2. Contrast media are agents which permit visualization of details of internal
structure or organs that would not otherwise be demonstrable.
Classification
3. Positive contrast.-the use of a contrast material that is
radiopaque such as insoluble salt barium sulfate and a
variety of organic iodine compounds.
- Barium is used for gastrointestinal studies.
- Water-soluble, iodinated contrast media are used for
many procedures, including all types of angiography,
intravenous and retrograde urography,
hysterosalphingography, sialography , myelography ,
cholangiography etc
Negative contrast material that is not radiopaque such as air
or carbon dioxide
4. CLASSIFICATION
CONTRAST MEDIA
X-RAY & CT ULTRASOUND MRI
BaSO4 Oily CM Water soluble IODINATED CM
Hepatic excretion Renal excretion
Iopanoic acid
High osmolar low osmolar
Ionic monomers Ionic dimers Non-ionic monomers Non ionic
dimers
Diatrizoate Ioxaglic acid Iopromide
Iotrol
Iothalamate Iohexol
Iotrolon
5. BARIUM SULPHATE
• Has high atomic number 56, highly radiopaque.
• Non absorbable, non toxic.
• Insoluble in water/lipid.
• Inert to tissues.
• Can be used for double contrast studies.
• Uses: barium swallow, barium meal, barium meal follow through, enteroclysis,
barium enema
6. WATER SOLUBLE IODINATED CONTRAST MEDIA
IODINE
• Atomic number 53 & atomic weight 127
• Iodine is preferred because
*High contrast density due to high atomic number
*Allows firm binding to highly variable benzene ring
*Low toxicity
7. USEFUL FACTORS TO REMEMBER
• OSMOLALITY:- Is dependent on no. Of particles of solute in solution.
• RADIO OPACITY:- Is dependent on the iodine concentration of the solution & is
therefore dependent on the no. Of iodine atoms in each molecule of the contrast
medium.
• HIGH RADIO OPACITY & LOW OSMOLALITY ARE OF DESIRABLE
REQUIREMENTS.
• IODINE PARTICLE Ratio-the ratio of the no. Of iodine atoms per molecule to the
no. Of osmotically active particles per molecule of solute in solution is therefore a
fundamental criteria.
8. CLASSIFICATION OF IODINATED
CONTRAST MEDIA
• There are four chemical varieties of
iodinated RCM in clinical use.
• All four are tri - iodo benzene ring
derivatives with three atoms of iodine at
2,4,6 positions (in monomers) and six
atoms of iodine per molecule of the ring
anion (in dimers).
9. CLASSIFICATION OF IODINATED CONTRAST
MEDIA
1. IONIC MONOMERS (CONVENTIONAL/HIGH OSMOLAR CONTRAST
MEDIA [HOCM]).
2. IONIC DIMERS.
3. NON-IONIC MONOMERS .
4. NON-IONIC DIMERS.
Class 2, 3 , 4 are collectively known as low osmolar contrast
Medias.
10. IONIC MONOMERS (HIGH OSMOLAR
CONTRAST MEDIA [HOCM])
• All ionic monomers are salts consisting of a sodium or meglumine (n-
methyl glucamine) as the non-radio opaque cation and a tri-
iodinated benzoate as the radio opaque anion.
11. EG:-
IOTHALAMATE
• Anions consisting of a benzoic acid molecule with
three atoms of iodine firmly attached at C2, C4 &
C6.
• The c3 & c4 are connected to amines e-nh2 (r3 & r5)
which reduces toxicity & increase solubility.
• These anions include
• Diatrizoate (urograffin, angiograffin,
hypaque)
• Iothalamate (conray)
• Ioxithalamate,
• Metrizoate
• Iodamic acid
12. • Each molecule completely dissociates in water solution into two ions – one non-
radio opaque cation and one tri-iodinated radio opaque anion, giving an
iodine: particle ratio of 3 : 2
• Iodine content at 0.3 osmol/kg H2O - 70mg I/ml
• Osmolality at 280mgi2/ml - 1500 osmol/kg H2O
• LD-50 = 7(g of I/kg wt of mouse)
DISADVANTAGE : high osmolality (8 times that of plasma- 300 mosm/kg
water), responsible for the adverse effects, because of the non radiopaque
cations( na & meg)
13. DIFFERENCES B/W MEGLUMINE & SODIUM SALTS
MEGLUMINE SALTS SODIUM SALTS
• SOLUBILITY BETTER SAME, LESS IN SOME ACIDS
• VISCOSITY HIGH LOW
• TOLERANCE BETTER LESS, NAUSEA & VOMITING
• BLOOD BRAIN NO EFFECT CROSSES BBB
BARRIER
• VASCULAR EFFECTS LESS MARKED
• DIURETIC EFFECT STRONG LESS
• OPACIFICATION POOR BETTER
• BRONCHOSPASM CAUSES NO
SO CI IN ASTHMA
14. LOW OSMOLAR CONTRAST MEDIA
IONIC DIMERS- IOXAGLATE(HEXABRIX), IOCARMATE
• Only compound, mixture of sodium and meglumine salts
• Two benzene rings (each with 3 iodine atoms) are linked by a bridge to form a large
compound, carries only one carboxyl group, so known as monoacid dimers
15. IONIC DIMERS- IOXAGLATE(HEXABRIX)
• In solution each molecule dissociates into one radio-
opaque hexa-iodinated anion and one non-radio
opaque cation (sodium and/or meglumine).
