Dynamic range requirements for MRI

in order to realize the full potential in an MR receiver, the digitizer must capture a signal magnitude range from the central k-space peak to the thermal noise floor of the system. This dynamic range can exceed the performance of standard 16-bit data converters. For example, a whole-body mouse scan in a 7 Tesla magnet requires 20 bits of dynamic range. A 3D high-resolution mouse scan at 75 mu m isotropic voxel resolution using a 16-bit spectrometer shows an eightfold improvement in image SNR by gain stepping the receiver prior to digitization to cover the full magnitude dynamic range compared to a standard fixed gain approach. A method is presented to determine the dynamic range requirements of any experiment. (c) 2005 Wiley Periodicals, Inc.