This document discusses contrast media used in medical imaging. It begins by classifying contrast media as either iodinated or non-iodinated, focusing on barium sulfate as a common non-iodinated contrast agent used for gastrointestinal imaging. The document then discusses gadolinium-based contrast agents used in MRI and microbubble contrast agents used in ultrasound imaging. It covers the properties, mechanisms, safety considerations and future directions for these different contrast media types.

1. Contrast media II
Presenter
Sujan poudel
Moderator: Mr. Mukesh Kumar Jha
Demonstrator, BPKIHS

2. CLASSIFICATION OF
CONTRAST MEDIA
nature of material
1. Non-Iodinated based :
• Contrast media is used in radiography to
increase the clarity of the image.
• A non-iodinated contrast media is one that
does not contain iodine and may instead
contain barium or other non-iodinated
media as the radio opaque substance.

3. BARIUM SULPHATE
• Barium suspension is made up of pure barium sulphate (BaSO4 ).
• Occurs in nature as the mineral barite
• Barium Sulfate is the sulfate salt of barium, which is an alkaline, divalent
metal.
properties
• 0.1-3micrometer particles size
• Atomic number: 56
• PH: 5.3 which makes it stable in gastric acid
• Non absorbable and non toxic
• Barium is an ideal radiographic contrast, as its k-edge of 37 Kev
approximately, is closed to mean energy of x-ray used in diagnostic
radiography.
• Used in GI studies because of its better mucosal coating properties.

4. Concentration of barium used in various GI studies
• Barium swallow : E-Z HD 200-250 % w/v1ooml
• Barium meal : E-Z HD 200-250 % w/v 3ooml
• Barium follow through : E-Z paque 60-100 %
350ml
• Small bowel enema : E-Z paque 60% w/v 1500ml
• Barium Enema : Polibar 115% w/v 500ml

5. Contd..
Advantages
• Better mucosal coating
• Low cost
Disadvantages
• Subsequent radiological
examinations cannot performed
patient needs to wait up to 2
weeks for proper clearance of
barium.
• High morbidity associated with
barium in peritoneal cavity.

6. Complications
• Perforation: High morbidity if there is leakage
of barium into peritoneal cavity it will produce
severe hypovolemic shock.
• Intravasations : may result in pulmonary
embolus
• Aspiration.
• If perforation is suspected than water soluble
contrast media generally LOCM is preferred.

7. Classification
MRI contrast media
Exogenous
IV
Oral
Endogenous
Uses body water as
contrast media
Gadolinium or
iron based
compound
MRI Contrast media Classification

8. Classification of gadolinium based
contrast Agent (GBCA)
Ionic
Ablavar
Gadofosveset
Sodium
Dotarem
Godoterate meglumine
(Gd-DTOA)
Non Ionic
Omniscan
Gadodiamide
(Gd-DTPA-BMA)
Gadavist
Gadobutrol
(Gd-Do3A-Butriol)
Eovist
Gadoterate
meglumine
(Gd-DToA)
Optimark
Gadoversatamide
(Gd-DTPA-BMEA)

9. Omniscan
• Not for intrathecal use: intrathecal
use of Omniscan has caused
convulsions, coma, sensory, and
motor neurologic deficits.
• Omniscan MRI contrast is a sterile,
clear, colorless to slightly yellow,
aqueous solution containing 287
mg/mL of Gadodiamide
in polymer bottles,
• Product should be protected from
strong daylight and direct exposure
to sunlight. Freezing should be
avoided.
• Storage should be at a controlled
room temperature 20°-25°C (68°-
77°F); excursions permitted to 15°-
30°C (59°-86°F)

10. Properties of Gadolinium based contrast
Agents (GBCA)
Gadolinium (Gd, atomic number 64) is a paramagnetic heavy metal.
 Gd(III) ion is quite toxic to humans, so chelated- Gd(III) compounds
are much less toxic and are referred to as Gd-based contrast agents
(GBCA).
GBCAs are manufactured by a chelating process in which large organic
molecules encapsulate the gadolinium.
This procedure reduces the chances of toxicity due to free Gd ions
because these stable chelated compounds are predominantly eliminated
via the kidneys before the compounds degrade and release free Gd ions.
Dose is generally 0.1 (mmol/Kg) of body weight.

11. Mechanism of Gadolinium based
Contrast Agents (GBCA)
 GBCAs are paramagnetic, they generate a magnetic moment
when placed within a static magnetic field, influencing water
protons within their local magnetic field and shortening T1, T2,
and T2* relaxation times to enhance image contrast.
T1 is the spin-lattice or longitudinal relaxation time, which
measures how fast the proton magnetization recovers to its
equilibrium position.
Shortening T1 increases the recovery speed and further
increases MR signal in the tissue thus producing bright images on
T1 weighted sequence and are so called T1 contrast agents.

12. Reason for choosing gadolinium as contrast agent
 It has seven unpaired electrons and have magnetic
moment 500000 times that of a hydrogen proton.
 This large magnetic moment creates fluctuations in local
magnetic fields.
 In body water tumbles faster than Larmor frequency
resulting in inefficient relaxation. So, the magnetic field
fluctuations created by gadolinium reduces nearby water
spins resulting in Increased signal intensity on T1
weighted images.
 Relatively Safer when chelated, when chelated it bind to
the available sites of metal ion decreasing its toxicity.
 The first chelate that was accepted was DTPA
(diethyelene triaminepentaacetic acid) it binds to eight of
none binding sites of gadolinium ion leaving ninth for
close approach for water molecules.

