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Thrall’s Textbook! > Chapter 5 Contrast Media > Flashcards

Chapter 5 Contrast Media Flashcards

1
Q

What are the two types of radiographic contrast media?

A

Positive and negative contrast media

Positive contrast media increase radiographic opacity, while negative contrast media reduce it.

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2
Q

What is an example of positive contrast media?

A

Barium (Z=56) and iodine (Z=53)

Positive contrast media increase absorption of x-ray photons.

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3
Q

What is the K-absorption edge (K-edge) effect?

A

An abrupt increase in photoelectric absorption when x-ray beam energy is beyond the binding energy of inner k-shell electrons.

This effect is utilized to enhance contrast in imaging.

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4
Q

What is an example of negative contrast media?

A

Room air, CO2, NO2

Negative contrast media reduce the absorption of x-ray photons.

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5
Q

What is the primary formulation of barium used in veterinary medicine?

A

Micro-pulverised liquid barium preparations

Barium sulfate is commonly used in GI contrast studies.

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6
Q

What is the purpose of emulsifiers, stabilizers, and dispersants in barium preparations?

A

To maintain barium in suspension

This ensures even distribution in the barium-water mixture.

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7
Q

What concentration expressions are used for barium sulfate suspension?

A

Weight/volume (w/v) and weight/weight (w/w)

These expressions indicate the percentage of barium sulfate in relation to the final product.

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8
Q

What are potential adverse effects of barium leakage?

A

Mediastinitis, peritonitis/septic peritonitis, fibrinous adhesions, granulomatous nodules

Leakage can occur from GI perforation.

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9
Q

What is recommended if GI perforation is of concern?

A

An iodinated, nonionic, water-soluble contrast medium

This is safer in cases of potential perforation.

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10
Q

What can aspiration of barium lead to?

A

Pneumonia and acute respiratory distress

Large volumes of aspirated barium can cause severe respiratory issues.

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11
Q

What are the two main classifications of iodine-based contrast media?

A

Water-soluble and water-insoluble

Water-soluble media are primarily used in clinical practice.

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12
Q

What is the most common route of administration for iodinated contrast media?

A

IV administration

Other routes include oral, rectal, injection into the urinary system, or intrathecal injection.

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13
Q

How does protein binding affect the excretion of iodinated contrast media?

A

Higher protein binding leads to longer plasma retention and less renal excretion

This can result in more biliary excretion.

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14
Q

What is the difference between ionic and nonionic contrast media?

A

Ionic media dissociate into ions; nonionic media do not

Nonionic media have a higher solubility due to polar hydroxyl groups.

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15
Q

What is the osmolality of contrast media expressed as?

A

Milliosmole per kilogram of water (mOsm/kg water)

Osmolality is influenced by the number of independent particles in solution.

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16
Q

What is the effect of higher osmolality in contrast media?

A

Increased adverse reactions

High-osmolality media draw fluid into the bowel, diluting the contrast.

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17
Q

What does the contrast ratio represent?

A

The number of iodine atoms per number of particles in solution (I/P ratio)

A higher I/P ratio implies greater opacity.

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18
Q

What is the effect of viscosity on contrast media?

A

High viscosity can complicate injection

Viscosity is inversely affected by factors that improve solubility and hydrophilicity.

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19
Q

What is the only available water-insoluble contrast medium?

A

Ethiodized oil medium (Lipiodol)

It is used in embolization solutions during interventional radiology.

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20
Q

What are acute and delayed adverse reactions to iodinated contrast media?

A

Acute: within 1 hour; Delayed: within hours to 1 week

Acute reactions are often hypersensitivity, while delayed reactions are typically T-cell mediated skin reactions.

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21
Q

What are common mild reactions in humans to iodinated contrast media?

A

Nausea, vomiting, urticaria

Severe reactions can include bronchospasm and pulmonary edema.

22
Q

What are two risk factors for hypersensitivity reactions to iodinated contrast media?

