  We perform general relativistic ray-tracing calculations of the transfer of
polarized synchrotron radiation through the relativistic accretion flow in
Sagittarius (Sgr) A*. Based on a two-temperature magneto-rotational-instability
(MRI) induced accretion mode, the birefringence effects are treated
self-consistently. By fitting the spectrum and polarization of Sgr A* from
millimeter to near-infrared bands, we are able to not only constrain the basic
parameters related to the MRI and the electron heating rate, but also limit the
orientation of the accretion torus. These constraints lead to unique
polarimetric images, which may be compared with future millimeter and
sub-millimeter VLBI observations. In combination with general relativistic MHD
simulations, the model has the potential to test the MRI with observations of
Sgr A*.
