MRI is magnetic resonance imaging of brain tissue, a general brain scan that shows the basic structure of brain tissue and the changes caused by ischemia and hemorrhage in brain tissue; its imaging principle: the nucleus is positively charged, and the nuclei of many elements, such as 1H, 19FT and 31P, undergo spin motion. Normally, the arrangement of the nucleus spin axes is disordered, but when placed in an applied magnetic field, the spatial orientation of the nucleus spins transitions from disorder to order. In this way, the spinning nucleus simultaneously spins around the applied magnetic field vector at an angle between the spin axis and the vector direction of the applied magnetic field, which is called Larmor spinning, just like the rotation of a spinning gyroscope under the gravity of the Earth. The magnetization vector of the spin system grows gradually from zero, and when the system reaches equilibrium, the magnetization intensity reaches a stable value. If the nuclear spin system is subjected to external effects, such as a certain frequency of radio frequency excitation of the nucleus can cause resonance effects. In this way, the spin nucleus also has to spin in the direction of the RF, this superposition of the spin state is called chapter motion. After the RF pulse stops, the spin system has been excited nuclei, can not maintain this state, will return to the original arrangement of the magnetic field state, while releasing a weak energy into the radio signal, the many signals detected, and make it possible to spatial resolution, the distribution of nuclei in motion image. The process of returning the nucleus from the excited state to the equilibrium arrangement is called the relaxation process. The time it takes is called the relaxation time. There are two types of relaxation times i.e. T1 and T2, T1 is the spin-dot or longitudinal relaxation time and T2 is the spin-spin or transverse relaxation time. MRA is cerebrovascular magnetic resonance imaging, which is a magnetic resonance scan of the blood vessels in the brain that can determine the presence of thrombosis, hemorrhage, or stenosis in the brain vessels and can identify the exact site of stenosis and occlusion. The basic principle is based on the saturation effect, inflow enhancement effect, and flow dephasing effect. mRA is performed by placing a pre-saturated band at the head end of a 3D layer block to saturate venous blood flow, and reverse flowing arterial blood enters the 3D layer block, which is not saturated and thus produces an MR signal. The scan splits a thicker volume into multiple thin excitation layers to reduce the thickness of the excitation volume to reduce the inflow saturation effect, and it can ensure the scanning volume range and obtain several thin images of adjacent layers, which makes the image clear and shows the fine structure of blood vessels well and improves the spatial resolution. Therefore, MRI and MRA are two different kinds of examinations. Patients with cerebrovascular diseases such as cerebral infarction and cerebral hemorrhage are best to have both examinations done at the same time.