Although MRI and B-ultrasound belong to the same category of imaging examination, comprehensively speaking, MRI is far superior to B-ultrasound in terms of imaging diagnosis. MRI has very high resolution, especially for the examination of internal soft tissues, which is beyond the reach of B-ultrasound. In addition, in the diagnosis of malignant tumors, such as lung cancer, liver cancer, pancreatic cancer, etc., MRI can make qualitative diagnosis, which CT cannot do. Moreover, the diagnostic accuracy of MRI is only lower than the results of pathological tissue puncture biopsy.