I am 10 weeks pregnant and need a ct angiography of the brain to rule out an aneurysm. is this safe during pregnancy and what are the possible risks?

Nothing is risk free: Erin, Yes, a CT uses radiation, and therefore presents some risk to a developing fetus. That being said, a brain CT has slightly lower risk because the radiation beam is directed at your head, not the fetus. The IV contrast does not cross the placenta, so unless you have an allergic reaction, it is pretty safe. The risk of an aneurysm is death, so the benefits probably outweigh the risks here.

Safer with MRA: A MRA is safer that a CTA, either way the diagnosis of a Brain aneurysm and treatment trumps pregnancy because if it ruptures both you and the fetus can die or be severely compromised. Secondly, if diagnosed it needs immediate treatment and coiling or clipping may cause loss of the fetus.