Real-time-functional Mri Explorer

In this paper we present a system that allows onlinecontrol of functional magnetic resonance imaging (fMRI) experiments. With the beginning of the fMRI experiment, the functional volumes are real-time exported to an external PC. The statistical relevance of each voxel's activation is then calculated by correlation analysis. After calculation, the activation maps are overlaid to an anatomical data set. The real-time visualization of the activated voxels in combination with the morphology gives relevant information to the physician at experiment’s run time. The physician can set different levels of significance for activation, can investigate both slice-wise and as a 3d rendered volume, and can take localization measurements in Talairach coordinates. The system is in use in cooperation with the German Cancer Research Center in Heidelberg and the Otto-SelzInstitute at the University of Mannheim. The aim is to detect activated brain areas during somatosensory stimulation with experimental pain models. The presented system allows monitoring ongoing fMRI experiments in order to optimize experimental design and slice positioning. Introduction Functional magnetic resonance imaging (fMRI) is a noninvasive method that allows monitoring neuronal activation to external stimulation. Since the difference between active and non-active regions is about 2-3% of the total MRI-signal, averaging, and in particular, statistical testing are mandatory in order to locate active brain areas. An fMRI measurement can take some tens of minutes, and requires an even longer statistical postprocessing of the data. Unsuccessful experiments may often turn out to be unsuccessful after a long delay only, when subjects or patients are no longer available for investigation. Real-time functional MRI allows adaptation of experimental parameters or removal of artifact sources during the same experimental session. Measuring brain activation due to somatosensory and especially painful stimulation requires careful experimental design and slice positioning. Real-time fMRI can be used for a first check of the stimulation design and may also be used to select a reduced set of slices for monitoring specific brain regions with improved time resolution, compared with a wholebrain fMRI acquisition. The only fMRI-online evaluation program we know is that of the fire-project [1-3]. In contrast to this project we only use a standard PC and a newer rendering library VGL3.1 with our own rendering software. RT-fMRI-Explorer The basic idea of the RT-fMRI-Explorer is to support fMRI measurements by online monitoring. In order to realize this, we have chosen the following system design: first, an anatomical data set is acquired and sent to an external PC via TCP/IP. When starting functional measurements, a data collector is started on the hostcomputer of the MR scanner, which collects the functional data volumes and sends them to the external PC via TCP/IP during ongoing measurements. The software on the external PC performs a sliding-window correlation analysis of the last N incoming functional data volumes with a predefined ideal stimulus function f(x) which indicates the time course of stimulation. Classical fMRI “blocked-designs”, where the stimulus is alternately switched on and off, are coded by a sequence of 0 (=OFF) and 1 (=ON). The resulting square wave might be additionally convoluted with an ideal hemodynamic response function (HRF), to provide an ideal estimator for stimulation effects. Fig. 1: Internal architecture of the RT-fMRI-Explorer. Fig. 2: Volume rendering of the brain in combination with the activated areas in one image (red and yellow). The sliding window correlation analysis provides a simple functional activity measure for each voxel, which is transformed onto a parametric functional map. Anatomical data and functional maps are rendered together by the VGL rendering engine (using VGL3.1 as rendering library) and then displayed on the screen of the external PC. Talairach coordinates [4] for functional Font size: Times New Roman 10 all through, Bold Titles and Authors, Underline presenting author