- 1. History of Magnetic Resonance Imaging (MRI)
- 2. How Does MRI Work?
- 3. Types of MRI Examinations
- 4. Applications or Uses of MRI
- 5. Risks associated with MRI Exams
- 6. Final Words
MRI stands for magnetic resonance imaging. It is a painless and safe diagnostic tool that uses radio waves and magnetic fields to produce detailed images of structures and organs inside the body. The technology is different from computer tomography (CT) because it does not use radiation.
An MRI image is produced when hydrogen atoms within the body come in contact with a magnetic field and tuned radio waves. A powerful antenna picks up the reaction of hydrogen atoms and sends signals to a computer that converts the data into high-resolution pictures of the body.
Doctors use MRI to visualize different abnormalities within the human body, such as problems with the spine, brain, heart, and abdomen. MRI helps diagnose problems with the nervous system, ears, and eyes. Unlike ultrasound, Computed Tomography (CT), and x-rays, an MRI scan provides more accurate information and images.
History of Magnetic Resonance Imaging (MRI)
Before the development of MRI, scientists studied magnetic resonance within different chemicals, and this was known as nuclear magnetic resonance or NMR. In 1945, it was discovered that the nucleus of atoms resonates in a magnetic field.
Spectroscopy is the study of the biological, physical, and chemical properties of matter. It studies the chemical shift, a variation in electron distribution throughout chemicals. Research shows that spectroscopy later transformed into magnetic resonance imaging.
In 1969, Dr. Raymond Damadian experimented on cancer cells and hypothesized that they could be differentiated from non-cancerous cells using magnetic resonance. According to Dr. Damadian, cancer cells can hold more water, which means they show up on magnetic resonance due to the higher number of hydrogen protons.
In 1971, Paul Lauterbur performed a similar experiment to observe the difference between cancerous and non-cancerous tissues. He imaged two water-filled test tubes with the help of magnetic resonance to produce the first MR image. Sir Peter Mansfield studied chemical shift anisotropy and observed that a magnetic field gradient helps analyze the atomic structure of chemicals.
All three scientists made substantial efforts to develop techniques for producing such images. Damadian developed a human scanner, Lauterbur focused on the projection method used in motion reconstruction, and Mansfield’s work involved scanning pieces of structure that combine to produce the image. In 1974, Mansfield successfully produced an image of a finger within 15-20 minutes.
In 1977, Damadian creating the first body scanner and named it “Indomitable.” The images produced by the scanner showed more details than those produced by CAT and X-rays. In 1978, Damadian founded “FONAR,” a company that would develop MRI scanners. In 1984, the FDA approved the first MRI scanner for use in hospitals and clinics.
How Does MRI Work?
MRI is a non-invasive imaging technology that produces 3D anatomical images. Health professionals often use this technology for diagnoses, disease detection, and treatment monitoring. MRI is a powerful technology that detects the changes in the rotation axis of protons found in water.
MRI employs a powerful magnetic field that forces protons in the body to come in contact with the field. The MRI machine pulses a radiofrequency current through the patient’s body to stimulate protons, which stain against the pull of the field.
Sensors in the machine detect the energy when the field is turned off. As a result, the protons begin to realign with the magnetic field. The chemical structure of the molecules, time, environment and amount of energy released will determine the realignment of protons with the magnetic field. Based on magnetic properties, doctors distinguish between different types of tissues.
The procedure involves placing the body of the patient in a large magnet where he or she remains still to avoid blurred images. A doctor may give a contrast dye like Gadolinium to the patient intravenously before the MRI. The purpose is to speed up protons to make them realign with the magnetic field. As a result, the machine produces a much brighter and clearer image.
Performing an MRI examination does not require any special preparation. On the day of the MRI appointment, a patient must leave objects containing metal, such as jewellery, eyeglasses, belts, etc. at home. The rule of thumb is to remove all electronic devices from the MRI room. Although dental fillings and braces are safe, they can interfere with some scans.
A doctor may ask parents if the child has metal implants from previous surgery because it can cause problems due to a strong magnetic field. The patient may also receive sedation if he or she has difficulty staying still. In such a situation, a nurse will supervise the procedure and take care of the patient. Fasting may be required if the patient’s MRI exam is scheduled with sedation.
