Cameron... medicine by nature is a risky profession, and right now you're working in what's probably the most dangerous area of the field. Mistakes happen, especially on a procedure like a brain biopsy. Even if you do everything perfectly, this kind of thing can still happen.

As to whether it was necessary, well, I'm sure you wouldn't have done this without thinking it was the only option. Sometimes we need to make decisions in a fraction of a second, and they can't always be right. What matters is that he's alright in the long run - and it is certainly not your fault.