What is contrast agent & why it is used in Diagnostic scans?

With the increased lifestyle diseases in India, usage of diagnostic scans is doubling each year according to WHO and other national health reports. Most common diagnostic scan procedures used by patients are CT scans, MRI scans, Ultrasound scans, Mammography & PET-CT Scans.

In order to obtain more clear pictures inside our body, contrast agents also called as contrast materials/contrast media are used during the diagnostic scan procedure. Using contrast materials in diagnostic scans helps the radiologists to assess and distinguish normal and abnormal conditions more precisely.

Contrast materials color the internal organs, structures and blood vessels temporarily for a certain period of time and make them more clear for better diagnosis on any medical conditions.

Types of Contrast Agents

Oral Contrast Media (Taking the contrast material as a food by mouth)

Barium sulfate contrast materials are often swallowed through mouth to produce clear images of the structures in gastrointestinal tract such as pharynx, small & large intestine, stomach and esophagus. For some diagnostic procedures, iodine-based contrast will be used instead of barium contrast materials.

Rectal Contrast Media (a procedure where the liquid is injected through the rectum)

This is process of applying the contrast material into the rectum where Iodine based & barium sulfate contrast agents will be used to diagnose the lower gastrointestinal tract.

Intravenous Contrast Media (Injecting through vein or artery which then gets mixed into the blood)

Gadolinium/Iodine-based agents will be injected into the vein in order to produce enhanced pictures of internal organs including heart, lungs, liver, kidneys, adrenal gland, pancreas, spleen, uterus and bladder, gastro-intestinal tract, arteries and veins, blood vessels in brain, pelvis, legs, abdomen and chest, soft tissues like muscle, breast and skin.


Contrast dye used in CT scans

There are several chemical substances used as contrast material for CT scan procedure. Most common type of contrast material are Iodine-based and barium sulfate compounds. These contrast materials usually injected into the veins/arteries, spine disks, fluid space of spine and other cavities in human body.

Another type of contrast material called barium sulfate is most commonly taken as a food orally. This chemical compound will occur in the form of powder, liquid, paste and tablet. Here is a clean summary about contrast vs non contrast CT scan (source: http://forums.studentdoctor.net/)

CT Abdomen Scan: 
Non contrasts are widely used for diagnosing trauma, headache, stroke and so on.
CT Abdomen with Contrast scans are commonly used for evaluating infection (menigeal enhancement, abcess) or tumor (mets) where the impact of the infection is clearly diagnosed.

CT Chest Scan
CT Chest Scans without Contrast is commonly used for the evaluation of parenchymal lung diseases, interstitial lung diseases etc.
CT scans with Contrast are more helpful in evaluation of the mediastinum (lymph nodes, infection), vascular or heart structures.

CT Abdomen/Pelvis
CT abdomen Pelvis Non-contrast scans are commonly used for analyzing calculi in the kidneys or ureters. Because contrast enhanced scans can obscure calculi if the contrast is beginning to get excreted already.

CT abdomen pelvis with contrast are helpful in diagnosing pancreatitis, diffuse abdominal pain, abcess, diverticulitis, liver mass etc.,

CT Angiogram
CT angiogram scans are usually contrast enhanced scans for the evaluation of the aorta, mesenteric vessels, renal arteries, etc. In hematuria evaluation, non contrast procedure is followed to diagnose the stones and contrast procedure will be used to look for renal masses and bladder lesions.

Contrast dye used in MRI scans

MRI Contrast scans uses the contrast dye called gadolinium which consists of complex molecules arranged with chemical bonds. A chelating agent is used in order to prevent the toxicity of galonium and to maintain its contrast properties.

Gadolinium is injected into patients through IV’s and will be flushed out from the body by taking plenty of fluids. MRI contrast scans are used 1 in 3 scans for improvisation of the image clarity in internal structure of body. MRI contrast material are less allergic as compared to the iodine based contrast material used in CT scans.

MRI Head Scan with contrast

MRI head scans with contrast are more helpful in identifying the location and impact of brain tumours. After the treatments, MRI brain scans with contrast can help the physicians to exactly monitor the tumor, dilation of fluid spaces within the brain ventricles, hemorrhage in trauma patients, eye disorders, and problems in ear, pituitary gland disorders and more.

Also, MRI head scans with contrast are good in diagnosing the vascular problems such as aneurysm, arterial occlusion and venous thrombosis.

MRI Chest Scans with contrast

Chest MRI with contrast helps to assess the heart functioning and its blood flow. It is very good in identifying the abnormal tumors with its size and impact.

MRA Angiography with Contrast

MRA scans are usually done by using contrast materials which is performed in order to identify the proper blood flow in arteries and veins. It can obtain the detailed view of blood vessels of brain, neck, heart, chest, pelvis, legs, feet, arms and hands.

MRI Abdomen with Contrast

To check the blood flow, identifying the types of tumors and to show the exact areas of inflammation or infection, MRI abdomen with contrast is used. It helps to identify the blockages in liver, gall bladder, pancreas and kidneys.

MRI Pelvis with Contrast

MRI pelvis with contrast scans produces more accurate pictures between the area of hip bones. The blood vessels in bladder, male/female reproductive organs, lymph nodes and pelvic bones will be captured more clearly to identify any abnormalities.

