Strategically Acquired Gradient Echo(TAGE) Imaging

Quantitative magnetic resonance imaging(qMRI)is becoming increasingly important in every day clinical practice.Quantitative proton density(PD),T1,T2* and quantitative susceptibility mapping(QSM)all have important clinical applications.Fast three-dimensional(3D)gradient-echo(GRE)imaging has been widely used for producing whole brain T1 weighted(T1W)and proton density weighted(PDW)images.Using multiple flip angles(FAs),it can be used to create T1 and PD maps.When multi-echo data are collected,T2* maps can also be calculated.These images provide essential anatomical and quantitative information of brain tissues for studying various neurodegenerative diseases.In addition,the visualization of tissues with different susceptibilities(e.g.cerebral veins,microbleeds,and calcification)in GRE data can be enhanced using susceptibility weighted imaging(SWI),through the utilization of the phase information.Furthermore,quantitative susceptibility mapping(QSM)can be generated to quantify local susceptibilities in a geometry and orientation independent fashion,with the ability to differentiate iron from calcification.However,these various qualitative and quantitative images are normally acquired in separate scans which leads to a long scanning time and possible image misregistration.Furthermore,the T1 W image from a GRE sequence with a single flip angle(FA)yields limited grey matter(GM)and white matter(WM)contrast and has inherent image inhomogeneity from both the RF transmit(B1+)and receiver coil signal response variations(B1-).To address these problems,and to develop a rapid imaging protocol to provide whole brain coverage in just 5 minutes,we introduce a STrategically Acquired Gradient Echo(STAGE)imaging approach to create T1 W images,PDW images,T1 map,PD map,R2* map,SWI,true-SWI(or tSWI)images,enhanced T1 W contrast(T1WE)between GM and WM and improved multi-echo QSM data(ME-QSM).Also a novel T1 mapping and RF transmit and receive field correction method using two flip angles is presented.The standardization of a brain imaging protocol like STAGE has the potential to provide both qualitative and quantitative information that should be comparable across manufacturers and field strengths in a clinically practical scan time.