Magnetic resonance imaging (MRI) of the intestine

Magnetic resonance imaging of the intestine is an imaging test that provides detailed pictures of the intestine. This method can help the doctor diagnose inflammation, bleeding, obstruction, and other problems. It is non-invasive and does not use ionizing radiation. An MRI uses a magnetic field to create detailed images of the intestines. The computer analyzes the images. Before the exam, oral and intravenous contrast material is administered to highlight the bowel. Medication may also be given to reduce bowel movement (peristalsis), which can interfere with images. It is very important to tell the doctor about any health problems, recent surgeries or allergies, and if there is any possibility that the patient is pregnant. The magnetic field is not harmful, but may cause some medical devices to malfunction. Most orthopedic implants pose no risk, but one should always tell the technologist if there is any device or metal in the body.

What does the equipment look like?

Typically, an MRI scanner consists of a large cylindrical tube surrounded by a circular magnet. The patient lies on a movable examination table that slides into the center of the magnet. Some newer MRI machines have a larger bore, which may be more comfortable for larger or claustrophobic patients.

Other MRI machines are open on the sides (open MRI). Some MRI scanners, called squirrel-cage systems, are designed so that the magnet does not completely surround the person. The open ones are especially useful for examining larger or claustrophobic patients. Newer open MRI units provide very high quality images for many types of examinations. Older open MRI devices may not provide the same image quality. Some types of examinations cannot be performed using an open MRI. The computer workstation that processes the image information is located in a separate room.

How is this procedure

Unlike conventional x-rays and CT scans, MRI scans do not use ionizing radiation. Instead, RF pulses reconfigure the hydrogen atoms that naturally exist inside the body when the patient is in the scanner, without causing any chemical changes in the tissues. As the hydrogen atoms return to their normal alignment, they release different amounts of energy, which vary depending on the type of body tissue from which they come. The MRI scanner captures this energy and creates a picture of the tissues scanned based on this information. Electric current does not come into contact with the patient. The signals are then processed by a computer and a series of images is generated, each showing a thin section of the intestine. The images can then be examined from different angles by an interpretive radiologist. Often, differentiation of abnormal (diseased) tissue from normal tissue is better with MRI than with other imaging modalities such as x-rays, CT, and ultrasound.

Применение МРТ кишечника

Doctors use MRI to determine the presence and location of these bowel disorders:

• the presence and complications of Crohn’s disease, and other inflammatory bowel diseases;
• inflammation;
• источники кровоточивости и сосудистые аномалии;
• swelling;
• abscesses and fistulas;
• bowel obstruction.

How to prepare

Medicines and food can be taken as usual. Some MRI exams may require the use of a contrast agent. The radiologist, technologist, or nurse should ask if the patient has any kind of allergy, such as an allergy to iodine or radiopaque material, drugs, food, or the environment, or if they have asthma. The contrast material most commonly used for MRI examinations contains a metal called gadolinium. Gadolinium may be used in patients allergic to iodine contrast. It is much less common for a patient to be allergic to a gadolinium-based MRI contrast agent than to an iodinated CT contrast agent. However, even if the patient is known to be allergic to gadolinium contrast, it can still be used after appropriate prior treatment. You also need to tell the radiologist if you have any serious health problems or any recent surgeries. Some conditions, such as severe kidney disease, may prevent the use of gadolinium contrast for MRI. If there is a history of kidney disease or a liver transplant, a blood test will be needed to determine if the kidneys are functioning adequately.

Ювелирные изделия и другие аксессуары следует оставлять дома, если это возможно, или удалять до сканирования МРТ. Поскольку они могут влиять на магнитное поле, металлические и электронные предметы не допускаются в комнату для экзаменов. Помимо воздействия на изображения МРТ, эти объекты могут причинить ущерб.

These items include:

• watches, hearing aids;
• metal zippers and hairpins;
• removable dentures;
• glasses, pens, pocket knives;
• пирсинги.

In most cases, the MRI test is safe for patients who have metal implants, except for some types. People with these implants cannot undergo this test and are not allowed to enter the area where the MRI scan takes place:

• cochlear (ear) implant;
• some types of clamps used for brain aneurysms;
• almost all cardiac defibrillators and pacemakers.

Tell your doctor if you have medical or electronic devices in your body. These items may interfere with the examination or potentially pose a risk depending on their nature and the strength of the MRI magnet. Some implanted devices may take time after placement before being safe for MRI, usually no more than six weeks. Examples include, but are not limited to: artificial heart valves, implanted drug infusion ports, artificial limbs or metal articular prostheses, implanted nerve stimulators, pins, screws, plates, stents. If there is any question about their presence, X-ray diagnostics can be used to locate and identify the location of any metallic objects. The magnetic field does not affect dental fillings and braces. Family members accompanying patients to the scanning room should also remove metal objects and inform the doctor of any medical or electronic devices they may have.

