The MRI system consists of the following components, which operate in relation to each other to produce images of various organs of the patient for diagnosis, such as magnet system, gradient system, RF system, patient table, control system, main computer, RF and magnet shielding, phantoms, and supporting systems. Resistive magnets, superconductive magnets, magnet shielding, and SHIM are discussed. Refrigerator system is discussed. In superconductive magnets the coil is immersed in liquid helium. Various parameters like temperature, pressure and liquid helium level in the magnet are continuously monitored and appropriate action is automatically taken if any parameter is varied beyond permissible limit. This system has transmitter and receiver section. A transmitter is used to produce RF to excite the protons from the subject. Patient table is also a very important part of MR scanner. This table is generally computer controlled and is used to take patient into imaging area. The movement of the table can be controlled through the operating console. The raw data (signal) received from the subject is being sent to the imager. Here, this data is mathematically analyzed by performing Fourier transform. By this process the image data is created, which is transferred to the main computer for display and further processing. This procedure in new systems is performed by software while in earlier systems dedicated hardware was used for this purpose. The system operator gives input to the scanner through the main computer while scanned images are displayed on the computer monitor. Phantoms are being used to test the performance of the scanner. Phantoms are used as a substitute to the patient, for quality assurance programs. They contain material, which can produce MR signal. Water is the most commonly used material in the MR phantom. There are a number of supportive systems, which help the above-described main components of the MR scanner to perform their activities.