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Dear Hweeling, If you do simple averaging over time-courses acquired with different TEs then you could also specify only the average TE in the DCM.TE field. If you do the weighted sum as I have recommended then you could use the TE that is theoretically optimal for the magnetic field strength data (represented mainly by tissue parenchyma) were acquired with. This assumes that the optimal TE was covered within your TE range. Practically speaking, if you have acquired data with 3 T, and I assume that your voxels will be mixture of gray matter tissue but possible also some larger vessels, then you can pick for optimal TE anything between 30 to 45 ms. Hope this helps. Best, Martin On 07/08/2018 14:45, Hwee Ling Lee wrote: > Dear all, > > Thanks for the suggestions and feedback. > > I have another question with regards to spectral DCM analyses using > multi-echo EPI images. > > What should be the input for DCM.TE in the case of multiple echos? I > assume that the variable only accepts one input numerical value? > > Cheers, > Hweeling > > > > On Mon, 23 Jul 2018 at 22:27, Martin Havlicek > <[log in to unmask] <mailto:[log in to unmask]>> wrote: > > Dear Hweeling, > > Although one could come up with more accurate and specific model > of multi-echo BOLD data, reasonably good solution can be obtained > by optimally combining different echo-times as suggested by Poser, > A.B. and Norris D. (2009): Investigating the benefits of > multi-echo EPI for fMRI at 7 T, NeuroImage. > > 1./ First you fit T2* (and S0) using mono-exponential model > (S0*exp(-TE/T2*)) into your multi echo ROI data (in resting-states > data it could be based on time and ROI average as you are trying > to fit T2* for "baseline") > > 2./ Then you fitted T2* in Equation (1) from Poser and Norris > (2009) to calculate weights. > > 3./ Optimally weighted BOLD signal is obtained as linear > combination of multi-echo BOLD signals; e.g. BOLD(OPT) = > w(1)*BOLD(TE1) + w(2)*BOLD(TE2) + w(3)*BOLD(TE3) + ... > > Hope this helps. > > Best regards, > > Martin > >> >> On 23/07/2018 08:01, Adeel Razi wrote: >>> Dear Hweeling >>> >>> I am not an expert on this but are these multi-echo sequences >>> simultaneous acquisitions or are different runs? If they are >>> simultaneous then averaging these out would be >>> easiest/sensible(?) while if different sessions then >>> concatenating them would be more appropriate. You can then use >>> the standard pipeline for preproessing. However I would leave >>> this to experts here having more experience with these acquisitions. >>> >>> Best wishes, >>> Adeel >>> >>> On Fri, Jul 20, 2018 at 6:31 PM, Hwee Ling Lee >>> <[log in to unmask] <mailto:[log in to unmask]>> wrote: >>> >>> Dear DCM experts, >>> >>> I was wondering if there would be an issue with using >>> multi-echo EPI images to examine the intrinsic dynamics of >>> resting state. >>> >>> Could someone also refer to me the preprocessing and >>> analyses pipeline using multi-echo EPI images in SPM? I >>> searched on google but I find limited information with >>> regard to this. >>> >>> Thanks. >>> >>> Cheers, >>> Hweeling >>> >>> >> >>