It would be interesting to know a bit more about why you are having a CT scan of your head. CT scans should not of course be done lightly, as they involve exposure to a significant amount of radiation. This can potentially increase your risk of cancer later in life. Of course, if the test is necessary according to your doctors then you should have it done.
CT scans of the brain are used most commonly to look for acute issues, such as bleeding into the brain or swelling in the brain. They may also detect large brain tumors. However, CT scans are not the test of choice for looking for brain tumors. The are not very good at detecting smaller or more subtle tumors and in particularly they are not good at looking at the cerebellum, which is a part of the brain that sits low and in the back of the skull.
The test of choice for looking for brain tumors, and in fact for most other abnormalities in the brain, is an MRI
scan rather than a CT scan. I suggest that you sit down and talk with your primary care doctor
to make sure that you are getting the right test, or if a test is necessary.