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Contrast agents
Tereza Kopřivová
Diagnostic imaging methods - practice (aVLDI7X1c)

Adobe Systems
Diagnostic imaging methods - practice (aVLDI7X1c)
Learning objective
̶Student will learn most comon contrast agents used in radiology and their adverse effects
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Adobe Systems
Diagnostic imaging methods - practice (aVLDI7X1c)
Classification of contrast agents
̶By modality
̶US
̶MRI
̶Methods using X-rays
̶By way of application
̶i.v., i.a., p.o., intrathecally, intravesically, into fistulas…
̶By type of contrast
̶Positive
̶Negative

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Diagnostic imaging methods - practice (aVLDI7X1c)
Contrast agent for US
̶Mikrobubbles of sulphur hexafluorid (SF6) stabilized by phospholipids (SonoVue)
̶Contrast created by differences of impedance on interface gas/liquid
̶Administered i.v., is strictly intravascular – shows microcirculation
̶Eliminated through lung capillaries (in cca 15 minutes)
̶Can be administered to patients with renal failure, adverse reactions are extremely rare
̶Contraindications: significant right-left shunts, severe lung hypertension, recent heart attack…
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Adobe Systems
Diagnostic imaging methods - practice (aVLDI7X1c)
C.a. for methods using X-rays
̶I.v. and any other way of administration
̶Iodine c.a. (viz dále)
̶P.o. podání (event. per rectum, sondami do GIT)
̶Positive
Baryum k.l. (BaSO4) – in CT, fluoroscopy. Can not be used in suspected GIT perforation
̶Negative
Water – in CT for distension of upper GIT (water is absorbed aborally)
Mannitol – in CT for distension of lower GIT (it is hyperosmolar)
Gas – CO2 - in CT colonoscopy (administered p.r.), efervescent powder in fluoroscopy of oesophagus
and stomach – for distension
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Adobe Systems
Diagnostic imaging methods - practice (aVLDI7X1c)
Iodine c.a. 1
̶Positive – iodine absorbs X rays (high nucleon number)
̶Administered anywere: i.a., i.v., p.o., intravesically, into tubes, drains, fistulas…
̶Moves to interstitium, does not move through normal hematoencephalic barrier
̶Mostly eliminated by kidneys (normally in cca 2h), elimination depends on glomerular filtration,
critical for adverse reaction to kidney function is the first pass through kidneys, they can
removed by dialysis
̶Now only non-ionic c.a. used
̶Main characteristics of iodine c.a. – concentration, osmolality, viscosity

Adobe Systems
Diagnostic imaging methods - practice (aVLDI7X1c)
Iodine c.a. 2
̶Adverse effects
̶Acute adverse reaction – different types (allergic, alergoid, chemotoxic…)
Different severity: nauzea, vomiting, erythema, urticaria, seizures, arrythmias, anaphylaxis…
̶Post contrast acute kidney injury
= increase of serum creatinin by more than 26,5 umol/l 48-72h after administration of c.a., many
different factors
̶Contraidications are relative – considering risk/benefit
̶Alergic reaction to iodine c.a. in personal history
̶Renal failure
̶Metformin – when renal function decreases, metformin excretion is impeded and can cause lactic
acidosis

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Diagnostic imaging methods - practice (aVLDI7X1c)
Contrast agents for MRI
̶I.v.
̶Gadolinium c.a.
̶P.o.
̶Blueberry/pineapple juice
Negative contrast -  Negative contrast in MRCP to cancel artifacts from stomach contents
̶Mannitol
In MR enterography – mainly for distension of bowels
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Adobe Systems
Diagnostic imaging methods - practice (aVLDI7X1c)
Gadolinium c.a. 1
̶Gd is paramagnetic, we do not see c.a. itself but how it influences magnetic field around it, it
mainly shortens T1 time (= increase of signal on T1 weighted images = positive contrast)
̶Chelated Gd (Gd by itself is heavy toxic metal)
̶Moves into interstitium, does not move through normal hematoencephalic barrier, can be removed by
dialysis
̶Excreted by kidneys, elimination halftime in normal renal functions is cca 90 min
̶There is a tissue specific Gd c.a. that is excreted half by kidneys, half by bile ducts, used for
liver lesions and bile ducts imaging
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Adobe Systems
Diagnostic imaging methods - practice (aVLDI7X1c)
Gadolinium c.a. 2
̶Adverse effects
̶Acute adverse reaction – analogically to iodine c.a., compared to them are less frequent (Gd c.a.
are less hyperosmolar, chelated, there are smaller volumes administered…)
̶Postcontrast acute kidney injury – minimal risk compared to iodine c.a.
̶Nefrogenic systemic fibrosis (NSF)
Rare systemic disease – thickening and induration of skin, pruritus, contractures, multiple organs
affected, proved link to Gd c.a
At risk patients – on dialysis, GF less than 15ml/min (Gd is released from chelates and causes
damage) – carefully consider the indication
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Take home message
̶Referring physician should know adverse effects of commonly used contrast agents and provide
relevant info = history of allergic reactions, current values of creatinin, use of metformin, can
patient have p.o. c.a.?, is there GIT perforation suspected…
Diagnostic imaging methods - practice (aVLDI7X1c)

Lékařská fakulta Masarykovy univerzity
2021
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