Research Report 2010 - MDC

Structure of the GroupThoralf NiendorfGroup LeaderProf. Dr. rer.nat Thoralf NiendorfScientistsTobias FrauenrathFabian HezelAndreas Pohlmann (as of 11/09)Davide SantoroLukas Winter (as of 01/10)Graduate StudentsThibaut de Geyer d’Orth (as of 10/09)Nishant PatelJan RiegerMagnetic ResonanceThe group’s research concentrates on the development of MR-methodology and MR techno -logy with a focus on new ways of mapping and probing morphology, function, physiology andmetabolism together with explorations of the benefits and challenges of ultrahigh-field imagingto advance cardiovascular, neurovascular, molecular and other MRI applications. These efforts aredesigned to spatially resolve and characterize (patho) physio logical processes and biophysicalmechanisms to promote a transfer from basic research to (pre)clinical studies and vice versa.However, signal-to-noise ratio (SNR) and imaging speed have become an increasingly stringentlimit in new MRI applications. Promising in this regard is the increase in magnetic field strengthsavailable for both animal (9.4 T) and whole-body MR (7.0 T) scanners, though ultrahigh-field MRIhas earned the moniker of being among the most challenging MRI applications.Myocardial T 2 * MappingEmerging cardiovascular MRI applications include T 2 *relaxation sensitized techniques which are increasinglyused in basic research and (pre)-clinical imaging. Forthese reasons, an imaging strategy that avoids imagedistortions and has the advantage that susceptibilityweighting can be adjusted from zero upwards is anappealing strategy in anatomically accurate T 2 * mappingof the heart. Members of our group patented andestablished a free-breathing, cardiac-gated, susceptibilityweighted fast spin-echo technique in conjunctionwith black blood preparation and navigator gated respiratorymotion compensation. The applicability of thisapproach has been demonstrated in myocardial T 2 *imaging/mapping (Figure 1) at 3.0 T and is now beingtransferred to the 7.0 T whole body scanner and the 9.4T animal system.Development of Novel SynchronizationTechniquesObtaining MRI images of moving organs requires speedand efficiency due to physiological motion and flowconstraints, which dictate the viable window for dataacquisition. Cardiac motion is commonly dealt withusing electrocardiographic (ECG) gating techniques tosynchronize data acquisition with the cardiac cycle. Asultrahigh-field cardiac MRI becomes more widespread,the sensitivity of ECG recordings to interference fromelectromagnetic fields and to magneto-hydrodynamiceffects increases, requiring a practical gating/triggeringalternative. For these reasons, an MR-stethoscope hasbeen proposed and clinically evaluated by members ofour group to successfully meet the demands of cardiactriggered MRI at 7.0 T (Figure 2).Rapid Functional Brain Mapping Free of ImageDistortionThe potential of higher magnetic field strengths forfunctional brain mapping in clinical practice and basicresearch has yet to be fully realized. Here, one importantquestion is the choice of pulse sequence for optimalimage quality in functional brain imaging. EchoPlanar Imaging (EPI) is the most frequently appliedtechnique for fMRI because images may be acquiredrapidly and they are inherently sensitive to BloodOxygen Level Dependent contrast. However, a significantdrawback of EPI is its sensitivity to inhomogeneitiesin B 0 , leading to signal loss and image distortionin regions of spatially varying magnetic susceptibility.These effects are more apparent at high and ultra-46 Cardiovascular and Metabolic Disease Research