It sounds like you have some significant concerns about your mental function and are pursuing testing to make sure that you are in good health. If you are concerned about your health, specifically your cognitive function, the best place to start is with your primary care physician
. The only completely accurate way to diagnose many of the conditions associated with dementia
(Alzheimer's disease, for example) is an autopsy, which is clearly not useful for you. Imaging of the brain can provide some indication of certain conditions, but generally, identifying dementia depends upon a thorough clinical history, review of past medical history (your age and family history, for example, will be important here), as well as cognitive or neuropsychiatric testing. There are some relatively short and simple in-office tests that can give a good sense of your cognitive function overall. In addition, your doctor
can speak with you about ways to preserve your memory and health as you age, including the importance of regular activity and physical exercise. If you have undergone and MRI and PET scan already, it sounds like there might be concern about some sort of central nervous system process. However, the best thing you can do about these concerns is to continue to work with your physician with any new symptoms you might notice.