Imaging tests are important diagnostic tests that are crucial to aid the diagnosis of many injuries, diseases, and medical conditions. An MRI scan and a CT scan are types of diagnostic imaging tests that play a significant role in helping doctors diagnose various conditions. Many people consider MRIs and CT scans to be the same while in reality, both are quite different. The modes of action, the kind of structures they visualise, their preparation, and many other factors are quite different for both MRI and CT scans.
In this article, we discuss in detail what CT scans and MRI scans are, what they are used for, their differences, and everything else you need to know about these diagnostic imaging tests.
MRI stands for Magnetic Resonance Imaging, it is a non-invasive imaging procedure. MRI scanner uses a large magnet and strong magnetic field to create detailed images of the body’s organs, soft tissues, bones, and other structures. It is a medical imaging technique used in radiology that uses strong magnetic fields, radio waves, and magnetic field gradients to create detailed inside images of the scanned part of the body. MRI scans take a series of cross-sectional images of the inside of the body that are combined to produce 3D images that can be viewed from different angles.
MRI works by creating images by utilising the hydrogen and oxygen atoms inside the body. The human body is composed of water molecules that have hydrogen and oxygen atoms. Inside the nucleus of each atom is a proton that has a positive charge. These protons act as small magnets that are affected by magnetic fields. Inside an MRI imaging machine are the powerful scanner magnets, all protons in your body line up because of the attraction of these protons with the magnets. After which, small bursts of radio waves are sent to particular areas of the body that cause these protons to knock out of alignment. Once the radio waves are stopped, the protons align once again under the power of the magnet and send out radio signals. These signals are then picked up by receivers which allow the computer to generate detailed images. Since the protons in different types of body tissues and structures have different speeds of alignment and give out different signals, the computer is able to create complex, distinguished images of different areas of the body.
The high resolution images of the body created by an MRI scan can be used to diagnose several conditions of different parts of the body. Depending on the body part whose MRI is being taken, the doctor can diagnose different conditions.
An MRI is commonly used to diagnose conditions related to the brain and spinal cord. These conditions can include:
An MRI that is done on the heart and blood vessels can be used to diagnose conditions including:
When an MRI is ordered for bones and joints, it can help diagnose the following problems:
MRI scans can be done for all the internal organs of the body if the doctor suspects any tumour or disease of a particular organ. MRI can be done for the liver, kidneys, bile ducts, intestines, pancreas, ovaries, uterus, prostrate, spleen, and bladder etc.
MRI of breasts might be ordered to screen for breast cancer, to check for silicon breast implant leaks or to determine the extent of breast cancer. A breast MRI uses a dedicated breast coil and a mammography can be used to diagnose and detect breast cancers or tumours.
Check out the video below for what to expect during your MRI Scan
A CT Scan or Computed Tomography Scan is a diagnostic imaging technique that uses a series of X-rays to create detailed images of the inside of the body. It is more sophisticated and detailed than a standard x-ray as it is able to visualise a lot more details of the internal organs and structures that are not visible through a standard x-ray. CT scans are able to generate detailed images of organs, blood vessels, muscles, bones, and fat.
A CT scanner works differently than a conventional x-ray machine. A standard x-ray uses a fixed x-ray tube through which a beam of energy is aimed at a part of the body. As the beam passes through the internal structures and body parts, the variation in energy is captured on a plate behind the body part. However, in case of a CT scan, there is a motorised x-ray source that rotates in a circular motion around the tunnel inside the scanner. As the x-ray source rotates, it shoots narrow x-ray beams through the patient’s body. The CT scanner has digital x-ray detectors that capture the rays as they leave the patient’s body. The detected rays are then transmitted to the computer where it generates the images.
When the x-ray source completes one rotation, the computer generates a 2D image slice which is stored. The bed on which the patient lies then moves into the cavity in small increments. Every time the x-ray source makes one complete rotation, it transmits the detected rays to the computer where it generates another image slice. Once the required number of image slices have been achieved, the images are displayed individually or combined together to create a 3D image of the organ or structure. These slices of images allow the doctor to effectively locate the source of a disease or problem.
A CT scan can be done with or without a contrast. A contrast agent is a dye that allows soft tissues, blood vessels, and other less dense structures in the body to become highly visible in the scan results. Otherwise, a standard x-ray technology cannot effectively detect soft tissues and similar structures. These contrasting agents can be administered intravenously or orally. IV contrast agents are usually based on iodine that helps illuminate blood vessels. Oral contrasting agents are usually barium-based compounds that help illuminate the organs in the digestive system.
A CT scan is usually done to diagnose various diseases and conditions of the body. It may also be used for guiding procedures. CT scan uses include the following:
Although MRI scans and CT scans appear quite similar in the kind of imaging they produce and the conditions that they help detect, there are some significant differences between the two of them. The following table describes these differences:
An MRI scan uses a powerful magnet and computer-generated radio waves to generate images of the body while a CT scan uses a motorised x-ray source to visualise the inside of the body, both either with or without a contrasting agent.
