Ultrasound Basics Chapter 4

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Questions and Answers

What is the relationship between frequency and wavelength?

Higher frequency results in a longer wavelength

Wavelength and frequency are directly proportional

Frequency does not affect the wavelength

Higher frequency results in a shorter wavelength (correct)

At what temperature is the speed of sound in air 331 m/s?

10°C

0°C (correct)

20°C

-10°C

Which medium demonstrates the highest speed of sound at 20°C?

Liquid helium

Steel (correct)

Air

Water

What happens to the speed of sound as the temperature of the medium decreases?

The speed decreases (A) Signup and view all the answers

How does sound intensity relate to the amplitude of sound vibrations?

Greater amplitude results in greater sound intensity (C) Signup and view all the answers

What defines pure sound?

Sound with a single frequency (A) Signup and view all the answers

Which factor does NOT influence the speed of sound?

Humidity of the surrounding air (C) Signup and view all the answers

What is the speed of sound in air at 30°C?

349 m/s (B) Signup and view all the answers

What is the primary reason for the low quality of ultrasound images from low-frequency waves?

Lower distance traveled by low frequencies (C) Signup and view all the answers

What does acoustic impedance measure?

The resistance a medium offers to the passage of sound waves (D) Signup and view all the answers

What does the formula Z = 𝝆.𝒗 represent?

Acoustic impedance as a function of density and propagation speed (D) Signup and view all the answers

What happens to ultrasonic waves when they encounter organs in the body?

They can get reflected or refracted (D) Signup and view all the answers

Why is gel applied before performing an echography?

To enhance contact between the skin and probe (A) Signup and view all the answers

How does the probe function during an echography?

Acting alternately as a transmitter and receiver (A) Signup and view all the answers

What is one of the primary applications of ultrasound in the medical field?

Focused ultrasound thermotherapy (D) Signup and view all the answers

What is the role of reflection and refraction in ultrasound imaging?

They contribute to the formation of the ultrasound image (C) Signup and view all the answers

Which of the following types of waves requires a medium for propagation?

Mechanical waves (A) Signup and view all the answers

Which medium offers the greatest resistance to ultrasound propagation?

Seawater (B) Signup and view all the answers

What development in ultrasound applications occurred after 1945?

Expansion into biology and medicine (C) Signup and view all the answers

Which statement best describes the role of acoustics in ultrasound?

It studies the properties, production, propagation, and effects of sound waves. (C) Signup and view all the answers

What principle is essential for understanding ultrasound image formation?

Transmission and reception of ultrasound waves (C) Signup and view all the answers

What distinguishes ultrasound from electromagnetic waves?

Ultrasound requires a physical medium to propagate. (C) Signup and view all the answers

Which application does NOT commonly utilize ultrasound technology?

Sound wave analysis in a vacuum (B) Signup and view all the answers

What role does ultrasound play in agriculture?

It promotes root oxygenation by creating aerosolized water. (D) Signup and view all the answers

What are the three essential elements required for sound to exist?

A source, a medium, and an ear (B) Signup and view all the answers

How do longitudinal waves propagate?

Through compression and rarefaction of molecules (D) Signup and view all the answers

What is the range of frequencies that are audible to humans?

20 Hz to 20,000 Hz (C) Signup and view all the answers

What happens to particles in a medium when sound is not propagating?

They remain evenly spaced and stationary (C) Signup and view all the answers

What is the relationship between frequency and period?

Frequency is the inverse of the period (C) Signup and view all the answers

What defines infrasound and ultrasound?

Infrasound is below 20 Hz, ultrasound is above 20 kHz (B) Signup and view all the answers

Which statement accurately describes pure sound?

It can only be generated by electronic devices. (D) Signup and view all the answers

Which statement accurately reflects the characteristics of sound waves?

Sound waves are longitudinal and travel through compression and rarefaction (C) Signup and view all the answers

Which of the following statements about sound generation is incorrect?

Sound can exist without a source of vibration (A) Signup and view all the answers

What is the role of the ultrasonic transducer?

To convert electrical energy into mechanical energy and vice versa. (D) Signup and view all the answers

What does the term ultrasound refer to?

Imaging technique using reflected high-frequency sound waves. (D) Signup and view all the answers

How is the distance to an object calculated in ultrasound imaging?

By timing the echo return after sound emission. (A) Signup and view all the answers

Which frequency range is typically used for studying deep areas such as the abdomen?

1.5 - 4.5 MHz (B) Signup and view all the answers

What frequency range would be used to visualize structures near the skin, such as veins or arteries?

5 - 7 MHz (B) Signup and view all the answers

Which of the following features characterize complex sounds?

They are formed by combining multiple pure sounds. (A) Signup and view all the answers

Why is piezoelectricity important in ultrasound technology?

It allows for the conversion of electrical energy to mechanical energy and vice versa. (A) Signup and view all the answers

What determines the distance from the ultrasound probe to the organ?

The time elapsed between the emitted signal and the received echo (D) Signup and view all the answers

How is the path traveled by the sound wave related to the distance to the object?

It is double the distance to the object (B) Signup and view all the answers

What type of structures cause an anechogenic image?

Water and liquid substances (A) Signup and view all the answers

What visual appearance is associated with echogenic images?

They appear in shades of grey (C) Signup and view all the answers

What characteristic determines the hyperechogenic images?

