Head MRI

MRI Scans with Contrast and How They Differ From MRI Scans Without Contrast

When recommending MRI examinations, physicians often encounter concerns from their patients—which is understandable, but largely unnecessary. Compared with other imaging technologies, MRIs provide high-quality images with very limited risks.

Even so, physicians should certainly understand the current science surrounding various gadolinium-based contrast dyes when making their recommendations. Gadolinium dyes provide enhanced clarity, which can be essential when making a diagnosis, but they’re not always necessary, and in some cases, they may be unsafe. Speak with a radiologist in order to make appropriate decisions on a case-by-case basis.

In this article, we’ll address several recent studies; note, however, that this is not intended as a comprehensive set of recommendations or as a thorough analysis of health risks.

What are the risks of gadolinium-based contrast agents?

Research shows that gadolinium can accumulate in the brain, most notably in the dentate nuclei and globus pallidus. As these regions of the brain are involved in motor function, it’s conceivable that motor function could be affected over time, particularly in patients who undergo numerous MRIs. Some forms of gadolinium may also disrupt the action of thyroid hormone, which is an important concern to keep in mind when administering MRIs to pregnant patients.

One perinatal in vivo study (performed on adult mice) found that:

… when gadoterate meglumine or gadodiamide was intravenously injected into dams during perinatal period (embryonic day 15–19, single injection/day), which is the critical period for the functional organization of neuronal circuits, both GBCAs disrupted motor coordination and impaired memory function [8]. The magnitude of disruption was higher with gadodiamide.

However, in human patients, these neurological effects haven’t been established. There’s no evidence to suggest that gadolinium deposition in the brain affects neurological function, and the mere presence of gadolinium deposits shouldn’t be perceived as a reason to forego dye-enhanced MRIs, particularly when dyes would provided a diagnostically useful image that wouldn’t be attainable otherwise.

A more pressing concern is nephrogenic systemic fibrosis, a rare condition which has been proposed as causally linked to gadolinium contrast dyes. This typically isn’t a concern in healthy patients, but gadolinium agents should not be administered to patients with severe kidney issues.

In the vast majority of cases, gadolinium contrast agents could allow for faster, more thorough treatment of serious health conditions, and the benefits of contrast dyes will greatly outweigh the potential risks.

Should physicians recommend contrast-free MRI scans to patients?

Since gadolinium deposits accumulate in the brain, contrast dyes shouldn’t be used haphazardly. A 2017 review from the International Society for Magnetic Resonance in Medicine (ISMRM) recommended that the MRI community avoid using gadolinium-based contrast agents when they are not necessary.

Of course, this is a fairly obvious conclusion for physicians—the real question is what constitutes a medical necessity. The ISMRM stopped short of recommending wide changes to the way that contrast dyes are used, and to date, there’s no evidence linking gadolinium deposits in the brain and adverse health effects.

It’s also important to note that different contrast dyes accumulate in different ways. While all gadolinium-based agents seem to form deposits in the aforementioned regions of the brain, the size of these deposits vary; gadoterate meglumine (macrocyclic GBCA), for instance, does not seem to significantly change thyroid hormone action.

With this in mind, physicians should recommending MRI scans with gadolinium-based contrast agents to pregnant women. When patients are likely to undergo numerous MRI scans, gadolinium-based contrast agents should be used as infrequently as possible.

Finally, patients who have a high susceptibility to renal failure should not be exposed to gadolinium-based contrast dyes, unless there is no viable alternative. When this is the case, lower-risk gadolinium agents are obviously preferable.

However, it’s important to note that, at this point, there is no evidence showing that gadolinium is inherently unsafe. When compared with the iodine-based agents used for x-ray examinations, gadolinium contrast dyes are largely preferable.

Physicians who need fast access to MRI services can make referrals through the Precise Imaging physician’s portal. This online tool provides anytime access to the crucial services we provide.

Call Precise Imaging at 800-558-2223 to make a referral or schedule an appointment today.

