Chapter One
Contrast media By: RT Hikma Ali
Lecturer , MRT
Department, MIIMHSC
Objectives
At the end of this session you will be able to:
Discuss about contrast agent and their effect
Differentiate types of contrast media
Identify the routes of administration of contrast media for various
radiographic examinations
Compare and contrast the use of ionic and nonionic iodinated
contrast media
Describe possible reactions to contrast media and categorize them
according to their severity
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INTRODUCTION
Contrast studies are those examinations in which contrast media are
used to enhance visualization of specific body structures.
Because of the low subject Its also used to evaluate other
contrast of the abdomen, contrast areas of the body, such as
media are used to demonstrate
The spinal canal,
the anatomic structures of
Female reproductive
The urinary,
system, and vasculature.
Digestive, and biliary systems.
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Basic principle of contrast media
Many structures and organs within the body have similarly
low tissue densities. This is determined by their atomic
number.
More X-rays are absorbed by structures having a high atomic
number, resulting in less radiation reaching the film, whereas
fewer X-rays are absorbed by structures having a low atomic
number. This accounts for the visible difference in densities
on radiography.
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Basic principle of contrast media
A contrast medium is a pharmaceutical agent
that is administered to a patient for a
radiographic examination to enhance the
contrast of a particular structure.
Without CM With CM
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Types of contrast media
The two basic classifications of contrast media are
1. Negative contrast agents and
2. Positive contrast agents.
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1. Negative contrast
agents
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1. Negative contrast agent
It is radiolucent and has a low atomic number
Allows x-rays to pass through quite easily.
As more x-radiation reaches the film, the structure that is
filled with a negative contrast agent appears dark (black) on
radiography.
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Negative contrast agent
Gases, such as oxygen, carbon dioxide, and nitrous oxide, may be used
as negative contrast media, although room air is the most common agent.
For example, the air in the lungs serves as a negative contrast medium on
chest radiography.
A negative contrast medium may be used alone, as in the case of an air
arthrogram,
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Negative contrast agent
It can also be combined with a positive contrast agent to produce a
double-contrast effect, such as a barium enema examination with air.
The uses of negative contrast media are limited, however, as they may
not provide sufficient contrast of a structure when used singly.
They must never be injected intravenously; doing so will have
serious, if not fatal, consequences.
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2. Positive Contrast Agent
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2. Positive Contrast Agent
Is radiopaque and has a high atomic number.
As it absorbs approximately three times more x-rays than bone and five
times as many x-rays as soft tissue,
An organ filled with a positive contrast agent appears light on the
resulting radiography.
Barium sulfate (BaSO4) and Iodinated compounds are most commonly
used.
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BARIUM SULFATE
Properties
Barium is a heavy metal having an atomic number of 56.
It is combined with oxygen and sulfate to form the inert compound barium
sulfate (BaSO4).
It is a white, crystalline powder that is insoluble in water.
For use in radiography, it is mixed with water and stabilizing agents to
form a suspension.
Barium sulfate is used for examination of the entire alimentary canal.
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BARIUM SULFATE
The products are available commercially in paste, liquid,
powder, and tablet form.
Paste, having a viscosity approximate to that of honey, may
be recommended for an esophagram.
A liquid barium sulfate suspension can also be used for
radiographic examination of the esophagus, as well as the
stomach and both small and large intestines.
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BARIUM SULFATE
It can be purchased in premixed liquid form or in powder form, which
must be mixed with water prior to use. In either case, it should be shaken
immediately before administration, as suspension tends to settle.
Barium sulfate tablets are helpful in evaluating foreign objects or
strictures in the esophagus.
They dissolve in either the esophagus or stomach when mixed with water
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Contraindications
Because of its inability to be absorbed by the body, barium sulfate cannot be
used intravascularly or intrathecally.
Also, its use is contraindicated in the case of
A suspected perforation in the alimentary canal.
Recent or impending abdominal surgery.
Aspiration.
Leak into the peritoneal cavity, causing a vascular adhesions and
peritonitis.
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IODINATED COMPOUNDS
Properties
Iodine is the element of choice for use as a contrast agent, as it
forms stable compounds and does not break down in the body.
It has a relatively low toxicity and
High atomic number.
Unlike barium sulfate, it is generally absorbed by the body and
excreted by the kidneys within 24 hours of intravascular
administration.
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IODINATED COMPOUNDS
The viscosity, or thickness, of the contrast medium is greatly
determined by the size the concentration of the molecules in the
solution.
It is recommended that the liquid iodinated contrast media be pre
warmed to body temperature prior to use.
As iodinated contrast media have a tendency to break down in the
light, they should be shielded from bright light.
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IODINATED COMPOUNDS
An iodinated contrast agent with a higher concentration is generally
used for cardiovascular studies, whereas a lower concentration is
used for urography and cholegraphy.
