My wife has had several T-3 MRIs. Some scan modes show her original tumor cavity as a black circle. It is simply where CS Fluid is filling the void. The degree of black looks similar to the ventricle cavities, which are also filled with CSF. In other scan modes, I believe this same cavity looks white, possibly the ones with contrast, but I can't recall. We get an extra copy of all her scans on disc and add them to our personal files, in case we ever have to share this information with another medical team, it's in our back pocket. Occasionally we look at the scans ourselves at home, after our neuro-oncologist has reviewed them with us. We are lucky in that each time my wife gets a scan, we immediately see the doctor and he reads them right away, so we are not left waiting days for some one to tell us the results. I can't imagine how frustrating that would be. It sounds like you are pretty pro-active with everything, that is good. Just don't drive yourselves into a panic by guessing at what the MRIs show. All the best.
-Brandon.