Real-time quantification of T(2)(*) changes using multiecho planar imaging and numerical methods.
Conventional approaches to quantify whole brain T(2)(*) maps use nonlinear regression with intensive computational requirements that therefore likely limit quantitative T(2)(*) mapping for real-time applications. To overcome these limitations an alternative method, NumART(2)(*) (NUMerical Algorithm for Real-time T(2)(*) mapping) that directly calculates T(2)(*) by a linear combination of images obtained at three or more different echo times was developed. NumART(2)(*), linear least-squares, and nonlinear regression techniques were applied to multiecho planar images of the human brain and to simulated data. Although NumART(2)(*) may overestimate T(2)(*), 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(2)(*), 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(2)(*) for continuous on-line T(2)(*) mapping in real time fMRI studies is shown.
Hagberg
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GE
Laboratory of Functional Neuroimaging, Fondazione Santa Lucia IRCCS, Rome, Italy. g.hagerg@hsantalucia.it
Indovina
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I
Sanes
J N
JN
Posse
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D000328:Adult; D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology*; D003199:Computer Systems; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008962:Models, Theoretical