This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'The CT severity index in acute pancreatitis is described by: \nSelect and explain. \nA. Balthazar, B. Mengini, C. Chapman, D. Napelon', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The CT severity index (CTSI)-described by Balthazar Balthazar CT Severity Index CT Grade Score A. Normal- 0 B. Enlarged gland -1 C. Peri-pancreatic inflammation- 2 D. One fluid collection- 3 E. Two or more collections- 4 Necrosis Score 30%-50%- (4) >50% -(6) Ref: ACR Appropriateness Criteria,Acute Pancreatitis.', 'role': 'assistant'}]