Dear Dr Fedorov,
Since there is an option of computing fpv(i.e vp) with 3-parameter model,
I assume you are using extended Tofts model, not Kety model
because extended Tofts model contains 3 parameters Ktrans, vp and ve, and Kety model only contains 2.
I will double check the results from calculation with pkmodeling module.
Thanks again!
-Tiger Hu