Katrina,
My MRI guided biopsy was 6 weeks ago. I was face down with a plastic rack under my chest. It’s not too uncomfortable but I had two areas on the same side and for one they used the needle to extract the sample and the other they used a scooop-like probe to remove a tissue sample. The lidocaine helps numb the area but the scoop procedure was a bit painful for a short while. I had quite a lot of bleeding and ended up with a huge hematoma and my lumpectomy was delayed for a few days in order for it to heal more.
The position you are in during the procedure makes it difficult for the radiologist to get to to perform the biopsy. I hope you have a painless biopsy.