Differences between MRI and CT scans

Many studies have concluded that MRI is one of the safest technologies for imaging the body. The examination causes no pain, and the magnetic field produces no known tissue damage of any kind.

Differences between MRI and CT scans

MRI scans and CT scans are both help to diagnose patients. However, they each have their own specialties.

  1. CT scans are more often used to assess bone injuries, problems in the lungs, or cancer-related issues. 
  2. A CT scan only shows an image from one viewpoint. Images are horizontal and only display one slice of the interior of the object. An MRI, however, can produce an image from virtually any angle, and it shows you a 360-degree view of the object.
  3. MRI scans are generally more detailed than x-rays and CT scans, however, MRIs are better for viewing soft tissue, particularly tendons and ligaments. High-resolution MRIs, such as a 3 Tesla MRI, are also ideal for examining tumors and other issues in the brain.

Difference between CT and MRI scans

Alt text = MRI vs CT Scan. A significant difference between CT and MRI scans is that CT scans expose patients to ionizing radiation, while MRI does not.
MRI vs CT Scan

A significant difference between CT and MRI scans is that CT scans expose patients to ionizing radiation, while MRI does not. The amount of radiation used during this test is higher than the amount used in an x-ray. Therefore, a CT scan slightly increases your risk of cancer.

What is a CT scan?

A computerized tomography (CT) scan combines a series of X-ray images taken from different angles around your body and uses computer processing to create cross-sectional images (slices) of the bones, blood vessels, and soft tissues inside your body. CT scan images provide more detailed information than plain X-rays do.

A CT scan, or CAT scan, is a painless diagnostic procedure that allows your doctor to examine your organs, soft tissue, and bones. This imaging procedure is especially effective at capturing the details in bone structure, but it can also capture soft tissue and blood vessels, as well. Additionally, many people find that CT scans boast the benefit of rarely igniting claustrophobia during the procedure, unlike an MRI.

CT scan is a quick procedure than MRI

A CT scan can take anywhere from 10 to 30 minutes it depends on how much of your body the doctors want to look at. It often takes more time to get you into position and give the contrast dye than to take the pictures. Contrast dye may take some more time. The greatest benefit of a CT scan is that they are typically much quicker than MRIs, and they tend to cost roughly half the price.

Process CT scan

CT scans are typically complete in five minutes or less. This minimizes patient discomfort and gets them in and out in much less time. Additionally, with CT scans patients aren’t required to lie perfectly still since a slight movement won’t really disrupt the imaging process.

How are CT scans done?

You’d probably get a scan at a hospital or radiology clinic. Your doctor might tell you not to eat or drink for a few hours before the procedure. You may also need to wear a hospital gown and remove any metal objects, such as jewelry.

During a CT scan, you lie in a tunnel-like machine while the inside of the machine rotates and takes a series of X-rays from different angles. These pictures are then sent to a computer, where they’re combined to create images of slices, or cross-sections, of the body. You can hear a whirring or buzzing noise, the process which is normal. Movement can blur the image, so you’ll be asked to stay very still. You may need to hold your breath at times.

What Is a CT Scan with Contrast?

In a CT scan, dense substances like bones are easy to see. But soft tissues don’t show up as well. They may look faint in the image. To help them appear clearly, you may need a special dye called a contrast material. They block the X-rays and appear white on the scan, highlighting blood vessels, organs, or other structures.

Barium sulfate is a contrast material as iodine. You might receive these drugs in one or more of three ways:

  • Injection: The drugs are injected directly into a vein. This is done to help your blood vessels, urinary tract, liver, or gallbladder stand out in the image.
  • Orally: Drinking a liquid with the contrast material can enhance scans of your digestive tract, the pathway of food through your body.
  • Enema: If your intestines are being scanned, the contrast material can be inserted into your rectum.

After the CT scan, you’ll need to drink plenty of fluids to help your kidneys remove the contrast material from your body.

The disadvantage of CT scan and MRI

Like CT scans, MRIs have some disadvantages, as well. For example, although they are more versatile than x-ray machines, they tend to produce less detailed results. Additionally, some people may experience anxiety during the procedure. Because the MRI is a small, enclosed space.

What is MRI and how does it work?

Magnetic resonance imaging, or MRI, gives detailed images of organs and tissues throughout the body without the need for x-rays or “ionizing” radiation. Instead, MRI uses a powerful magnetic field, radio waves, rapidly changing magnetic fields, and a computer to create images that show whether or not there is an injury, disease process, or abnormal condition present.

The shape of the MRI is of a large donut that opens on both ends. The powerful magnetic field aligns with atomic particles called protons that exist in most body tissues. The radio waves then interact with these protons to produce signals. The MR scanner picks these signals. With the help of computer processing, images of tissues are created as “slices” that can be viewed in any orientation.

