Will a cat scan of my head rule out ms or a brain tumor better than mri? had one before but am having another one due to vertigo.im 18.am i in danger?

No: Mri is by far the test of choice for ms. Either way will detect brain tumors, but actual better picture of the tumor itself with a mri. There is no danger to mri. Cat scans have radiation, but your doctor will guide you in consultation with a radiologist as to which test is most appropriate for your symptoms.

MRI: Mri is more sensitive for detecting subtle abnormalities such as ms or small tumors. Preferrably an MRI with contrast. You should discuss with a neurologist before getting the scan.