Have a question about scans and tests

I was wondering if they can spot brains mets with a bone scan or a whole body CAT scan? I was dx in April of 03 Stage3c her2+++ and I am on Herceptin evry three weeks for a year. However I have headaches and memory loss. I am not sure if it is lingering "chemo brain" since I finished chemo in Aug. of 03 or if I should be worried. My onc keeps telling me that since all of my scans were clear that the headaches are from the Herceptin. I also read that Her2 girls should have an MRI of the brain just to be sure. Is this true? Thanks for the help.
Stay well Chris