MRI is harmless

An MRI exam causes no pain, and the electromagnetic fields produce no known tissue damage of any kind. The MR scanner may make loud tapping, knocking, or other noises at times during the procedure. You may need to wear earplugs to prevent problems with this noise. You can communicate with the MRI technologist or the MR scanner operator using an intercom system or by other means.

What is MRI used for?

MRI is the preferred procedure for diagnosing a large number of potential problems or abnormal conditions that may affect different parts of the body. In general, MRI creates pictures that can show differences between healthy and unhealthy or abnormal tissues. Physicians use MRI to examine the brain, spine, joints (e.g., knee, shoulder, hip, wrist, and ankle), abdomen, pelvic region, breast, blood vessels, heart, and other body parts.

How safe is MRI?

Many studies have concluded that MRI is one of the safest technologies for imaging the body. The examination causes no pain, and the magnetic field produces no known tissue damage of any kind. People of all ages can undergo an exam, but you should follow proper safety guidelines

Metal may interfere with the magnetic field used to create an MRI image and can cause a safety hazard. The magnetic field may damage electronic items. Do not have an MRI scan if you have an implantable cardioverter-defibrillator or pacemaker.

Risk of metallic objects

Ferromagnetic screwdrivers and oxygen tanks are not brought into the MR system area. As a patient, you should remove all metallic belongings in advance of an MRI exam. Including external hearing aids, watches, jewelry, cell phones, and items of clothing that have metallic threads or fasteners. Also, makeup, nail polish, or other cosmetics that may contain metallic particles should be removed, before the procedure.

The powerful magnetic field of the MR system will pull on any iron-containing object in the body. Such as a medical implant, certain aneurysm clips, or certain medication pumps. Every MRI facility has a comprehensive screening procedure and protocols.

Precautions of implant or device

Some special precautions are essential. In the presence of an unacceptable implant or device, the exam may have to be canceled. For example, the MRI exam will not be performed if a ferromagnetic aneurysm clip is present. There may be a risk of the clip moving and causing serious harm to the patient. In some cases, some medical implants can heat substantially during the MRI exam. This heating may result in an injury to the patient. It is very important to inform about any implant or other internal object, before entering the MR scanner room.

The powerful magnetic field of the MR system may damage an external hearing aid. Also heart pacemaker, electrical stimulator, or neurostimulator to malfunction or cause injury. There could be a potential risk if you have a metallic bullet or fragment in your body. It can change position and possibly cause an injury.

Signal loss due to metallic implants or objects

In addition, a metallic implant or other objects may cause signal loss or alter the MR images making it difficult for the radiologist to see the images correctly. This may be unavoidable, but if the radiologist knows about it, allowances can be made when obtaining and interpreting the MR images.

What is a gadolinium contrast agent?

To improve the quality of the MR images the radiologist will inject a gadolinium contrast agent into the vein. Unlike the contrast materials used in x-ray exams or computed tomography (CT) scans, a gadolinium contrast agent does not contain iodine. and, therefore, rarely causes an allergic reaction or other problems. However, if you have a history of kidney disease, kidney failure, kidney transplant, liver disease, or other conditions, you must inform the MRI technologist and/or radiologist before receiving a gadolinium contrast agent. If you are unsure about the presence of these conditions, please discuss these matters with the MRI technologist or radiologist prior to the MRI examination

How should I prepare for my MRI exam?

You will typically receive a gown to wear during your MRI examination. Before entering the MR system room. Next, you need to remove all metallic objects from pockets and hair, as well as metallic jewelry. Additionally, any individual that will be going with you to the MRI scanner room will also follow these same instructions and procedures.

Items that may create a health hazard or other problem during an MRI include:

  • Certain cardiac pacemakers or implantable cardioverter defibrillators (ICDs)
  • Ferromagnetic metallic vascular clips placed to prevent bleeding from intracranial aneurysms or blood vessels
  • Some external or implanted medication pumps (such as those used to deliver insulin, pain-relieving drugs, or chemotherapy)
  • Certain cochlear (i.e., for hearing) implants
  • Certain neurostimulation systems
  • Catheters that have metallic components
  • A bullet, shrapnel or other type of metallic fragment
  • A metallic foreign body located within or near the eye (such an object generally can be seen on an x-ray; metal workers are most likely to have this problem)

MRI Contraindications

Patients who have a heart pacemaker may not have an MRI scan. Patients who have a metallic foreign body (metal sliver) in their eye, or who have an aneurysm clip in their brain, cannot have an MRI scan since the magnetic field may dislodge the metal.

