In AVRT addiction is defined as ambivalence where you drink against your better judgement. The addiction is the AV not the physical Beast brain. With this model, the biochemical model and brain imaging is not really relevant because there is no way to objectively map particular brain states with subjective mental states.
You may take a brain image and ask the person what he is thinking and feeling at that time and in this way build up a kind of translation dictionary between his brain states and his thoughts/feelings but this would not constitute scientific data. It would be dependent on what the person tells you is going on inside his own head and there is simply no way to verify this - he may be lying to you for example.