Hi,

I want to use multi-echo images to compute T2 values for evaluating lesions. I have done this successfully using other software, but if I can do everything in afni I'll be a happier camper, so I was wondering if there is a way.

The equation looks like this:

S = S0 * exp (-TE/T2)

where S is a time series of measured signal values, S0 is the initial signal value, TE is a time series of fixed echo times at which each image is aquired, and T2 is the value that we want to solve for. So this is a single exponential decay, and we want to solve for the time constant. Typically, this is done by a least-squares fit. So I am wondering if there is a program in afni that can do this. So far, my snooping suggests that it could be done in 3dNLFim if I am willing to do some C-programming to design a new signal model for the single exponential decay. So I am calling that plan B, but just wondering if I can find a plan A. Has anyone done this before, or know of any easier way to do it?
Thanks,

Jed