Diagnostic Value of Optical Enhancement Technology in Early Esophageal Squamous Neoplasia

Inclusion Criteria: 1. Patients with high-risk factors for esophageal squamous cell carcinoma who meet any of follows： * Long term living in the high incidence area of esophageal squamous cell carcinoma ； * First degree relatives have a history of esophageal squamous cell carcinoma ； * Previous history of esophageal lesions （ esophageal squamous neoplasia ）； * The patients having a history of cancer； * A long history of smoking ； * A long history of drinking ； * Having bad eating habits such as eating fast, hot diet, high salt diet, eating pickles. 2. Patients aged between 40 to 74 years old. Exclusion Criteria: 1. Having advanced esophageal carcinoma; 2. After esophageal surgery or endoscopic treatment ; 3. Known esophageal radiotherapy or chemotherapy ; 4. Esophageal stenosis; 5. Acute bleeding; 6. A known allergy to iodine; 7. Coagulopathy (prothrombin time \<50% of control, partial thromboplastin time \>50 seconds); 8. Having food retention; 9. Severe hepatic ,renal, cardiovascular or metabolic dysfunction ; 10. Being pregnant or lactating;