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': 'Which of the following is not true regarding ossified posterior longitudinal ligament (OPLL)? \nSelect and explain. \nA. Most commonly involves thoracic spine, B. Gradient echo MR sequence may overestimate the canal stenosis, C. MRI is best for diagnosis, D. Low signal intensity on all MR sequences', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ossification of the posterior longitudinal ligament most commonly involves the cervical spine and not the thoracic spine.', 'role': 'assistant'}]