Magnetic Resonance Imaging (MRI) is an indispensable tool in modern medicine with around 23 million patient examinations in the EU each year and an excellent safety record. However, some new advances in MRI scanning have not yet made it into hospitals because of unresolved safety issues for both patients and medical staff.
The EMRP project HLT06 Metrology for nextgeneration safety standards and equipment in MRI improved risk assessments for next generation of MRI scanners, which are using 7 Tesla magnetic fields, providing more complete and robust safety data for both patients and medical staff. The project has enabled better image quality, improved diagnoses and shorter scan times; and evaluated safety margins for patients with metal implants.
- Developed traceable measurement methods for RF electromagnetic fields for determining absorbed RF power generated by 7 Tesla MRI scanners and used these to validate patient body simulations.
- Calculated the Specific Absorption Rates (SAR) and temperature increases for different examples, demonstrating that the temperature increase in the tissue was less than expected due to internal cooling mechanisms and much safer for the patient than expected.
- Confirmed that there no violations of regulatory limits under normal clinical working conditions for staff working near an MRI scanner either in the low frequency or radio-frequency (RF) ranges.
- Established that the photons for targeted radiation therapy are not affected by the magnetic field of an MRI scanner which allows the two techniques to be used simultaneously.
- Used simulations and sensors to measure the tissue temperature close to different shaped metal implants and found that this can pose a risk to patients. Careful risk assessment is required for safe MRI scanning of patients with metal implants.
The project demonstrated that the levels of both low frequency and RF fields near MRI scanners are safe, which will facilitate the routine clinical use of high magnetic field 7 Tesla MRI scanners. Philips, a key European MRI manufacturer is already using the research findings, tools and techniques to assess the performance of a novel measurement method being incorporated into its new scanners. This will help clinicians make more accurate risk assessments for patients with implants, who are not currently able to benefit from MRI scans. Philips, working in partnership with Elektra, has used the projects portable calibration device in an MRI-targeted external radiotherapy machine to enable traceability to the SI.