An MRI (magnetic resonance imaging) scan is a medical imaging technique that uses strong magnetic fields and radio waves to create detailed images of the inside of the body. MRI scans are often used to diagnose health conditions as they can detect problems in the brain, spinal cord, muscles, joints, nerves, and other tissues.
How does an MRI work?
During an MRI scan, the patient lies inside a large magnet that generates a strong magnetic field. This aligns the protons in the body’s cells. Short bursts of radio waves are then sent to certain areas of the body, knocking the protons out of alignment. When the radio waves are turned off, the protons realign with the magnetic field, sending out radio signals. These signals provide information about the exact location of the protons in the body. An MRI scanner detects the signals, and a computer processes the data to create two or three dimensional images of the body.
What conditions can an MRI detect in the brain?
An MRI scan of the brain can detect a wide range of conditions, including:
Brain tumors
An MRI can identify brain tumors, show their exact location, and help distinguish between cancerous tumors and benign growths. MRIs can also monitor the progress of brain tumors.
Stroke
MRI scans can detect areas of bleeding or damaged tissue in the brain caused by a stroke. It can identify which type of stroke occurred and the extent of damage.
Multiple sclerosis
MRI images can reveal plaques associated with multiple sclerosis in the brain and spinal cord. It can help track the progression of the disease.
Alzheimer’s disease
While MRI cannot definitively diagnose Alzheimer’s disease, it can rule out other causes of dementia and detect changes in brain structure caused by Alzheimer’s.
Epilepsy
An MRI scan may be used to detect abnormalities in the brain that cause epilepsy, such as scarring, tumors, blood vessel defects, and cortical dysplasias.
Concussions
MRIs can determine if a concussion has occurred and identify any bruising or damage to the brain caused by injury.
Encephalitis or meningitis
Inflammation of the brain (encephalitis) or lining of the brain and spinal cord (meningitis) can be detected by MRI.
Abscesses
MRI scans may identify brain abscesses caused by infection. The images can show where pus has accumulated in the brain.
Cranial nerve disorders
Problems with the cranial nerves, such as optic neuritis or Bell’s palsy, can sometimes be seen on an MRI scan.
Pituitary gland tumors
MRI images can reveal pituitary tumors and identify if they are pressing on the optic nerves or other areas of the brain.
What spinal problems can an MRI detect?
Some conditions of the spine that may be diagnosed by MRI include:
Herniated discs
MRI can reveal herniated discs in the spine that may be pressing on spinal nerves.
Spinal stenosis
Narrowing of the spinal canal, known as spinal stenosis, is readily seen on an MRI scan.
Radiculopathy
Impingement of spinal nerves caused by conditions like a herniated disc can be identified.
Fractures
MRI is very sensitive for identifying spine fractures that may not be visible on X-rays.
Spinal tumors
Tumors affecting the bones, nerves or tissues of the spine may be detected by MRI.
Abscesses
Abscesses in the spinal cord or between the vertebrae can be identified.
Multiple sclerosis
Areas of inflammation in the spinal cord caused by MS can be revealed through MRI scanning.
Transverse myelitis
MRI findings may help diagnose transverse myelitis, an inflammation of the spinal cord.
Cauda equina syndrome
Compression of the nerves at the base of the spinal cord, known as cauda equina syndrome, can be identified on an MRI.
What problems in joints and bones can an MRI detect?
MRI scans are very helpful in diagnosing many conditions affecting the joints, bones, and soft tissues, including:
Torn ligaments or tendons
MRIs can determine if important ligaments like the ACL and MCL or tendons like the rotator cuff are torn.
Sports injuries
MRIs are routinely used to assess sports-related injuries without exposing the patient to radiation.
Fractures
In addition to spinal fractures, MRI scans may detect unseen fractures in the wrists, knees, ankles, and other bones.
Osteoarthritis
Degeneration of joints from osteoarthritis is well visualized on MRI scans.
Rheumatoid arthritis
MRI can detect joint damage and inflammation caused by rheumatoid arthritis.
Osteonecrosis
Loss of blood supply to bone tissue, known as avascular necrosis or osteonecrosis, can be identified.
