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This paper reports the first in vivo testing of a resonant-heating stent toward wireless hyperthermia treatment of in-stent restenosis. The stent, made of gold-coated medical-grade stainless steel, is designed to function as an electrical inductor and forms a radiofrequency (RF) resonant circuit with an integrated capacitor microchip. Upon implantation and deployment with the balloon catheter, the stent device serves as a wireless heater as part of the resonant wireless power transfer system, which allows for the device to produce mild heat only when the stent is resonated with a tuned RF electromagnetic field supplied from the external antenna. The wireless power transmitter includes an independent omnidirectional booster antenna that enhances the power delivery to the implanted stent device. The entire stent device is packaged with 40-μm-thick Parylene C film that is shown to be essential for minimizing electrothermal damping in a conductive liquid like blood. The in vitro tests of the prototype system show a temperature increase of 3.3 °C in the stent device couple in a flow loop of saline pumped at a flow rate relevant to the condition of coronary stenosis. In swine models, the system demonstrates RF heating of the stent devices expanded to different diameters, in live blood stream, achieving temperature rises of up to 2.6 °C in a consistent and repeatable manner. These results bring the technology one step closer toward clinical realization of wireless thermal therapy of in-stent restenosis. [ABSTRACT FROM AUTHOR]

• Wirelessly powered "hot" stent is investigated for hyperthermia restenosis treatment. • Inductive stent device acts as resonant heater activated with external RF field. • Resonant mechanism offers 102× higher heating efficiency than non-resonant heating. • Optimized coatings on inductive stent is key to effective resonant heating in saline. • Wireless heating in flow of saline at stenotic flow rate is demonstrated in vitro. In-stent restenosis remains the most common problem with stent implantation. Hyperthermia therapy through moderate heating of implanted stent is expected to be an effective treatment for restenosis. Toward this goal, this work investigates a wirelessly powered resonant-heating stent device, with a focus on design improvement and experimental analyses of power transfer and electrothermal behaviors of the developed prototype. The stent device, configured to form a passive resonator with a capacitor-integrated inductive stent, is coated with optimized layers of gold and Parylene C to raise the quality factor and heating performance of the device. Wireless testing of the device deployed in artificial artery shows its promising thermal performance in physiological saline with a flow rate relevant to stenotic blood flow, while revealing clear merits of resonant-based heating with up to ˜220× and ˜40× higher heating rates compared with off-the-resonance conditions in air and saline flow, respectively. The results are used to evaluate wireless heating efficiency, as well as the effects of saline temperature and flow rate on the device performance along with other parameters. The study will pave the path to further design optimization and performance improvement for resonant stent technology towards its application to wireless thermal treatment of in-stent restenosis. [ABSTRACT FROM AUTHOR]