Inability to undergo MRI (e.g., due to safety reasons, such as presence of a pacemaker, or severe claustrophobia) Subjects with severe claustrophobia that is unresponsive to oral anxiolytics History of claustrophobia. Claustrophobia MRI MONITORING SUB-STUDY: Claustrophobia (a fear of enclosed spaces) Difficulty laying supine and still for up to hours in the MRI unit or claustrophobia Claustrophobia Severe claustrophobia Inability to undergo SRS due to claustrophobia Claustrophobia Claustrophobia requiring anxiolytics or sedation; or Inability to undergo breast MRI (e.g. claustrophobia) Symptomatic claustrophobia Symptomatic claustrophobia History of claustrophobia Symptomatic claustrophobia Have a history of severe claustrophobia Claustrophobia Subjects with severe claustrophobia unresponsive to oral anxiolytics Claustrophobia Claustrophobia Unmanageable claustrophobia Have severe claustrophobia Claustrophobia Subjects with severe claustrophobia unresponsive to oral anxiolytics Subjects with severe claustrophobia unresponsive to oral anxiolytics Severe claustrophobia not relieved by oral anxiolytics per institutional standard practice Known history of severe claustrophobia Claustrophobia Patients who due to severe claustrophobia cannot tolerate MRI scanning Uncontrollable claustrophobia Patients with inability to cooperate for an MRI exam due to claustrophobia or high levels of anxiety Known history of claustrophobia Claustrophobia Claustrophobia Subjects that exhibit noticeable anxiety and/or claustrophobia Claustrophobia Claustrophobia Extreme claustrophobia that precludes MRI scan Claustrophobia Known history of severe claustrophobia Claustrophobia Severe claustrophobia Claustrophobia Participants with severe claustrophobia unresponsive to oral anxiolytics Subjects with severe claustrophobia unresponsive to oral anxiolytics Subjects with severe claustrophobia unresponsive to oral anxiolytics Have a history of severe claustrophobia NORMAL VOLUNTEERS: Have a history of severe claustrophobia