Using a PC To Process MRI Data

Abstract

Summary Nuclear magnetic resonance (NMR) imaging techniques are used to measure changing fluid saturations and relative permeabilities in porous materials.1, 2 The recorded signals are a measure of the volumes of the fluids residing in the pore spaces.3’4 A technique coupling public-domain image processing programs with in-house programs for downloading and interpreting NMR data has been developed at Texas A&M U. The new method permits a PC or Macintosh II computer system to be used in place of the more sophisticated and expensive graphics workstations. Raw NMR data files are downloaded by a parallel to serial link as 256 × 256 matrices of positive even integers. In-house developed C programs are used to convert the text files to binary data to reduce both storage requirements and image noise level. An interactive portion of the program permits the operator to choose the level where the good data start. These data are then extracted and processed into colored images. The extracted data are divided by 256 and a color table ranging from 0 to 255 is arranged. The end points are quantified by measuring these saturation values during the experimental run. The data are stored in binary form once a color has been assigned to each pixel. The process of converting the NMR files to binary files and assigning colors to the pixels takes 90 to 120 seconds of computer time. This process produces images with sufficiently good resolution to show saturation fronts and to distinguish features within the image.