MRI safety

Also check: https://www.acr.org/-/media/ACR/Files/Radiology-Safety/MR-Safety/Manual-on-MR-Safety.pdf

FLOWchart for bullets: https://www.ajronline.org/doi/abs/10.2214/AJR.20.23648

Bullets, even Ferromagnetic, did not result in significant heating at 3T for 15 minutes of scanning. There was movement which may be dangerous if near critical structures. https://pubmed.ncbi.nlm.nih.gov/23562330/

"Magnetic resonance imaging–related heating experiments performed on the five bullets tested yielded a highest temperature change equal to or less than 1.7C, with a background temperature rise of 1.5C in each case."

Below from https://pubmed.ncbi.nlm.nih.gov/19912071/

"The duration of the MRI examinations was between 25 and 90 min (average 50 min). None of the patients reported any particular physical sensation, such as heating, burning, or itching, during the MRI examination. One patient reported a superficial migration of a fragment approximately 1 cm in size and located in the gluteus muscle after undergoing an MRI of the knee. He reported having noticed the migration only after leaving the MRI suite, but did not seek medical attention since he was aware from personal experience that such superficial fragments had a tendency to migrate. None of the other patients reported any adverse reactions following their MRI examination."

"Noteworthy, despite the fact that more than 10 years had passed since its impregnation, the surrounding granulation tissue of the fragment in one of our patients was not firm enough to prevent the fragment’s motion."

Fragments in the remaining 17 patients (18 MRI examinations) were inflicted by military or terrorist attacks that occurred 2–39 years prior to the MRI. The fragment size ranged between 1 and 10 mm. One patient reported a superficial migration of a 10-mm fragment after MRI. No other adverse reactions were reported.

Conclusion: Conducting 1.5T MRI examinations is safe in patients with retained metal fragments from combat and terrorist attacks not in the vicinity of vital organs. However, caution is advised.

Tattoos are generally safe https://pubmed.ncbi.nlm.nih.gov/32216450/

Tattooed patients undergoing magnetic resonance imaging (MRI) can develop cutaneous complications during the procedure. Our aim was to review all published case reports on MRI-induced tattoo complications to identify a possible pattern. So far, 17 cases have been reported. Five (29%) of the cases were in cosmetic tattoos. Symptoms are abrupt and painful with fast onset during MRI, sometimes requiring termination of the procedure. Clinical signs are absent or manifested as inflammation sensed as burning. No thermal skin burns have been recognized. Full recovery is fast, with no sequelae. MRI-induced tattoo complications are uncommon. Patients with cosmetic and traditional tattoos can undergo routine MRI.

From UCSF https://radiology.ucsf.edu/patient-care/patient-safety/mri/unable-to-complete-mri-screening:

Patients are normally screened for contraindications to MRI using a hospital-approved screening form prior to entering the scanner suite. This form is completed by the patient or by his or her healthcare provider, and reviewed by the scanning technologist prior to the patient’s MRI examination. Occasionally, urgent or emergent MRI studies are indicated in patients who are unable to complete the screening form due to neurologic issues. This policy is written to outline the procedure for obtaining MRI in patients who are unable to undergo the normal screening process.

A knowledgeable family member or caretaker for a patient can complete the screening form on behalf of the patient. In the case of family members, this should be a member familiar with the patient’s exposures and medical history, such as a spouse, partner, or child. Healthcare providers familiar with the patient’s medical history may also complete the screening form in consultation with the medical record. However, in the absence of sufficient history the following steps should be performed to document the safety of MRI:

1. Attending radiologist approval for the MRI, along with medical necessity for MRI documented in the medical record by the attending physician requesting the study.

2. Separate chest and abdominal (KUB) radiographs should be obtained and reviewed prior to scanning to ensure the absence of contraindicated devices (pacemakers, spinal stimulators, et al) or other metallic material (shrapnel in close proximity to a major vessel or organ) that may be a contraindication to MRI. It is the responsibility of the requesting provider to order these radiographs.

3. Screening orbits CT should be obtained and reviewed for metallic foreign bodies. The scout image for this CT can be used to screen for aneurysm clips. When the request is for a brain MRI, a full head CT should be obtained instead of orbits CT. The requesting provider is responsible for ordering these screening CT examinations.

Note that this policy does not apply to patients who cannot complete screening due to language difficulties. In this case, a translator should be retained to complete screening together with the patient in their native language.

Practical tips:

Even if a metal is found to contain iron but it is away from things like the orbits or spinal cord, it can be scanned. The CT brain is used to check for aneurysm clips because there are documented cases where ferric clips have moved and resulted in hemorrhage, but this doesn't happen with platinum etc. With the orbits, the main thing to avoid is movement of the metal to injure the eye. You want to check for pacemaker leads and spinal stimulators. "The most dangerous patients are the obtunded ICU patients with tattoos which can burn but nobody thinks/cares about the tattoos." All other patients (metal in the subcutaneous tissues around the skull, the stainless steel coils in the testicular vein) are OK for MRI. Think of all the cases worldwide that have gone into the MRI and nobody ever hears about them.

