The standard Siemens implementation of MP-RAGE is as a 3DFT technique. Following the non-selective 180º pulse, Mz is inverted and allowed to regrow via T1 relaxation mechanisms over inversion time interval (TI), at which time signal is acquired by using a spoiled GRE (“Turbo-FLASH”) with low flip angle.
Sequential ordering is typically used for both in-plane (Gy) and slice-select (Gz) phase encoding. All the (Gz) phase-encoding lines are collected following the inversion pulse, then repeated for the next value of the Gy gradient, and so forth. Because the number of partitions (Gz phase steps) is usually smaller than the number of Gy steps, this strategy results in the shortest scan time. Image contrast is determined by the effective inversion time (TIeff), which is the time between the 180º-pulse and the central Gz phase steps (i.e., kz near 0).
MP-RAGE contrast is determined strongly by T1-contrast, but spin density and T2* effects are also present. Use of high bandwidth and short data collection period reduces susceptibility effects including eddy currents associated with metal. It is widely used in isotropic mode for T1-weighted brain imaging.
Advanced Discussion (show/hide)»
Another variant, called MEMP-(“Multi Echo MP”)-RAGE, uses four echoes between about 2.5 and 7.5 ms, and is being increasingly used for ultra-high field MR imaging.
Marques JP, Kober T, Krueger G, et al. MP2RAGE, a self bias-field corrected sequence for improved segmentation and T1-mapping at high field. NeuroImage 2010; 49:1271-1281.
Mugler JP 3rd, Brookeman JR. Rapid three-dimensional T1-weighted MR imaging with the MP-RAGE sequence. J Magn Reson Imaging 1991; 1:561-7.
Tanner M, Bambarota G, Kober T, et al. Fluid and white matter suppression with the MP2RAGE sequence. J Magn Reson Imaging 2012; 35:1063-1070.
What is meant by an "IR-prepped" sequence? How is this different from "standard" inversion recovery?