Tissue contrast enhancement: image reconstruction algorithm and selection of TI in inversion recovery MRI.

It is clearly demonstrated that the proper application of the inversion recovery imaging pulse sequence is dependent on the method of image reconstruction and the selection of TI for optimum tissue contrast. There are two methods of 2DFT image reconstruction of IR sequence time-domain raw data. The first is a modulus-image reconstruction algorithm (contrast-obliterating option), and the second is a phase-correction routine for reconstructing "phase-sensitive" true IR-images. The second option generates proper "in-phase" images, retains proper scale of contrast, but can invert the algebraic sign of image-values under certain conditions. A series of "phase-sensitive" and "modulus" reconstructed brain images, obtained with conventional and optimized new IR pulse sequences, are shown to demonstrate these effects. They illustrate the considerable advantages gained, in practical clinical situations, if one generates "phase-sensitive" true IR-images from IR-sequence raw data at optimum TI for tissue contrast enhancement.