Causes more ultrasound reflection than normal (B) Signup and view all the answers

What specific information can be derived from the amplitude of the echo?

It helps to determine the depth, nature, and thickness of tissues (B) Signup and view all the answers

Which of the following organs typically appear echogenic on ultrasound images?

Liver and kidneys (D) Signup and view all the answers

The calculated distance to an object using ultrasound is derived from which formula?

$d = \frac{t \times v}{2}$ (D) Signup and view all the answers

Study Notes

Chapter 4: Ultrasound Basics

Ultrasound science blends modern electronics and acoustics, widely used since 1945, particularly in industrial and medical fields.
Ultrasound is crucial in industrial and medical contexts due to the increased number of ultrasonic devices.
This chapter explores ultrasound applications, principles, physical characteristics of acoustic waves, biological uses, and propagation in biological environments.

Ultrasound Applications

Industries use it in metal, plastics, and composites.
Medical uses include ultrasound and focused ultrasound thermotherapy.
In agriculture, it's used to vibrate water, creating an aerosol that supplies root systems with oxygen.
Remote sensing (sonar) and telemetry (distance measurement) are other applications.
Automotive industry uses it for obstacle avoidance.
Non-destructive control is another area of use.

Physical Acoustics and Definition of Sound

Acoustics is the study of sound waves, their production, propagation, and effects.
A wave is energy that disturbs a medium, categorizing into mechanical (needs a medium) and electromagnetic (no medium).
Sound is a mechanical wave resulting from a vibrating body in a medium (solid, liquid, or gas.)
Sound propagation requires three elements:
- A source producing vibration.
- A medium to transmit the vibration.
- A receiver to detect the vibration.

Mode of Propagation

Sound waves are longitudinal waves, propagating via compression and decompression of medium molecules.
Longitudinal waves have the same direction of vibration and displacement.

Sound Propagation Mode

No sound occurs when a medium is undisturbed; particles are evenly spaced with no vibration.
Oscillation and mechanical vibrations are absent, thus no sound is generated or transmitted.

Classification of Sound Waves

Audible sounds for humans are within the range of 20 Hz to 20,000 Hz (20kHz).
Frequencies below 20 Hz are infrasound; frequencies above 20 kHz are ultrasound.

Physical Parameters of Sound: Frequency

Frequency represents the number of periodic oscillations per second, measured in Hertz (Hz).
It's inversely related to the period (T), with the formula: f = 1/T

Physical Parameters of Sound: Wavelength

Wavelength (λ) is the distance travelled by an acoustic wave during a period.
It relates to the speed (C or V) and frequency (f) of the wave: λ = C/f = V/f, where C or V is the speed in m/s.

Physical Parameters of Sound: Velocity (Speed) of Sound

Sound speed depends on the medium (solid, liquid, or gas),
Temperature and pressure also influence the sound's speed.
Examples include air (340 m/s at 20°C), water (1480 m/s at 20°C), and steel (6000 m/s).

Sound Intensity

Sound intensity quantifies the distribution of sound energy in space.
Loudness is related to the amplitude (sound pressure) of sound waves, with a large amplitude indicating a high intensity.

Pure Sound

A pure sound consists of a single frequency.
Pure sounds are not naturally occurring; they are electronically generated.

Complex Sound

A complex sound is the sum of several pure sounds. This is the nature of most sounds heard in everyday life.

Production of Ultrasonic Waves

An ultrasonic transducer converts electrical energy into mechanical energy (ultrasound) and vice versa, using the piezoelectric effect.

Principle of Ultrasound (Echo)

Ultrasound utilizes the reflection of sound waves (echoes) to form images.
The time delay between the emitted signal and the reflected echo determines the target's distance, allowing for the creation of images that show different structures based on internal differences.

Ultrasound Frequency, Image, and Organ Depth

Ultrasound uses frequency between 1 MHz to 20 MHz (or up to 50MHz in certain applications).
The higher frequency, the smaller structures can be visualized, but they're less efficient for deep imaging.

Why is there an echo?

Echoes arise due to changes in the propagation medium (different acoustic impedance values). Acoustic impedance is a measure of how much a medium resists sound propagation.

Acoustic Impedance

Acoustic impedance (Z) is a property of a medium that characterizes its reflection and transmission of sound waves.
Z = ρ * v where ρ is the density of the medium and v is the speed of sound in the medium.

Ultrasound Interaction With Matter

When ultrasound encounters an object, several phenomena occur, most notably reflection and refraction.
These interactions are key in forming ultrasound images by providing information about both the medium through which the waves travel, and the nature/type of any encountered objects.
Information about the intensity (amplitude) and the time taken for the waves to return (delay).

Echography Image Formation

Applying gel to a patient's skin facilitates contact, minimizing interference.
The probe transmits and receives ultrasound waves, reflected by structures in the body to produce images.
Two essential parameters for ultrasound image quality are the distance between the probe and the tissue structure, and the intensity of the reflected echo.

Types of Echography Images

Anechogenic images correspond to media that transmit ultrasound without significant reflection (e.g., water, fluids). These appear dark.
Echogenic images arise from media that reflect ultrasound with moderate regularity, appearing as shades of grey.
Hyperechogenic images result from highly reflective media appearing as bright white.

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Description

Explore the fundamentals of ultrasound technology in this chapter. Learn about its applications in various industries, including medical uses and remote sensing. The chapter also delves into the principles of acoustics and the essential characteristics of sound waves.