In the outpatient clinic, many patients feel that they have already had a CT or MRI and are puzzled when the doctor suggests that other imaging tests, such as X-rays, MRI, or CT, are needed. In fact, different tests show different lesions and cannot replace each other. For example, X-rays (frontal and lateral and dynamic films) are very important tests that do not directly show signs of lumbar disc herniation, but can rule out some disorders. MRI shows soft tissue, such as discs and nerve lesions, which cannot be replaced by CT. Therefore, CT, MRI and X-rays must be complete to get the correct diagnosis.