Iodinated contrast media are available as either oil-based or water-
soluble agents.
Each type of medium is selected for use based on the anatomy to be
examined.
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Oil-based Iodinated Contrast Media
The use of oil-based iodinated contrast media in radiography is
relatively limited.
They are used primarily for studies of the lymphatic system
(lymphangiography).
In the past, they were also used for studies of the
Hysterosalpingography, Myelography, Bronchography, Sialography,
and Dacryocystography, but have been replaced by water-soluble
iodinated nonionic contrast media.
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Oil-based Iodinated Contrast Media
The oil-based iodinated contrast medium is used in hollow
anatomic areas, enhancing the radiographic contrast of the
structure.
The oily base of the contrast medium is a fatty acid, which is
responsible for making the solution viscous (thick) and
insoluble in water and body fluids.
Because it is not miscible with blood, it should never be
injected intravenously or intraarterially.
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Water-soluble iodinated contrast media
Water–Soluble (aqueous) iodinated contrast media are routinely used for
radiographic examinations of the
Urinary,
Biliary, and cardiovascular systems,
as well as the digestive system if barium sulfate is contraindicated.
It also used in special examinations of the skeletal system such as
myelography and arthrography.
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Water-soluble iodinated contrast media
They are available in liquid, tablet or granule form depending
on the intended use.
The injectable liquid media can be divided in to
Ionic and
Nonionic contrast agents.
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Water-soluble iodinated contrast media
An ionic contrast agent is an organic A nonionic contrast agent also contains
iodine compound that has triiodinated iodine and is derivative of the
benzoic acid as its base. triiodinated benzoic acid base,
The compound dissociates or but it does not contain an ionizing
separates in water into two group.
electrically charged particles. It is more soluble in water and
One of the particles, called a cation, Does not dissociate into changed
has a + charge; the other particle, an particles;
anion has a - charge.
It has a lower osmolality than an ionic
contrast agent.
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Triiodinated benzoic acid
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Classification of iodinated contrast
agents by their molecular structure
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Osmolality
Osmolality refers to the concentration or number of particles
(cations and anions) in the solution per kilogram of water and is
directly related to occurrence of adverse patient reactions.
It is measured in osmoles, which are units of osmotic pressure.
A contrast agent with a high osmolality has an increased number of
particles and more osmoles in the solution.
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Osmolality
Any time a foreign substance is injected into the bloodstream,
the homeostasis of the body can be affected.
Because of their hyperosmolality, ionic contrast agents can
cross the blood-brain barrier, which is also a factor in the
occurrence of adverse reactions.
Nonionic contrast agents have a much lower level of
neurotoxicity.
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Examples of ionic and non-ionic
Iodinated contrast agents
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Osmolality
High osmolar contrast agents Low osmolar contrast agents ( LOCA )
( HOCA ) – Ionic – Ionic and Non-ionic
Urovist. Non-ionic Ionic
Urogarfin Ultravist Hexabrix
Angiovist. Omnipaque
Conray. Visipaue
Renografin.
Oxilan
Renovist.
Hypaque.
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Contraindications
Allergic history to iodine.
Renal disease(Abnormal RFT)
In some cases, the patient can be premeditated without
causing an adverse reaction.
Allergic reactions to oil based iodinated contrast media can
occur but are rare.
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ROUTES OF ADMINISTRATION
Contrast media are considered to be pharmaceuticals (drugs), and as such
they must be administered appropriately to achieve the desired effect and
to avoid unwanted complications.
The five rights of medicine administration
1. The right patient should receive
2. The right medication
3. In the right amount
4. Via the right route
5. At the right time
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ROUTES OF ADMINISTRATION
The route of administration depends on the anatomy of
interest, type of examination, and particular contrast medium.
Contrast medium can be administered
Orally,
Rectally,
Intravascularlly, or Intramuscularly
Mechanically:- Introduced directly in to the intended site.
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ORAL/RECTAL ROUTE
Barium sulfate products are administered by means of the oral route
for examinations of the
Esophagus ,stomach, and
Small interesting.
Iodinated contrast agents such as Gastrografin and Hypaque can
also be administered orally for these same examinations.
It is administered rectally as an enema for an examination of the
large intestine.
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INTRAVASCULAR ROUTE
Only water- soluble iodinated contrast media can be administered
intravascularly.
Intravascular injection of contrast media includes both intravenous and
intra-arterial routes.
The intravenous route is employed for excretory urography, as well as
for CT and MRI Examinations using contrast media.
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INTRAVASCULAR ROUTE
The intra-arterial route is used for special radiographic
procedures of the cardiovascular system.
Access to the artery is accomplished via the seldinger
technique which is described in angiography.
