Ultrasound Imaging: Wavelength and Sound Wave Parameters

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Questions and Answers

What is affected by the wavelength of sound waves in ultrasound images?

Propagation speed

Diagnostic quality (correct)

Frequency of sound waves

Medium of sound wave travel

What is the wavelength of the sound wave in the given figure?

0.31 mm (correct)

0.15 mm

0.62 mm

1.54 mm

What is the propagation speed of sound waves in the given example?

1.54 mm/μs (correct)

1.54 mm/s

20 Hz/s

5 MHz/s

What is true about the propagation speed of sound waves within a specific medium?

It is consistent regardless of frequency Signup and view all the answers

How does the propagation speed of sound waves vary across different mediums?

It varies Signup and view all the answers

What is the frequency of the sound wave in the given example?

5 MHz Signup and view all the answers

What is the purpose of adjusting PRF?

To achieve optimal imaging depth Signup and view all the answers

What do sound waves carry that facilitates the displacement of particles within the medium?

Mechanical energy Signup and view all the answers

What is the relationship between PRP and PRF?

PRP decreases when PRF increases Signup and view all the answers

What is the unit of time for PRP?

Milliseconds Signup and view all the answers

What is the standard unit of power?

Watt Signup and view all the answers

What influences the determination of PRP?

Sound source Signup and view all the answers

How many milliwatts are in a single Watt?

1000 Signup and view all the answers

What is the typical range of PRP values in clinical imaging?

100 microseconds to 1 millisecond Signup and view all the answers

What is intensity in relation to sound waves?

The rate at which energy passes through a unit area Signup and view all the answers

What is the unit of beam area in ultrasound?

Centimeters squared (cm²) Signup and view all the answers

What is the formula to calculate PRP?

PRP = 1 / PRF Signup and view all the answers

What is the effect of increasing PRF on PRP?

PRP decreases Signup and view all the answers

What happens to intensity when the area is decreased?

It increases Signup and view all the answers

Who can adjust PRP?

The operator Signup and view all the answers

What is the term for the weakening of an ultrasound pulse as it travels through a medium?

Attenuation Signup and view all the answers

What is the unit of intensity in ultrasound?

Milliwatts per centimeter squared (mW/cm²) Signup and view all the answers

What is the unit of acoustic impedance?

kg/(m²·s) Signup and view all the answers

What happens when there are substantial differences in acoustic impedance across tissues?

Increased reflection Signup and view all the answers

What is the density of air in kg/m³?

1.3 Signup and view all the answers

What is the speed of ultrasound in water in m/s?

1500 Signup and view all the answers

What is the formula for calculating acoustic impedance?

Z = ρ x C Signup and view all the answers

What happens when there are similar impedance values across tissues?

Greater transmission Signup and view all the answers

What occurs when the ultrasound beam strikes the interface between two media at an angle other than 90°?

Oblique Incidence Signup and view all the answers

What is the conversion of sound energy into heat within a medium?

Absorption Signup and view all the answers

What affects the degree of reflection and refraction?

Acoustic impedance difference Signup and view all the answers

What type of reflection occurs at large and smooth interfaces?

Specular Reflection Signup and view all the answers

What is the result of slower molecular relaxation in a medium?

Increased absorption Signup and view all the answers

What is influenced by the incident angle?

Degree of reflection and refraction Signup and view all the answers

What type of incidence occurs when the ultrasound path is perpendicular to the boundary?

Normal Incidence Signup and view all the answers

What is the redirection of part of the ultrasound wave back towards the source?

Reflection Signup and view all the answers

Study Notes

Ultrasound Image Quality

Shorter-wavelength sound waves have superior spatial resolution but less penetration.
Wavelength is a crucial parameter that influences the diagnostic quality of ultrasound images.

Sound Wave Parameters

Propagation speed (c) refers to the rate at which a sound wave moves through a medium.
Within a specific medium, sound waves travel at a consistent speed, regardless of their frequency.
The speed of sound wave propagation varies across different mediums.

Propagation Speed

Sound waves carry mechanical energy that facilitates the displacement of particles within the medium.
The higher the power, the greater the wave's capacity to perform this work of displacing particles.

Power

The standard unit of power is the Watt (W).
Power in diagnostic ultrasound is commonly expressed in milliwatts (mW).

Intensity

Intensity (I) is the rate at which energy passes through a unit area.
Intensity units include milliwatts per centimeter squared (mW/cm2) and watts per centimeter squared (W/cm2).
An increase in area decreases intensity because power is less concentrated.
A decrease in area (focusing) increases intensity because power is more concentrated.

Attenuation

Attenuation is the weakening of an ultrasound pulse as it travels through a medium.
The sonographer can change PRF, and the adjustment is particularly relevant to achieve optimal imaging depth.

Pulse Repetition Period (PRP)

Pulse-repetition period (PRP) refers to the time from the beginning of one pulse to the beginning of the next one.
PRP decreases while PRF increases because, when more pulses occur in a second, the time between them decreases.
PRP is the reciprocal of PRF, expressed in milliseconds or any unit of time.
The determination of PRP is influenced by the sound source, and it can be adjusted by the operator.

Acoustic Impedance

Formula: Z = ρ x C, where ρ is measured in kg/m³ and C in m/s.
Units for Z are expressed in rayls (1 rayl = 1 kg/(m²·s)).
The transmission and reflection of ultrasound at tissue interfaces are influenced by acoustic impedance disparities.
Similar impedance values across tissues result in greater transmission; substantial differences cause increased reflection.

Incident Sound in Ultrasound

Types of incidence: Normal (perpendicular) and oblique.
Normal incidence occurs when the ultrasound path is perpendicular to the boundary.
Oblique incidence occurs when the ultrasound beam strikes the interface between two media at an angle other than 90°.

Factors Contributing to Attenuation

Absorption: conversion of sound energy into heat within a medium.
Factors affecting absorption: relaxation time, frequency.
Reflection: redirection of part of the ultrasound wave back towards the source.
Factors influencing reflection: acoustic impedance difference between the two media, boundary size and smoothness.
Types of ultrasound reflection: specular and non-specular.

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Description

This quiz covers the relationship between wavelength and resolution in ultrasound imaging, as well as sound wave parameters like propagation speed and frequency. Understand how these factors affect diagnostic image quality.