Overview of Gadolinium Magnetic Resonance Imaging
Contrast agents are drugs used to enhance the images produced during diagnostic tests. They work by changing the natural properties of tissues. This change helps improve the quality of images, making it easier for doctors to understand the state of your health. The MRI (Magnetic Resonance Imaging) scan is a unique diagnostic tool since it can study more than just one aspect of tissues.
In MRI scans, four factors determine the quality of the image: spin density, susceptibility, proton relaxation, and motion. These factors can be manipulated by using contrast agents to increase image clarity. As of now, there are four such agents approved for use.
Since 1994, three MRI contrast agents have been permitted for use in the United States, with an additional six received the approval from the Food and Drug Administration ( or FDA ) from 1995 to 2017. These additional agents include gadopentetate dimeglumine, gadodiamide, Gadoteridol, gadoterate meglumine, gadobenate dimeglumine, and gadobutrol.
However, two of these agents, gadofosveset trisodium and gadoxetic acid, are not approved for enhancing the contrast of images of the central nervous system (CNS). This is due to their unique properties that make them unsuitable. For example, Ablavar is only approved for imaging arteries close to the heart since it binds strongly to a protein found in blood and cannot cross into brain tissue. Similarly, Eovist is made specifically for liver imaging since it is absorbed and removed by liver cells.
While studies have confirmed the safety of these seven contrast agents, there’s still some misunderstanding about their differences. All these agents are essentially water-soluble mixtures that include the element gadolinium, which rapidly leaves the body via the kidneys. However, they still differ from each other in terms of their molecular structure, charge, and the kind of structure-based design they feature.
These differences in structure provide for more control over dosage and enhanced stability for some agents. For example, Gd-DTPA and Gd-DOTA are charged while Gd-HP-D03A and Gd-DTPA-MBA are uncharged, and they all have different molecular bases. All these properties affect the contrast in MRI images.
Concentration of these contrast agents in specific tissues depends on various factors, including the agent’s properties, the magnetic field strength, the tissue type, and more. Gadolinium-based contrast agents enhance imaging by increasing the signal intensity but decreasing the Longitudinal Relaxation time (T1) and Transverse Relaxation time (T2). Most of these agents produce a stronger signal in T1-weighted images.
We can classify these gadolinium-based contrast agents into three categories based on their usage and chemical structure: extracellular, blood pool, or hepatobiliary agents.
Extracellular agents are small, non-specific compounds primarily used in detecting tumors and inflammation, and in magnetic resonance angiography.
Blood pool agents are usually used in angiography. These remain in the bloodstream for longer periods, making the timing of image capture less critical than with extracellular agents. Such agents provide more leeway, as they can stay in the blood for a longer duration, making it easy to take pictures without needing precise timing.
Why do People Need Gadolinium Magnetic Resonance Imaging
MRI, which stands for Magnetic Resonance Imaging, is a type of scan that allows doctors to see detailed pictures of the inside of your body. Unlike CT scans and X-rays, MRIs do not use potentially harmful radiation. Instead, they use a very strong magnet, radio waves, and a computer to create images. These images can reveal if there’s an illness, injury, or any other unusual condition in your body.
During an MRI, you lie down inside a large, hollow, cylindrical magnet that is open at both ends, known as the MRI scanner. This machine has an extremely strong magnetic field that lines up tiny particles, called protons, found in the tissues of your body. Radio waves of a specific frequency are then sent out, which cause these protons to emit signals. These signals are picked up by receiver coils in the scanner and, with the help of a computer, they are turned into images. These images are like “slices” of your body that doctors can look at to check for anything abnormal.
One important thing to note is that the electromagnetic fields used during an MRI do not cause any known harm to your body, and the procedure doesn’t cause any pain. However, the scanner does make loud knocking, tapping, and other rhythmic noises during the procedure. To make you more comfortable, earplugs can be provided to minimize these sounds. There’s also a communication system to let you talk to the technician operating the scanner during the procedure.
To help doctors see the images more clearly, sometimes a contrast agent is injected into a vein in your hand or wrist during the scan. This special dye is commonly made from a substance called gadolinium. Unlike the contrast dyes used in CT scans and X-rays, gadolinium doesn’t contain iodine, so it’s unlikely to cause adverse effects or trigger allergies in most people. However, if you have a history of kidney or liver disease, or if you’ve had a kidney transplant, you should let the radiologist or MRI technician know before this dye is given. If you’re unsure about any allergies or reactions you may have, make sure to discuss this with them before your MRI procedure.
