Wirelessly Heating Stents via Radiofrequency Resonance toward Enabling Endovascular Hyperthermia

Abstract

Thermal therapy known as hyperthermia has served as an effective method for cancer treatment. This therapeutic approach has also been attracting attention for treatment of in‐stent restenosis, the most common complication of stenting. Mild heating of stents has been shown to be a possible path to addressing this problem. Despite various studies on stent‐based thermotherapy, this area still lacks a clinically viable method and technology. Here, a radiofrequency‐powered “hot” stent prototype is reported in vitro and in vivo. An implantable stent device based on medical‐grade stainless steel acts as an electrical resonator, or an efficient wireless heater operating only when resonated using tuned external electromagnetic fields. The system architecture uses a custom‐developed power transmitter for wireless resonant powering/heating of the stent. An eight‐shaped antenna is shown to be highly effective for near‐field power transfer to the device and potentially to other smart implants, revealing stent heating efficiencies of up to 120 °C W−1, 206% of the level provided by a conventional loop antenna. Testing with swine models, the prototyped system achieves stent heating in blood flow by powering through air and skin tissue in vivo in a fully controlled manner. The results advance stent hyperthermia technology toward possible future clinical application.

Sensors‐based monitoring and treatment approaches for in‐stent restenosis

“…The related R-WPT-powered stent device was demonstrated by bench tests 29,59 and in an animal model. 60,61 In References [59,60], the external RF excitation system consists of one primary power antenna and seven independent booster antennas. Boost antennas are employed to improve mutual inductance and coupling between transmitter and support device, thus increasing the wireless power transmission efficiency (PTE) and heating efficiency.…”

“…The wireless power transfer efficiency (PTE) and heating efficiency (HE) of the heating‐stent using different powering approaches are presented in the Table 1. The related R‐WPT‐powered stent device was demonstrated by bench tests 29,59 and in an animal model 60,61 …”

“…I G U R E 6 (A) Conceptual diagram of external RF excitation system and its equivalent circuit model for hyperthermia60 ; (B) Transcutaneous wireless heating test of the stent-deployed graft embedded beneath skin tissue in the animal model 61. Source: Adapted from References[60,61] be further increased to satisfy the demands of clinical operations.Enhancements in sensor design, sensor's data transmission ability, and external reader antenna's data receiving ability can extend the working distance. Resonant coupling is an effective method to wirelessly transfer the power, and lowering the power consumption of the active sensor as possible can make long-distance wireless transmission of data and power more feasible.…”

Flex‐circuit resonant chip with Y5V multilayer capacitor for wireless temperature tracking

“…They are designed and microfabricated with planar inductive antennas toward enabling a battery-less, low-cost wireless sensing chip that offers a broad range of potential applications. The physical flexibility and disposable nature of the device are expected to make it well suited for medical/healthcare applications, for example, continuous remote monitoring of patients' body temperature (Figure 1), and feedback control of hyperthermia treatments clinically used for various cancer therapies [8][9][10].…”

Flexible Induction Heater Based on the Polymeric Thin Film for Local Thermotherapy

“…[13,14] For example, magnesium and zinc have been used as bioresorbable components of the electronic circuit [15] and heater, [16] respectively, based on the concept of "transient electronics" in which all of the components are decomposed and disappear by hydrolysis after operating for a certain time. [17] In another example, a vascular stent [18,19] that aligns the resonant frequencies of the radio-feed and receiving side can prevent restenosis by heating the vessel with the wireless power transmission while physically dilating the vessel. This vascular graft connected to a porcine blood vessel increased the local temperature by ≈2 °C in less than 1 min.…”