Comment by bobim

Getting the US through the skull bone is next to impossible due to the acoustic impedance mismatch with surrounding tissues. As a stranger I'm deeply sorry for your situation, and thought your question should be answered somehow...

If you want to dig a little bit, the team of Mathias Fink in Paris explored "time reversal" techniques to get through the skull: one have to emmit from the tumor location, listen with a huge array, reverse the signature and blast. I don't know if this ended with a medical device.

Take care.