When a Person Should Avoid Gadolinium Magnetic Resonance Imaging
Before you get an MRI scan, you’ll need to fill out a form that asks about any substances or objects in your body that might interfere with the scan or pose a risk to your health. Things that could cause issues include:
– Metal objects in or near your eye, often a problem for people who work with metal or in machine shops
– Certain medication pumps placed inside or outside of your body
– Metallic clips put in your blood vessels to prevent bleeding from a brain aneurysm
– Certain systems used to stimulate your nervous system
– Some implants in your inner ear
– Catheters containing metal components
– Bullets, shrapnel, or other metal fragments
– Some devices that control your heart rhythm
It’s crucial to note that not all of these items are a problem – some are safe for MRIs. But your doctor and MRI technician need to know the specifics to keep you safe.
Before entering the MRI room, you’ll need to remove:
– Clothing with metal pieces or fibers
– Hair accessories
– Phones and pagers
– Hearing aids
– Coins, keys, paper clips, etc.
– Belts, shoes, safety pins
– Jewelry and watches
– Wallets, credit/debit cards, and other items with magnetic strips
Certain objects can distort the images from an MRI scan, including:
– Dental fillings, braces, or retainers
– Metal plates, screws, pins, or mesh used to fix joints or bones
– Some tattoos or tattooed eyeliner
– Metallic body jewelry, including piercings
– Replaced joints or other implanted devices
– Makeup or other cosmetics with metallic elements, nail polish
– Metal rods in your spine
If you’re pregnant or there’s a chance you could be, you should let the MRI technician and/or doctor know during your pre-scan screening. Using an MRI without a contrast agent (a substance that helps visualize certain areas) called gadolinium is generally safe in pregnancy, but it’s only used when necessary.
If you are breastfeeding, you should let your doctor know in case they need to use a contrast agent. If they do, you may need to pump and store some milk before your scan, then wait 24 to 48 hours after your scan before breastfeeding again. Your doctor can provide more information about this.
Be aware that atomic gadolinium, a metal sometimes used in MRIs, can be toxic, but is tolerated because it is surrounded by other protective chemicals during the scan. It can sometimes cause side effects like low or high blood pressure, headaches, fainting, skin flushing, stomach discomfort, anxiety, sleepiness, double vision, losing consciousness, seizures, numbness or tingling, throat irritation, sneezing, rash, sweating, itching, hives, face swelling, eye or ear pain, changes in taste, or a dry mouth.
Some people have reported experiencing severe reactions after using gadolinium-based contrast agents, including severe allergic reactions, difficulty breathing, swelling in the throat, heart or respiratory arrest, or a condition called nephrogenic systemic fibrosis. The most common reactions reported were nausea, vomiting, hives, and rashes. We aren’t sure what the effects of gadolinium in the brain are yet, and some people are currently suing over this issue. We usually use versions of gadolinium that don’t deposit much in the brain.
Equipment used for Gadolinium Magnetic Resonance Imaging
MRI, or Magnetic Resonance Imaging, is a technique used to take in-depth pictures of the body’s organs and tissues. Unlike X-rays, it doesn’t use radiation. Instead, it uses a strong magnetic field, magnetic field gradients, radio waves, and a computer to create these pictures. The result is clear images that can show normal body functions, as well as problems like infections or inflammation.
During an MRI, the patient is placed inside a large, tube-like machine that’s open at both ends, known as the MR scanner. This machine creates a strong magnetic field that aligns the hydrogen protons (tiny particles) found in most of the body’s tissues. It then sends out radio waves, which cause these protons to send back signals. The scanner picks up these response signals and a computer uses them to produce images of the body.
The images appear as “slices” of the body, which doctors can look at from different angles – side-on (sagittal), front-on (coronal), cross-sectional (transverse), and at an angle (oblique). The doctors can examine these images to check for any problems.
