Flexible multi-purpose coil array for high resolution 7T MRI (FLEXAR7)

Magnetic resonance imaging has become one of the major tools in non-invasive medical diagnostics, providing a multitude of quantitative and functional information with ever increasing performance. For applications demanding very high spatial or temporal resolution, sensitivity and, thus, image quality frequently becomes the limiting factor. To improve sensitivity, MR scanners with a higher static magnetic field may be employed, the performance of the radio frequency detection systems can be enhanced or more efficient image acquisition and reconstruction methods can be developed. The scientific objective of this multi-disciplinary project is the combination of all these strategies to outperform currently available technologies for ultra-high resolution (<100 m) MRI in humans. The biomedical application concerns imaging of joint injuries, nerve damage, and early detection of bony erosions in chronic polyarthritis. The technological objective represents a major instrumental innovation in the form of a flexible, highly sensitive RF coil array comprising 32 miniature coil elements with diameters of 2-3 cm for imaging in a 7T whole-body scanner. By its flexibility, the array can be form-fitted to the target organ`s shape, rendering it a highly sensitive multi-purpose instrument for various anatomical sites. The detection system to be developed will be based on the monolithic transmission line resonator principle. It will be designed by numerical simulation and fabricated on flexible Teflon substrate. Concurrently, electronic circuitry and imaging protocols will be developed. Electromagnetic characterization on the bench will be carried out and imaging performances of will be determined to evaluate the added diagnostic value. The final output of the project is an innovative, high-sensitivity detection system and optimized acquisition protocols for 7T MRI allowing 3D-visualization of joint and nerve structures in vivo, at scales undetectable up to now. The project is thoroughly structured in four tasks to ensure efficient parallel advances in instrumental and methodological work. Back-up solutions for critical tasks guarantee the timely accomplishment of the project aims. We put in synergy the multi-disciplinary and complementary competences of the laboratory of Imagerie par Résonance Magnétique Médicale et Multi-Modalités (IR4M, Université Paris-Sud, Orsay, France) and of the Magnetic Resonance Center of Excellence (MRCE, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria). This consortium has been specifically assembled to address all essential questions arising in the context. The combination of the strong expertise of IR4M in methodology and instrumentation for MRI and the internationally outstanding experience of MRCE in ultra-high field MR micro- imaging unique regroups scientific and technological knowledge perfectly matching this highly ambitious project. The sensitivity improvement achieved in this project is essential for the diagnostics of joint and nerve pathologies and will also benefit other biomedical applications of MRI for demanding high detection sensitivity, such as investigations in cardiology, dermatology and neurosciences.

Magnetic Resonance Imaging (MRI) grants valuable insights in the human body and allows early detection of disease. For the acquisition of the images, in addition to the magnet bore, so-called coils are required. The data quality these devices can deliver is increased when they are closely fit to the area of the body to be examined. The research project FLEXAR7 was concerned with the development of such coils with the particularity that they are constructed in a mechanically flexible fashion. This allows them to tightly adapt to the contours of the body. Also, these coils are used with MR scanners exhibiting a very high magnetic field (3 and 7 Tesla), additionally increasing the measured signal. Exploiting the gained data quality, the measurement can deliver more detailed images and/or the measurement time can be reduced. Within the framework of an Austrian-French collaboration, the research teams around Dr. Elmar Laistler (Medical University of Vienna) and Dr. Jean-Christophe Ginefri (University Paris South) have developed a method, how such flexible coils can be produced. The essential technological advancement consists in the use of structures that do not require discrete components or solder joints. By prior calculation, the geometry can nonetheless be chosen in a way to achieve the desired resonance frequency. In this project, the technique has been applied to a coil for cardiac imaging, a multi-purpose coil for detailed examination of the brain and various joints, as well as a coil for MR microscopy of tissue samples. The essential idea of coil flexibility from the successfully completed FLEXAR7 project is being continued jointly by both research groups, together with a third group around Prof. Jacques Felblinger (University of Nancy/Lorraine, France) within a next, already granted research project. Its goal is the development of a soft, flexible vest to be used for breast cancer diagnosis using MRI.