A

Previous reaction to contrast medium and having asthma or severe allergies

These factors increase the likelihood of adverse reactions.

23
Q

What is contrast-induced acute kidney injury (CI-AKI)?

A

A sudden decrease in kidney function within 48 hours of IV injection of iodinated contrast medium

CI-AKI can result from various pathophysiological mechanisms.

24
Q

What are some risk factors for CI-AKI in humans?

A

Pre-existing renal impairment, dehydration, diabetes, older age

High-osmolar ionic contrast media are associated with greater nephrotoxicity.

25
Q

What is the primary method to decrease the risk of CI-AKI?

A

IV fluids

Nonionic contrast media should be used in patients with renal impairment.

26
Q

What does the urine protein:creatinine ratio (UPC) indicate in relation to IV contrast medium administration?

A

It can indicate changes within 1 week following IV contrast medium administration, but the clinical relevance is unknown.

27
Q

What is the primary method to decrease the risk of contrast-induced acute kidney injury (CI-AKI) in patients with renal impairment?

A

IV fluids.

28
Q

What type of contrast media should be used in patients with impaired renal function?

A

Nonionic contrast media.

29
Q

True or False: Contrast studies can be performed on dehydrated patients regardless of their pre-existing renal status.

A

False.

30
Q

What is the primary treatment for suspected CI-AKI in humans?

A

IV fluid therapy.

31
Q

What adverse effect was reported in a dog after IV contrast administration?

A

Haemorrhagic cystitis.

32
Q

What should be performed prior to iodinated contrast medium administration if needed?

A

Urinalysis.

33
Q

What rare condition can occur in susceptible individuals weeks to months after iodinated contrast media administration?

A

Iodine-induced thyrotoxicosis.

34
Q

In hyperthyroid cats, what dose of iohexol was used prior to I-131 treatment?

A

Low-dose iohexol (65 mI/kg).

35
Q

What is the atomic number of gadolinium (Gd3+)?

A

64.

36
Q

What is relaxivity in the context of gadolinium-based contrast media?

A

The ability of gadolinium contrast media to shorten the relaxation time.

37
Q

What are the two types of ligands used to minimize the toxicity of gadolinium?

A
  • Linear ligands
  • Macrocyclic ligands
38
Q

What is nephrogenic systemic fibrosis (NSF)?

A

A rare, very late, adverse reaction resulting in an irreversible scleroderma-like condition.

39
Q

What is the primary route of administration for ultrasound contrast media?

A

Intravenous.

40
Q

What is the typical size of ultrasound microbubbles?

A

1–7 um.

41
Q

What adverse reactions are commonly associated with ultrasound contrast media in humans?

A
  • Warm sensation
  • Itching
  • Nausea
  • Vomiting
42
Q

What is the incidence of any adverse reaction reported in a study of ultrasound contrast media used in animals?

A

About 1%.

43
Q

Fill in the blank: Gadolinium in its free form is _______.

A

toxic.

44
Q

What kind of imaging techniques can use gadolinium-based contrast media?

A

Magnetic resonance imaging (MRI).

45
Q

What are the primary applications for contrast-enhanced ultrasound (CEUS) in animals?

A
  • Liver
  • Spleen
  • Pancreas
  • Lymph nodes
  • Intestinal and urogenital tracts
46
Q

What is the importance of mechanical index (MI) in ultrasound contrast media?

A

It affects microbubble behavior and signal production during imaging.

47
Q

What is a common negative contrast medium used in imaging?

A

Room air.

48
Q

What is a key difference in the x-ray attenuation between iodinated contrast media and gadolinium contrast media?

A

Iodinated contrast media has about three times the x-ray attenuation of gadolinium contrast media.

49
Q

What are the two types of reactions reported with gadolinium-based contrast media in animals?

A
  • Hemodynamic effects
  • Mild to severe hypersensitivity reactions
50
Q

True or False: Gadolinium deposition can occur in organs other than the skin.

A

True.

Thrall’s Textbook! (3 decks)

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