Browsing by Subject "Heating reduction"

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    RF Safety of Active Implantable Medical Devices
    (John Wiley & Sons, Ltd. All rights reserved., 2019) Silemek, Berk; Açıkel, V.; Atalar, Ergin; Harris, R.K.; Wasylishen, R.L.
    The radiofrequency (RF) safety of active implantable medical devices (AIMDs) during an magnetic resonance imaging (MRI) scan is discussed in this article. The problem arises from the RF interaction of an AIMD with the MRI scanner is presented. The researchers simulated and modeled to understand the problem. They also developed techniques to resolve the RF safety problem by altering the design of AIMDs. Furthermore, implant friendly imaging solutions are developed. Validated the findings novel in vivo techniques. Clinical investigations are carried out to understand the extent of the problem. In this article, an incomplete summary of the investigations in this field is given.
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    ItemOpen Access
    A temperature sensor implant for active implantable medical devices for in vivo subacute heating tests under MRI
    (John Wiley and Sons, 2018) Silemek, B.; Açıkel, V.; Oto, C.; Alipour, A.; Aykut, Z. G.; Algın, O.; Atalar, Ergin
    Purpose: To introduce a temperature sensor implant (TSI) that mimics an active implantable medical device (AIMD) for animal testing of MRI heating. Computer simulations and phantom experiments poorly represent potential temperature increases. Animal experiments could be a better model, but heating experiments conducted immediately after the surgery suffer from alterations of the thermoregulatory and tissue properties during acute testing conditions. Therefore, the aim of this study was to introduce a temperature sensor implant that mimics an AIMD and capable of measuring the electrode temperature after implantation of the device without any further intervention at any time after the surgery in an animal model. Methods: A battery-operated TSI, which resembled an AIMD, was used to measure the lead temperature and impedance and the case temperature. The measured values were transmitted to an external computer via a low-power Bluetooth communication protocol. In addition to validation experiments on the phantom, a sheep experiment was conducted to test the feasibility of the system in subacute conditions. Results: The measurements had a maximum of 0.5°C difference compared to fiber-optic temperature probes. In vivo animal experiments demonstrated feasibility of the system. Conclusion: An active implant, which can measure its own temperature, was proposed to investigate implant heating during MRI examinations. Magn Reson Med 79:2824-2832, 2018.
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    ItemOpen Access
    Wireless control of induced radiofrequency currents in active implantable medical devices during MRI
    (International Society for Magnetic Resonance in Medicine, 2020) Açıkel, V.; Silemek, Berk; Atalar, Ergin
    Purpose To introduce a prototype active implantable medical device (AIMD) for which the induced radiofrequency currents can be controlled wirelessly. Methods The modified transmission line method is used to formulate how the lead‐case impedance of an AIMD affects the temperature rise around the electrode. A prototype AIMD is designed with the aim of controlling the unwanted temperature rise around its electrode during an MRI examination by altering the impedance between the lead and the case of the implant. MRI experiments were conducted with this prototype implant, which also has a built‐in temperature sensor at its electrode. During the experiment, the implant’s lead‐case impedance was controlled using Bluetooth communication with a remote computer, and the lead tip temperature was recorded. Results Ten different lead‐case impedance values and their corresponding tip temperature rises were examined during MRI experiments. The experimental results confirmed that the tip temperature rise can be controlled by varying the lead‐case impedance wirelessly. Conclusion The feedback from the temperature at the AIMD tip, together with variable lead‐case impedance, enables control of the safety profile of the AIMD during an MRI examination.