  We present the first VLBI images of SiO masers in the circumstellar envelope
of an S-type star obtained with the newly developed capabilities of the Very
Long Baseline Array (VLBA) at 86 GHz. We combine these data with those obtained
quasy simultaneously at 43 GHz. These observations provide information on the
structure and dynamics of the innermost circumstellar shells, where the return
of large quantities of stellar material to the interstellar medium starts.
Despite of the fact that these are prelimininary results, we report that the
maser emission of the $v$=1 J=1--0 and J=2--1 present a very different emission
distribution, being not coincident in most case.
