The costs and potential complications (side effects) of therapies currently used to treat Crohn's disease could be reduced if a non-invasive test existed that determined which therapies benefit patients and which do not. A non-invasive test is a test that does not involve cutting or entering the skin. Currently, once therapies are prescribed, doctors rely solely on clinical parameters to gauge whether the therapies are helpful. This includes evaluation of overall general well-being, abdominal pain, and number of liquid stools per day. There is no established and reliable non-invasive test that can predict whether a person is responding to therapy early in the course of treatment when these evaluations may be inconclusive.||During this research study we will look for changes in sugar metabolism on low-dose PET/CT before and 2 weeks after the first infusion of infliximab therapy. This is to find out if these changes can predict clinical response and steroid-free remission at two, six and 12 months, in patients with Crohn's disease.