No abstract

Modified gradient-echo MR techniques were applied to study the effects of inflow on functional brain imaging studies using visual and motor cortex stimulation. The results demonstrate that the large signal changes, seen in previously reported gradient-echo studies at 1.5-2.0 T, are dominated by direct inflow effects, in particular when using a large flip angle and a thin slice. The findings suggest that inflow-based functional imaging, along with Blood Oxygenation Level Dependent (BOLD) functional MRI, may play an important role in future research towards the functional organization of the human brain.

Since image acquisition times in MRI have been reduced considerably over recent years, several new important application areas of MRI have appeared. In addition to pure static anatomic information, the evolution of a dynamic process may be visualized by a sequence of temporal snapshots of the process acquired within a short time period. This makes applications like interactive or interventional MRI as well as the acquisition of additional functional information feasible. For high temporal resolution, all these applications require a quasi real-time image acquisition during the time the interaction or dynamic process evolves. We present an approach to real-time imaging using a continuous radial acquisition scheme. The intrinsic advantages of radial or projection reconstruction (PR) techniques are used to minimize motion-related image distortions. Modifications of the acquisition scheme as well as dedicated reconstruction techniques are used to further reduce the temporal blurring due to the finite acquisition time of one entire data set in our approach. So far we have used this technique for the visualization of active joint motion.

Correlations between functional and biochemical outcomes of eccentric exercise and between these outcomes and "delayed-onset muscle soreness" (DOMS) were studied. Maximal isotonic force, extension and flexion angle of the elbow, creatine kinase activity, and myoglobin concentration in serum were measured in 27 male subjects during 5 days after 120 maximal eccentric contractions of the forearm flexors. Significant correlations were found between values at 1 to 96 h after exercise for force (r = 0.55 to 0.96), flexion (0.52 to 0.94), extension (0.41 to 0.95), and myoglobin (0.55 to 0.97) and at 24 to 96 h for creatine kinase (0.67 to 0.96) and DOMS (0.45 to 0.72). Clusters of significant correlations (0.32 to 0.91) were found among all functional and biochemical measures. DOMS, however, showed only few and lower correlations with the other parameters (0.34 to 0.63). These results can practically be interpreted as follows: 1) subjects need more time to recover completely when early deviations after eccentric exercise are large, 2) a large change in one measure is accompanied by large deviations in other measures, and 3) objective outcomes of eccentric exercise are more accurate parameters than a DOMS score for use in effect studies.