Magnetic resonance imaging or MRI scan is an advanced diagnostic aid which utilizes magnetic fields and radiowaves to produce images of the human body. An MRI scan is one the most advanced, appropriate and accurate scans which has minimal risks associated with it. An MRI scan is used to diagnose medical conditions, assess the medical status of individuals who are undergoing a medical or surgical treatment.
What is the principle of an MRI scan ?
An MRI scan is based on the principle of magnetic waves and radiowaves and its interaction with the water molecules in the human body. Human body is primarily made of water and this water in molecular form has two hydrogen atoms and one oxygen atom. The hydrogen atom has a proton or a positive charge at the center and this proton behaves like a tiny magnet when it is placed in a magnetic field. When the protons are excited by a magnetic field they arrange themselves, at the same time radiowaves are used to disturb the proton arrangement. When the radio waves are stopped the protons re-arrange themselves and radio-signals are generated. These radio-signals are picked up by the receivers in the form of images. The control room has software and hardware attached to the scanning room which are used to do detailed imaging of the whole body or the required organ.
Is MRI scanning safe ?
MRI scans are usually safe and painless procedure. They are safe because they do not use any radiation which can be harmful to the human body. Any type of scanning or diagnostic procedures other than an ultrasonography are usually not advised during pregnancy, but in cases of emergency an MRI can be performed after the first trimester. Since MRI scans work on the principle of magnetic field, there are certain conditions where an MRI cannot be done, those are discussed later in contra indications of an MRI. Only issue with an MRI is that if you have a fear of closed spaces you might feel claustrophobic during the scan procedure. Hence, it is always advised to ask your treating doctor or the concerned radiologist about the procedure in detail before going ahead with it.
What are the indications of an MRI scan ?
An MRI is indicated by a doctor to either diagnose a pathology or monitor your recovery from a disease or help you plan appropriate treatment plan. The MRI imaging is so precisely detailed that it has help clinicians in diagnosing ailments which were very difficult to be diagnosed few decades back. An MRI scan can be performed on a particular organ like the lungs, kidney, liver and stomach or on the whole body. MRI of spine and spine and brain is usually considered to yield the best imaging. Whole body MRI imaging is usually performed in patients who are affected with cancer and is used to detect cancer in any other part of the body or monitor the treatment progress in cancer patients.
When is an MRI not advised ?
An MRI scan is not advised in pregnant women during their first trimester and if you are pregnant it is advised that you inform the radiologist beforehand. In individuals which have any kind of metal implant such as a pacemaker in the heart, a cochlear (ear) implant or a metal clip in your brain, an intrauterine device, artificial limbs and who have a medicine infusion pump. An MRI scan is also not advised in individuals who are difficult to stay still during the test and who are claustrophobic.
Which medical conditions permit an MRI scan ?
Though MRI is not advised in cases of any metal implants as it may interfere with the magnetic field and the test itself, there are certain instances where an MRI can be safely performed. Those conditions include artificial cardiac valves, cardiac stents, brain shunts, artificial joint replacements and surgical sutures or staples.
What is approximate duration of an MRI scan ?
An MRI scan depending on the part of the body which needs to images can range between 40 minutes to about two hours.
Is a contrast media used when an MRI is performed ?
Yes, a contrast media can occasionally be used during an MRI scan to improve the quality of images and details of the scan, especially when visualizing vasculature or scanning deeper portions of the human body. A dye of gadolinium is most commonly used as a contrast media during an MRI. Patients who have kidney diseases or weak kidneys are not advised to get an MRI with contrast done as it may cause damage to the kidneys. The contrast media is administered with the help of an IV (intravenous) cannula before the start of the scan. It is important to ask your treating doctor if a contrast scan is safe for you.
What are the types of MRI ?
Depending upon the type of magnetic field or design of scanner we have low field, high field MRI scanners, open or closed MRI scanners, scanners with sitting and standing option. High field or closed scanners produce the best image quality when imaging organs like heart but are not advised in claustrophobic patients. On the other end low field or open MRI scanners are used in patients who cannot lie still and are claustrophobic. Advance MRI scanners include sitting and standing scanners which are made to increase the comfort and reduce the anxiety of the patient. Depending upon the organ which can be scanned an MRI is named after it such as a Brain MRI scan for brain and abdominal MRI scan for abdomen. MRI to study the blood vessels of the heart is called as an MRA or magnetic resonance angiogram. Brain and spine MRI are being developed with latest technologies to detect brain and spinal cord disorders.
How do you prepare for an MRI scan ?
A patient is usually informed well in advance about the scan. In cases of emergency an MRI can be urgently advised. The doctor will ask you not to drink and eat anything a few hours before the procedure. You will also be asked to room any metal jewelry, watches, wallets and any coins before entering the MRI room. The radiologist might ask you to change into a hospital gown and remove any lingerie which have underwire (in women) to avoid its effect in the magnetic room. If a contrast MRI has to be performed, the contrast material is administered IV before the start of the scan. The MRI machine looks like a box and you will be made to lie on a table which moves in the magnetic field, hence a claustrophobic feeling can occur. If you are not comfortable the doctor might give you some relaxing agents during the procedure to reduce your anxiety.
What happens during an MRI scan ?
Once you are made to lie on the examination table, the radiographer or radiologist will have the controls of the MRI machine in a connected room. You will also have a buzzer at your hand to contact the radiographer during the scan. The components of MRI scan move making a noisy sound while imaging the body, hence you should be aware of this and should be still during the scanning process as slight movement can also distort the images. The entire scanning process can take about forty minutes to about two hours depending upon the type of scan. Once the scanning is completed and images are captured by the radiographer in the panel room, you will be asked to slowly get up from the MRI table. If a contrast media was used, the cannula will be removed. You can go home after an MRI, incase if you are feeling a little heavy or dizzy you should not drive back home alone.
When is the MRI report generated and who generates it ?
The report is generated ideally within 24hrs or earlier or later as per the hospital/diagnostic lab policy of the test being performed by the radiographer or the radiology technician who arranges all the images in an orderly fashion. In cases of emergency the reports are generated immediately.
Who signs an MRI report ?
An MRI report is usually signed off by the MRI in charge who is a radiologist or specialist in reading MRI images. The same images are also made available to your treating doctor for his opinion.
Do you get a hard copy of the MRI scan ?
Nowadays, mostly a CD is given with all the required images and a software installed to view those images more feasibly. In case if you request for a hard copy of the scan, you should ask the respective hospital/diagnostic lab if they can provide the same at request.
What are the potential risks of an MRI scan ?
MRI usually is a safe procedure and the only risks could be associated with use of aa contrast media and an allergic reaction or damage to kidney towards it. It is therefore primarily advised to give your detailed medical history and clear all your doubts before going ahead with the procedure.
When an MRI is advised and when is a CT advised ?
An MRI scan is advised to diagnose all medical conditions or to monitor a treatment plan when detailed images are required. A CT scan is primarily used for the examination of hard tissues (example, the bones of head and neck) and soft tissue details are not very accurate with it. An MRI is advised to obtain both hard and soft tissue details (example the brain and spinal cord) which are very precise. Also since MRI does not use any radiation, it can be performed in women who are pregnant (after first trimester) whereas a CT scan is contraindicated. Your treating doctor is the best person to advise you for a CT or an MRI depending upon your requirement.
Disclaimer: The content provided here is meant for general informational purposes only and hence SHOULD NOT be relied upon as a substitute for sound professional medical advice, care or evaluation by a qualified doctor/physician or other relevantly qualified healthcare provider.