МРТ кишечника для беременных

Women should always inform their doctor or technologist if there is any possibility that they are pregnant. MRI has been used to scan patients since the 1980s with no reported negative effects on pregnant women or their unborn children. However, because the unborn baby will be in a strong magnetic field, pregnant women should not have this exam during the first three to four months of pregnancy if the potential benefits of an MRI are thought not to outweigh the potential risks. Pregnant women should not take gadolinium contrast agent injections unless absolutely indicated for treatment.

MRI for children

Infants and young children usually require sedation, or anesthesia, to complete the MRI test without movement. Whether or not a child requires sedation, the choice of sedation depends on the child’s age, intellectual development, and type of examination. Moderate and conscious sedation can be provided in many facilities. A doctor specializing in sedation or anesthesia for children must be present during the examination for the safety of the child.

How is the procedure performed

Перед процедурой пациенту нужно выпить несколько стаканов водного раствора, смешанного с контрастным материалом. Ремни и валики могут использоваться, чтобы помочь пациенту оставаться на месте и поддерживать правильное положение во время визуализации. Устройства, которые содержат катушки, способные передавать и принимать радиоволны, могут быть размещены вокруг или рядом с областью исследуемого тела. Пациента поместят в магнит МРТ, и рентгенолог проведет обследование во время работы за компьютером за пределами комнаты.

What are the benefits and risks

Benefits of bowel MRI:

1. MRI is a non-invasive imaging technique that does not involve exposure to ionizing radiation.
2. МРТ позволяет обнаруживать аномалии, которые могут быть затенены костью, и не видны во время других методов визуализации.
3. The contrast material used in MRI is less likely to cause an allergic reaction than the iodine-based contrast material used for conventional x-rays and CT scans.
4. An MRI of the intestine helps identify areas of inflammation in the intestine due to diseases such as Crohn’s disease.
5. Because bowel MRI does not include ionizing radiation, the procedure may be preferable for evaluating young patients with inflammatory bowel disease, who may have multiple exams throughout their lives.
6. Bowel MRI may eliminate the need for invasive endoscopy.

Риски метода:

1. МРТ-исследование практически не подвержено риску для пациента при соблюдении соответствующих правил безопасности.
2. When using sedation, there is a risk of over-sedation. However, a technologist or nurse will monitor vital signs to minimize this risk.
3. While the magnetic field itself is not harmful, implanted medical devices containing metal can cause malfunctions or problems during an MRI scan.
4. Nephrogenic systemic fibrosis is a recognized but rare complication of MRI that is thought to be caused by the administration of high doses of gadolinium-based contrast material in patients with very poor kidney function. Careful evaluation of kidney function before considering a contrast injection minimizes the risk of this very rare complication.
5. There is a small risk of allergic reactions if contrast material is injected. Such reactions are usually mild and easily controlled with drugs.

What are the limitations of MRI of the intestine

High-quality images are only guaranteed if the patient can remain still and follow the breath-holding instructions during image recording. If the patient is anxious, confused, or in severe pain, it may be difficult for the patient to lie still during imaging. A person with a large weight may not fit into the parameters of certain types of MRI machines. The presence of an implant or other metal object sometimes makes it difficult to obtain clear images due to the appearance of streak artifacts from metal objects. The movement of the patient can have the same effect. While there is no reason to believe that MRI is harmful to the fetus, pregnant women are generally advised not to have an MRI exam during the first trimester unless medical intervention is required. For optimal results, the patient should consume the entire dose of oral contrast, remain still, and follow breathing instructions. Moreover, the results can be compromised if the patient cannot receive intravenous contrast material (gadolinium). A bowel MRI takes longer (30 to 45 minutes) than a CT scan (two to four minutes).

MRI or colonoscopy

When conducting an MRI of the intestine, there are both pluses and minuses, which are also observed during colonoscopy. However, unlike colonoscopy, this screening method does not require the introduction of a long tube into the rectum, that is, this research method is more tolerant. In addition, using a special technique, patients do not have to undergo the inconvenient bowel cleansing required with a conventional colonoscopy.

Новые данные показывают, что МРТ кишечника может точно обнаруживать полипы, которые могут стать злокачественными. Однако для более точного обнаружения небольших полипов необходимы улучшения данной методики. Эти результаты получены из исследования 315 взрослых старше 50 лет, прошедших МРТ-колонографический скрининг. За два дня до скрининга испытуемые выпили жидкость, которая «маркировала» любой стул в кишечник, что облегчает для врачей поиск полипов. Никаких чистящих средств для кишечника не давали, хотя ректальную водную клизму применяли во время визуализации для расширения кишечника. Никаких седативных или обезболивающих препаратов не было. Выводы по колонографии МРТ сравнивались с результатами, полученными при традиционной колоноскопии. Исследователи обнаружили, что колонография МРТ довольно хороша при обнаружении полипов диаметром более 5 миллиметров. В отличие от этого, МРТ-колонография почти всегда пропускала меньшие полипы. Хотя результаты обнадеживают, исследователи считают, что традиционная колоноскопия останется первым методом скрининга для лечения рака толстой кишки. Важным преимуществом традиционной колоноскопии является обнаружение полипов, которые могут быть удалены или биопсированы во время процедуры.