One reason IMRT is being used is to try to protect your parotid glands (the largest of the salivary glands) from receiving too much radiation. To check this, a study-related saliva test will be done. For this test, the amount of saliva your parotid glands create will be measured before treatment (within 7 days before Week 1) and at the last week of treatment (during Week 6 or 7). Do not eat or drink anything, or put anything in your mouth, for 1 hour before the saliva collections. You will be asked to let your saliva collect in your mouth for 5 minutes and then spit into a cup. After that, you will be given a mild citric acid solution (like lemon juice) to put in your mouth. You will let the saliva collect in your mouth for 5 minutes and then spit in a cup. Saliva testing will be performed under a separate protocol (LAB07-0050).