This test uses a magnetic field, radiofrequency pulses, and a computer to produce detailed images of body structures in multiple places. You may be asked to drink a contrast solution for better imaging, and you will most likely lie on a moving table as pictures are taken. MRI is a more detailed tool than x-ray and ultrasound and for certain organs or areas of the body, it provides better images than CT. MRI may not be recommended if you have a pacemaker or other metal implant.