Philips Research Technology Backgrounder
Quantitative MRI |
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Philips is currently developing fast quantitative Magnetic Resonance
(MR) acquisition and data-analysis techniques for molecular-imaging
applications. MRI, a non-invasive imaging method without ionizing
radiation and with excellent depiction of internal organs, offers
the required sensitivity and precision to detect targeted contrast
agents that play an important role in molecular imaging. Evaluation
of the new techniques in collaboration with luminary clinical sites
like the University Hospital Münster, Germany, the National
Institutes of Health (NIH) in Bethesda, USA, and the Washington
University in St. Louis, USA, has shown that quantitative MRI is
indeed a powerful tool for the early assessment of diseases and for
monitoring the effects of therapy in follow-up studies. Moreover, by
non-invasive measurements of drug effects, quantitative MRI can
speed up the development and approval of drugs.
A fast developing field in diagnostic imaging, molecular imaging provides early detection of pathological processes associated with disease at the cellular and molecular level rather than at anatomical level as in ‘classical’ diagnostic imaging. Key to molecular imaging is the development of targeted contrast agents that bind selectively to specific molecules. In addition, the quantification of molecular imaging agents is crucial for assessing disease progression or regression after therapy. In order to detect the small amounts of contrast agent involved, highly sensitive and precise imaging techniques are required. In this respect, MRI, as a non-invasive imaging method without ionizing radiation and with excellent depiction of internal organs, is expected to play an important role. To further extend the role of MRI as a molecular imaging tool, scientists at Philips Research are currently developing fast quantitative MR acquisition and data-analysis techniques for the determination of absolute contrast agent concentrations. With MRI, the influence of contrast agents on the relaxation rates of the MR signal (which provides the imaging information) is proportional to their local concentrations. Therefore, Philips is specifically focusing on developing tools to measure the values and changes of these relaxation rates. Philips has implemented fast, robust and easy-to-use fitting and correction software tools for the generation of relaxation rate maps. These tools correct for artifacts arising from local variations of the main magnetic field without lengthening the measurement time of the MR exam. These so-called ‘susceptibility artifacts’, which can obscure the measurement of exact contrast agent concentration, occur even with a perfectly homogeneous MR system due to the magnetic properties of the patient’s body introducing local field changes. The techniques have been evaluated in collaboration with luminary clinical sites, such as the University Hospital Münster, Germany, the National Institutes of Health (NIH) in Bethesda, USA, and the Washington University in St. Louis, USA, to test their effectiveness with newly-developed targeted agents in pre-clinical trials and also with clinically-approved contrast agents on patients. The results strongly support the conviction that quantitative MRI offers high potential as a tool for the improvement of diagnosis and staging of diseases, as well as for monitoring of treatment response. |
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