In recent years, fMRI based on multi-echo (ME) acquisition showed several advantages with respect to standard single-echo (SE) acquisition. With ME, multiple echoes are acquired, and the voxel-wise signal of each functional volume is modeled with the exponential decay function S = S0 exp (−TEn/T2*). The ME approach allows the possibility to optimize the BOLD contrast using a weighted combination of the signals obtained from the different echoes, with weights based on local estimation of T2*. This combination of ME data provides reduced thermal noise, recovery of functional signal from regions affected by susceptibility-related signal dropout and a better separation of BOLD (neuronal) and non-BOLD (artifactual) components based on the well-known echo-time dependence of the BOLD effect. A much less explored option offered by ME fMRI is the possibility to derive time series of T2* which are expected to be more specific to BOLD activation effects, whereas the acquired signal also depends on S0 which can be influenced by scanner drift, motion and inflow effects. In this study we evaluated the sensitivity of fMRI based on T2* time series during a language mapping paradigm, and showed that it is a viable option with respect to standard SE acquisition.
Evaluation of T2* time series as an fMRI approach for task paradigms: a language mapping application
Ponetti G.
Primo
;Bosello G.Secondo
;Dono F.;Tomaiuolo F.;Bubbico G.;Chiacchiaretta P.;Della Cuna M.;Sensi S.;Caulo M.;Perrucci M. G.Penultimo
;Ferretti A.Ultimo
2025-01-01
Abstract
In recent years, fMRI based on multi-echo (ME) acquisition showed several advantages with respect to standard single-echo (SE) acquisition. With ME, multiple echoes are acquired, and the voxel-wise signal of each functional volume is modeled with the exponential decay function S = S0 exp (−TEn/T2*). The ME approach allows the possibility to optimize the BOLD contrast using a weighted combination of the signals obtained from the different echoes, with weights based on local estimation of T2*. This combination of ME data provides reduced thermal noise, recovery of functional signal from regions affected by susceptibility-related signal dropout and a better separation of BOLD (neuronal) and non-BOLD (artifactual) components based on the well-known echo-time dependence of the BOLD effect. A much less explored option offered by ME fMRI is the possibility to derive time series of T2* which are expected to be more specific to BOLD activation effects, whereas the acquired signal also depends on S0 which can be influenced by scanner drift, motion and inflow effects. In this study we evaluated the sensitivity of fMRI based on T2* time series during a language mapping paradigm, and showed that it is a viable option with respect to standard SE acquisition.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