13. Other T1 contrast agents
• Manganese – used iv for liver imaging
• Hyperpolarized helium – Ventilation agent
used for evaluation of lungs.
• Oral and rectal agents
• Iron oxide.
• Blueberry juice and mango juice.
• Dilute gadolinium
• Air is used in rectum.

14. Adverse Reaction of Gadolinium Based
Contrast Agents (GBCA)
• Delayed Reaction
• NSF (Nephrogenic systemic fibrosis) may result in fatal or
debilitating fibrosis.
• Patients with acute, chronic, and severe kidney disease
(glomerular filtration rate [GFR] < 30 mL/min/1.73 m2)
have very poor elimination of GBCAs and could have an
increased risk of developing NSF due to GBCAs.
• Because GBCAs increase the risk of NSF, patients with poor
elimination should not be administered such contrast
agents.
• Blood urea and creatinine should be checked prior to
injection of contrast agents.

15. o Acute complication
 Mild : eg. nausea, vomiting, dizziness,
itiching, shaking
Moderate : eg. Tachycardia, dyspnoea,
bronchospasm
Severe: laryngeal oedema, unresponsivness,
cardiac arrhythmias.

16. Precautions for prevention of adverse
reactions
• Acute adverse reactions
• Identify the patients at increased risk of reaction
because of previous gadolinium reactions,
allergies, asthma.
• Consider giving premedication like oral 30 mg
prednisolone 12 and 2 hour before contrast
medium
• Delayed adverse reactions
• Identify patients with risk of NSF particularly with
renal impairment, infants, neonates and elderly

17. Contd..
• MRI contrast media should not be given to
pregnant patients it may accumulate in
amniotic fluid.

18. Future of MRI contrast
• A newer manganese-based magnetic resonance (MR) imaging
contrast agent manganese-N-picolyl-N,N’,N’- trans-1,2-
cyclohexenediaminetriacetate (Mn-PyC3A) is likely to replace
gadolinium based contrast agents.
• Experimental trials has been performed in baboons shows
that Mn-PyC3A enables contrast-enhanced MR angiography
with comparable contrast enhancement to gadolinium based
agents and may overcome concerns regarding gadolinium-
associated toxicity and retention.
• High-performance liquid chromatography examination of
blood plasma and urine reveals that Mn-PyC3A is cleared
intact without undergoing metabolism or degradation.

19. Ultrasound contrast media
• Contrast-enhanced ultrasound (CEUS) involves the administration of
intravenous contrast agents containing micro bubbles.
• Micro bubbles have a high degree of echogenicity (the ability of an
object to reflect ultrasound waves). There is a great difference in
echogenicity between the gas in the micro bubbles and the soft
tissue surroundings of the body.
• Properties
• Non- toxic, non-allergic and easily eliminated.
• Comfortably injected into vascular system and travels easily via
blood circulation.
• Should be stable for the period of the diagnostic examination.

20. Contd…
• Small in size similar to that of red blood cells (RBC), so
that they can pass easily through vascular bed or
pulmonary capillaries.
• Provide stable acoustic response of sub- harmonics,
ultra- harmonics and harmonics.
• Micro bubbles sizes ~1-4 micro meter.
• Gas dissolves in blood - ventilated through lungs
• Shell is reduced into biocompatible elements
• Half-life of a few minutes

21. Micro bubbles
• Gas core determines the echogenicity.
• Shell material determines how easily the
micro bubble is taken up by the immune
system.

22. Commonly used ultrasound contrast
media
• Ablunex
• Stabilized by encapsulated shell.
• air micro bubbles are coated with human serum albumen
• Used in echocardiography
• used in Liver, Kidneys and heart contrast imaging.
Echovist
• bubbles are in galactose solution but no palmitic acid present
as a thin layer
• Used in tubal patency
• Used in Right heart Myocardium, Liver and gynaecological
applications.

23. Contd..
Levovist
• Most widely used
• Microbubble of air are enclosed by thin layer of
palmitic acid in a galactose solution.
• Stable in blood for 1-4 minutes
EchoGen
• An emulsion of dodecafluoropentane which changes its
phase converting into echogenic gas microbubbles by
hypobaric activation prior to i/v injection.

24. Contd…
SonoVue
• An aqueous suspension of stabilized sulphur
hexafluoride microbubbles is used.
• The suspension is stable and can be used for
upto 4 hours
• Used in study of Liver, Kidneys and
Gynaecological studies

25. Advantages of ultrasound contrast
agents
• Strong safety profile
• No ionizing radiation
• No iodinated dye
• No risk of nephrotoxicity
• Allows real-time evaluation of blood flow.
• Portable - may be used at patient’s bedside
• Potential for screening, prevention, and ongoing monitoring of care

26. Disadvantages of ultrasound contrast
agents
• Microbubbles don’t last very long in
circulation.
• Ultrasound produces more heat as the
frequency increases.
• Microbubbles burst at low ultrasound
frequencies and at high mechanical indices
(MI) . Microbubble destruction could cause
local microvasculature ruptures and
hemolysis.

27. Future
• Molecular imaging
– CA attaching to specific cells (receptors) through ligands or
peptides
– Allows for imaging of specific cells (cancer, inflammations)
• Targeted drug delivery
– Encapsulating a drug inside a micro-bubble
– Release with ultrasound by breaking the bubbles locally
Targeted contrast agents