The main and only means to determine whether there is a tumor in the brain is to “take a film”. The scientific name of “film” here is “imaging test”, which includes CT and MRI, with or without contrast, and there are various types. The main concern of patients is what kind of film is suitable for their disease. According to the equipment used for the examination, there are CT and MRI in general, in addition to PET/CT, ultrasound Doppler and other less common tests. CT and MRI are each divided into plain and enhanced, depending on whether or not a contrast agent is injected. Overall, CT is less expensive, takes less time to perform, and has a shorter queue for appointments, while MRI is the opposite. For most intracranial tumors, the general examination procedure is to do an initial screening with CT plain scan, and if problems are found and tumors are suspected, an enhanced MRI is done, and if the enhanced MRI is not good enough, special examinations such as MRS and PET/CT are added. Generally speaking, for patients with intracranial tumors requiring surgery or radiotherapy, enhanced MRI is a must-do test. In patients with intracranial tumor, there will be a large amount of contrast gathering in the tumor area, and the tumor area will appear white on the film, while in non-tumor lesions such as cerebral infarction, there will be no contrast gathering and it will be gray or black. Therefore, enhancement examination is mainly used to distinguish tumor lesions from non-tumor lesions. 3.Enhanced CT In patients with intracranial tumors, since the clarity of enhanced MRI is much higher than that of enhanced CT, enhanced CT has been rarely used in recent years. At present, it is mainly used in patients who have paramagnetic metals in their bodies and cannot do MRI, or in hospitals without MRI equipment in remote areas. The principle of enhanced CT contrast agent is similar to that of enhanced MRI, but the probability of allergy is much higher, which is worth noting. MRI plain scan MRI plain scan is not very commonly used in intracranial tumors, since we have spent money and time to do MRI, why not do an enhanced one by the way? Nowadays, MRI scan is mostly used for non-tumor diseases such as cerebral infarction and inflammatory encephalopathy. 5.MRS, also known as magnetic resonance spectroscopy, is a relatively new technology in recent years, and its basic principle and the equipment used are the same as ordinary MRI, which is a special type of MRI. MRS is mainly used to differentiate tumor and non-tumor lesions. At present, MRS can only be examined in a few large tertiary hospitals, so patients should consult clearly before the examination. DTI, sometimes referred to as MRI diffusion imaging, is also a special type of MRI. It is mainly used to determine the relationship between tumor and important nerve conduction bundles in the brain in order to guide surgical operation. This examination is also a new technology that has been promoted only in recent years. PET/CT is a special type of MRI which is mainly used to determine the relationship between tumor and important nerve conduction bundles in the brain in order to guide the operation. 7. PET is expensive, thousands to 10,000 dollars, and the drug is radioactive, so its application is limited. 8.CTA, also known as CT angiography, belongs to a special type of CT. CTA is mainly used to show the morphology of large intracranial arteries and the relationship between arteries and tumors, which is a good guide for the surgery of intracranial tumors near the large arteries. To sum up, in patients with intracranial tumors, CT plain scan is the means of initial tumor screening, and enhanced MRI is a mandatory test, and patients who cannot do MRI should do enhanced CT. MRS, DTI, PET/CT, CTA, etc. are done only according to the needs of specific conditions. In general, hospitals in China recognize the films taken in other hospitals, so it is not necessary to repeat the examination when going to different hospitals, but too old films cannot be used.