MRI for Bone and Joints:

MRI bone and joints scan rarely uses contrast material. Some conditions like inflammatory arthritis uses MRI joints with contrast scan to identify the formation of discrete erosions. It is also helpful in diagnosing the infections in bone marrow more accurately.

Before and after Contrast Agents

Safety Measures before taking contrast agents

You have to clearly inform the radiologist about your previous medical history. If you are have any kind of allergies to the contrast materials, specific food, drugs or preservatives, and then you have to take the contrast material with some additional medications to tackle the allergies during the scan procedure.

Even if you are taking any herbal supplements for any of your surgeries or for the medical conditions, then you have to take alternative medications before taking the contrast materials. Also, if you have any history of diabetes, thyroid problem, skin allergies, kidney/heart disease you have to be careful and follow the guidelines from your radiologists before the contrast scans.

Pregnant women should not breastfeed their babies for 24-48 hours after using the contrast materials. For MRI imaging, using gadolinium contrast is usually avoided apart from rare urgencies. During CT scans with contrast, patients and their referring physicians will be consulted by the radiologists.

Before and after taking Barium-Sulfate Oral/Rectal Contrast Materials

While taking oral contrast:

Before taking barium sulfate orally, you have to remain fasting for few hours before the scan procedure. The taste of the barium sulfate contrast materials will be unpleasant but it is very mild and will not last for long time. After the scan procedure, you can flush out the contrast materials from the body by taking more fluids

While taking rectal contrast:

When applying barium sulfate via rectum, you will sense the feel of stomach fullness and an urge to expel the liquids. Later it is expelled from your body through feces and the bowel movements will be in white color for few days.

Before and after taking Iodine based Contrast Materials

When the iodine based contrast materials are injected through IV, you may experience a little discomfort during insertion. Once the contrast material starts dissolving in your blood stream, you might feel a warm sensation with a metallic taste. You will be advised to take more fluids in order to flush out the iodine contrast materials from your body.

Before and after taking Gadolinium based Contrast Materials

Injection with Gadolinium based contrast materials will give you a little pain during insertion and after removal, but will not last for long time. You might feel sudden chillness in the IV injected arm and slowly it disappears after a minute or two.

Is Contrast agents are safe?

Contrast agents are safe to use and it is used from over many decades. There will be some discomfort and it will not last for long period of time. Some people are allergic to the contrast materials and they have to inform the radiologist before the below symptoms become more severe.

Allergic symptoms on Barium Sulfate contrast scans will be stomach cramps, diarrhea, nausea, vomiting and constipation. Inform your physician immediately if you have hives, itching, red skin, swelling of the throat, difficulty breathing or swallowing, hoarseness, agitation, confusion, fast heartbeat, bluish skin color. If the patients have any history of asthma, cystic fibrosis or any intestinal blockage, they have to go with alternative medications before taking the contrast.

Iodine-based Contrast Material side effects include nausea and vomiting, headache, itching, flushing, mild skin rash and some patients have wheezing, abnormal heart rate, blood pressure variations and swelling of throat.

MR Gadolinium Contrast Material will not produce allergic reactions like iodine-based contrast agents. It is very mild and rarely people experience hives and itchy eyes.

Pregnant patients should try to avoid contrast scans apart from urgent and critical conditions. After the contrast material intake, Breast feeding women should not feed the babies for 24-48 hours.

Hence, contrast materials are safe apart from some rare adverse reactions. But even for patients with allergic reactions, most of the diagnostic scan centres are well equipped to treat them.

How long it takes for contrast dye to leave the body?

If you need to do any other additional tests like urine test or blood test after taking the contrast materials, then you have to wait for a day or two because the contrast agents usually interfere with the urine test results.

All the oral contrast materials will leave from your body naturally if you take more fluids after the scan procedure. If patients are taking rectal contrast materials through enema, then it will drained after the exam. Based on the type of contrast material, it will stay in your body for not more than 8-24 hours.

Patient Experiences who took contrast dyes

 “I had the warm feeling for my CAT scan but luckily none of the nausea. I would say water, lots of water. If the iodine is making you nausea, then drinking more water would help flush it out of your system faster. Iodine is a type of salt, so water should flush it out pretty quick. Just an idea”

 “I had the massive warm feeling as well but it was okay”  

 “What bothered me most about the procedure was the metallic taste. I don’t recall any lasting side effects, though.”

 “I’ve had ink injections for all of my MRIs, but I do not know if it is the same kind that use for CAT scans. I never had any side effects from the ink I had injected. “

 “Slight warm feeling running up arm down to stomach, no vomiting”

Contrast Scan Prices (Delhi, Bangalore, Chennai, Hyderabad, Delhi, Coimbatore)

MRI contrast scan price starts from Rs.3150 to Rs.4500, which differs in every scan center. CT contrast scan prices range from Rs.2500 to Rs.3500. But, if you fix appointments for MRI contrast scans or CT contrast scan through www.bookmyscans.com , then the charges will be between Rs.1000 to Rs.3000 only. The most common contrast scan widely done is MRI abdomen scan with contrast  & ct abdomen with contrast.

For booking appointments, please check the below pages:

MRI scan in ChennaiMRI scan in Bangalore | MRI scan in Hyderabad | MRI scan in Mumbai |

MRI scan in Delhi


CT scan in ChennaiCT scan in BangaloreCT scan in HyderabadCT scan in Mumbai |

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