STAINLESS STEEL coils appear to be MR safe and cook medical has changed their safety rating to MR conditional https://pubmed.ncbi.nlm.nih.gov/26260092/

Stainless steel embolization coils (SSEC) have been used for over four decades for vascular occlusion. Recently, the safety of these coils in a magnetic resonance environment has been called into question, with important ramifications for thousands of patients with existing coils in place. We performed a retrospective chart review at five tertiary care pediatric centers evaluating all children and young adults with implanted SSEC who underwent magnetic resonance imaging (MRI). Data reviewed included demographics, coil implantation, MRI studies, and follow-up evaluations. Complications such as heating, discomfort, or device migration were specifically sought. Two hundred and ninety-seven patients with implanted SSEC underwent 539 MRI examinations. The median age at SSEC implantation was 2.3 years (1 week-23.2 years). The MRI studies were performed a median of 7.4 years (4 days-23.1 years) after implantation. No patients experienced any reported complications associated with their MRI examinations during the study or at median follow-up post-MRI of 4.8 years (1 day-23 years). In this large, retrospective review of patients with implanted SSEC undergoing MRI, there were no reported adverse events. These findings support the recent change by Cook Medical Inc. of their standard embolization coils from a designation of magnetic resonance unsafe to conditional.

From http://www.mrisafety.com/SafetyInformation_view.php?editid1=192

Safety Topic / Subject

Pellets, Bullets, and Shrapnel

The majority of pellets and bullets tested in the MR environment were found to be composed of nonferromagnetic materials, however, these items are often “contaminated” by ferromagnetic metals. Ammunition that proved to be ferromagnetic tended to be manufactured in foreign countries and/or used for military applications. Shrapnel typically contains steel and, therefore, presents a potential hazard for patients undergoing MR procedures. |

Because pellets, bullets, and shrapnel are frequently contaminated with ferromagnetic materials, the risk versus benefit of performing an MR procedure should be carefully considered. Additional consideration must be given to whether the metallic object is located near or in a vital anatomic structure, with the assumption that the object is ferromagnetic and can potentially move.

In an effort to reduce lead poisoning in “puddling” type ducks, the federal government requires many of the eastern United States to use steel shotgun pellets instead of lead. The presence of steel shotgun pellets presents a potential hazard to patients undergoing MR procedures and causes substantial imaging artifacts at the immediate position of these metallic objects. In one case, a small metallic BB located in a subcutaneous site caused painful symptoms in a patient exposed to an MR system, although no serious injury occurred. Accordingly, MR healthcare professionals should exercise caution when deciding to perform MR procedures in patients with pellets, bullets, shrapnel or other similar ballistic objects.

Smugar, et al. (1999) conducted an investigation to determine whether neurological problems developed in patients with intraspinal bullets or bullet fragments in association with MR imaging performed at 1.5-Tesla. Patients were queried during scanning for symptoms of discomfort, pain, or changes in neurological status. Additionally, detailed neurological examinations were performed prior to MRI, post MRI, and at the patients’ discharge. Based on these findings, Smugar, et al. concluded that a patient with a complete spinal cord injury may undergo MR imaging with an intraspinal bullet or fragment without concern for affects on the physical or neurological status. Thus, metallic fragments in the spinal canals of paralyzed patients are believed to represent only a relative contraindication to MR procedures.

Eshed, et al. (2010) conducted a retrospective investigation of the potential hazards for patients undergoing MRI at 1.5-Tesla with retained metal fragments from combat and terrorist attacks. Metallic fragments in 17 patients were in ranged in size between one and 10-mm. One patient reported a superficial migration of a 10-mm fragment after MRI. No other adverse reaction was reported. The authors concluded that 1.5-Tesla MRI examinations are safe in patients with retained metallic fragments from combat and terrorist attacks not in the vicinity of vital organs. However, caution is advised as well as an assessment of risk versus benefit for the patient.

Dedini, et al. (2013) studied bullets and shotgun pellets that were a representative sample of ballistic objects commonly encountered in association with criminal trauma using 1.5-, 3- and 7-Tesla MR systems. The findings indicated that non-steel containing bullets and pellets did not exhibit substantial magnetic field interactions at 1.5-, 3-, and 7-Tesla, and that both steel-containing and non-steel-containing bullets did not significantly heat, even under extreme MRI conditions at 3-Tesla. Steel-containing bullets were potentially unsafe for patients referred for MRI due to their potential to move in vivo, although this recommendation must be interpreted on a case-by-case basis with respect to the restraining effect of the specific tissue environment, time of the bullet in situ, proximity to vital or delicate structures, and with careful consideration given to the risk versus benefit for the patient.

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