MRI is a medical imaging technique that examines tissues, organs and skeletal system. Magnetic resonance imaging scanners create highly detailed two- and three-dimensional images of human anatomy using a strong magnetic field and radio waves. MRI is very common in the diagnosis and treatment of diseases of the brain, spine, joints and abdomen. Its major advantage compared to other imaging techniques is that it does not need ionizing radiation. MRI is a revolutionary technology, particularly in neurology and brain research.
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Magnetic resonance imaging (MRI) creates cross-sectional images of organs and tissues in the body using magnetic field and computer generated radio waves. It produces high resolution images of body parts that cannot be imaged by X-ray and computed tomography or ultrasound. A MRI device is a magnet with an open tube at both ends.
The signal that forms the magnetic resonance image comes mostly from the nuclei in the body’s fat and water molecules. Magnetic field or radio waves are not felt during the scan, the process itself is painless.
A regular MR unit is in the form of a large cylinder surrounded by a circular magnet. It has a desk that slides towards the center of the magnet. There is a possibility to have an Magnetic resonance imaging device open on its sides. The magnetic field produced by the MRI scanner produces images by temporarily rearranging the water molecule nuclei (protons) in the body.
At the center of each hydrogen atom that forms water molecules, there is a smaller particle called a proton. Protons are like tiny magnets and are very sensitive to magnetic fields. The magnetic resonance scanner temporarily realigns protons by creating a very strong magnetic field. When the magnetic field is closed, the protons gradually return to their normal alignment.
During this return, the protons generate a radio signal that is measured by the receivers in the scanner and converted into an image. These signals carry information about the location of protons in the body. They also help to distinguish between various tissue types in the body, because protons of different tissue types line up at different speeds and produce different signals.
This process does not cause chemical changes in the tissues. Scanner settings can be adjusted to create a contrast between different body tissues. Additional magnetic fields can produce 3D images that can be viewed from different angles. (1)
Magnetic Resonance Spectroscopy (MR Spectroscopy – MRS) is a special MRI technique. It is an advanced MRI application that measures the biochemical changes of lesions detected in the brain and gives definitive diagnostic value.
Magnetic resonance imaging results help diagnose, plan treatments, and assess how effective the previous treatment is. MRI scans create much clearer images than normal X-rays and computed tomography (CT). MRI is used for imaging of organs particularly:
It gives us very detailed pictures of the brain, and is mostly used to examine problems such as headaches, seizures, weakness or hearing loss. It is alsot used to evaluate abnormalities observed in the CT scan in more detail. Magnetic resonance can distinguish between white matter and gray matter in the brain, and is also used to diagnose aneurysms and tumors.
Because MRI does not need radiation, it is a preferred method especially for diagnosis or treatment in the brain. Nevertheless, magnetic resonance imaging is more costly than x-ray or CT scan. (3)
It is mostly used to diagnose a herniated disc or spinal stenosis in people with neck, arm, back and/or leg pain. Additionally, it is the most appropriate analysis for the diagnosis of recurrent hernia (Disk Hernia) in people with a previous history of back surgery. (4)
It checks up almost all bones, joints and soft tissues. MRI also diagnoses damaged tendons, ligaments, muscles, cartilages and bones. In addition, it helps search infection and mass.
It specifically looks for abnormalities observed in another test, such as ultrasound or CT scan. Abdominal MRI checks tumors or other abnormalities of many organs such as liver, bile ducts, kidneys, spleen, pancreas, uterus, ovaries, or prostate.
It gives a detailed overview of the ovaries and uterus, mostly tracks an abnormality detected on ultrasound, and evaluates the spread of uterine cancer. For men, pelvic MRI may help diagnose prostate cancer. Pelvic MRI examines pelvic bones and muscles. (5)
Gadolinium rarely causes allergic reactions, but sometimes lead to side effects such as nausea, skin rash, headache. They are usually mild and short-term. However, a blood test may help determine how well the kidneys work in a kidney disease or whether it is safe to continue screening.
Cases before an MRI, the doctor should be informed:
Because MRI employs strong magnets, the presence of metals in the body can be dangerous when attracted to the magnet. Even if they are not affected by magnet, metal objects may disrupt the magnetic resonance image. Before an MRI, you must inform your doctor or technical specialist if your body has metal or electronic equipment.
On examination day, the patient should wear large and comfortable clothes with no metal parts. During screening, the patient may be asked to undress and wear an apron. No preparation is required for scanning. The only exception is magnetic resonance cholangiopancreatography (MRCP), a special screening of the bile ducts. In this case, it is not allowed to eat or drink for 2-3 hours before the test.
It is not allowed to enter the MR room with mobile phone, coins, dentures, glasses, hearing aids, keys, jewelry, watches, hairpins, underwire bras, wigs, cosmetics containing metal parts.
There are many types of MRI, but Diffusion Weighted MRI and Functional MRI (fMRI) are the main ones.
This type of MRI identifies the character of tumors and diagnoses acute brain ischemia.
It examines the anatomy of the brain and identifies which parts of the brain perform critical functions and which areas of the brain are active (consuming more oxygen) during various cognitive tasks. It can also assess damage due to head trauma or disorders such as Alzheimer’s disease. (6)
Perfusion imaging is a dynamic examination using contrast agent, and helps diagnose and treat stroke, brain tumors and cerebral pathologies.
Magnetic resonance angiography (MRA) monitors blood vessels. It examines the areas of narrowing or expansion of blood vessels in the neck and brain. It can visualize the arteries that provide blood to the kidneys, as well as the vessels in the arms and legs.
MRI focusing on the heart or blood vessels can assess:
It is an MRI scanning from head to toe. It searches for cancers, infections and blockages in body. This scan takes approximately 45 minutes and starts from brain first. Then, neck, lungs, chest, liver, pancreas, kidney, adrenal gland, abdominal organs, bladder, prostate, testes, uterus are screened. Also, leg bones and muscles up to knee are examined in same session.
MRI is used together with mammography to detect breast cancer, especially in women with dense breast tissue or high risk of disease. It diagnoses, treats and follows-up breast cancer and checks up the status of implanted breast implants.
3 Tesla Multiparametric MRI diagnoses early prostate cancer and determines accurate and precise location of the biopsy. It helps evaluate prostate cancer, abscess, enlargement, congenital abnormalities and complications after prostate surgery.
This type of MRI helps to evaluate joint abnormalities, disc abnormalities in the spine, bone infections, bone and soft tissue tumors caused by traumatic or recurrent injuries such as torn cartilage or ligaments.
It is usually used for diagnosis of such conditions as:
Open MRI helps claustrophobic, obese and pediatric patients. Contrary to conventional MRI scanners, open MRI does not surround the entire body. Two or three sides are open. Open MRI makes the examination less stressful by providing a more comfortable, less restrictive environment and a lower noise level.
The radiologist analyzes the images in the scan, interprets the results and reports the findings to the doctor. How quickly the doctor will receive reports depends on the imaging center where the examination is done. The doctor will discuss important findings and the next steps with the patient.
MRI does not use ionizing radiation as used in X-ray and CT imaging; instead, it uses a strong magnetic field.