Patients who have undergone ablation for Barrett's Esophagus (BE) and High Grade Dysplasia (HGD) or Low Grade Dysplasia (LGD) with Photodynamic Therapy (PDT)/Radiofrequency ablation and endoscopic mucosal resection who have no endoscopic and histologic evidence of specialized intestinal metaplasia on biopsies from the esophagus on two successive endoscopies post ablation will be offered enrollment in the study.