Pacemaker

Medical Implants and MRI Scans: Updating the Research

Millions of potential MRI patients already live with a medical implant. The use of pacemakers has seen a more than 50 percent increase between 1993 and 2009, while the first nationwide study of knee and hip arthroplasties show that over 7.2 million Americans are living with implants.

These implants can increase mobility and improve a patient’s quality of life and life expectancy; there’s no question that they’re a net medical plus. But implants also come with new restrictions, including some that affect our use of MR technologies to obtain diagnostic images.

To be clear, MRI scans are incredibly helpful, low-risk, non-invasive imaging options. But sometimes those with medical implants aren’t able to take advantage of this imaging choice, and the list of affected implants is constantly in flux. That’s why it’s important for all physicians to stay up-to-date on the research regarding medical implants and MRI scans.

Understanding Interactions Between Medical Implants and MRI Scans

Because MRI scans use strong magnets, metal implants could potentially cause negative reactions or distort the images created during the test. Pacemakers, defibrillators, cochlear implants, or other small metal hardware can heat up or be drawn to the machine during an MRI. Electronic devices can also potentially malfunction during a scan, posing a risk to the patient.

That said, medical device manufacturers are always innovating. Increasingly, designers of these devices plan for MRI safety when they’re building their products. So where does the latest generation of medical implants stand when it comes to the safe use of MR modalities during the diagnostic process? That, of course, depends on the implant itself.

New Research on Common Medical Implants and MRI Scans

Pacemakers and defibrillators have long been on the MRI-unsafe list. Recent studies suggest that this abundance of caution is not necessary for most people. One piece in the Journal of Clinical Electrophysiology, labeled a “proof of concept study” by its authors, suggests that the benefits of conducting an MRI scan on patients with pacemakers and defibrillators justified the risk.

Meanwhile, a safety study of nearly 40 medical implants in a 7 Tesla MRI scanner found that only four of them — one heel implant, two stints, and one fibular implant — failed safety tests and earned the designation MR-unsafe for 7-T MRI usage.

Leading hospitals are also building the case for MRI procedures in patients with pacemakers and defibrillators. The Johns Hopkins Hospital has safely conducted MRI studies on more than 300 patients with cardiac implants at the time of this writing.

Of course, none of this is to say that all medical implants are always safe for MRI scans. But as the research continues, and as device manufacturers learn more about which materials and designs interact with MR fields and which don’t, it seems that the diagnostic power of MRI scans will become more and more available to patients who have implanted medical devices. That’s a good thing for patients and for medical science more broadly.

test tubes

What Are the Chances of an MRI Contrast Dye Allergy?

As we’ve covered in other articles, gadolinium-based contrast dyes play an essential role in magnetic resonance imaging (MRI) examinations. Contrast dyes allow technicians to capture high-quality images of various body structures, and for the most part, they’re extremely well tolerated. Patients rarely suffer side effects from gadolinium, and when they do, those side effects are typically mild.

With that said, many patients have understandable concerns about magnetic resonance contrast media. If you’ve got a history of serious allergies, will gadolinium endanger your health?

To put it plainly, probably not. Hypersensitivity is extremely rare, and while patients should always discuss medical concerns with their physicians, we did some research to try to put gadolinium allergies in perspective.

If you’re not sure why gadolinium is necessary, be sure to read our article on contrast dyes.

How Common Are Gadolinium Allergies?

A 2012 study looked at 84,367 patients. Of those participants, 102 patients had hypersensitive reactions to gadolinium. That’s about 0.121 percent of the test group. If you’re otherwise healthy, the chances of an allergic reaction are extremely remote.

Other important takeaways from that study:

  • Women were more likely to have gadolinium allergies than men. Female patients had about 1.687 greater odds of suffering a hypersensitive reaction.
  • Patients with allergies were more likely to suffer a reaction. The odds ratio increased to about 2.829 for these patients, so if you have a history of asthma or allergies, be sure to tell your MRI team.
  • Patients who received multiple doses were more likely to suffer a reaction. If you regularly receive MRIs, you might eventually have a reaction, even if you haven’t had any side effects yet. Still, we’d like to hammer home this point: Reactions of any kind are extremely rare.
  • Most of those hypersensitive reactions weren’t severe. 91.1 percent of patients only suffered urticaria (the medical name for hives). A more severe anaphylactic reaction occurred in 11 cases (9.8 percent of allergic patients). Due to one fatality — and remember, this study looked at more than 84,000 patients — the mortality rate was 0.0007 percent.
  • Some dyes were more likely to cause a reaction than others. Gadodiamide, for instance, had a hypersensitivity rate of only 0.013 percent. That means that if you do have an allergy, your technicians can probably find a dye that you can tolerate.

