CT Scan and MRI

By Medical Expert Team

Dec 22 , 2022 | 3 min read

Computed Tomography or CT scan is a non-invasive method of producing body images. It utilises X-rays and computers to create 2D and 3D images, which are more detailed than standard X-ray films. It has a 360-degree image acquisition. It can be used to see any internal body part, such as bones, muscles, organs, fat and blood vessels. MRI, on the other hand, utilises magnetic fields and radio waves to create images. It is also a non-invasive method of producing high-resolution 2D and 3D images of tissues, organs, bones and joints. It has no radiation here, which is much safer than CT. MRI is the mobility of choice for the evaluation of the muscular-skeleton brain.

When do doctors advise a CT scan and MRI?

Doctors may advise you to get a CT scan in the following cases.

To detect bone tumours, fractures, heart disease, and lung nodules, fluid in the lungs. It can also detect the location of a blood clot, infection, internal injuries or internal bleeding site, and main lesions.
To perform procedures such as biopsy, needle aspiration, surgery and radiation therapy with the guidance of CT scan, thus reducing the need for invasive open surgery or repeated exploration.
To analyse the effect of treatment modality on cancer treatment.

Doctors may advise you to get an MRI done in the following cases:

To diagnose diseases of the brain and spinal cord, and muscular skeleton system (Most frequently used diagnostic modality)
Diagnose diseases of the heart and blood vessels.
To detect diseases of bones and joints.

What is a CT scan with contrast?

A contrast medium is used to get more clear 2D images as compared to standard CT scans. Contrast medium Add value in detecting various abnormalities in the body, but these are not dyes and do not cause permanent discolouration. Your doctor can provide contrast medium in the following three ways depending on the area to be visualised.

Orally:You will be asked to drink the contrast medium if your gastrointestinal tract, including the pharynx, oesophagus, stomach, small intestine and large intestine, needs to be visualised. You have to drink it within 1 to 2 hours. Usually, gastrograffin/iodinated contrast is used as a contrast medium; oral contrast is safe and does not cause adverse effects.
Intravenously:Iodine based for CT Scan or gadolinium-based contrast medium is injected in your arm to visualise your heart, lungs, kidneys, liver, adrenal glands, urinary tract, gallbladder, spleen, blood vessels, gastrointestinal tract, brain and breast.

For a CT scan with contrast, you are advised to fast for at least 4 hours. Fasting is required to prevent nausea and vomiting. Moreover, if a CT scan is being performed for the gastrointestinal tract, food or liquid can impact the visualisation of internal organs due to the presence of content inside. A kidney function test (B.urea & S.creatine) is done before giving IV contrast. In the case of deranged KFT. Discuss with your Radiologist for IV contrast.

How to prepare for a CT scan?

You will have to remove accessories/jewellery, denture, eyeglasses and belt, and you will be given a gown to wear. Avoid eating or drinking four hours before your test.

How to prepare for an MRI?

You can eat and drink as usual, but in some instances, you may be advised to refrain from eating and drinking for 6 hours before getting MRCP in all other cases. No fasting is required in MRI.
Like a CT scan, you will have to remove accessories/jewellery, denture, eyeglasses and belt, and you will be given a gown to wear.
You should inform your doctor if you are claustrophobic (fear of closed space)
Inform the radiology technician and radiologist if you have the following implant. Pacemaker, Neurosimulator, intracardiac defibrillator, metallic eye, metallic chips in the brain, cochlear implant and joint implant.
You should also inform your doctor if you are claustrophobic ( Fear of closed space).>

Can a pregnant patient undergo CT Scan/MRI?

CT scans should be avoided in pregnant patients. MRI can be performed during pregnancy only in the 2nd and 3rd trimesters. Moreover, these diagnostic tests should be done only when necessary. Tell your doctor if you are pregnant before undergoing any imaging tests.

Can a Lactating patient undergo CT Scan/MRI?

Yes, a lactating mother can undergo a CT scan/MRI. A minimal amount of contrast medium comes out in milk after an MRI, and there is no evidence that the contrast medium is harmful. Consult your doctor regarding this when you go for a CT or MRI.