• Iodine particle ratio is 6:2 or 3:1
• Molecular weight is 1269
• Iodine content at -0.3 osmol/kg H2O- 150mg I/ml
• Osmolality at 280mgi2/ml - 560 osmol/kg H2O
• LD-50 = 12(g of I/kg wt of mouse)
Eg:-Ioxaglate
16. NON-IONIC MONOMERS
• Include iohexol (omnipaque), iopamidol,
iopromide (ultravist), ioversol, ioxilan.
• None of these molecules dissociate in
solution.
• They are tri-iodinated non-ionizing
compounds and therefore in solution they
provide three atoms of iodine to one
osmotically active particle (the entire
molecule), producing an iodine: particle
ratio of 3:1.
17. NON IONIC MONOMERS
• Iodine particle ratio is 3:1
• Molecular weight 600-800
• Iodine content at 0.3 osmol/kg H2O - 150mg I/ml
• Osmolality at 280mgi2/ml - 600 osmol/kg h2o
• Ld-50 = 22(g of i/kg wt of mouse)
Eg:- iohexol
(omnipaque)
18. NONIONIC DIMERS
*Iotrolan(isovist)
*Iodixanol (visipaque)
• Each molecule contains 2 non ionosing tri-
iodinated benzene rings linked together
• They do not ionize or dissociate in
solution.
• Each molecule therefore provides in
solution six atoms of iodine for one
molecule, i.E. An iodine:particle ratio of
6:1.
19. NONIONIC DIMERS
• Iodine particle ratio is 6:1
• Molecular weight 1550-1626
• Iodine content at 0.3 osmol/kg H2O- 300mg
I/ml
• Osmolality at 280mgi2/ml - 300 osmol/kg h2o
• Ld-50 = >>26(g of i/kg wt of mouse)
Eg:- iotrolan
20. PHARMACOKINETICS
• After intravascular injection, the contrast media are distributed
rapidly because of high capillary permeability into the
extravascular, extracellular space (whole body opacification)
(except in the central nervous system) & is simultaneously
excreted.
• Then equilibrium is reached b/w intra & extravascular space in
about 10 min. Continued excretion & re entry of contrast media
from ECF to ICF leads to decrease in plasma level.
• Plasma half life is 30 – 60 min.
• They do not enter the interior of blood cells or tissue cells and
they are rapidly excreted, with over 90 % being eliminated by
passive glomerular filtration by the kidneys within 12hrs.
21. ADDITIVES USED IN CONTRAST MEDIA
1) stabilizer – Ca or Na EDTA
2) buffers – stabilizes ph during storage – Na acid phosphates.
3) preservatives.
4) flavouring substances & emulsifiers for git media.
22. IDEAL CONTRAST MEDIA SHOULD HAVE:-
1) high water solubility.
2) heat & chemical stability (shelf life) - ideally 3-5 yrs.
3) biological inertness (non antigenic).
4) low viscosity.
5) low or iso osmolar to plasma.
6) selective excretion, like excretion by kidney is
favourable.
7) safety: ld50 (lethal dose) should be high.
8) reasonable cost.
23. IMP POINTS TO REMEMBER
• Contrast media used for myelography are non-ionic CM.
• Cm used for cerebral angiography, are cm containing only meglumine
cation.
• Cm containing only meglumine cation- conray 280, triovideo 280,
trazograff60% and angiograffin.
• Cm which cause max nausea & vomiting are – ioxaglate (hexabrix).
• Meglumine salts cause bronchospasm, so ci in bronchial asthma.
• Among newer cm, iohexol is most hyperosmolar
• Viscosity increases as conc increases & tends to be higher for big sized
molecules (dimers). High viscosity interferes with mixing of contrast media
with plasma & body fluids. Omnipaque240 has least viscosity.
