench of two stimulation channels, two stimulation tripoles and a saline bath was used to measure the direct current flowing through the electrodes under two different single fault conditions. The electrodes were passively discharged between stimulation pulses. For the particular condition used (16 mA, 1 ms stimulation pulse at 20 Hz with electrodes placed 5 cm apart), the current ranged from 38 to 326 lA depending on the type of fault. The variation of the fault current with time, stimulation amplitude, stimulation frequency and distance between the electrodes is given. Possible additional methods to improve safety are discussed. © International Federation for Medical and Biological Engineering 2012. Source


Annkah J.K.,Malet Place Engineering Building | Annkah J.K.,Ghana Atomic Energy Commission | Rosenberg I.,Malet Place Engineering Building | Rosenberg I.,University College London | And 5 more authors.
Journal of Medical Physics | Year: 2014

The dosimetric accuracies of CATPhan 504 and CIRS 062 have been evaluated using the kV-CBCT of Varian TrueBeam linac and Eclipse TPS. The assessment was done using the kV-CBCT as a standalone tool for dosimetric calculations towards Adaptive replanning. Dosimetric calculations were made without altering the HU-ED curves of the planning computed tomography (CT) scanner that is used by the Eclipse TPS. All computations were done using the images and dataset from kV-CBCT while maintaining the HU-ED calibration curve of the planning CT (pCT), assuming pCT was used for the initial treatment plan. Results showed that the CIRS phantom produces doses within ±5% of the CT-based plan while CATPhan 504 produces a variation of ±14% of the CT-based plan. © 2014 Journal of Medical Physics. Source

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