An MRI procedure takes much more time as compared to a CT scan. On average, a CT scan takes about 5-7 minutes without contrast. On the contrary, an MRI scan can take up to 1 hour or longer to get the final images depending on the region of scan.
MRI cost scan in Singapore and the rest of the world is almost double the cost of a CT scan.
MRIs can be noisy with whirring and thumping sounds, these are normal. Usually patients are given ear plugs or headphones to be worn during the procedure to reduce these noises. A CT scan is relatively much quieter than an MRI and patients do not normally require any ear protection.
Both MRI and CT scans are relatively low risk. CT scans has radiation exposure and can cause certain risks such as harm to an unborn baby and increased risk of cancer. There is also a low chance of allergy reaction to the contrasting agent or dye administered. On the other hand, an MRI has no radiation exposure. As MRI scanner uses a magnet, people having metallic implants in their bodies, artificial joints, or pacemaker have to inform imaging centres ahead of scan to make the necessary arrangements.
Check out the video below for what to expect during your CT Scan
An MRI and a CT scan are painless procedures and there is not much preparation required for both these tests. However, there are a few considerations and restrictions for each scan which are discussed below:
Before an MRI scan, you can eat normally and continue taking any medicine that you take or unless specified. Before the procedure, you may be asked to remove the following items from your body or clothes that may interfere with the magnetic imaging. These include:
The MRI machine comprises a long tube that is hollow on both ends and has a movable bed/table that can slide in and out of the tube. You will be asked to lie on the table either head in or feet in depending on the body part that is being scanned. The table then slides into the narrow tube and the procedure starts.
During the procedure, you will be advised to remain still otherwise the images can get blurred. The radiographer monitors the procedure from another room and you can be in communication with him/her through a microphone. People who are claustrophobic may be given a sedative or relaxant to help them feel less anxious. Depending on the type of scan, it may take 15 minutes to an hour for the scan to complete. Once the scan is over, you can carry out your normal activities.
MRI scan results are usually available after a couple of days after they have been reviewed and interpreted by a radiologist.
Depending on the type of T scan your doctor has ordered, you may be given an oral contrast to drink prior to the scan or intravenous contrast. The contrast is used to outline your organs to ensure defined visualisation. Please let our staff know if you have had any form of contrast allergies before.
Before a CT scan, you may be asked to remove any metallic elements from your clothes and body. These can include:
The CT scan will generate images of your body’s organs from multiple angles, to ensure images are captured accurately, it is essential for you to remain still throughout the scan. The process usually last a few minutes after which you will be allowed to go home. The CT scan is a painless procedure that requires minimum preparation.
The CT scan images are sent to a radiologist who interprets the images and gives his detailed report.
Patients who want to get an MRI scan or CT scan in Singapore can get them done through public hospitals or private medical and healthcare centres. In RadLink, you can easily get an appointment either on the same day or next day. It is important to note that you must have a doctor’s referral either from your GP or a specialist in order to proceed with a MRI or CT scan, without a referral, you will not be able to proceed with any of these scans.
MRIs and CT scans are effective diagnostic imaging techniques that play a vital role in helping doctors reach a definitive diagnosis and proceed with the treatment accordingly. Each of these scans have their own pros and cons. In some cases, an MRI would be more suited for a particular patient while in other cases, a CT scan will be more effective. CT and MRI scans in Singapore are highly effective ways to diagnose various diseases and medical conditions and help devise and monitor treatment for the patients. Your doctor will determine the best approach tailored to your diagnosis.
RadLink is Singapore’s premium healthcare centre that offers state-of-the-art diagnostic imaging tests. Our experienced radiologists with multidisciplinary subspeciality and team of nurses are on the ground to guide you through the procedures. For more information about CT and MRI scans in Singapore and other bespoke specialised services offered by RadLink, contact us today.
MRI and CT scans are considered highly safe in Singapore when they are used appropriately by skilled radiologists and technologists. MRIs are considered an even safer option since they use magnetic imaging methods as opposed to x-rays in CT scans that involve radiation exposure.
An MRI scan usually takes longer than a CT scan. An MRI scan can take anywhere from 15 minutes to an hour or even 90 minutes depending on the size of the body part being scanned and the number of images being taken. A CT scan typically ranges from 10-15 minutes.
There are certain risks associated with an MRI scan such as for individuals having any metallic implant in their body, they may not be allowed to have an MRI scan since the metal can get affected by the powerful MRI magnet. Similarly for a CT scan, there is a risk to an unborn baby because of potential radiation exposure. If you are pregnant, do inform our staff before the scan. it is advisable to consult your doctor for an alternative test.
Usually, anyone would be able to have either an MRI or a CT scan.
A CT scan usually takes much less time as compared to an MRI. A CT scan can normally take 10-15 minutes to complete. In some cases, it may take up to 30 minutes for the procedure to complete.
After having an MRI or CT scan, you will be allowed to leave the clinic and can continue with your normal activities. However, if you were given a sedative or anti-anxiety medicine to make you feel less anxious during the scan, you should take caution while driving and operating other heavy machinery until the symptoms wear off.
Your doctor will determine which scan either an MRI or a CT scan is suitable for you depending on your diagnosis and individual factors.