Some items, including certain cardiac pacemakers, ICDs, neurostimulation systems, cochlear implants, and medication pumps are acceptable for MRI. However, the MRI technologist and radiologist must know the exact type that you have in order to follow special procedures to ensure your safety. Therefore, in order to help with the pre-MRI screening procedure, it is important for you to obtain information about any implant that you may have and to provide it to the MRI technologist.

What should remove before entering the MR room

Items that need to be removed by patients and individuals before entering the MR system room include:

  • Purse, wallet, money clip, credit cards, cards with magnetic strips
  • Electronic devices such as beepers, cell phones, smartphones, and tablets
  • Hearing aids
  • Metallic jewelry and watches
  • Pens, paper clips, keys, coins
  • Hair barrettes, hairpins, hair clips, and some hair ointments
  • Shoes, belt buckles, safety pins
  • Any article of clothing that has metallic fibers or threads, metallic zippers, buttons, snaps, hooks, or underwire

Interference with image quality

Objects that may interfere with image quality if close to the scanning area include:

  • Metallic spinal rod
  • Plates, pins, screws, or metal mesh used to repair a bone or joint
  • Joint replacement or prosthesis
  • Metallic jewelry including those used for body piercing or body modification
  • Some tattoos or eyeliner (these alter MR images, and there is a chance of skin irritation or swelling; black and blue pigments are the most troublesome)
  • Makeup (such as eye shadow and eyeliner), nail polish, or other cosmetics that contain metal
  • Dental fillings or braces (while usually unaffected by the magnetic field, these may distort images of the facial area or brain; the same is true for orthodontic braces and retainers)

An example of the MRI examination

You will be escorted into the room by a staff member of the MRI facility and asked to lie down on a comfortably padded table that gently glides you into and out of the scanner. The typical scanner is open on each end, or at least two sides.

You may need to wear earplugs or headphones to protect your hearing because many scanning procedures produce loud noises. These loud noises are normal and should not worry you.

Gadolinium

For some MRI exams, a contrast agent called gadolinium may be injected into a vein to help obtain a clearer picture of the area being examined. Typically, at the beginning of the imaging procedure, a nurse or MRI technologist will place an intravenous line in your arm or hand vein using a small needle. This will allow injection of the gadolinium contrast agent. The line will be connected to a saline solution that will drip through the intravenous line to prevent clotting until the actual contrast agent is injected at some point during the exam. Sometimes the contrast agent is injected with an automatic device and sometimes it is necessary for the technologist or nurse to come into the room to inject the contrast agent. They may even have to slide the table out of the scanner to do this.

The most important thing for the patient to do is to lie still and relax. Most MRI exams take between 15 to 45 minutes to complete the procedure. Some exams may take up to 60 minutes or even some more time.

You may remain perfectly still during the time the imaging takes place, but between sequences, some minor movement may be allowed. The MRI technologist will advise you, accordingly.

When the MRI exam begins, you may breathe normally. However, for certain examinations, it may be necessary for you to hold your breath for a short period of time.

After the exam, you have no restrictions and can go about your normal activities. Once the entire MRI examination is completed, the images will be reviewed by a radiologist, a physician who has been specially trained to interpret the scans for your doctor.

The question of anxiety or claustrophobia

Some patients who undergo MRI examinations may feel confined, closed-in, or frightened. Perhaps one out of every twenty people may require a mild sedative to remain calm. Today, many patients avoid this problem when examined in one of the newer scanners that have a more “open” design. Some MRI centers permit a relative or friend to be present in the MR system room, which also has a calming effect on the patient. If patients are properly prepared and know what to expect, it is almost always possible to complete the examination.

Pregnancy and MRI

If you are pregnant or suspect you are pregnant, you should inform the MRI technologist and/or radiologist during the screening procedure. In general, there is no known risk of using MRI in pregnant patients. In any case, MRI is safer for the fetus than imaging with x-rays or (CT) scans. 

Breast-feeding and MRI

You should inform the MRI clinic that you are breastfeeding when scheduling your MRI exam. This is particularly important if you receive an MRI contrast agent. One option under this circumstance is to pump breast milk before the MRI exam, which can be used to feed the infant until the contrast agent has been cleared from the body. It usually takes about 24 hours for the contrast agent to clear the body. The clinic or radiologist will provide additional information to you regarding this matter.

Cost

Though it’s not a big difference, CT scans are usually less expensive than MRI scans. For instance, a typical CT scan may cost between $1,200 and $3,200, while an MRI might cost up to $4,000. If you have good insurance, then your insurance provider might pick up some or all of the scan costs.

Ultimately, there are pros and cons to each method. It is the responsibility of the doctor to determine which diagnostic imaging procedure is right for each patient.

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