Discuss the hospital's policy with your doctor or surgeon prior to admittance. Take necessary jewelry removal and insertion tools with you, just in case. In the case of emergency treatment or surgery, such as after an accident, your jewelry may be removed by hospital staff if you are unable to do so. CT scans of the head require removal of all facial jewelry. The MRI, or Magnetic Resonance Image, uses magnetism to obtain an image.
Most hospitals require that all metal jewelry be removed for MRIs.
Any metal in or on the body will greatly distort the image. Whether or not MRIs produce a magnetic force strong enough pull jewelry out of the body is debated. Even stuff like fillings would artefact images, and so all metal except for seriously permanent stuff would have had to come off. Whether or not you should remove your jewelry hinges on departmental policy and your personal reasons for the procedure. The good news is that your jewelry probably is not magnetic.