• Meticulous heparinization is required during angiography as incidence of
25. IDEAL ULTRASOUND CONTRAST AGENT
• Be injectable by a peripheral vein
• Be non toxic
• Small enough to pass through pulmonary, cardiac & capillary
systems
• Stable enough to undergo the shear forces, hydrostatic pressure
changes & diameter changes
• Half life should be sufficient to allow complete examination
• Should require little preparation
26. • Contrast agents might act by their presence in the vascular system,
from where they r ultimately metabolized (blood pool agents) or by
their selective uptake in tissue after a vascular phase.
• Also called echo enhancing agents.
• These agents increase the echogenicity of blood, which heightens
the tissue contrast & allows better delineation of body cavities.
27. MECHANISM OF ACTION
• Pri mechanism of signal enhancement is microbubble backscatter,
which relates to differences in microbubble versus blood
compressibility.
• Increased echogenicity may be seen as an increased signal in color or
spectral doppler signal strength or gray scale image intensity.
• The half life or persistence of microbubble depends on –
*size(<7um passes through pul cirltn)
*surface tension & gas diffusion across the bubble shell.
*Transducer frequency & power
• Mechanical index (MI) –peak pressure of usg beam calculated from
frequency & power of usg beam. Higher the MI, more likely the bubble
will break
28. GAS MICROBUBBLE CONTRAST
MEDIA
• Gas bubbles have a tremendous difference in acoustic impedance as compared to surrounding fluid
due to the large differences in density, elasticity and compressibility.
• Microscopic gas filled bubbles whose surface reflect sound waves.
• Their extremely high reflectivity(backscatter) arises from the fact that microbubbles easily change
their size, contracting in compression part of the ultrasonic cycle & expanding in the rarefaction part.
• Thus they resonate in the ultrasound beam when there is a mismatch b/w their diameter and
ultrasonic wavelength, which occurs for microbubbles in 2 to 7um at usg freq of 2-10 mhz
• Free gas bubbles
The bubbles may pre-exist in the liquid, or they may be created via cavitation during injection.
Solution used r saline, indocyanine green or renograffin.
Iv injection of physiological saline has been used as a contrast medium in echocardiography since the
late sixties, but the utility of free gas bubbles is highly limited due to:-
• Low stability
• Large bubble size to pass the pulmonary vasculature
29. • For gas bubbles to be used as transpulmonic contrast media, the gas bubbles should
be stable and smaller than 5 µm.
• Bubbles larger than 10 mm may transiently obstruct the capillaries and act as gas
emboli.
• Several stabilizing coatings have been developed to produce encapsulated gas
microbubble contrast media.
• The coatings include albumin(albunex), gelatin, galactose microspheres & palmitic acid
(levovist), polyglutaminic acid, lipophilic monolayer surfactants, and lipid bilayers
(liposomes).
30. GENERATIONS OF ECHO
ENHANCERS
• FIRST GEN- UNSTABILISED BUBBLES IN INDOCYANINE GREEN , CANT SURVIVE
PULMONARY PASSAGE, THEREFORE USED ONLY FOR CARDIAC & LARGE VEIN
STUDY.
• SECOND GEN- LONGER LASTING BUBBLES COATED WITH SHELLS OF PROTEIN,
LIPIDS OR SYNTHETIC POLYMERS.
• THIRD GEN- ENCAPSULATED EMULSIONS OR BUBBLES, OFFER HIGH
REFLECTIVITY.
31. TYPES OF AGENTS
NON
ENCAPSULATED
MICROBUBBLES
• Formed by hand
agitation
• Unstable & breech
quickly
• Large size, small
fraction pass through
pul cirltn
• Adequate for right
heart visualization
ENCAPSULATED
MICROBUBBLES
Encapsulated air
Microbubbles
*Albunex
*Echovist (galactose)
*Levovist (galactose
& palmitic acid)
*Cavisomes –gas
filled cyanoacrylate
microspheres for
Liver, spleen & LN
Encapsulated
Perflurocarbon MB
*Optison: albumin
coated microspheres
that contain
Octafluropropane gas
Uses:Cardiac app
32. LOW SOLUBILITY GAS BUBBLES
• Since the effective duration of action of encapsulated air bubble
is very short, newer agents designed both to increase
backscatter enhancement further & to last longer in the blood
stream, r currently under intense development.
• Instead of air, many of these take advantage of low solublity
gases such as perfluorocarbons, having lower diffusion rate &
thereby increasing the longevity of the agent in the blood.
