Getting analysis of changes in MY brain upon cannabis consumption I want to know if/how my brain differs from other brains. I'm also interested in knowing exactly how my brain changes when I smoke marijuana, as it is claimed that it affects individuals differently. Fortunately I live in the Netherlands. Is it likely that researchers would welcome me to come, scan my brain, let me get high and do some more scanning? If the case is that researchers crave material, then this seems like a win-win.
Both the Amsterdam University (UvA) and Radboud University use a public online system for applying for participation in experiments. I forget which system UvA uses, but Radboud uses the sona system (just google it, you can creat an account). There you can see ongoing studies and apply for experiments. Both these cities are big research hubs for neuroimaging. And other universities surely also have similar systems for recruiting participants, but I don't have experience with them so I don't know.

That being said, nobody will tell you about the difference between your brain and other brains. This is simply not a topic of research. It's kind of like asking what's the difference between this grain of sand and all other grains - there are too many to list, the similarities stick out more clearly, and even if there are some differences who knows which ones are important. Neuroscience is a new thing, and we're still cataloging the basics. Unless there's something grossly distorted about your brain, nobody can give it a casual look and tell you something about your personality or behaviour. And if there is something grossly distorted, they'll contact your doctor, and not discuss it with you directly.

On the other hand, if there are marijuana studies you can take part and ask for feedback. At the Donders Institute in Nijmegen you can get a CD with your brain scan for your participation. But the feedback you get will depend on the question the researcher is asking. Typically this question would pertain to shared effects of marijuana on everyone, and not to individual differences. Individual differences studies are still rare, as they require huge numbers of participants while scanning resources are very limited and costly.