Calcification of my avm?

Does know or has anyone heard of this. My doctor told me that my avm presents calcification. When I asked her what it is all she told me was the blood had less room to flow and I had a higher risk of bleed. Being that I am one for details I’d like to know more about what exactly calcification is. Everything on the net I find is reading foreign, you all are usually more helpful. I’m hoping someone knows thanks