If there are intracranial aneurysm clips, dental implants, infusion pumps and indwelling catheters in the body, can the mri be performed? On the safety of mri, a consensus of Chinese experts was released in 2017
1. Intracranial aneurysm clamp
Aneurysm clips are composed of a variety of substances with different magnetic sensitivities and have different shapes. The amount of ferromagnetic substance in them will lead to the risk of MRI examination. Aneurysm clips with strong ferromagnetic materials are prohibited for MRI examination. Aneurysm clips made of non-ferromagnetic or weakly ferromagnetic materials can be used for MRI examination up to 1.5t (inclusive). If it is not clear whether there is aneurysm clip in the patient's skull, X-ray plain film should be performed first, or recent (postoperative) X-ray plain film and CT images of the brain should be checked to determine whether there is aneurysm clip. For patients with aneurysm clips of unknown nature, the risk-benefit ratio should be carefully evaluated, all potential risks should be informed to the examinant, and the informed consent should be signed by the patient and/or guardian.
2. Heart-implanted electronics
Cardiac implantable electronic devices, including pacemakers, icds, implantable cardiovascular monitors (CM) and implantable circulatory recorders (ILR), are growing in variety and complexity. Most of the cardiac implantable devices currently in clinical use are not compatible with MRI.
Radiologists and cardiologists must be familiar with the conditions and limitations of each device and be aware that each MRI device is unique and does not have "universal" safety criteria. Careless use of equipment without following product instructions may cause serious adverse consequences.
3. Cochlear implants
Cochlear implants are electronic devices. MRI scan may cause the reversal of cochlear magnetic pole, which needs to be reduced through invasive surgery. It is recommended to fully evaluate the risk-benefit ratio of MRI before scanning. In the head scan, the probability of the reversal of the magnetic plate was lower than that of the chest and abdomen scan and the lower limb scan, which may be related to the frequent bed shifting in the chest and abdomen scan and the lower limb scan, as well as the large magnetic field gradient at the edge of the MRI scan hole. Patients with cochlear implant should pay attention to the slow bed shifting when performing MRI examination. Although cochlear implants are at risk of producing heat in MRI scans, they are relatively safe in magnetic fields below 1.5t (including).
4. Orthopedic implants
Orthopedic implants (such as steel plates, needles, screws, and various artificial joints, etc.) are mostly non-ferromagnetic or a small amount of weak magnetism and usually do not move because they have been firmly fixed to bones, ligaments or tendons during surgery. However, the implant may introduce image artifacts that affect the observation of surrounding tissues. There is also a risk of thermal burns.
5. Surgical and interventional equipment
All kinds of puncture biopsy operations, including all kinds of MRI guided treatments (such as drainage, radiofrequency ablation, microwave treatment and anhydrous ethanol injection, etc.), the puncture positioning needle, guidewire, catheter, radiofrequency ablation, microwave treatment and other equipment should be non-ferromagnetic. The ferromagnetic puncture needle may shift and mispuncture under the strong magnetic field.
At present, there are all kinds of puncture needles, biopsy needles, catheters, guidewires and corresponding monitoring devices specially used for MRI guided interventional surgery. In addition, the implantation of radioactive particles under the guidance of MRI also requires corresponding non-ferromagnetic equipment. The shell of radioactive particles is made of titanium alloy, so MRI examination after implantation is safe.
6. Infusion pump and indwelling catheter
The infusion pump is usually implanted under the skin of the chest and consists of a puncture seat and a venous catheter system. The materials are mainly alloy, silicone rubber and plastic, etc., showing non-ferromagnetism and weak magnetism. Therefore, MRI examination is safe. Patients with insulin pumps should remove the pump when entering the MRI exam room, as a strong magnetic field may impair the function of the pump.
7. Dental implant
Many dental implants (such as implants, fixed dentures, and porcelain teeth) contain metals and alloys, and some are even ferromagnetic. Because the implant tooth is firmly fixed on the alveolar bone or adhered to the corresponding connector, it has high strength, and usually does not move and deform in the MRI equipment with the field intensity below 3.0t (including), but some artifacts may appear in the place where the dental implant is located.
8. Iud and breast implants
Metal intrauterine devices are generally made of copper. At present, no obvious adverse reactions of iud in MRI examination below 3.0t (inclusive) have been found, but artifacts may occur.
Most of the implants used in breast plastic surgery and breast augmentation are non-ferromagnetic. These patients are safe for MRI examination, but a few plastic surgery accessories may contain metal, which should be noted.
9. Coronary and peripheral vascular stents
Almost all commercially available coronary stent products are safe on MRI and can be examined on MR devices below 3.0t (inclusive). Periarterial stents before 2007 May be weakly magnetic, but it is generally accepted that MRI can be performed 6 weeks after surgery.
10. Artificial heart valves and valvuloplasty rings
Almost all artificial heart valves and valvular rings on the market are MRI safe and can be examined in a MR scanner below 3.0t at any time after surgery. However, due to the differences of products from different manufacturers, the materials should be confirmed before MRI examination.
11. Eye implants
MRI examination is not suitable for patients with magnetic intraocular implants, which may be displaced in strong magnetic field.
In addition, considering the radiofrequency field thermal effect (thermogenic effect), consensus points out that MRI examination should not be performed in patients with high fever, and the following issues should be noted:
➤ before MRI, to remove the client all unnecessary conductive material in vitro. If client's clothing contains non-removable conductive material, it is recommended to replace the specified clothing.
➤ as long as the metal pin on the surface of the skin or stitches are not ferromagnetic, but also not radiofrequency radiation area, or near, client can check by MRI.
➤ if imaging area covers a large area or dark tattoo (including grain line), in order to reduce the quantity of heat accumulation, it is recommended to apply ice packs in MRI scanning cooling; The subjects were also told that the MRI scan might blur the tattoo within 48 hours.
➤ metal is contained in some patche, MRI scan strips in order to avoid overheating danger, can generally be put ice packs in metal strips on the ice; However, this can sometimes affect drug delivery rates and absorption.
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