If you had surgery for un-ruptured brain aneurysm do you have to follow up with a cta 2 months later or is there something less invasive?

May be less sens.: You do an MRA without contrast and just use what are referred to as pulse sequences at whatever strength of the magnetic field is but it is not nearly as good at detecting small items as CTA with contrast. Transcranial doppler can be used but not nearly as sensitive as CTA with contrast or MRA. Maybe MRA with contrast would be slightly less toxic to kidneys but it's equally invasive as CTA.

Ask your surgeon.: It depends on whether your aneurysm was treated with surgical clipping or endovascular coiling. I typically obtain some kind of follow-up imaging for either method to make sure that the aneurysm is not trying to grow back. Ask your surgeon for more details.