Real‐time quantification of T changes using multiecho planar imaging and numerical methods

Abstract Conventional approaches to quantify whole brain T maps use nonlinear regression with intensive computational requirements that therefore likely limit quantitative T mapping for real‐time applications. To overcome these limitations an alternative method, NumART (NUMerical Algorithm for Real‐time T mapping) that directly calculates T by a linear combination of images obtained at three or more different echo times was developed. NumART , linear least‐squares, and nonlinear regression techniques were applied to multiecho planar images of the human brain and to simulated data. Although NumART may overestimate T , it yields comparable values to regression techniques in cortical and subcortical areas, with only moderate deviations for echo spacings between 18 and 40 ms. NumART , like linear regression, requires 2% of the computational time needed for nonlinear regression and compares favorably with linear regression due to its higher precision. The use of NumART for continuous on‐line T mapping in real time fMRI studies is shown. Magn Reson Med 48:877–882, 2002. © 2002 Wiley‐Liss, Inc.