Many patients believe that the more advanced and expensive the imaging test is, the better it is. But is this really true? In fact, the imaging examination items have their own advantages, but also their own limitations, not completely replace each other. In orthopedics, some patients ask their doctors to prescribe CT exams to see if there is a herniated disc when they see them. It is good that a typical patient with lumbar disc herniation can have a CT examination to clarify the diagnosis and the location and degree of herniation, which can help to choose a suitable treatment method. Professor Liang Biling, chief expert of the imaging and testing center of the Sixth Hospital of Sun Yat-sen University, said that the most common and preferred examination method in diagnosing diseases such as limb fractures is still the general X-ray examination. The radiation dose of CT is still relatively high compared to that of radiography. It can be said that reasonable examination is the only way to reduce radiation damage, therefore, in the examination of orthopedic diseases, it must not be discriminated against because X-ray examination is cheap. Magnetic resonance imaging (MRI), on the other hand, although more expensive (about twice as expensive as CT), is now far more commonly used in spine surgery than CT. Patients always feel that once CT is performed, they basically know what disease they have. This is not the case. Many lesions manifest as soft tissue lesions, such as tumors and herniated discs, and MRI is much clearer than CT (except for the resolution of bone tissue) and sees a much larger area, which is more helpful for early diagnosis. Myth 2: It is unnecessary to repeatedly check CT and MRI when you have tumor The diagnosis and treatment of tumor need to determine its typing and staging before deciding which plan to choose, which must be done with detailed examination. Professor Biling Liang said, for example, it is pointed out in “Nasopharyngeal Cancer 2008 Staging” that CT and MRI should be done before surgery for nasopharyngeal cancer, and there are also re-examinations of CT and MRI after radiotherapy, three months, and six months later. The reason why such frequent reexaminations are arranged is that tumors are generally particularly prone to recurrence within 6-12 months. It can be said that the preoperative examination and postoperative review of tumor must be done according to the standard, the purpose of which is to observe the effect of treatment and detect the recurrence at an early stage. Myth 3: PET scan can screen whole body tumor Many people say that “PET can screen whole body tumor”. “When you hear such words, you know you are a layman. Prof. Biling Liang said, “Each test has its own indications, generally speaking, ultrasound is preferred for abdominal examination (liver, gallbladder and spleen, etc.) and CT for chest (lung cancer, etc.), unless there is a suspicion of tumor metastasis, then PET is considered.” Prof. Liang emphasized that PET is based on the status of human glucose metabolism, but there are differences in glucose metabolism in different parts of the body. For example, glucose metabolism in the brain is very high. Therefore, sometimes, brain diseases may not be detected by PET, and there is a certain degree of false negativity in PET. In addition, to do a PET test, an isotope is injected into the body, which is radioactive and can cause some damage to the body. Therefore, in foreign countries, PET is not used for tumor screening, but for understanding the clinical stage of tumor patients, whether there is systemic metastasis, etc. It is a big mistake to take PET as a screening means of tumor. Myth 4: To do a big wrap-around examination in order to confirm the diagnosis faster Both imaging doctors and clinicians will tend to choose the most effective method to confirm the disease, and do not use the complicated ones if they can be simple. For example, to screen small lesions in the lungs, chest X-ray is not sensitive to small lesions below 5 mm and misses many, but if you choose low-dose spiral CT, you can see lesions smaller than 1 mm very clearly. However, for fractures (especially those of the extremities), X-ray is the best way to examine them, whereas spinal fractures can only be detected with CT, because spinal fractures taken with X-ray are likely to be aggravated during the moving process. A brief comparison of common imaging indications X-rays: for diseases such as pneumonia and fractures. CT: Applicable to brain , spinal cord, mediastinum, lung, liver, bile, pancreas and organs of the pelvis, spine and other examinations. MRI: Applicable to neurological lesions, such as cerebral infarction, brain tumor; infection, tumor, trauma in bone; pelvic tumor and other examinations. B ultrasound: applicable to heart; liver, bile and pancreas of abdominal cavity; examination of uterus and its adnexa, bladder and other organs of pelvis; pregnancy examination.