New Insights into MR Safety for Implantable Medical Devices

Evidence-based recommendations for comprehensive regulatory guidelines in medical devices: the imperative for global harmonization

The medical device industry has experienced a significant upsurge in the number, diversity, and complexity of devices over the last two decades. As the global demand for medical devices grows, regulatory frameworks across major economies, including the USA, Europe, India, China, and Australia, have evolved to ensure safety, quality, and efficacy. This review critically examines the regulatory guidelines for medical devices across these regions, emphasizing the need for harmonization to streamline approval processes and reduce regulatory barriers. While countries like the USA and Europe have well-established regulatory systems-such as the Food and Drug Authority (FDA) and European Medicines Agency (EMA)-other nations, including India, are rapidly advancing their frameworks, as seen with the introduction of the Indian Medical Device Rules, 2017, and subsequent amendments. Global initiatives, such as the Global Harmonization Task Force (GHTF), Central Drug Standard Control Organisation (CDSCO), EU Medical Device Regulations (MDR), In Vitro Diagnostic Regulation (IVDR), and the International Medical Device Regulators Forum (IMDRF), have made strides in fostering collaboration, yet disparities remain. Harmonized regulations would mitigate challenges related to device registration, manufacturing, and post-market surveillance, expediting access to high-quality, safe medical devices. The review also highlights the growing prevalence of drug-device combination products, their regulatory complexities, and the importance of aligning regulatory practices globally. A harmonized regulatory framework is essential to promote innovation, reduce duplication of work, and ensure the timely availability of medical devices to patients in need. This review explores the evolution of medical devices from ancient practices to modern technologies, emphasizing projected market growth and the need for regulatory harmonization to facilitate innovation and access. It also assesses how emerging technologies are shaping future regulatory frameworks.

Updates on the MR safety guidelines - Essentials for radiologists

Magnetic Resonance Imaging (MRI) is a sophisticated diagnostic tool that utilizes the magnetic properties of biological tissue to generate detailed images of internal structures without the use of ionizing radiation. Despite its benefits in providing high-contrast images of soft tissues, the strong magnetic fields used in MRI present a unique safety challenge. Increasing MRI-related accidents and the prevalence of patients with metallic implants in recent years underscore the critical need for stringent MR safety protocols. This article reviews the latest 2024 updates in the MRI safety manual by the American College of Radiology (ACR), highlighting the comprehensive efforts to manage risks associated with MRI, including projectile and burn incidents, patients with medical devices, and emerging complex MRI environments. The manual emphasizes the importance of specialized training for healthcare professionals to navigate the complexities of MRI safety to ensure patient and staff safety. This review also touches on the dynamic landscape of MRI safety standards, driven by technological advances and evolving clinical practices, aiming to provide a thorough understanding of current best practices in MRI safety management. LIST OF UPDATES.

MRI of Implantation Sites Using Parallel Transmission of an Optimized Radiofrequency Excitation Vector

Postoperative care of orthopedic implants is aided by imaging to assess the healing process and the implant status. MRI of implantation sites might be compromised by radiofrequency (RF) heating and RF transmission field (B1+) inhomogeneities induced by electrically conducting implants. This study examines the applicability of safe and B1+-distortion-free MRI of implantation sites using optimized parallel RF field transmission (pTx) based on a multi-objective genetic algorithm (GA). Electromagnetic field simulations were performed for eight eight-channel RF array configurations (f = 297.2 MHz), and the most efficient array was manufactured for phantom experiments at 7.0 T. Circular polarization (CP) and orthogonal projection (OP) algorithms were applied for benchmarking the GA-based shimming. B1+ mapping and MR thermometry and imaging were performed using phantoms mimicking muscle containing conductive implants. The local SAR10g of the entire phantom in GA was 12% and 43.8% less than the CP and OP, respectively. Experimental temperature mapping using the CP yielded ΔT = 2.5-3.0 K, whereas the GA induced no extra heating. GA-based shimming eliminated B1+ artefacts at implantation sites and enabled uniform gradient-echo MRI. To conclude, parallel RF transmission with GA-based excitation vectors provides a technical foundation en route to safe and B1+-distortion-free MRI of implantation sites.

Study on TiO2 Nanofilm That Reduces the Heat Production of Titanium Alloy Implant in Microwave Irradiation and Does Not Affect Fracture Healing

Background

Metal implants can produce heat and damage adjacent tissues under microwave irradiation, which makes local metal implants in the body a contraindication for microwave therapy. However, with the wide application of titanium alloy implants which have low permeability and low conductivity, this concept has been challenged. Our team members have confirmed through previous research that continuous low-power microwave irradiation does not cause thermal damage to the surrounding tissues of the titanium alloy. Is there any other way to further increase the dose of microwave irradiation while reducing the heat production of titanium alloy implants? In this study, the effect of TiO₂ nanofilm on reducing the heat production of titanium alloy implants in microwave field was verified by animal experiments, and the effect of TiO₂ nanofilm on fracture healing was observed.

Methods

30 rabbits were selected. In the experiment of temperature measurement, 10 rabbits were randomly divided into experimental group (n = 5) and control group (n = 5), and the contralateral lower limb of the rabbits in experimental group was set as the sham operation group. The right femurs in the experimental group were implanted with Ti6Al4V plates coated with TiO₂ nanofilm, and the right femurs in the control group were implanted with common titanium alloy plates without TiO₂ nanofilm. The same surgical procedure was used in the sham operation group, but no plate was implanted. The temperature of the deep tissue above the metal implant was measured with an anti-interference thermocouple thermometer during 20 minutes of microwave irradiation. The other 20 rabbits were randomly divided into two groups, experimental group (n = 10) and control group (n = 10). The femoral shaft fracture models were established again. Ti6Al4V plates coated with TiO₂ nanofilm and common titanium alloy plates were implanted in the two groups, respectively, and both groups were exposed to continuous microwave irradiation with a power of 40 W or 60 W for 30 days after operation. The fracture healing was evaluated by X-ray at 0 day, 14 days, and 30 days after microwave irradiation, respectively. The animals were sacrificed at 30 days after operation for histopathological assessment.

Results

The temperature in the experimental group, control group, and sham operation group increased significantly after 40 W and 60 W microwave irradiation (2.18 ± 0.15°C~6.02 ± 0.38°C). When exposed to 40 W microwave, the temperature rise of the control group was 4.0 ± 0.34°C, which was significantly higher than that of the experimental group 2.82 ± 0.15°C (P < 0.01) and the sham operation group 2.18 ± 0.33°C (P < 0.01). There was no significant difference in temperature rise between the experimental group and the sham operation group (P = 0.21). When exposed to 60 W microwave, the temperature rise of the control group was 6.02 ± 0.38°C, which was significantly higher than that of the experimental group 3.66 ± 0.14°C (P < 0.01) and sham operation group 2.96 ± 0.22°C (P < 0.01), and there was no significant difference between the experimental group and the sham operation group (P = 0.32). X-ray evaluation showed that there was no significant difference in callus maturity between the experimental group and the control group at 14 days (P = 0.554), but there was significant difference in callus maturity between the two groups at 30 days (P = 0.041). The analysis of bone histologic and histomorphometric data at 30 days was also consistent with this.

Conclusion

Under the animal experimental condition, compared with the common titanium alloy implant, the TiO₂ nanofilm can reduce the heat production of the titanium alloy implant in the 2450 MHz microwave field and has no adverse effect on fracture healing. This study opens up a promising new idea for the application of microwave therapy to metal implants in human body.