When you set up your MRI, be sure to tell your physician and your imaging team about any allergies or any reactions you suffered in past procedures. However, don’t worry about the dye; it’s extremely safe, and even if you have a reaction, it will probably be treated easily before you leave the examination room.

Remember, if you need an MRI, you can save a tremendous amount of money by comparing costs. Precise Imaging has evaluated a large network of professional MRI clinics, and our convenient online tools help to make the process much less stressful. Call us at 800-558-2223 to book your appointment or email [email protected] to get started.

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.

The Mammography Quality Standards Act (MQSA): What Physicians Should Know

More than 65 percent of U.S. women aged 40 and over had mammograms between 2013 and 2015, and all of them were protected by a little-known 1992 law called the Mammography Quality Standards Act, or MQSA. Understanding this law is important for radiologists and referring physicians alike, so they can explain it to assure patients that their care meets strict standards of quality. This increases trust between patients and health care providers, ultimately leading to better outcomes.

 

So what does the MQSA do, exactly? The short answer is that it requires diagnostic imaging providers to produce mammogram images that meet high standards of quality. For a longer, more in-depth answer, we need to look back at the years before Congress passed the law, to a time when breast cancer was “the most compelling health threat to American women,” as a 1993 article in the American Journal of Law & Medicine states.

 

(Though breast cancer rates have been decreasing since 2000, one in 8 women in the U.S. will still develop the illness in 2018. More than 40,000 American women are expected to lose their lives to breast cancer that year.)

 

In the early 1990s, the American College of Radiology maintained a set of accreditation standards that required monitoring for mammography equipment and staff qualifications. But those guidelines, strict though they were, were entirely voluntary. And as Dr. Charles Smart of the National Cancer Institute told Newsday in 1991, “Unless mammography is done with quality, there is no use doing it…It isn’t enough to get a woman to get a mammogram. It has to be a good mammogram. And it has to be interpreted by someone who is experienced and trained in it.”

 

That wasn’t always the case at the time. The Physician Insurers Association of America studied the efficacy of mammograms in the early 1990s and found that 35 percent of women with breast cancer actually had negative results on their mammograms. Another study found that image quality and radiation exposure differed greatly from one diagnostic imaging provider to the next.

 

By 1992, the effects of this lack of quality had gained the attention of Congress. They acted to pass a bill that would require all diagnostic imaging facilities that conduct mammograms to meet certain standards of quality and to be issued a certificate from the Secretary of Health and Human Services: The Mammography Quality Standards Act of 1992.

 

What the Mammography Quality Standards Act Requires from Imaging Providers

 

In order to obtain a certificate, diagnostic imaging providers must meet a distinct set of standards, including, in part:  

 

  • They must pass a review of their clinical images at least every three years.

 

  • These images will comprise a random sample and must be inspected by qualified physicians.

 

  • These reviewers must not have a conflict of interest with the sites they inspect.

 

  • In addition to the review of images, facilities must pass an annual survey conducted by a medical physicist.

 

  • All personnel involved in the preparation and reporting of a mammogram must be certified by the Secretary of Health and Human Services.  

 

A major component of retaining accreditation is the quality of mammogram images themselves. Certified MQSA review physicians carefully inspect a representative range of a mammogram-provider’s images. They score these images based on the quality of at least eight criteria:

 

  1. Correct positioning, such that the chance of missing signs of cancer are reduced.
  2. Adequate compression that avoids conflating motion artifacts and actual tissues.
  3. Perfect exposure; neither underexposed nor overexposed.  
  4. There must be enough contrast between light and dark to easily show subtle differences in tissue density.
  5. The image must be sharp, not blurry.
  6. A minimum of visual “noise,” or visible artifacts from the imaging process.
  7. No processing artifacts, such as scratches or lint, may be allowed to obscure the structures of the breast.
  8. All images must include identification and other exam details.  

 

The U.S. Food and Drug Administration oversees the MQSA program, and has approved a small group of organizations as “accreditation bodies,” or entities that can legally provide the accreditation necessary for conducting mammography procedures. The American College of Radiology is the main accreditation body under the MQSA, but the states of Arkansas, Iowa, and Texas can also provide credentials for facilities located within their borders.