It’s important to note that MRIs are painless and the magnetic fields used don’t cause any known tissue damage. The MRI scanner does make some knocking or tapping sounds which some people find annoying, but earplugs can be used to block out most of this noise. During the procedure, you’ll be monitored continuously, and there’s an intercommunication system that allows you to talk to the radiology technologist operating the scanner if you need to.
Who is needed to perform Gadolinium Magnetic Resonance Imaging?
There are specific safety rules for people working near a Magnetic Resonance Imaging (MRI) machine, which is a device used in radiology to take pictures of the inside of your body. These people are labeled as MR personnel and they’re expected to stay updated on MRI safety lectures or presentations every year, which is confirmed with appropriate paperwork. This helps to ensure their own safety and the safety of the patients.
MR personnel are grouped into two levels:
- Level 1 MR personnel: These people have completed the basic safety training enabling them to work near the MRI machine.
- Level 2 MR personnel: These people have received more extensive training, covering wider MRI safety issues such as the risk of burns from the MRI machine or the risk of muscle twitching from rapid changes in the magnetic field. The person in charge of MRI safety, known as the MR medical director, decides who qualifies as Level 2 MR personnel.
People who haven’t completed or kept up-to-date with this training are categorized as non-MR personnel to highlight the fact that they have not been trained in MRI safety within the last year.
The terms MR personnel and non-MR personnel, helps in separating those trained to work in the MRI environment from those who are yet to be trained. Among MR personnel, there are also MRI machines technologists. These people should be registered with the American Registry of Radiologic Technologists (ARRT), meaning they’ve earned a professional certification to operate an MRI machine. They must also be trained as Level 2 MR personnel before they are allowed to work near the MRI machine on their own.
All MRI technologists need to know basic life-saving measures which is usually certified through the American Heart Association. Usually, there should be a team of at least two people who have completed MRI safety training, present in the MRI workspace. However, in emergency situations, a single MRI technologist can work alone if backup is readily available.
Also, always remember that MRI machines are always “on” and can attract metal objects into the machine’s opening. The MRI workplace is divided into four areas known as zones, each with its own safety regulations.
Preparing for Gadolinium Magnetic Resonance Imaging
When you’re having an MRI, you’ll be asked to change into a hospital gown. You, or anyone with you, will need to answer some questions on a form about any metal objects or devices like implants in your body. That’s because the MRI machine uses powerful magnets which can attract any metal on or in your body. So, you’ll also be asked to remove any jewelry and empty your pockets of metal objects. Anyone with you will need to do the same for their safety if they’re going to be in the room with the MRI machine. If you have any other questions or concerns, you can always speak to the MRI technicians or the doctors who will perform the MRI.
If your MRI requires a contrast agent, a type of dye to make the images clearer, you’ll have a small tube (an IV catheter) placed into a vein in your arm or somewhere else that’s easy to reach. The technicians will usually take a few images without the dye first. Then they’ll give you the contrast agent, a specific substance called Gadolinium, through the tube. The dose will be based on your weight, about 0.10 mmole for each kilogram (2.2 pounds) you weigh. After the dye is injected, the tube will be flushed with a harmless salt solution (saline) to make sure all the dye has been used. Lastly, they’ll take a few more images with the dye. The whole process will take roughly 15 seconds for every 10 mL of dye that’s given.
The Gadolinium, which is the contrast agent, comes from the manufacturer in different amounts, such as single doses in small bottles (vials) or prefilled syringes. They also offer larger amounts (bulk packages) for use in hospitals and clinics.
How is Gadolinium Magnetic Resonance Imaging performed
An MRI scan is a type of medical imaging that uses powerful magnets and radio waves to create detailed images of the inside of your body. The procedure takes place in a special room that houses the MRI machine or ‘scanner’. The machine itself is usually shaped like a tube that opens at both ends. The patient lies on a padded, comfortable table that slides into and out of the scanner.
Before the procedure begins, patients are provided with earplugs or headphones. This is because the scanner can make loud, rhythmic noises when it’s working. While these sounds can be distracting, they’re perfectly normal and nothing to worry about.
In some cases, a dye (called a contrast agent) is injected into a vein to help make the images clearer. This dye is often made from a substance called gadolinium. If this is needed, you’ll be moved out of the scanner for the dye to be injected through a small tube (or catheter) into a vein in your hand or arm. This dye is then flushed out from your body after the procedure, usually by drinking plenty of water.
