Ultrasound Contrast Agents Overview

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Questions and Answers

Why is meticulous heparinization required during angiography when contrast media is mixed with blood?

To enhance the tissue contrast

To increase the echogenicity of blood

To reduce the viscosity of the contrast media

To prevent thromboembolic phenomenon (correct)

What is a characteristic of ultrasound contrast agents?

They increase the echogenicity of tissues

They are coated with shells of proteins, lipids, or synthetic polymers

They are ideal for angiography studies

They consist of microscopic gas-filled bubbles (correct)

What contributes to the extremely high reflectivity (backscatter) of ultrasound contrast agents?

The viscosity of the contrast agent

The speed of sound in the tissues

Microbubbles changing their size during the ultrasonic cycle (correct)

The frequency of ultrasound waves

Which generation of ultrasound contrast agents consists of longer-lasting bubbles coated with shells?

Third generation Signup and view all the answers

What is the main reason first-generation ultrasound contrast agents are limited to cardiac and large vein studies?

They cannot survive pulmonary passage Signup and view all the answers

What property allows microbubbles to resonate in the ultrasound beam?

Their diameter and ultrasonic wavelength mismatch Signup and view all the answers

What is the primary mechanism of signal enhancement for ultrasound contrast agents?

Microbubble backscatter Signup and view all the answers

Which characteristic is essential for an ideal ultrasound contrast agent?

Stable enough to undergo shear forces Signup and view all the answers

Which type of microbubbles is formed by hand agitation?

Encapsulated Air Microbubbles Signup and view all the answers

What is the main reason for the instability of non-encapsulated microbubbles?

Small size that allows quick breach Signup and view all the answers

Which Ultrasound Contrast Agent is ideal for liver, spleen, and lymph nodes?

Cavisomes Signup and view all the answers

What does the half-life or persistence of a microbubble depend on?

Size Signup and view all the answers

What is the purpose of a contrast medium in radiography?

Increase the radiographic contrast in an area Signup and view all the answers

What is the significance of using a substance with a high atomic number as a contrast medium?

It increases the radiographic contrast in the organ under examination Signup and view all the answers

Which type of study was first performed using Barium Sulphate as a contrast medium?

GI contrast study Signup and view all the answers

What is a common side effect associated with contrast media?

Metal taste Signup and view all the answers

Which of the following is NOT a common method for administering contrast media?

Intramuscular injection Signup and view all the answers

What property of iodine made it the basis of all modern contrast agents?

Its radio opacity to X-rays Signup and view all the answers

Study Notes

Contrast Media Overview

Contrast media is a chemical substance that increases or decreases the density of the organ under examination.
Contrast depends on the absorption coefficients of different tissues.

History of Contrast Media

1896: Walter Bradford discovered contrast media.
1897: First reported GI contrast study performed using Bismuth, which was toxic.
1910: Barium Sulphate was used as a safer alternative.
1920s: Sodium Iodide was used to treat syphilis, and iodine was found to be radio-opaque to x-rays.
1927: First reported IVU with iodised organic salts (Uroselectan).

Ultrasound Contrast Agents (Echo Enhancers)

Increase the echogenicity of blood, which heightens tissue contrast and allows better delineation of body cavities.
Consist of microscopic gas-filled bubbles.
High reflectivity arises from the fact that microbubbles easily change their size, contracting in compression and expanding in the rarefaction part of the ultrasonic cycle.

Generations of Echo Enhancers

First generation: Unstabilized bubbles in indocyanine green, used only for cardiac and large vein studies.
Second generation: Longer-lasting bubbles coated with shells of protein, lipids, or synthetic polymers.
Third generation: Encapsulated emulsions or bubbles, offering high reflectivity.

Types of Ultrasound Agents

Non-encapsulated microbubbles
Encapsulated microbubbles:
- Encapsulated air microbubbles (e.g., Albunex, Echovist)
- Encapsulated perfluorcarbon microbubbles (e.g., Optison)

Ideal Ultrasound Contrast Agent

Should be injectable by a peripheral vein
Should be non-toxic
Should be small enough to pass through pulmonary, cardiac, and capillary systems
Should be stable enough to undergo shear forces, hydrostatic pressure changes, and diameter changes
Should have a sufficient half-life to allow complete examination
Should require little preparation

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Description

Learn about the characteristics and benefits of ultrasound contrast agents, also known as echo enhancing agents. Understand how these agents increase the echogenicity of blood to improve tissue contrast and delineation of body cavities. Explore their composition of microscopic gas-filled bubbles and high reflectivity from microbubbles.