33. PARTICLE SUSPENSIONS OR EMULSIONS
• Several types of particles have been reported as ultrasound contrast
media
• Collagen microspheres (solid)
• Iodipamide ethyl ester (solid)
• Perfluorochemicals (inert, dense liquids).
• Perfluorocarbons lead to a large tissue impedance mismatch due to
their high density and compressibility.
• After iv injection, it can be detected in the intravascular space for
several hours. Due to the small particle size, the contrast medium
passes all capillary beds and will therefore enhance perfused tissue.
34. • Perfluorochemicals are eliminated either by phagocytosis of the
reticuloendothelial system or by evaporation in the lungs.
• Due to the selective phagocytosis, liver and spleen show late phase
enhancement.
• Particle suspensions are generally less effective than gas bubbles, and
much larger doses are needed for enhancement. Perfluorocarbons may
furthermore be less safe than the gas bubbles; a relatively high
percentage of mild allergic reactions have been shown in humans.
35. DOPPLER RESCUE:
• APPLICATION OF UCA RESULTS IN ENHANCEMENT OF COLOUR,
POWER & SPECTRAL DOPPLER WAVEFORM & THIS IMPROVES
DOPPLER IMAGING & IS TERMED AS “DOPPLER RESCUE “
36. APPLICATIONS
• Evaluating normal, increased or decreased vascularity.
• Detecting vascular stenosis & occlusions
• Improving neoplasm detection
• Analysing & characterizing tumour neovascularity
• Differentiating normal variants such as renal column of bertin from
neoplasm.
• Echocardiography – cardiac cavities, valves, coronary artery &
myocardial viability
40. ARTIFACTS
• Colour blooming – grey scale pixels are displayed as
colour pixel in areas that lack flow, occurs when high
conc of UCA is delivered by bolus inj.
• Bubble noise – audible sound accompanied on visible
spectral doppler tracing blips
• An increase (17 to 45 %) in maximum doppler shift
frequency
42. CONTRAST MEDIA USED IN
MRI
• GADOLINIUM CHELATES
• BLOOD POOL AGENTS
• LIVER CONTRAST AGENTS
• ENDOLUMINAL CONTRAST AGENTS
• TARGETED CONTRAST AGENTS
43. GADOLINIUM
• Is the standard exogenous contrast agent used in
clinical MR imaging.
• It is T1 relaxing agent and is paramagnetic.
• It belongs to lanthanide metal group with atomic
no. 64.
• It has a high spin contrast number which
produces desirable relaxivity contrast agents
• Three agents have been approved by FDA, they
are-
*Gd-HP-DO3A:gadoteridol/prohance (non ionic)
44. GADOLINIUM
• These function as extracellular contrast agents.
• They are rapidly excreted by glomerular filteration
with half lives b/w 1 – 2hrs.
• As these compounds are excreted by renal excretion,
caution shd be taken in renal impaired patients.
• 3 –5% of adverse reactions, occur in the form of
nausea
• Dose- 0.1 to 0.3mmol/kg body weight
• Disadvantages
*enhancement is non specific neither organ specific or
pathology specific.
*Short window for imaging of blood vessels as it is
diluted in blood stream and excreted rapidly.
45. BLOOD POOL AGENTS
• These agents reversibly bind to plasma albumin achieving
a substantial improvement in magnitude and duration of
blood pool enhancement.
• Eg- spio-super paramagnetic iron oxide crystals
-Uspio
-Magnetite
• These cause predominant T2 shortening.
Uses – to image small vessels(eg acc renal, cor ).
–vessels with slow flow (eg pul emb, dvt),
-Arteriovenous malformation
- Perfusion studies
• Disadv: overlap b/w arterial and venous structures and
separation is difficult
46. LIVER CONTRAST AGENTS
• Gadobenate dimeglumine (multihance,bracco)
• Small iron particles- endorem & resovist
• Manganese –containing contrast agents- teslascan –
absorbed by liver, pancreas and cortex of kidneys, T1
relaxation
47. ENDOLUMINAL CONTRAST AGENTS
• Negative contrast agents, based on iron particles(abdoscan,
nycomed-amersham) for use in MR enteroclysis & MR
imaging of rectal cancer.
• Combination of methyl cellulose solution for bowel
distention & iv gadopentate dimeglumine for bowel wall
enhancement.
• Natural contrast- blueberry juice acts as a negative
contrast in upper abdominal mr imaging, eg mrcp
48. TARGETED CONTRAST AGENTS
• BLOOD POOL AGENTS
• LIVER SPECIFIC AGENTS
• NECROSIS SPECIFIC AGENTS (BIS-GADOLINIUM-MESOPORPHYRIN)
• LYMPHOGRAPHIC CONTRAST AGENTS
• AGENTS TARGETED AT INFLAMMATION DETECTION.
