Image Fitting

     The image fitting tool is MRVision's image synthesis function. This takes a series of images and fits a mathematical function to the data, or performs other calculations, on a pixel by pixel basis. The result is one or more parametric maps, depending upon the function or calculation used. A simple example is fitting and exponential decay equation to a set of multi-echo MRI data to generate maps of the T2 relaxation parameter. A more complex example, shown in figure E, shows the measurement of a time resolved series of MR images during contrast agent injection to yield parametric maps related to cerebral blood flow. Other fitting functions include; linear, correlation (for f-MRI, see below) and peak-picking. This latter function can generate maximum intensity projections (MIP) from angiography (MRA) data or maps of chemical species from 2D CSI experiments.

Image Fitting Tool
     Figure E. Generating perfusion maps using the image fitting tool. Data are snapshot echo planar (EPI) images of 8 slices through the brain during a rapid bolus injection of MR contrast agent (Gd-DTPA). The ROI tool (lower right) is used to show the time profile of the signal variation from a small region of cortex; the signal dips and recovers during the first pass transit of the contrast agent. Analysis of these curves for each pixel, using the fitting tool, generates maps of bolus peak, arrival time and relative cerebral blood volume (rCBV) for each slice.