A patient (male, 39) who has had head trauma and reports light headaches and strong tinnitus has had a brain CT scan done soon after symptom onsets (but 5 weeks after the trauma). No contrast agent has been administered. The CT revealed no hematoma, and the patient was thereafter referred for a CT of the inner ear and temporal bones. The referral was not critical, i.e. no strong suspicions.

Is there a recommended time that needs to have passed between the first and the second CT? We found no conclusive information online about this specific case. For instance, the recommendation from the Radiological Society of North America, that "There is no recommended limit on how many computed tomography (CT) scans you can have.". However, that page assumes the CT has been referred in an emergency, which would counterbalance the risk of radiation exposure - which is not the case here.

  • I don't understand why time between CTs would matter. The patient's getting the same radiation dose no matter how long it is.
    – Carey Gregory
    Commented Aug 19, 2020 at 19:14
  • Right, but they add up. There are recommendations re the total amount of radiation dose received per unit of time, e.g. per year.
    – z8080
    Commented Aug 20, 2020 at 11:19


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