54. PHARMACOKINETICS
• The pharmacokinetics of all extracellular MRI contrast agents with the
exception of gd-bopta are similar to iodinated water-soluble contrast
media.
• After iv injection they are rapidly diffused into the interstitial extravascular
space.
• Gd chelates are eliminated unchanged from the intravascular compartment
by passive glomerular filtration.
• By 24 hours >95 per cent of the injected dose is excreted in urine with
normal renal function.
• A very small amount (<0.1 per cent) is eliminated via faeces. The biological
half-life is approximately 1.5h.
• Extracellular mri contrast agents do not cross the intact specialized
vascular blood–brain barrier .
55. CLINICAL USE OF EXTRACELLULAR MRI CONTRAST AGENTS
• These agents accumulate in tissues with abnormal vascularity
(malignant, infective and inflammatory lesions) and in regions where the
blood–brain barrier is disrupted.
• Dosage
• 0.1 millimol/kg or 0.2 ml/kg
• Max dose – 20 ml
• Lethal dose– 10 mmol/kg
56. SAFETY OF EXTRACELLULAR MRI CONTRAST
AGENTS
• Extracellular MRI contrast agents are well tolerated with a low
incidence of adverse effects.
• In blood, the osmotic load of all gd-based contrast media is
very low, compared to iodinated contrast media, because only
a small amount of the contrast agent is required to produce a
diagnostic mri examination.
57. • Side effects
• Minimal with standard dose.
• Slight transitory increase in bilirubin & blood iron.
• Mild transitory head ache (9.8%).
• Nausea (4 %).
• Vomiting ( 2%).
• Hypotension, rash ( 1%).
• Life-threatening reactions are very rare.
58. CONTRAINDICATIONS
• No known contraindication.
• Although , caution in
• Hematological disorders- hemolytic anemia.
• Pregnancy, lactation.
• Respiratory disorders- asthma.
• Previous allergy.
59. HEPATOCYTE SPECIFIC CM
• Gadolinium based compounds:
• These agents have a capacity for weak and transient protein binding and is
eliminated through both the renal and hepatobiliary pathways.
• The hepatic uptake represents 2–4 per cent of the injected dose.
• It behaves as a conventional extracellular contrast agent in the first
minutes following iv administration and as a liver-specific agent in a later
delayed phase (40–120 min after administration) when it is taken up
specifically by normal functioning hepatocytes.
• Gadobenate dimeglumine (gd- bopta)- multihance
• Gadoxetic acid ( gd-eob-dtpa)- eovist
60. • Mangafodipir trisodium – teslascan
• Is strongly paramagnetic due to unpaired electrons.
• Mn usually toxic , but made tolerable by complexing to a molecule
which facilitates binding to plasma protein.
• Primarily excreted by liver -70% (as similar chemical structure to vit
b6).
• Also taken by tissues with active aerobic metabolism- pancreas, renal
cortex, gi mucosa, myocardium, adrenals.
• So far approved by fda only for diagnosing liver lesions.
• Acts by shortening t1 relaxation time.
61. RETICULO ENDOTHELIAL CELL SPECIFIC
• FERUMOXIDES –
• ARE SPIO ( POLYSACCHARIDE COATED SUPER PARAMAGNETIC
IRON OXIDE) PARTICLES.
• CONTAIN A CENTRAL CORE OF IRON OXIDE PARTICLE
SURROUNDED BY A THIN INCOMPLETE DEXTRAN COATING,
THAT CAUSES INDIVIDUAL PARTICLES TO FORM
POLYCRYSTALLINE AGGREGATES.
• THEY HAVE A SIZE OF APPROX 50- 200 NM.
62. • RES IN LIVER, SPLEEN, BONE MARROW TAKE UP THE AGENT & HAS A
LOW SIGNAL IN TI OR T2*.
• LESIONS NOT CONTAINING RECELLS DO NOT TAKE UP THE AGENT &
REMAIN UNAFFECTED, SO HAVE A HIGH SIGNAL.
• IMMEDIATELY FOLLOWING IV ADMINISTRATION, THE CONTRAST AGENT
ALSO CAUSES T1 RELAXATION AND EARLY T1-WEIGHTED IMAGING MAY
BE PERFORMED.
• USES
• DIFFERENTIATE B/W HEPATIC ORIGIN TUMOR THAT CONTAIN RES &
TUMORS THAT DO NOT.
63. • DOSE
• IV SLOW INFUSION OVER 30 MIN.
• 0.56 MG OF IRON ( 0.05 ML FERIDEX) /KG.
