Various prosthesis/implants
An MRI examination of patients with knee prosthesis is possible. Most of the prostheses used today are MRI-compatible and do not pose any risk to the patient. A limitation of the image quality is possible.
This depends on the material and shape of the prosthesis. With the cobalt-chrome or titanium prostheses frequently used today, artifacts in the imaging are only slightly pronounced. An MRI examination of patients with hip prostheses is also possible.
Similar to knee prostheses, most of the prostheses used are MRI-compatible and therefore pose no risk to the patient. Only a limitation of the image quality is possible. These artifacts depend on the material and the shape of the hip prosthesis.
The prostheses used today, which are made of cobalt-chrome or titanium, among other materials, show only a few artifacts in the MRI imaging. Breast implants consist of an inner pouch filled with silicone gel and a cover filled with water.Neither substance poses a risk to MRI imaging. Possible cracks of the implant can even be made visible with the help of MRI, since silicone differs clearly from water in MRI.
In addition, MRI is often used to exclude possible recurrences of breast cancer. Problems can occur with so-called expanders, some of which contain a metallic port. An expander is a bag that can be filled with saline solution from the outside in order to pre-expand the space in the breast area for the insertion of a prosthesis.
Cochlear implants consist of three components: First of all, magnets are used to transfer information between the transmitter coil and the implanted receiver coil. An MRI can cause a strong movement and a cancellation of the magnetic effect of the implanted receiver coil. For this reason, an MRI examination is not possible in patients with cochlear implants.
The exception to this are new implants, some of which contain magnets that are easy to remove or operate completely without magnets. The patient should inform the physician about the construction of his cochlear implant in a conversation. If MRI imaging is urgently required, surgical removal of the implant may be necessary.
- An external hearing aid with microphone that registers incoming sound waves and transmits them to a transmitter coil on the scalp
- A transmitter coil that transmits the sound waves to an implanted receiver coil
- A receiving coil that transmits the stimulus via a long multi-channel electrode to the inner ear where it stimulates the auditory nerve.
In the area of the head, many different types of implants can be found: Implants in the area of the large vessels (including stents, clips), central implants of the brain stem and implants on the skull bone. The vascular implants (stents, clips) used today are generally MRI-compatible because they are made of titanium. Only older implants may contain magnetic metals, which is why imaging with MRI is not possible.
With stents it should be noted that MRI imaging should not be performed in the first 6 to 8 weeks after stent surgery. This is due to the fact that the stent needs approximately this time to fuse with the vessel wall. Brainstem implants (central auditory implants, ABIs) are designed to directly stimulate the auditory pathways in the brainstem region.
This is a modified cochlear implant in which the auditory pathway in the inner ear is electrically stimulated instead of the inner ear. MRI imaging is possible, but strong artifacts and image disturbances occur in the vicinity of the implant. Therefore, MRI imaging is not recommended.
In some cases, high-resolution computed tomography (CT) can be used. Implants of the facial or cranial bone are made of smooth-walled silicone and are therefore not a contraindication for an MRI. In addition, MRI imaging is also possible for dental implants, which are usually made of titanium, ceramic or gold.
