Contrast Materials

Contrast Materials
Muhammad Arif Afridi
Lecturer In Medical Imaging
Email: drarifafridi@gmail.com
MUHAMMAD ARIF AFRIDI | LECTURER IN MEDICAL IMAGING| DRARIFAFRIDI@GMAIL.COM 1

Contrast Materials
Radiocontrast agents are substances used to enhance the visibility of internal structures in X-
ray-based imaging techniques such as computed tomography (CT), radiography, and
fluoroscopy. Radiocontrast agents are typically iodine or barium compounds.
A medical contrast medium is a substance used to enhance the contrast of structures or fluids
within the body in medical imaging. It is commonly used to enhance the visibility of blood
vessels and the gastrointestinal tract.
Any substance that renders an organ or structure more visible than is possible without its
addition of contrast materials.
Allows visualization of structures that can not be seen well or at all under normal
circumstances.
2MUHAMMAD ARIF AFRIDI | LECTURER IN MEDICAL IMAGING| DRARIFAFRIDI@GMAIL.COM

“Contrast Media"
A contrast media is when
introduced into the body will
increase the radiographic
contrast in an area where it
was absent or low before.

Methods of administration
Orally.
Rectally.
Intra- venously – (injection / infusion).

TYPES OF CONTRAST MEDIA
Negative
- Air
- Oxygen
- Carbon Dioxide
- Nitrous Oxide
Positive
- Barium
- Iodine

Radiolucent & Radiopaque
Materials that inhibit the passage of radiation are called radio dense or radiopaque, while those
that allow radiation to pass more freely are referred to as radiolucent.
Bone is radio opaque (white) on X-ray film, air is radiolucent (black) on film X-ray.

Radiolucent
That portion of the radiograph that is dark
structures that lack density permit the passage of x-rays with little or no resistance.
These structures appear dark

Radiopaque
That portion of the radiograph that appears light.
Dense structures resist the passage of radiation.
These structures appear light on the image

Negative Contrast Agents
The absorption of x-rays by a substance is dependent upon several factors.
One of which is the atomic weight of the substance.
Those materials that have lower atomic weights will attenuate less radiation.
The resultant remnant radiation will produce a greater radiographic density (darker image) on
the image receptor.
Examples of radiolucent, or negative, contrast agents are air, oxygen, carbon dioxide, and
nitrous oxide.

Positive Contrast Agents
Positive Contrast Agents have high atomic numbers, positive contrast agents cause an increase
in the attenuation of x-rays and are considered to be radiopaque.
They produce an area of decreased radiographic density on the image receptor.
Contrast agents that are radiopaque contain elements with high atomic numbers such as
iodine, bromine, and barium.
When these substances are used to fill organs, they essentially make the organ radiopaque,
and the image appears clear or white on the radiograph.
They can take the form of tablets, powders, and liquids and can be introduced into the body
through a variety of routes.
They are relatively nontoxic in most cases, but certain patients may exhibit reactions of varying
severity, especially to agents containing iodine.
In some cases, small doses of these agents may cause death.

Examples of areas where contrast
agents are used
Arteriography
Angiography
Venography
IVU (intravenous pyelogram (IVP), also called an intravenous urogram (IVU))
Fluoroscopy (barium enema)
Computerized Tomography (CT)

LOCM and HOCM
low-osmolarity contrast medium (LOCM)
A water-doluble contrast medium with low osmolality.
These agents produce fewer undesired effects after intra vascular administration than do high-osmolarity contrast media.
They are generally nonionic, with the exception of Hexabrix (an ionicdimer).
high-osmolarity contrast medium (HOCM)
A water soluble contrast medium with high osmolarity.
These agents increase the probability of an adverse reaction and aregenerally ionic.
The LOCM are 5-10 times safer than HOCM.
HOCM is much less expensive than the LOCM
because LOCM so were widely used despite the higher risk of adverse reactions and nephrotoxicity.

Types of contrast material Positive &
Negative
A substance, such as barium or air, used in radiologic studies to increase the contrast of an
image.
In x-ray imaging, a positive contrast medium absorbs x-rays more strongly than the tissue or
structure being examined

Types of contrast media
Negative Contrast Agents
◦ - Air
◦ - CO2
◦ - O2
Positive Contrast Agents
Barium based
Iodine based agents
–Water soluble (Niopam)
–Non soluble (Lipiodol, Myodol)
The positive contrast agents increase the atomic number of the area to be demonstrated in
relation to the surrounding tissue.