Bone tumors
MRI scanning is very useful for detecting tumors of the bone as well as soft tissue masses.
Infections
MRIs can detect bone infections like osteomyelitis and infiltrative infections like cellulitis.
Developmental hip dysplasia
Abnormal development of the hip joint in infants, such as hip dysplasia, is diagnosed by MRI.
What conditions affecting muscles can an MRI identify?
MRI scans are often used to evaluate different muscle disorders:
Myositis
Inflammation and damage to muscle fibers from conditions like polymyositis is visible on MRI.
Rhabdomyolysis
MRI can help diagnose serious muscle breakdown seen in rhabdomyolysis.
Muscular dystrophy
MRI can detect characteristic patterns of muscle damage caused by muscular dystrophies.
Myotonic dystrophy
Fatty tissue deposits seen in myotonic dystrophy can be identified on MRI.
Polymyalgia rheumatica
MRI may reveal inflammation in the muscles around the shoulders and hips indicating polymyalgia rheumatica.
How can an MRI detect problems with organs?
MRI provides detailed images of abdominal and pelvic organs that often allows definitive diagnoses:
Appendicitis
MRI is highly accurate for diagnosing appendicitis and identifying complications like rupturing.
Pancreatitis
Inflammation of the pancreas from acute or chronic pancreatitis is readily seen on MRI.
Cirrhosis
MRI can assess scarring and damage to the liver caused by cirrhosis.
Hepatitis
MRI findings may include signs of infectious hepatitis like hepatomegaly or hepatic abscesses.
Kidney disease
Many kidney disorders including kidney stones, tumors, cysts, and renal artery stenosis can be evaluated by MRI.
Adrenal gland tumors
MRI scans frequently detect adrenal gland cancers and adenomas incidentally while imaging the abdomen.
Uterine or ovarian masses
MRI helps characterize gynecological masses and identify ovarian torsion.
Prostate cancer
MRI is used alongside a rectal coil to stage prostate cancer and guide biopsies.
Can an MRI detect vascular problems?
MRIs are beneficial for diagnosing certain conditions affecting blood vessels:
Aortic aneurysm
MRI can accurately identify aneurysms in the aorta without using contrast dye as in CT scans.
Arterial dissections
Dissections or tears in arteries feeding the brain, heart, and other organs are visible on MRI.
Peripheral arterial disease
MRI angiography can map out blockages in arteries of the legs due to atherosclerosis.
Venous thrombosis
MRIs may detect deep vein thrombosis in the legs and major pelvic veins.
Pulmonary embolism
Evidence of pulmonary emboli from blood clots is occasionally seen on MRI of the chest.
What types of cancer can MRI detect?
While MRI is not usually a first line screening test for cancer, it plays an important role in cancer diagnosis and staging:
Brain tumors
As discussed earlier, MRI is the gold standard test for diagnosing brain tumors.
Breast cancer
MRI is more sensitive than mammograms for detecting breast cancer and evaluating extent of disease.
Liver cancer
MRI can accurately stage liver cancer and guide biopsies of suspicious lesions.
Pancreatic cancer
MRI can help diagnose pancreatic cancer when other tests are inconclusive.
Prostate cancer
MRI is used to detect prostate cancer when PSA or ultrasound findings are abnormal.
Ovarian cancer
MRI complements ultrasound for diagnosing ovarian cancer and detecting metastasis.
Colorectal cancer
MRI provides detailed images of the colon and rectum to diagnose and stage colorectal cancers.
Lymphoma
MRI helps stage lymphomas and monitor response to chemotherapy.
Bone tumors
MRI excels at evaluating bone tumors without exposing patients to radiation.
Conclusion
MRI scanning is an extremely versatile imaging technique that can detect a broad spectrum of problems throughout the body without using ionizing radiation. It provides key diagnostic information about conditions affecting the brain, spine, joints, muscles, organs, and blood vessels that cannot be obtained easily by other tests. While MRIs are not appropriate in all situations, they are vital for diagnosing certain cancers, spinal problems, sports injuries, and soft tissue conditions. With recent advances in technology and the development of new scanning techniques, MRIs will likely become even more important in medical imaging in the future.