An MRI scan can take anywhere between 15 to 60 minutes, or sometimes even longer. During that time, it’s really important for you to lie still and relax. This helps to ensure the images are as clear as possible. However, during certain parts of the scan, you may be allowed to make small movements – the radiologist will let you know when you can and can’t move.
Once your scan is done, the images will be reviewed by a radiologist – a doctor specialized in interpreting medical images. They will then send a report to your primary care physician, who will discuss the findings with you.
The technical aspect of an MRI involves a complex interaction between the hydrogen protons (type of particles) in your body, a magnetic field, and radio waves. To put it simply, the MRI machine creates a magnetic field around the part of your body that’s being scanned. This affects the protons in your body, and when radio waves are sent into this area, the protons react by sending back signals. These signals are collected and turned into the images that doctors review.
There are two important timing factors involved in creating these images, called T1 and T2. These ‘relaxation’ times help the machine tell the difference between different types of tissue in your body, allowing it to create detailed, clear images. By adjusting the settings of the machine, the radiologist can change how the images look and what types of tissue they highlight – this helps doctors to better diagnose and monitor various medical conditions.
Possible Complications of Gadolinium Magnetic Resonance Imaging
Some people who go for MRI scans might feel scared or claustrophobic. Around one out of every twenty patients might even need a calming medication to help them stay relaxed during the procedure. These patients could consider using one of the newer wide-bore or “open scanner” designs to ease their feelings of confinement. The downside to the open scanner is that its magnetic field strength is lower. Most MRI centers allow a friend or relative to be with the patient in the scanning room which can also help reduce anxiety and fear. Properly preparing patients for what to expect can also make it possible for most clinical studies to be completed without issues.
Patients with kidney issues may develop a serious side effect from the contrast agent (a special dye) used in some MRIs; this condition is called nephrogenic systemic fibrosis (NSF). NSF is a rare disorder that primarily affects people with kidney problems. It often occurs in the context of gadolinium-based contrast agents, which are a type of dye used in MRIs to get better pictures. It’s important to know that while NSF is associated with these agents, it can still occur without them. However, almost all NSF cases are seen in patients having certain stages of chronic kidney disease or acute kidney injuries.
The risk of developing NSF varies depending on the specific type of contrast agent used. In particular, a class of contrast agents known as macrocyclic agents, which look like cages wrapped around the gadolinium ion, have a lower risk. They are considered more stable and thus less likely to release free gadolinium, which can cause NSF. The contrast agent Omniscan is among the least stable and has been associated with most NSF cases, even though it only makes up 15% of all gadolinium-based contrast agent use.
It should also be noted that the gadolinium-based MRI contrast agents can harm unborn babies. That’s why they usually aren’t used in pregnant women unless the potential benefits outweigh the risks.
What Else Should I Know About Gadolinium Magnetic Resonance Imaging?
Magnetic resonance imaging (MRI) is a medical imaging technique that gives doctors a detailed look inside your body. However, it’s crucial to understand that unlike a similar technique used in chemistry called nuclear magnetic resonance (NMR), MRI isn’t sensitive enough to image individual molecules. Instead, it displays how molecules move and are distributed based on the characteristics of nearby tissues.
One tool that can enhance this process is a Gadolinium-based MRI contrast agent. This agent is a special substance that can detect changes and differences in how molecules move and are arranged. By doing so, it helps bring out the details in the MRI scan, making it an important tool in the development of molecular imaging – the visualization of molecules in a biological context.
Use of these Gadolinium-based agents requires an interprofessional team of researchers, including experts in cell biology, chemistry, biochemistry, physiology, biomedical engineering, and radiology. Their combined knowledge allows for the applicability of these agents to various biological or biomedical studies.
Gadolinium-based MRI contrast agents have significantly improved the way we diagnose and treat diseases. Over the past 25 years, over 100 million patients worldwide have benefited from them. These agents function by influencing the magnetic properties of water molecules in our bodies, which enhances the quality of the MRI images.
Finally, using Gadolinium-based MRI contrast agents improve the visualization of specific organs, tissues, and blood vessels. This means that doctors can diagnose and treat a variety of health issues more accurately, as they can see these areas in greater detail.