• SHOULD BE DILUTED IN 100 ML OF 50% DEXTRAN.
• FURTHER DELAY OF 30 MIN PRIOR TO IMAGING ALLOW FOR MAXIMUM
UPTAKE BY RE CELLS.
• CONTRAST ENHANCEMENT OBSERVED FROM 30 MIN TO 4 HRS
FOLLOWING INFUSION.
64. • SIDE EFFECTS
• HAS A GOOSAFETY PROFILE.
• BUT IN <3 % PTS- LOW BACK ACHE DURING INFUSION, USUALLY SELF
LIMITING, DISAPPEAR AFTER STOPPING/ SLOWING, ALSO LEG, GROIN
PAIN, HEAD, NECK PAIN.
• RARELY -GI- NAUSEA, VOMITING, DIARRHEA, ANAPHYLAXIS,
HYPOTENSION.
• C/I - PTS WITH ALLERGY, HYPERSENSITIVE TO IRON, PARENTERAL
DEXTRAND.
65. BLOOD POOL AGENTS
• These agents reversibly bind to plasma albumin achieving a substantial
improvement in magnitude and duration of blood pool enhancement.
• Circulate in intravascular space for a longer time, cause significant
reduction in t1 relaxation time of circulating blood.
• So best for mra.
• Eg- spio-super paramagnetic iron oxide crystals
-Uspio
-Magnetite
• These cause predominant T2 shortening.
• Uses - to image small vessels(eg acc renal, cor ).
- vessels with slow flow (eg pul emb, dvt),
- Arteriovenous malformation
- Perfusion studies
• Disadv: overlap b/w arterial and venous structures and separation is
difficult
• Gadofosveset (ms-325)
66. OTHER TISSUE SPECIFIC MR CONTRAST MEDIA
• ATHEROSCLEROTIC PLAQUES (ASP)
• USPIO S ACCUMULATE IN MONOCYTE -MACROPHAGES OF ASP.
• GADOFLUORINES ACCUMULATE IN FOAM CELLS & CELLULAR DEBRIS
DEEP TO INTIMA AT SITES OF ASP.
• NECROSIS- GADOPHORINS –USED TO ASSESS MYOCARDIAL NECROSIS.
• TUMOR SPECIFIC MR CM -
• EG: MONOCLONAL ANTIBODY LABELED PARAMAGNETIC & SUPER
PARAMAGNETIC NANOPARTICLES.
• PERFLUORINATED GASES, GD BASED AEROSOLS , HYPERPOLARIZED HE &
O2 GAS – IMAGING LUNGS .
67. ORAL CONTRAST MEDIA
• NON SPECIFIC.
• USED IN ABDOMEN & PELVIS STUDIES TO PROVIDE RELIABLE
DIFFERENTIATION OF BOWEL FROM ADJACENT STRUCTURES & TO
PROVIDE BETTER DELINEATION OF BOWEL WALL.
• POSITIVE CM.
• NEGATIVE CM.
68. POSITIVE CONTRAST MEDIA
• INCREASE THE OVERALL SIGNAL INTENSITY WITHIN THE IMAGE, BY
SHORTENING T1 TIMES OF TISSUE WATER.
• GENERALLY SOLUTION OF PARAMAGNETIC METAL IONS.
• MOSTLY PRESENT IN NATURAL PRODUCTS ( MN IN TEA).
• SPECIFICALLY FORMULATED AGENTS-
• MN CHLORIDE ( LUMENHANCE)- T1 RELAXING
• GD DTPA (MAGNEVIST ENTERAL)- ,,
BUT THE INCREASED SIGNAL MAY INDUCE GREATER ARTIFACTS DUE TO
PERISTALSIS. USE OF ANTISPASMODIC AGENTS & ULTRA FAST IMAGING
TECHNIQUES CAN SOLVE THIS.
69. NEGATIVE CONTRAST MEDIA
• ELIMINATE TISSUE SIGNAL FROM THE AREA OF INTEREST BY:-
• REDUCING THE T2 RELAXATION TIME – BY USING
SUSPENSION OF FUROMOXIDE PARTICLES.
• OR BY USING AN AGENT THAT CONTAINS NO PROTONS, &
THEREFORE PRODUCE NO VISIBLE MR SIGNAL.
• BARIUM SULPHATE, USED FOR INTRA LUMINAL STUDIES.
