MRI CONTRAST RADIOLOGY

1. h
BY
Henock.N (r2)
MRI CONTRAST AGENT
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2.  MRI contrast agents are a group of contrast
media used to improve the visibility of internal
body structures in magnetic resonance
imaging (MRI).
 The most commonly used compounds for contrast
enhancement are gadolinium-based. MRI contrast
agents alter the relaxation times of atoms within
body tissues where they are present after oral
or intravenous administration.
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3.  Most clinically used MRI contrast agents work
through shortening the T1 relaxation time of
protons located nearby.
 T1 shortens with an increase in rate of stimulated
emission from high energy states (spin anti-aligned
with the main field) to low energy states (spin
aligned).
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4.  To, enhance the inherent contrast between tissue,
Mri contrast must alter rate of relaxation of the
proton within tissue.
 Relaxation must be vary for different tissues in
order to produce differential enhancement of signal
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5.  MRI contrast agent must exert a large magnetic
field density( a property imparted by their unpaired
electron) to interact with the magnetic moment of
proton in the tissue and shorten their relaxation
time
 The electron magnetic moment also cause the local
change in magnetic field promting more rapid
proton dephasing and shortens the relaxation time
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6.  Agents with unpaired electron pair spins used asMRI
contrast agent. This may be classifiedinto three group
 Ferromagnetic
 Paramagnetic- example gadolinium…
Used as major contrast agent made soluble by
chelation …shortens T1 relaxation..bright signal on T1
weighted image i.e Hyperintense
 Super-magnetic-ferrite.. Used for reduction of T2
relaxation time.. Decreased signal intensity seems
black
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7. Chelates
 Chelate means “claw”
 Chelates surround an ion and make a cage around it
 A chelate of gadolinium occupies all available space
around the ion except water molecule
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8. Gd chelate
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9.  MRI contrast agents may be administered by injection into the
blood stream or orally, depending on the subject of interest.
 Oral administration is well suited to G.I. tract scans, while
intravascular administration proves more useful for most other
scans. A variety of agents of both types enhance scans
routinely.
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10.  MRI contrast agents can be classified in
many ways, including by their:
 chemical composition
 administration route
 magnetic properties
 effect on the images
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11.  biodistribution and applications:
 Extracellular fluid agents (also known as intravenous
contrast agents)
 Blood pool agents (also known as intravascular contrast
agents)
 Organ specific agents (i.e.Gastrointestinal contrast agents
and hepatobiliary contrast agents)
 Active targeting/cell labeling agents (i.e. tumor-specific
agents)
 pH-sensitive agents
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13. Gadolinium containing MRI contrast agents (often termed simply
"gado" or "gad")
Used for enhancement of vessels in MR angiography or
for brain tumor enhancement
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14.  For large vessels such as the aorta and its branches, the
gadolinium(III) dose can be as low as 0.1 mmol per kg
body mass.
 Higher concentrations are often used for finer
vasculature.
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15.  Types of gadolinium contrast agents
 Extracellular fluid agents
Ionic (i.e. Magnevist and Dotarem)
Neutral (i.e. Omniscan, Prohance, Gadavist, OptiMARK)
 Blood pool agents
Albumin-binding gadolinium complexes
(i.e. Ablavar and Gadocoletic acid)
 Polymeric gadolinium
complexes (i.e. Gadomelitol
and Gadomer 17)
 Organ-specific agents
(i.e. Primovist and Multihance which are used as hepatobiliary
agents)
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16.  Gadolinium-containing contrast agents approved for human
use Presently, nine different types of gadolinium-containing
contrast agents are available in different territories
gadoterate (Dotarem)
gadodiamide (Omniscan)
gadobenate (MultiHance)
gadopentetate (Magnevist, Magnegita, Gado-MRT ratiopharm)
gadoteridol (ProHance)
gadoversetamide (OptiMARK)
gadoxetate (Primovist)
gadobutrol (Gadovist)
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17.  Iron oxide: Superparamagnetic
Two types of iron oxide contrast agents exist:
superparamagnetic iron oxide (SPIO)
and ultra small superparamagnetic iron oxide (USPIO).
when injected during imaging reduce the T2/ T2* signals of
absorbing tissues.
SPIO and USPIO contrast agents have been used successfully in
some instances for liver tumor enhancement
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18. Liver Contrast Agents
Iron Magnetite,
super
paramagnetic
agent
Makes liver
black on T2WI,
mets show up as
bright white.
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19.  Oral administration of contrast
agents
 A wide variety of oral contrast agents can enhance images
of the gastrointestinal tract.
 They include gadolinium and manganese chelates, or iron
salts for T1 signal enhancement.
 SPIO, barium sulfate, air and clay have been used to lower
T2 signal.
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20. Other contrast agents
For MR colonography& MRCP
 Water/saline contrast
 Negative oral contrast
 Geritol
 Blueberry juice, pineapple juice
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21. Negative contrast agents
 Used to make stomach contents black in MRCP
 Geritol, blueberry juice, pineapple juice
 Iron in Geritol
 Mn in these juices
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22. MRCP
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23. Side effect of MRI contrast
 The most common, so called normal, side effects of
MRI contrast agent are mild and temporary in nature.
They include
 warmth
 pain or burning at the injection site,
 low blood pressure,
 minor skin rash,
 mild headaches,
 changes in blood clotting,
 light headedness and nausea.
 Typically these side effects do not require any treatments.
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24.  The most common allergic reaction symptoms to MRI contrast
agents include
 swelling of the face,
 rashes,
 itching,
 sweating,
 watery or itchy eyes, and
 shortness of breath.
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25. NSF
 Nephrogenic Systemic Fibrosis
 Fatal
 2-10 wks
 Progressive thickening and hyperpigmentation of skin
 Most likely caused by free Gd
 Prevent by screening patients for renal disease
 Calculate estimated creatinine clearance
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26. NSF
 Risk factors
 CKD
 AKI
 Dialysis
 Indications for creatinine
 Age>60 yr
 Hx of kidney disease
 Single kidney or kidney surgery
 HTN or DM
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27. CONTRAINDICATION
 Patient have history of CKD/renal failure i.e.
no normal renal clearance
 Allergic history
 pregnancy
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28. Pregnant and lactating
 Assumed to cross the placenta
 exreted via urinary tract to amniotic fluid
 No subsequent evidence of teratogenesis
 Small percent excreted in breast milk
 No reported direct toxicity
 Discard breast milk 12-24 after GBCAS if possible
 In children ,it should be used when necessary

29. References
Safe use of contrast media :what the radiologist needs
to know; radiographics 2015
 ACR manual on contrast media, 2017Needs to Know1

30. Thank you!!!Radiologist Needs to Know1