Ines,
Yes those parameters are estimated too using the priors given in the
2010 paper. The prior mean for tau (both tissue and MV) can be set from
the command line using the --bolus option. The prior on the MV arrival
time is set in the code, it is possible to over write the value
externally, but altering the value in the code and recompiling might be
easier unless you need to to it a lot. You are unlikely to find it makes
much difference in practice though. Saving the images for these
parameters is a little easier as these are generated during the
execution of oxford_asl, but simply not kept at the end.
Michael
On 18/12/2012 17:00, Ines Sousa wrote:
> Hello,
>
> When inferring the macro vascular component using oxford_asl, I assume the macro vascular timing parameters (dt_a and tau_a, arrival time and duration of the arterial bolus, referred in Chappell et al., MRM, 2010) are estimated in addition to aBV, since I got the following echo during the process:
> Spatial VB (6 param: CBF, ^t, bCBF, b^t, tau, btau)
>
> First, I would like to confirm that the prior values used for these parameters are those reported in Table 1, Chappell et al., MRM, 2010.
>
> I would also like to save the dt_a and tau_a estimations and be able to change the values of the initial priors for these parameters. Is it possible with the actual version of the code?
>
> Thanks in advance,
>
> Ines
>
|