70. CONTRAST MEDIA RELATED TO SPECIFIC CLINICAL
AREAS
• RENAL TRACT
THERE IS NO DOUBT THAT HIGH DOSES OF CONTRAST MEDIA IMPAIR
RENAL FUNCTION, USUALLY PEAKING AT 3–5D, CAUSING A DECREASE IN
URINE OUTPUT AND AN INCREASE IN SERUM CREATININE AND UREA
LEVELS, DECREASED CREATININE CLEARANCE AND REDUCED
GLOMERULAR FILTRATION RATE (GFR). IN SOME PATIENTS THIS MAY
PROCEED TO RENAL FAILURE WITH ANURIA, URAEMIA AND DEATH.
RENAL DIALYSIS (EITHER INTRAVASCULAR OR PERITONEAL) IS VERY
EFFECTIVE AND MAY BE LIFE-SAVING AS AN ALTERNATIVE METHOD OF
EXCRETING RCM AND URAEMIC METABOLIC PRODUCTS.
71. • THESE SEVERE ADVERSE REACTIONS ARE VERY UNLIKELY TO OCCUR IF THE PATIENT IS
WELL HYDRATED AND HAS NORMAL RENAL FUNCTION BEFORE THE RCM INJECTION.
PARTICULARLY IMPORTANT ADVERSE FACTORS ARE PRE-EXISTING RENAL FAILURE
AND OLIGURIA, DIABETIC NEPHROPATHY, NEPHROTOXIC DRUGS, PATIENTS WHO ARE
NOT WELL HYDRATED AND PATIENTS WHO ARE LIABLE TO BE INJECTED WITH VERY
HIGH DOSES OF RCM FOR MULTIPLE SEQUENTIAL EXAMINATIONS REPEATED WITHIN A
FEW DAYS. ALTERNATIVE IMAGING PROCEDURES MUST ALWAYS BE CONSIDERED.
72. • THE USUAL RECOMMENDED DOSE FOR IV UROGRAPHY IN THE NORMALLY WELL-
HYDRATED ADULT WITH NORMAL RENAL FUNCTION IS 15–25 G IODINE; THIS DOSE
MAY BE INCREASED PROVIDED THE PATIENTS ARE WELL HYDRATED (BY IV NORMAL
SALINE IF NECESSARY BEFORE, DURING AND AFTER RCM INJECTION). A MAXIMUM
OF ABOUT 70 G OF IODINE (1 G IODINE KG-1 BODY WEIGHT IN ADULTS) IS
GENERALLY ADVISABLE EVEN IN PATIENTS WITH GOOD RENAL FUNCTION, BUT
CONSIDERABLY LARGER QUANTITIES (UP TO 200 G OR EVEN 300 G OF IODINE, I.E.
UP TO 600 G OF RCM) MAY BE REQUIRED, PARTICULARLY IN DIFFICULT
ANGIOGRAPHIC AND INTERVENTIONAL PROCEDURES.
73. • AFTER EARLY UNCERTAINTY, IT IS NOW ESTABLISHED THAT HOCMS ARE MORE
NEPHROTOXIC, AND LOCMS ARE PREFERRED FOR ALL PATIENTS CONSIDERED TO
BE AT INCREASED RISK, ESPECIALLY WITH DIABETIC NEPHROPATHY. THERE IS
INCREASING EVIDENCE THAT RCM (PARTICULARLY HOCM AND LARGE DOSES)
MAY INDUCE DAMAGE TO THE TUBULES IN THE RENAL MEDULLA AND REDUCE
INTRA-MEDULLARY BLOOD FLOW IN PATIENTS WITH ACUTE CALCULUS RENAL
COLIC.
74. NERVOUS SYSTEM
• LOCMS ARE MUCH MORE COMFORTABLE FOR CEREBRAL ARTERIOGRAPHY IN THE
CONSCIOUS PATIENT AND ARE ALWAYS PREFERRED. CEREBRAL RCM PHOTOGRAPHIC
ARTERIOGRAPHY IS BEING STRONGLY CHALLENGED AND PARTIALLY DISPLACED BY CT
AND MR ANGIOGRAPHY (MRA).
CEREBRAL ANGIOGRAPHY
• ADVERSE REACTIONS TO RCM INCLUDE DILATATION OF THE EXTERNAL CAROTID
ARTERIAL TERRITORY CAUSING FACIAL PAIN AND HEAT. DAMAGE TO THE BLOOD–BRAIN
BARRIER MAY CAUSE DANGEROUS CEREBRAL OEDEMA, BRADYCARDIA AND
HYPOTENSION.
