Imaging Parameters and Image Attributes

Abstract

The acquired matrix size, together with the field of view in each direction determines the pixel dimension in each direction and therefore the spatial resolution of the image. These parameters, together with the thickness of the selected 2D image slice, also determine the voxel dimensions. The voxel volume strongly influences the size of the signal. The signal to noise ratio (SNR) is a major determinant of image quality in MRI. There is an interdependence between SNR, spatial resolution (voxel volume), receiver bandwidth and image acquisition time. Increasing spatial resolution (same field of view) reduces SNR and increases image acquisition time. Increasing spatial resolution by decreasing field of view reduces SNR for same imaging time Reducing image acquisition time reduces spatial resolution or SNR or both. Signal averaging increases SNR but also increases image acquisition time. Increasing receiver bandwidth leads to faster echo sampling, shorter TE and TR hence shorter image acquisition time, but reduces SNR. In comparison to 2D imaging, 3D imaging allows thinner, contiguous slices to be acquired with improved SNR but with a longer acquisition time.