 The goal of this study is to prove that the HXe MRI is an excellent imaging test to show the state of lung health among COPD patients and also to obtain new informations on how lung health changes with drugs that are already approved by US FDA. This work is anticipated to help develop HXe MRI as a new clinical test which can guide how to treat patients with COPD and if new therapies can improve lung health of patients with COPD. 