75. CARDIOVASCULAR SYSTEM
• PERIPHERAL ARTERIOGRAPHY
THE USUAL IODINE CONCENTRATION REQUIRED FOR
CONVENTIONAL FILM-SCREEN ANGIOGRAPHY IS ABOUT 300 MG
I ML-1 CONTRAST MEDIUM. CONVENTIONAL HOCM (1500
MOSMOL KG-1 WATER) HAS BEEN COMPLETELY DISPLACED FOR
PERIPHERAL ARTERIOGRAPHY BY LOCM (600–700 MOSMOL KG-1
WATER), BECAUSE THE LATTER CAUSES MUCH LESS WARMTH,
DISCOMFORT, PAIN AND MOVEMENT. LOCM PERMITS ALMOST
PAINLESS ANGIOGRAPHY IN ALL TERRITORIES, USUALLY
ELIMINATING DISCOMFORT, MOVEMENT AND THE NEED FOR
76. PERIPHERAL VENOGRAPHY
• VENOGRAPHY OF THE LEG FOR POSSIBLE DEEP VEIN THROMBOSIS
(DVT) IS THE MOST FREQUENT VENOGRAPHIC STUDY. THE
PROCEDURE IS PERFORMED BY INJECTING RCM INTO A SMALL VEIN OF
THE FOOT, WITH THE LEG DEPENDENT AND TOURNIQUETS
RESTRICTING PERIPHERAL VENOUS RETURN. IF THE DEEP VEINS ARE
ALREADY COMPROMISED AND PARTLY THROMBOSED, PERIPHERAL
VENOGRAPHY OF THE LEG IS A POTENTIALLY DANGEROUS
PROCEDURE, AS BOTH DEEP AND SUPERFICIAL VENOUS RETURN FROM
THE LEG ARE COMPROMISED, AND SOME CASES OF VENOUS
GANGRENE DUE TO VENOUS ENDOTHELIAL DAMAGE AND
THROMBOSIS HAVE BEEN INDUCED BY ATTEMPTED VENOGRAPHY.
77. • LOCM IS STRONGLY ADVISED BECAUSE OF ITS LOWER OSMOLALITY
AND ITS LESS IRRITANT EFFECT ON THE VENOUS ENDOTHELIUM.
ENDOTHELIAL CONTACT TIME SHOULD BE REDUCED TO THE MINIMUM
BY WASHING OUT WITH SALINE, MASSAGING AND EXERCISING THE LEG
IMMEDIATELY AFTER SATISFACTORY RADIOGRAPHS HAVE BEEN
OBTAINED. TERMINATION OF THE INJECTION OF CONTRAST MEDIUM
MUST BE SERIOUSLY CONSIDERED IF THE INJECTION CAUSES PAIN OR IF
THE DEEP VEINS ARE SEEN TO BE EXTENSIVELY THROMBOSED, FOR ALL
RCM MAY INDUCE THROMBOPHLEBITIS.
78. CARDIAC AND CORONARY ANGIOGRAPHY
• INTRACARDIAC INJECTIONS LOCM INJECTIONS ARE MUCH
PREFERRED AS THEY CAUSE LESS DISTURBANCE OF CARDIAC
FUNCTION, DEPRESSION OF MYOCARDIAL CONTRACTILITY,
PERIPHERAL VASODILATATION, HYPERVOLAEMIA, SYSTEMIC
HYPOTENSION AND ECG CHANGES. THEY ARE ALSO MUCH
BETTER TOLERATED SUBJECTIVELY THAN HOCM.
• PULMONARY ANGIOGRAPHY LOCM INJECTIONS SHOULD BE USED
FOR PULMONARY ANGIOGRAPHY AS THEY CAUSE LESS
ELEVATION OF THE PULMONARY ARTERY PRESSURE, COUGHING,
MOVEMENT AND DISCOMFORT. SEPARATE UNILATERAL
PULMONARY ARTERY INJECTIONS SHOULD REPLACE MAIN STEM
PULMONARY ARTERY INJECTION.
79. • AORTOGRAPHY INJECTIONS OF LOCM AT THE 300–400 MG ML-1 IODINE
CONCENTRATION ARE GREATLY PREFERRED AS THEY CAUSE MUCH LESS
DISCOMFORT AND VASODILATATION.
• CORONARY ANGIOGRAPHY HOCMS (E.G. UROGRAFIN 76 PER CENT) WITH
PHYSIOLOGICAL LEVELS OF SODIUM AND WHICH DO NOT BIND AVIDLY TO SERUM
CALCIUM (RELATED TO BUFFER AGENTS) HAD A GOOD REPUTATION FOR SELECTIVE
CORONARY ANGIOGRAPHY, BUT LOCMS ARE EVEN SAFER FOR THEY CAUSE LESS
MARKED HAEMODYNAMIC, MYOCARDIAL AND PHYSIOLOGICAL CHANGES AND
DEPRESSION