Some MRI exams require the doctor to give contrast to the patient. It is used to highlight certain body areas like blood vessels and tissues. A contrast solution is painless and safe, but some patients may show allergic reactions. The patient needs to inform the doctor if he or she experienced any problems during a previous MRI procedure.
If the patient needs a contrast for the MRI exam, the doctor will give him intravenous contrast before starting the procedure. When the MRI exam is about to begin, the health professional will help the patient onto the exam table. Then, he will slide the table into the circular area of the scanner.
The doctor or MRI technologist will leave the room and start taking images. Again, the patient must remain still in the scanner so that the machine can produce high-quality and accurate images.
During the MRI exam, the patient will hear loud sounds from the scanner machine. Remember, these sounds are normal and do not cause any harm to the patient. If the patient becomes uneasy, he or she can communicate with the doctor through an intercom.
Once the exam is finished, the professional will help the patient off the table. If the doctor has used sedation, he will move the patient to the recovery area where a nurse will monitor the effects of the sedation. Next, the nurse provides discharge instructions and contact information in case of an emergency to the patient.
Types of MRI Examinations
Health professionals use MRI examinations to evaluate different health conditions, such as brain, neck, spinal cords, and other organs. It can also be used to observe abnormalities in different parts of the body, including blood vessels, joints, heart, chest, and abdomen.
Functional MRI is used to detect abnormities in the brain. It is also used to measure brain activity by analyzing changes in the blood flow to the central nervous system. The concept is all about detecting changes in blood flow and oxygenation, which occurs due to neural activity.
When your brain consumes more oxygen, it becomes more active. That’s why there is an increased blood flow to the active area of the brain. Like other MRI procedures, a functional MRI uses a large device that contains a powerful magnet and radio waves to display structures and organs in the body. Typically, the procedure takes less than 60 minutes to produce images.
Magnetic Resonance Venography
It is a non-invasive imaging technique used to focus on veins in the body. Veins are responsible for carrying blood from different organs of the body to the heart. When the blood reaches the heart, it is sent to the lungs for oxygen. At the same time, it regains vital nutrients.
Magnetic resonance venography or MRV assesses the flow of blood and detects abnormalities like blood clots. The procedure can also be used to detect structural abnormities in veins, blood flow problems in the brain, and venous thrombosis.
A health professional likewise uses MRV to evaluate conditions that can severe neurological symptoms like normal pressure hydrocephalus, intracranial hypertension, and others.
Cardiovascular MRI uses a powerful magnetic field to produce a detailed image of the heart and surrounding areas, including the blood flow. Health professionals use cardiac MRI to monitor health conditions associated with the heart.
It is also used to detect problems with the heart’s structure and anatomy. Keep in mind that the procedure does not use ionizing radiation for the formation of images. Cardiac MRI helps produce high-quality images of the cardiovascular organs.
MRI of the breast is a diagnostic test to monitor the anatomy of the breast and detect tumours. The procedure is used to capture different images of the breast, which are combined and processed through a computer to produce clearer and high-quality images.
Although MRI is more effective than ultrasound, it is an expensive procedure. Typically, a doctor decides whether to perform an MRI or ultrasound of the breast depending on the patient’s condition and symptoms.
Magnetic Resonance Angiography
Magnetic Resonance Angiography or MRA is one of the MRI methods that use radio waves and a powerful magnetic field to produce images of blood vessels. It is an effective procedure that can effectively detect abnormalities within the internal structures of the body.
It is a diagnostic test that does not use radiation, but the doctor may inject contrast material into the patient’s body. Most often, the contrast material used for this procedure does not cause any allergic reactions. On the other hand, the contrast material used for CT can lead to allergic reactions. Consider this, we can say that MRA is safer than CT for patients.
Applications or Uses of MRI
MRI scanners or machines are best used for producing images of soft tissues or non-bony parts of the body. MRI is different from CT because it does not use x-rays or ionizing radiation that can damage the soft tissue. The use of MRI is more beneficial than CT in terms of high-quality images.
MRI exams are performed to produce more accurate images of different body organs, including the brain, spinal cord, muscles, ligaments, nerves, tendons, etc. Also, MRI is used for getting clearer images of shoulder and knee injuries.
