There are so many patients with lumbar disc herniation who often ask and have never had a specific test done. I was advised to have a CT of the lumbar spine. What is the difference between several modalities such as X-ray, CT and MRI? Which is the better choice for the first examination of the lumbar spine? Generally, the specific circumstances of the onset of the disease should be combined to determine. 1.For patients with short duration of disease and mild symptoms such as lumbar pain, if the specialist thinks that the medical history is clear, the diagnosis is clear and imaging examination is not needed, the patient can be treated directly with functional exercise, physical therapy, internal or external medication, which not only reduces the damage of radiation and the economic burden of the patient, but also achieves the curative effect. For patients with long duration and typical symptoms, such as lumbar pain with lower limb radiating pain, numbness and muscle atrophy, if the specialist thinks there is a possibility of nerve root compression, it is recommended that lumbar spine X-ray (front and side, hyperextension and hyperflexion) and magnetic resonance imaging (MRI) be performed to evaluate the stability of the bony structure of the lumbar spine and to further understand the degree of nerve compression. 3, some patients with low back pain combined with weakness and numbness of both lower limbs, walking difficulties, thoracic and abdominal strapping sensation and “stepping on cotton” when walking, if the symptoms increase rapidly in a short period of time, it may not be caused by simple lumbar disc herniation compression of nerves, and compression of high nerves above the lumbar region should be excluded (such as cerebral infarction, cervical and thoracic segment, lumbar disc herniation, ligamentum flavum, etc.). It should be excluded that the nerves above the lumbar region are compressed (such as cerebral infarction, cervical and thoracic segments, disc herniation, ligamentum flavum, posterior longitudinal ligament calcification, or intraspinal occupancy compressing the spinal cord). MRI can clearly show the degree of spinal cord nerve compression, which can lead to a clear diagnosis and early treatment. As for CT examination of the lumbar spine, its advantage is to distinguish the lesions of the lumbar vertebral body, vertebral roots and articular processes, but it cannot clearly show the lesions of soft tissues such as intervertebral discs or nerve roots, and it is difficult to judge the degree of lesions based on this, or even to suggest the location of lesions. In short, each patient with lumbar disc herniation may not have the same morbidity characteristics, and the examination should be selected individually according to the condition.