How to become a certified yoga therapist?

I am currently an occupational therapist and I practice yoga daily. I have done a lot of research on yoga therapy and am very interested in it. I am wondering if anyone knows of a credible program where I can become certified in yoga therapy. And also, if anyone know how much time commitment is required. Thanks.

kripalu yoga center or check out http://www.iytyogatherapy.com/
Iyengar training also can be seen as yoga therapy…