References:

Ariyani, W., Khairinisa, M.A., Perrotta, G. et al. The Effects of Gadolinium-Based Contrast Agents on the Cerebellum: from Basic Research to Neurological Practice and from Pregnancy to Adulthood. Cerebellum. (2018) 17: 247. https://doi.org/10.1007/s12311-017-0903-4

Goischke, HK. MRI With Gadolinium-Based Contrast Agents: Practical Help to Ensure Patient Safety. J Am Coll Radiol. 2016;13(8):890. https://doi.org/10.1016/j.jacr.2016.05.007

Gulani V, Calamante F, Shellock FG, Kanal E, Reeder SB. Gadolinium deposition in the brain: summary of evidence and recommendations. The Lancet. 2017;16(7):564-570. Published 2017 Jul 1. doi: doi.org/10.1016/S1474-4422(17)30158-8

Khairinisa MA et. al. The Effect of Perinatal Gadolinium-Based Contrast Agents on Adult Mice Behavior. Invest Radiol. 2018;53(2):110-118. Published Feb 2018. doi: 10.1097/RLI.0000000000000417

Schlaudecker JD, Bernheisel CR. Gadolinium-associated nephrogenic systemic fibrosis. Am Fam Physician. 2009:80(7):711-4. Published Oct 1 2009. PMID: 19817341.

Metal Worker

The MRI for Metal Workers: Hazards and Solutions

Sheet metal workers, welders, and others exposed to tiny metal fragments face particular risks during an MRI scan. An adequate screening questionnaire will ask patients if they’ve been exposed to metal fragments well before they enter the MRI suite. In order to minimize anxiety both before and during imaging procedures, physicians should educate patients who work with metal early in the conversation.

Here are the key things to communicate to metal workers when referring them to a diagnostic imaging provider:

  • The presence of metal in the body may not present a health risk, but may still contraindicate MRI as an imaging modality. Even if metal fragments don’t react to the magnet in ways that can cause harm, they can still disrupt magnetic field homogeneity. This can cause visual artifacts and signal loss, limiting the diagnostic value of the resulting images.

    Senol and Gumus present a novel example of this distortion in a brief submission to the journal Quantitative Imaging in Medicine and Surgery. The patient they describe was a metal worker; despite the fact that he had showered and washed his hair prior to his MRI scan, some metal dust remained on his scalp. These fragments created strange circular objects, like water bubbles, on the resulting images. (These images were obtained on a 1.5 Tesla MRI scanner.)

  • Sheet metal workers are more likely than others to have tiny metal shards in their eyes, and these objects may not produce any symptoms at all. Patients are often unaware of the presence of intraocular foreign bodies. For instance, see this article from the American Journal of Ophthalmology Case Reports.

    Even if patients aren’t experiencing discomfort or pain, physicians may elect to obtain images of the eyes via nonmagnetic means before progressing to the MRI study.

  • Standard procedure is to order a CT orbit scan prior to MRI for patients who face higher risks of metal fragments in their eyes. CT scans don’t use magnets at all, and are safe for patients who have metal shavings in their eyes. The orbit CT scan is a quick, noninvasive way to make sure patients can safely receive an MRI in scanners of any strength.

  • Regardless of the findings of preliminary scanning, patients will always have a way to stop the MRI procedure for any reason. Patients will always have a route of communication with the attending technologist. If they have any concerns during the procedure, they can always tell their technologist, who will stop the scan and evaluate the situation before proceeding.

  • If the MRI scan poses any health threat at all, plenty of alternative imaging modalities are available to meet diagnostic goals. In the rare event that technologists and radiologists do find ferromagnetic metal fragments within the patient’s eyes or body, they can always use an alternative imaging technique. Scans involving X-rays don’t create magnetic fields, and won’t interact with metal implants or particles.

The pre-MRI screening process is designed to ensure safety for patients, and a big part of the effort is discerning the presence of ferromagnetic metallic objects within the body. The high-powered magnetic fields involved in an MRI scan can cause these objects to heat up, vibrate, or even shift location — clearly, this presents a health risk for patients, contraindicating MRI as a diagnostic imaging modality.

Despite these risks, physicians can help to provide a more comfortable treatment experience by discussing the above issues with qualifying patients from the beginning of the diagnostic process. Doctors can continue to order the MRI for metal workers with a high degree of confidence in the safety, efficacy, and comfort of their patients, and communication plays a central role in the process.

References:

Platt AS, Wajda BG, Ingram AD, Wei XC, Ells AL. Metallic intraocular foreign body as detected by magnetic resonance imaging without complications- A case report. Am J Ophthalmol Case Rep. 2017;7:76-79. Published 2017 Jun 22. doi:10.1016/j.ajoc.2017.06.010

Senol S, Gumus K. A rare incidence of metal artifact on MRI. Quant Imaging Med Surg. 2017;7(1):142-143.

Search

+