In lymphangiography, the contrast medium is injected
intravascularly into the lymphatic vessels.
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DIRECT ROUTE
Some radiographic examinations require that the contrast medium
be introduced directly into the anatomy of interest.
This can be achieved by means of a catheter or needle. For
example, in a cystogram a catheter is inserted into the urinary
bladder and a water-soluble iodinated contrast medium is allowed
to flow into the bladder until it is full.
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Direct route
During a myelogram, an intrathecal injection is performed by
inserting a spinal needle into the subarachnoid space.
Examples of other examination in which contrast media are directly
administered include
Arthrography,
Hysterosalpingography,
Sialography, and percutaneous transhepatic cholangiograhy.
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REACTIONS TO CONTRAST
MEDIA
The potential exists for an adverse reaction to occur when a contrast
medium is administered to a patient.
Although reactions can take place with the use of any contrast agent,
they are more likely to occur after intravascular injection.
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REACTIONS TO CONTRAST MEDIA
The technologist or radiographer should be aware of the possibility of
adverse reactions and be prepared to handle them according to the
institution’s protocol.
An emergency drug box or crash cart should be in the examination
room or readily available.
It is recommended that the patient’s blood pressure, pulse, and
respiration be assessed prior to contrast medium administration.
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REACTIONS TO CONTRAST MEDIA
▸ Following any examination in which barium sulfate is
administered; the patient should be advised to drink plenty
of fluids to prevent a bowel obstruction.
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REACTIONS TO CONTRAST MEDIA
The reactions seem to be directly related to the following factors.
Degree of chemotoxicity of the contrast medium
Concentration of iodine in the contrast medium
Certain properties of the contrast medium including
osmolality, viscosity, and purity of the solution
Dosage administered
Pace of the injection
Physical condition of the patient
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REACTIONS TO CONTRAST MEDIA
An anaphylactic reaction closely resembles a true allergic reaction in
which the patient demonstrates hypersensitivity when a foreign
substance is injected.
Although such a reaction cannot be predicted, certain patients seem
to be predisposed to experiencing adverse reactions.
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REACTIONS TO CONTRAST MEDIA
A vasovagal reaction is one that occurs in response to anxiety or fear.
It generally involves a vascular as well as a neurogenic response, with
the patient experiencing mild symptoms of pallor, dizziness,
diaphoresis, nausea ,and possibly bradycardia.
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REACTIONS TO CONTRAST MEDIA
Extravasations Occurs during injection if some of the contrast medium seeps
out of the vein to the surrounding tissue.
Usually involves pain and discoloration at the site of injection.
The technologist should apply a warm, moist compress to the site to
decrease pain and aid in the absorption of the contrast medium.
Reactions are classified as mild, moderate, or severe according to the
symptoms experienced by the patient.
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Mild
Signs and symptoms appear self-limited without evidence of progression
▸ Nausea, vomiting ,altered taste, sweats, cough, itching, rash, hives
▸ Warmth (heat) Pallor, Nasal stuffiness
▸ Flushing, Swelling: eyes, face ,Dizziness Chills Anxiety
▸ Treatment: Observation and reassurance.
▸ Usually no intervention or medication is required;
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Moderate
Reactions which require treatment but are not immediately life-threatening
Tachycardia/bradycardia, Hypotension Bronchospasm, wheezing
Hypertension. Dyspnea Laryngeal edema
Pronounced cutaneous Pulmonary edema reaction
Treatment: Prompt treatment with close observation
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Severe
Life-threatening with more severe signs or symptoms including:
Laryngeal edema, Profound hypotension
Unresponsiveness
severe or progressive Convulsions
Cardiopulmonary arrest
Clinically manifest arrhythmias (irregular heart beat)
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Patients at increased risk
History of a previous reaction to iodinated contrast agents or
History of allergy ,History of asthma, History of renal disease or
conditions predisposing to renal impairment such as:
Previous renal surgery, Diabetes Mellitus ,Proteinuria,
Hypertension Cardiac Failure
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Patient care before administering CM
Hydrate the body prior to administration
Warm CM to body temperature
Keep emergency drugs like adrenalin
Ask patient history
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During anaphylactic reaction
Stop the injection immediately
Monitor vital sign
Observe for respiratory distress
Call emergency team (physicians and nurses)
Place the patient in Semi-fowler’s or sitting position (for
cardiopulmonary distress)
If the patient becomes breath less and pulse less, administer
cardiopulmonary resuscitation
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Patient care and instruction after receiving
iodinated contrast agent
Instruct the patient to increase fluid intake to
3000ml for at least 24 hours to assist with the
dilution and excretion of the agent from the body.
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“ There are dark shadow s on
the earth,but its light are
stronger in the contrast. ’’
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