This will be an abbreviated description of the MRI scanner. To get a general idea of the major components of a MRI scanner I have included the following schematic diagram:
Starting from the right hand side, we have the computer that directs all of the action in the MRI acquisition and acquires and processes the data. The computer tells the gradient amplifiers and RF transmitter when to turn on and off to obtain the proper pulse sequence. The RF receiver amplifier is also controlled by the computer and relays the signal received by the RF coil from the patient to the A-D converter that digitizes the signal, and from there to the computer to be reconstructed into an image.