How long does it take for a contrast head ct to cause brain cancer?

It shouldn't: Contrast enhanced ct scans are not a risk for brain cancer. In fact more tumors have been cured by finding them early with ct scans and mris than have ever been caused. There was a scare with ct angiograms at one time because a few machines gave large doses of radiation. For the most part, this is no longer the case.

No answer: While ct imaging uses x-rays, the radiation exposure alone is probably not enough to cause brain cancer. If it were to contribute to brain cancer, lag time would be expected to be in years if not decades.

Contrast is not the: Issue, and overdose of radiation may cause increased risk to scalp, bones and all head and neck tissues. Cancers induced by radiation exposure usually occur beyond 7 years, but there can be a small increase risk over lifetime. Since brain tumors are uncommon, it is difficult to prove. Contrast allows vessels to be seen, and tumors leak or "enhance".