• Powder contrast in a form of tablets e.g. Biloptin, Cistobil.
• Oily contrast e.g. myodil, dinosil & lipidol.
• Water soluble ( addition of sugar).
Ionic e.g. urografine, urovideo, uromiro, conray, hexbric & angoigrafine.
Non ionic e.g. Amipaque, omnipaque, ultravist & isovist.
Note:- all nonionic C.M. are more safety than ionic one.

Contraindications Iodine (DO NOT USE)
hypersensitivity to iodine
heart or renal failure
liver disease

Double contrast agents
Incorporates the use of both positive & negative contrast media e.g during a double contrast
Barium enema examination.

Characteristics of a good contrast
medium
The basic principle of contrast agents is are administered in such a way as to alter the absorption
of x-rays by specific anatomic structures in relation to their surroundings.
Contrast agents may be positive (iodine or barium compounds, for example), or negative (gases).
The use of iodine compounds was initially related to low toxicity and excellent radio-opacity
rather than physical considerations.

Contrast materials enter the body in one
of three ways
swallowed (taken by mouth or orally)
administered by enema (given rectally)
injected into a blood vessel (vein or artery; also called given intravenously or intra-arterially)
Following an imaging exam with contrast material, the material is absorbed by the body or
eliminated through urine or bowel movements.

There are several types of contrast materials:
Iodine-based and barium-sulfate compounds are used in x-ray and computed tomography (CT)
imaging exams.
Contrast materials can have a chemical structure that includes iodine, a naturally occurring
chemical element.
These contrast materials can be injected into veins or arteries, within the disks or the fluid
spaces of the spine, and into other body cavities.
Barium-sulfate is the most common contrast material taken by mouth, or orally. It is also used
rectally and is available in several forms, including:
◦ powder, which is mixed with water before administration
◦ liquid
◦ paste
◦ tablet

When iodine-based and barium-sulfate contrast materials are present in a specific area of the
body, they block or limit the ability of x-rays to pass through.
As a result, blood vessels, organs and other body tissue that temporarily contain iodine-based
or barium compounds change their appearance on x-ray or CT images.
Gadolinium is the key component of the contrast material most often used in magnetic
resonance (MR) exams.
When this substance is present in the body, it alters the magnetic properties of nearby water
molecules, which enhances the quality of MR images.
Saline (salt water) and air are also used as contrast materials in imaging exams. Microbubbles
and microspheres have been administered for ultrasound imaging exams, particularly exams of
the heart.

imaging exams use contrast materials
Oral Contrast Materials
Barium-sulfate contrast materials that are swallowed or administered by mouth (orally) are used
to
enhance x-ray and CT images of the gastrointestinal (GI) tract, including:
◦ pharynx
◦ esophagus
◦ stomach
◦ the small intestine
◦ the large intestine (colon)
In some situations, iodine-based contrast materials are substituted for barium-sulfate contrast
materials for oral administration.

Rectal Contrast Materials
Barium-sulfate contrast materials that are administered by enema (rectally) are used to enhance
x-ray and CT images of the lower gastrointestinal (GI) tract (colon and rectum).
In some situations, iodine-based contrast materials are substituted for barium-sulfate contrast
materials for rectal administration.

Intravenous Contrast Materials
Iodine-based and Gadolinium-based
Iodine-based contrast materials injected into a vein (intravenously) are used to enhance x-ray
and CT images.
Gadolinium injected into a vein (intravenously) is used to enhance MR images.
Typically they are used to enhance the:
1.internal organs, including the heart, lungs, liver, adrenal glands, kidneys, pancreas, gallbladder,
spleen, uterus, and bladder.
2.gastrointestinal tract, including the stomach, small intestine and large intestine
3.arteries and veins of the body, including vessels in the brain, neck, chest, abdomen, pelvis and
legs
4.soft tissues of the body, including the muscles, fat and skin
5.brain
6.breast

The contrast material used in MR called gadolinium is less likely to produce an allergic reaction
than the iodine-based materials used for x-rays and CT scanning.
Intravenous Contrast Material (Iodine and Gadolinium) and Breast-feeding:
Manufacturers of intravenous contrast indicate mothers should not breast-feed their babies for
24 to 48 hours after contrast medium is given.

Thank you!
MUHAMMAD ARIF AFRIDI | LECTURER IN MEDICAL IMAGING| DRARIFAFRIDI@GMAIL.COM 30

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