The above suggestions, and link are helpful. The only thing I can add is that if your blood glucose level is over 200 they may not do the test, until it goes lower. As mentioned, a low carbohydrate diet 12 hrs before...vegetables are all carbs, so choose ones that are low on the glycemic index. I even heard no exercise 2 days before the exam, and no heavy lifting. Avoid excessive taking before the test, crossing legs, and no talking during the scan,, except if necessary, and try not swallowing, moving mouth either during the test since these can show up as uptake. An hour before the test drink 16 ounces of water, if directed, or may be told to do it before you come in, and relax. Stress can also effect glucose, and thus effects the PET scan.

Good luck!