 

The Costs of Failing to Comply with MQSA

 

All diagnostic imaging providers that offer mammograms must comply with the quality standards set forth under the MQSA. If they violate any part of the standards, the Secretary of Health and Human Services might issue any of a series of corrective actions, including:

 

  • Providing a plan and a timeline for the facility to correct its violation.
  • The Secretary may order on-site monitoring at the facility’s cost.
  • In egregious cases, the Secretary may order the violator to send notifications to all of their patients, explaining the situation.
  • For certain violations, the Secretary can issue a fine of up to $10,000.

 

Ultimately, violating MQSA regulations can shutter a business in two ways. The accrediting body, such as the ACR, could withdraw a facility’s accreditation. Or the Secretary of Health and Human Services can revoke the certificate. Owners and operators of facilities that lose their certificates may even be banned from offering mammograms for two years.  

 

How Effective is MQSA at Improving the Quality of Mammograms?

 

As of the latest report, 8,726 facilities were certified to perform mammograms in the United States, not including VA hospitals. Inspections turned up no violations for 88.5 of these providers.

 

Patients who are new to mammography may be encouraged to learn that nearly 90 percent of the mammogram providers in the country meet the strict standards of quality required by the MQSA. To learn more about the Mammography Quality Standards Act, see the FDA’s website about the program here.

TIA-MRI

MRI Scans and Transient Ischemic Attack (Mini-Strokes): Timeliness Makes a Difference

29 Jan 2018 Uncategorized

A transient ischemic attack (TIA) or commonly referred to as a mini-stroke has traditionally been regarded as a minor and temporary condition, but timely MRIs have proven that these events belong on the same spectrum as strokes. However, because TIAs, by definition, only last a short time, MR imaging must take place as quickly as possible for the fullest yield of useful information.

 

There is now a consensus that having a TIA increases a person’s risk of a stroke.

 

Approximately one in six people who survive a TIA suffer a stroke within 90 days. Undergoing an MRI as soon as possible after a TIA can detect crucial warning signs that computed tomography (CT) alone cannot see.

 

Previous consensus guidelines from the American Heart Association (AHA) do not recommend MRI for all TIA patients because of the higher cost. However, mounting evidence suggests that an MRI within 1 to 2 days of a TIA could spot evidence of a stroke that may disappear in time.

 

MRIs can detect tissue damage even when symptoms are temporary.

 

The sophisticated imaging technique can detect stroke lesions that may become less apparent quickly. A study from the journal Stroke followed 263 patients who had suffered a TIA or minor stroke and received a baseline MRI within 24 hours. After 90 days, a follow-up MRI was conducted.

 

The results of each patient’s two MRIs were assessed independently and the results confirm the importance of early scans. Thirty percent of patients with a negative scan at 90 days had a clearly identifiable stroke in the baseline image. Without the early scan, physicians would not know that a stroke had occurred in this large group of patients.

 

In spite of this evidence, some physicians settle for a less-precise CT scan. A recent study from Neurology found that just 40 percent of patients with TIA or minor stroke had an MRI performed within 48 hours.

 

New guidelines offer options for those at high-risk of stroke.

 

The AHA and American Stroke Association have published new consensus guidelines for preventing strokes in patients with a history of strokes or TIA. Reducing hypertension and statin therapy remain at the top of the list. Increasing physical activity, reducing sodium intake, and following a Mediterranean-style diet (as opposed to a low-fat diet) are recommended. Other practices, such as sleep assessments and anti-platelet therapy immediately following a TIA may be considered.

 

For patients with a history of stroke or TIA, the average annual rate of future stroke is at an all-time low. That’s great news, but a more nuanced understanding of TIAs and timely MRI of those who suffer them could yield even more impressive results.

 

References:

 

AHA and ASA Release Guideline for Prevention of Future Stroke in Patients with Stroke or TIA. American Family Physician. January 2015;91(2):136-137. Available from: https://www.aafp.org/afp/2015/0115/p136.html

 

Chaturvedi S et al. Have clinicians adopted the use of brain MRI for patients with TIA and minor stroke? Neurology. January 2017;88(3):237-244. doi:10.1212/WNL.0000000000003503

 

Krieger D. Should patients with TIAs be hospitalized? Cleveland Clinic Journal of Medicine. August 2005;72(8):722-724. Available from: http://www.clevelandclinicmeded.com/medicalpubs/ccjm/august2005/krieger.htm

 

Moreau F et al. Early Magnetic Resonance Imaging in Transient Ischemic Attack and Minor Stroke: Do it or Lose it. Stroke. March 2013;44(3)671-674. doi:10.1161/STROKEAHA.111.680033

 

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