51st Heidelberg Physics Graduate Days

APPLICATIONS OF NMR IN BIOMEDICINE

Frank Zöllner

During the last 30 years Magnetic Resonance Imaging (MRI) underwent strong progress with exciting new applications in biomedicine. New MR techniques using gradient echoes, dynamic contrast enhanced MRI, magnetic resonance angiography, blood bolus tagging, and detection of X-nuclei in tissue (3He, 13C, 19F, 23Na, 31P, 37Cl) allow the measurement of important physiological parameters in human tissue. These are diffusion, perfusion, oxygenation, lung ventilation, energy metabolism, with clinical impact in therapy planning and monitoring. Fast imaging techniques can be used to evaluate hemodynamic parameters (blood flow, pulse wave velocity) in humans. At high field strength of > 3.0 Tesla nuclei like sodium offer the possibility to image tissue viability non-invasively by measuring the sodium-potassium pump. Especially in radiotherapy treatment planning, MRI can be used to develop methods for an improved fit of the therapeutic dose to the target volume while bypassing normal tissue and neighbouring organs at risk because of its high soft tissue contrast. Furthermore, the potential of non-invasive functional MRI of brain stimulation offers the possibility of definition of structures at risk in high dose therapy ( e.g. heavy ion therapy). Using powerful gradient system of modern scanners, a successful transfer of interesting measuring techniques from head to body is the focus of actual clinical developments. Thereby, imaging of the human lung is a very challenging topic of today where hyperpolarized 3He can be used for improvement of lung ventilation measurements. In addition, techniques for non-invasive determination of tissue oxygenation and perfusion (T2*- and T1-techniques) can be adapted for studying the myocardial viability, and are of general interest in oncology of moving organs. The lecture covers a brief introduction in the physical basics of NMR and imaging for understanding these new techniques with clinical examples of ongoing clinical studies accomplished by live experiments using a small bore table MRI system operating at 0.5 Tesla at the end of the course.