Finnish imaging project to promote MRI guidance for minimally invasive procedures

Oulu 21 February 2001The Oulu University and Hospital in Finland are partnering with the London Imperial College of Science, Medicine, and Technology and with two technology partners, the German company Daum and Marconi Medical Systems Finland Oy, in a project focusing on Advanced Minimally Invasive Therapy (AMIT) procedures, utilising improved magnetic resonance imaging (MRI) techniques. The initiative which receives funding from the European Commission, started on January 1, 2000 and will last for 30 months. The AMIT project will address and try to solve some of the crucial shortcomings in the current "state-of-the-art" of MRI-guided interventions.

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Within the field of minimally invasive surgery where an excellent image guidance is of the utmost importance, today's most popular imaging modalities are x-ray fluoroscopy, ultrasound, and optical endoscopy. The use of MRI however includes a variety of clinical benefits ranging from a good soft tissue contrast and a superior lesion sensitivity to patient-safe non-radiation qualitative imaging. The AMIT researchers want to promote the application of MRI in minimally invasive procedures by overcoming the typical weaknesses in this powerful imaging modality. As a result, the AMIT team aims to design innovative tools for accurate, reliable instrument tracking and for adequate visualisation, as well as to develop an interactive and intuitive user interface and to use preoperative images together with intra-operative real time visual data.

In fact, MRI is not a real time imaging method. It is possible to obtain images within one second but often a much longer scanning time is needed in order to acquire high-quality images. If the AMIT partners succeed in developing a means for combining intra-operative real time images with pre-operative data of superior quality, the latencies for image acquisition can be alleviated. The University of Oulu will develop an operation driven user interface which will help the surgeons interact with and control the interventional image-guided surgery system to accurately position the instrument tip inside the patient's body.

In the AMIT project, a novel technology will be developed for instrument tip localisation in MRI, based on electron spin resonance (ESR) to measure the magnetic field. This innovative approach enables the miniaturisation of the measurement probe making it small enough to fit into the tip of a practical instrument. The ESR marker technology will facilitate the tracking of biopsy needles and catheters. Nonetheless, instrument tip location is not always sufficient, when highly flexible instruments such as catheters, are inserted into a patient's body. Therefore, Nuclear Magnetic Resonance (NMR) profiling and Overhauser profiling will be applied for tracking profiles of catheters.

The technique consists in measuring a proton signal from the vicinity of the catheter with use of a special purpose RF antenna. The acquired signal is processed after which the catheter profile is automatically reconstructed. As such, the entire instrument can be tracked down interactively through the patient's body during an operation. Using the ESR, NMR, and Overhauser technologies, it becomes possible within MRI-guided procedures to perform accurate and safe needle biopsies, and drainage of abscesses, and to monitor the temperature during thermal ablation of tumours.

In this regard, the AMIT partners intend to also develop sample applications for operations performed under MRI guidance with needles and catheters. The aim is to advance the clinical state-of-the-art, as well as to promote the usage and marketing of interventional MRI via good reference procedures. The team expects the AMIT project to serve as a vehicle for a more frequent use of MRI as a guidance method for minimally invasive procedures. More technical details and information about the project are available at the AMIT Web site.


Leslie Versweyveld

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