Ultrasound Imaging: Sound Wave Parameters

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Questions and Answers

What is the primary factor that influences the diagnostic quality of ultrasound images?

The wavelength of the sound waves

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

0.31 mm

What does the propagation speed of a sound wave refer to?

The rate at which a sound wave moves through a medium

Do sound waves with different frequencies travel at different speeds in the same medium?

No, sound waves travel at the same speed regardless of frequency Signup and view all the answers

What is a characteristic of sound wave propagation speed?

It is consistent within a specific medium Signup and view all the answers

What is the relationship between the wavelength of a sound wave and its penetration?

Shorter wavelength sound waves have less penetration Signup and view all the answers

What is the term for the range of frequencies emitted by a pulsed transducer?

Frequency bandwidth Signup and view all the answers

What type of ultrasound diagnostic images are generated by pulsed wave transducers?

Both real-time and static images Signup and view all the answers

In which medical field is continuous wave ultrasound predominantly employed?

Echocardiography Signup and view all the answers

What is the purpose of Pulse Repetition Frequency (PRF) in ultrasound?

To define the number of sound pulses per second Signup and view all the answers

What is the relationship between imaging depth and PRF?

As imaging depth increases, PRF decreases Signup and view all the answers

What determines the determination of PRF?

The sound source Signup and view all the answers

Who can adjust the PRF?

The sonographer Signup and view all the answers

What is the limitation of continuous wave sound?

It is incapable of creating anatomic images Signup and view all the answers

What is the purpose of adjusting Pulse Repetition Frequency (PRF)?

To achieve optimal imaging depth Signup and view all the answers

What is the relationship between Pulse Repetition Period (PRP) and Pulse Repetition Frequency (PRF)?

PRP is inversely proportional to PRF Signup and view all the answers

What happens to the Pulse Repetition Period (PRP) when Pulse Repetition Frequency (PRF) increases?

PRP decreases Signup and view all the answers

What is the typical range of Pulse Repetition Period (PRP) in clinical imaging?

100 microseconds to 1 millisecond Signup and view all the answers

What is Pulse Repetition Period (PRP)?

The time between the beginning of one pulse and the beginning of the next one Signup and view all the answers

What is the unit of Pulse Repetition Period (PRP)?

Milliseconds or any unit of time Signup and view all the answers

Who influences the determination of Pulse Repetition Period (PRP)?

The operator and the sound source Signup and view all the answers

What is the formula to calculate Pulse Repetition Period (PRP)?

PRP = 1 / PRF Signup and view all the answers

What is the unit of measurement for pulse duration?

Microseconds Signup and view all the answers

How many cycles are typically found in a sonographic pulse?

2 or 3 cycles Signup and view all the answers

What is the effect of increasing the frequency on pulse duration?

Pulse duration decreases Signup and view all the answers

What is the formula to calculate pulse duration?

PD = n × T Signup and view all the answers

What is the duty factor in continuous wave ultrasound?

100% Signup and view all the answers

What is the duty factor in pulsed wave ultrasound?

Pulse duration/pulse repetition period Signup and view all the answers

What is the purpose of the listening time in ultrasound?

To receive echoes Signup and view all the answers

What determines the percentage of time that the ultrasound system transmits sound?

Duty factor Signup and view all the answers

What is necessary for refraction to occur?

The sound wave must hit the boundary at an angle that is not 90 degrees Signup and view all the answers

Why does refraction occur?

Due to the difference in propagation speeds of sound in different media Signup and view all the answers

What determines the direction of the refracted beam?

The speed of sound in the second medium relative to the first medium Signup and view all the answers

What is the condition for refraction to occur?

The speed of sound must differ between the two media Signup and view all the answers

What is refraction?

The change in direction of a sound wave Signup and view all the answers

What law defines the refraction process?

Snell's Law Signup and view all the answers

Study Notes

Ultrasound Image Quality

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

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

Pulsed Wave Transducers

Pulsed wave transducers are responsible for generating all types of ultrasound diagnostic images
They emit ultrasound waves that span a variety of frequencies, referred to as the 'frequency bandwidth'

Continuous Wave (CW) Ultrasound

Continuous wave ultrasound is predominantly employed in echocardiography for acquiring CW Doppler information
It is incapable of creating anatomic images

Pulse Repetition Frequency (PRF)

PRF refers to the number of sound pulses generated by the transducer per second
The determination of PRF is attributed to the sound source and can be adjusted by the sonographer
There is an inverse relationship between imaging depth and PRF, meaning as imaging depth increases, PRF decreases

Pulse Repetition Period (PRP)

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 (PRP = 1 / PRF)

Pulse Duration (PD)

PD is the time that it takes for one pulse to occur
PD is equal to the period (the time for one cycle) times the number of cycles in the pulse (n) and is expressed in microseconds (PD(μs) = n ×T(μs))
PD decreases if the number of cycles in a pulse is decreased or if the frequency is increased (reducing the period)

Duty Factor (DF)

The duty factor is the percentage of time that the ultrasound system transmits sound
DF is the fraction of the PRP that the sound is on
DF = Pulse duration/pulse repetition period

Factors Contributing to Attenuation: Refraction Process

Refraction is the change in direction of a sound wave as it passes across a boundary between two different media at an oblique angle
Refraction only occurs if the sound wave hits the boundary at an angle that is not 90 degrees (Oblique Incidence)
The speed of sound must differ between the two media; if the speeds are the same, no refraction will occur
Refraction occurs due to the difference in propagation speeds of sound in different media, as defined by Snell's Law

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