MRI is an effective procedure that can help the doctor differentiate between the grey and white matter in the brain. It is also helpful for diagnosing tumours and aneurysms. MRI does not use any type of radiation.
Most health professionals use this modality when they require more frequent imaging for diagnoses and therapy, particularly in the brain. However, MRI is more expensive than CT scans and x-rays.
As mentioned above, functional magnetic resonance or fMRI is a special procedure that is used to observe brain structure. Also, it is used to determine the active areas of the brain that consume more oxygen.
FMRI is a sophisticated procedure that can help health professionals to understand the advanced organization of the brain and assess the neurological status of the patient. Research shows that MRI is one of the safest procedures for producing images of the human body.
Most often, the examination does not cause any pain, and the magnetic field does not lead to tissue damages. However, health professionals must follow the safety guidelines to carry out the procedure accurately. Likewise, an MRI exam is suitable for people of all ages.
Risks associated with MRI Exams
Research shows that MRI machines do not emit the ionizing radiations of x-rays. In general, ionizing radiation is found in CT scans and x-ray imaging. However, MRI uses a strong magnetic field and radio waves to produce high-quality images.
The magnetic field applies powerful forces on a few types of magnetic objects, including irons and steels. The magnetic force used in the MRI can toss a wheelchair across the room. That’s why patients must inform the doctor about any form of metal or implant in his or her body before undergoing an MRI exam.
Patients with different types of implants, pacemakers, cardioverter-defibrillator, cochlear implants, insulin pumps, and loop recorders must undergo an MRI exam. The strong magnetic field can cause damage to the internal organs, especially in patients with implants.
Some patients that undergo MRI exams require special ear protection. In general, the MRI machine produces noise or sounds like beeping and clinking. If the intensity of these sounds is above 120 decibels, then the patient should wear ear protection equipment. Remember, the high noise intensity does not occur in all types of MRI exams.
Some patients may feel twitching sensations while they undergo an MRI exam. It is primarily due to the switching of the field in the procedure. A doctor or technologist is required to run the machine carefully or as per the guidelines.
Some MRI exams require the doctor to inject contrast agents in the patient’s body to get high-quality images. However, patients who suffer from renal failure and those that require dialysis should inform the doctor about their condition.
The reason is that some patients with renal failure that undergo an MRI exam can develop a disorder called nephrogenic systemic fibrosis. Patients who receive gadolinium agents are highly prone to this disorder.
Research shows that dialysis patients should not receive gadolinium agent until it becomes essential. Also, the patient should undergo dialysis as soon as possible after the MRI exam to remove the contrast agent from the body.
Although there is little evidence on the effects of an MRI procedure on the fetus, it is essential to avoid MRI scans in pregnancy, especially in early pregnancy. It is because the baby’s organs are formed in the first trimester and there is a risk that the contrast agent can enter the bloodstream of the fetus. So, it is a wise decision to avoid MRI scans in early pregnancy.
People with symptoms of claustrophobia should not undergo an MRI exam. Most often, they find it difficult to stay still on the machine. Also, it is not easy for some people to stay in the machine for a long time.
That’s why health professionals should ensure providing enough information to patients on MRI machines, sedation, anesthesia, and visualization techniques. Providing information and instructions to the patient can help psychologically and the patient might not feel any discomfort during the procedure.
Some other ways to overcome problems are watching a movie or listening to music, covering the eyes, or holding the panic button. Some MRI machines are open on the sides, which allows the patient to feel comfortable.
The concept behind the open MRI machine is to help the patient feel comfortable and easy during the procedure. Although open MRI machines come with the latest technology, they may not produce quality images of the internal structures.
Magnetic resonance imaging or MRI is an advanced procedure that use a powerful magnetic field and radio waves to examine different organs and structure within the body. MRI scans are used by healthcare professionals to diagnose a wide range of health conditions, from torn ligaments, damaged tissues, and tumours to brain and spinal cord issues.
It is essential to know that MRI is a painless and safe procedure for patients. However, some patients may find it difficult to tolerate the loud sounds produced by the machine. Also, patients with implants must not undergo an MRI procedure. Lastly, it is a powerful tool that produces more high-quality and accurate images than many other radiology methods.