Magnetic resonance imaging (MRI) is a non-invasive, relatively safe test. MRI examination has the characteristics of no ionizing radiation, high resolution of soft tissues, multi-directional scanning, multi-parameter imaging, and strong resistance to bone interference, but is it safe for patients with metal implants in the body to be examined in magnetic resonance examination?
Magnetic resonance scanning.
Magnetic resonance imaging (MRI) is a non-invasive, relatively safe test. Compared with CT, MRI examination has the characteristics of no ionizing radiation, high resolution of soft tissue, multi-directional scanning, multi-parameter imaging, and strong anti-bone interference.
Sometimes, in our work, we encounter patients who have had arterial stents, aneurysm clips, or orthopedic metal implants in their bodies, expressing confusion and concern about the safety of MRI examinations.
Even some radiologists or clinicians have expressed uncertainty about MRI for patients with similar conditions. So, is it safe for patients who have metal implants in their bodies to have an MRI?
According to the Chinese Expert Consensus on Magnetic Resonance Imaging Safety Management (2017), we understand the following recommendations for MRI-related examinations for patients with the following 11 types of metal implants in the body:
1 Intracranial aneurysm clip: Normally, we need to confirm the nature and properties of the aneurysm clip with the clinician who surgically placed the aneurysm clip for the patient, which is usually indicated on the instructions of the aneurysm clip. Aneurysm clips with strong ferromagnetic materials are contraindicated for MRI examinations;Aneurysm clips of non-ferromagnetic or weakly ferromagnetic materials can be used for 1MRI examination of 5 t or less.
2 Cardiac implantable electronic devices: mainly including pacemakers, etc. At present, the vast majority of pacemakers in clinical use are not compatible with MRI, and MRI examinations are prohibited for such patients.
3 Cochlear implants: MRI scans may flip the magnetic poles of the cochlear implant, which needs to be reduced by invasive surgical methods, and cochlear implants will also have the risk of heat production during MRI scans, so MRI examinations are not recommended unless necessary.
4. Orthopedic implants: such as steel plates, steel needles, screws and various artificial joints, most of them are non-ferromagnetic or a small amount of weak magnetism, and usually do not cause displacement and movement because they have been firmly fixed during surgery. However, the implant may produce magnetosensitive artifacts that can interfere with the visualization of local and adjacent tissues, and there is also a risk of thermal burnIf necessary, MRI is recommended after multifaceted evaluation.
5 Surgical and interventional equipment: For all kinds of needle biopsy procedures (such as drainage, radiofrequency ablation, microwave** and absolute ethanol injection, etc.), the puncture positioning needle, guidewire, catheter, radiofrequency ablation and microwave** equipment used should be non-ferromagnetic equipment dedicated to MRI. Ferromagnetic puncture needles and ferromagnetic equipment may be displaced, punctured by mistake or even ejected under a strong magnetic field, which is very dangerous.
6 Infusion pumps and indwelling catheters: Infusion pumps are usually implanted under the skin of the chest and are mainly composed of non-ferromagnetic or weakly magnetic alloys, silicone rubber, plastics and other materials, so it is safe to perform MRI examinations. Patients with insulin pumps, finger pulses, or other related electronic monitoring devices should be removed when they enter the MRI room, as they can be damaged not only by strong magnetic fields, but also by sucking onto the MRI scanner.
7 Dental implants: Many dental implants, such as dental implants, fixed dentures, and porcelain teeth, contain metals and alloys. It is recommended that the removable denture be removed and kept in a safe place before the MRI scan. Dental implants and fixed dentures can usually be found in 30 T and below field strength MRI devices, but some magnetic sensitivity artifacts may appear in their immediate vicinity.
8 Intrauterine devices and breast implants: Feasible for patients with metal intrauterine devices in the body3MRI at 0 t and below, but magnetic sensitivity artifacts may occur in this area of the pelvis, and it is recommended that the IUD be removed first if a pelvic MRI is required. Most of the implants used in mammoplasty and breast augmentation are non-ferromagnetic and are relatively safe for these patients to undergo MRI.
9 Coronary and peripheral vascular stents: Almost all coronary artery stents on the market are available in 30 t and below on MR equipment. Peripheral arterial stents prior to 2007 may have weak magnetism, but MRI is generally considered to be available 6 weeks after surgery.
10 Prosthetic heart valves and valvuloplasty rings: Almost all prosthetic heart valves and valvuloplasty rings on the market today are MRI safe and can be performed at any time after surgery3MRI examination of 0 T and below. However, due to the differences between different manufacturers' products, it is recommended to confirm the properties of these materials with the surgeon before MRI examination.
11 Intraocular implants: Magnetic intraocular implants, which may be displaced by strong magnetic fields, are contraindicated for MRI examinations. Healthy Wintering Program