Chpts 1-7 Flashcards by Ibonne Ramirez

All of the following are acoustic parameters EXCEPT : -Density -Period -Frequency -Propagation Speed

Density

How well did you know this?

Not at all

Perfectly

Which units are used to report the pressure in the sound beam? - cm - cm/s - pascal - watt

pascal

How well did you know this?

Not at all

Perfectly

How much bigger is a kilometer bigger than a meter?

1000 times

How well did you know this?

Not at all

Perfectly

How many hertz are there in 2 MHz?

2 millions

How well did you know this?

Not at all

Perfectly

Which of the following is an appropriate unit of length (distance)? - second - meter/second - cm - pascal

How well did you know this?

Not at all

Perfectly

All of the following are acoustic variables EXCEPT : - Pressure - Power - Density - Distance

Power

How well did you know this?

Not at all

Perfectly

The unit that is used to describe density is :

Kg/cm3

How well did you know this?

Not at all

Perfectly

All of the following are true of sound waves EXCEPT : - They are pressure waves - They are transverse - They move energy - They are acoustic

They are transverse

How well did you know this?

Not at all

Perfectly

Which types of waves will exhibit both constructive and destructive interference?

Waves of different frequency

How well did you know this?

Not at all

Perfectly

Which of the following waves are exhibiting constructive interference?

B and C

How well did you know this?

Not at all

Perfectly

The typical values of frequency in diagnostic ultrasound is:

2 - 15 MHz

How well did you know this?

Not at all

Perfectly

Which of the following two parameters are NOT related?

Frequency and Period
Power and Amplitude
Intensity and Power
Period and Power

Period and Power

How well did you know this?

Not at all

Perfectly

Which of the following parameters are determined by both sound source and medium?

Frequency
Period
Power
Wavelength

Wavelength

How well did you know this?

Not at all

Perfectly

If period is 0.5 microseconds, Frequency is :

2 MHz

(remember: period and frequency are inversely related to each other. They are reciprocal, meaning when they are multiplied together, the result is 1)

How well did you know this?

Not at all

Perfectly

If the wavelength is 4 mm (in soft tissue) , frequency is :

38 MHz
remember: wavelength (mm) = 1.54 mm/us

frequency (MHz)

How well did you know this?

Not at all

Perfectly

The relationship between power and amplitude can be described as :

Power is directly related to amplitude²

How well did you know this?

Not at all

Perfectly

The only parameter that is determined by the medium is :

Propagation Speed

How well did you know this?

Not at all

Perfectly

If the amplitude is halved, the intensity will be :

Quartered

How well did you know this?

Not at all

Perfectly

All of the following are true regarding the 3 bigness EXCEPT :

They are determined by the sound source only
They are adjustable (initially)
They are directly related to propagation speed
Watt is the unit of power

They are directly related to propagation speed

How well did you know this?

Not at all

Perfectly

Propagation speed :

Directly related to stiffness and inversely related to density

↑ Stiffness = ↑ Speed

↑ Density = ↓ Speed

How well did you know this?

Not at all

Perfectly

Duty factor for continuous-wave is :

100 %

How well did you know this?

Not at all

Perfectly

What is the wavelength of 1 MHz sound in soft tissue?

1.54 mm

How well did you know this?

Not at all

Perfectly

What is the speed of sound in soft tissue?

1,540 m/s or 1.54 mm/us

How well did you know this?

Not at all

Perfectly

Why is wavelength important in diagnostic ultrasound?

Short wave = high frequency = better picture

How well did you know this?

Not at all

Perfectly

What characteristics of a medium determine the speed of sound in that medium?

Density & Stiffness

What other terms describe stiffness?

Elasticity & Compressibility

What is a pulsed sound?

A collection of cycles that travel together.

Which type of pulse is more desirable in diagnostic imaging, and why?

Shorter pulse durations. They create images of greater accuracy.

What is depth of view?

The maximum distance into the body that an ultrasound system is imaging. (Controlled by the sonographer.)

How are pulse repetition period and depth of view related?

Directly related. ↑ Depth = ↑ PRP Depth (mm) ȣ PRP (us) PRF (MHz)

How are PRF (transmit time) and depth of view related?

Inversely related. ↑ Depth = ↓ PRF The deeper (increase) the depth, the fewer (decrease) pulses transmit into the body. Depth (mm) ȣ PRP (us) PRF (MHz)

How is Duty Factor calculated?

Duty Factor (%) = _Pulse Duration (us)_ x 100 PRP (us)

How does the sonographer change duty factor?

By changing the image depth.

Of the 4 temporal (time-related) intensity measurements, which has the highest value?

Temporal Peak

Rank the 5 intensities from largest to smallest.

1. SPTP 2. Im 3. SPPA 4. SPTA 5. SATA

The unit of intensity is :

Watt/cm²

.... is the most relevant intensity with respect to tissue heating.

SPTA

.... has the lowest value.

SATA

..... has the highest value.

SPTP

Beam uniformity coefficient is also called :

SP/SA

It describes the relationship between the beam intensities with time.

Duty Factor

Which of the following is unitless and the typical value is 1 or greater? - SPTP - Duty Factor - SP/SA - I m

SP/SA

In pulsed-wave ultrasound, SPTA=SATA, and SATA=SAPA

False

Temporal average intensity is the average during pulse duration.

False

What is the meaning of 6 dB change?

4 times bigger

A wave intensity is 8 mW/cm². There is a change of -9dB. What is the final intensity?

1 mW/cm² [when a dB is -3, it is halved. In this question, the intensity will be halved 3 times (-3 ,-3, -3 = -9 dB). So half of 8 is 4, half of 4 is 2, and half of 2 is 1.] 3 dB = double 10 dB = ten times larger - 3 dB = half - 10 dB = one-tenth

Attenuation is .....

Directly related to path length and frequency

The process that is the most sizable component of attenuation is :

Absorption

If frequency was 2 MHz, and then becomes 4 MHz, Rayleigh scattering will .....

increase by 16 times (Rayleigh scattering ȣ frequency⁴⁾ ^{[When frequency doubles, Rayleigh scattering is 16 times greater (2 x 2 x 2 x 2 = 16)]}

Rayleigh scattering occurs when the structure's dimensions are .....

much smaller than the beam's wavelengths

In soft tissue, if the frequency is 4 MHz at 10 cm depth, calculate the total attenuation.

20 dB Total attenuation (dB) = attenuation coefficient (dB/cm) x distance (cm) attenuation coefficient (dB/cm) = _frequency (MHz)_ 2

Sound travels in a medium and strikes a boundary with normal incidence. If 60% of the wave's intensity is reflected, what is the intensity transmission coefficient?

40%

If the incident intensity is 10 mW/cm², the reflected intensity is 1 mW/cm², what is the transmitted intensity?

9 mW/cm²

Two conditions must be met for refraction to occur, what are they?

Oblique incidence and different propagation speeds

What are the 3 processes that contribute to attenuation?

1. Reflection 2. Scattering 3. Absorption

What are the 2 types of reflection?

1. Specular 2. Diffuse (backscatter)

Rayleigh scattering increases dramatically with increasing frequency.

True Rayleigh scattering ȣ Frequency 4

Distance and attenuation are related how?

Directly. ↑ Distance = ↑ Attenuation

Frequency and attenuation are related how?

Directly. ↑ Frequency = ↑ Attenuation

Absorption is related to frequency how?

Directly. ↑ Frequency = ↑ Absorption

What are the 3 types of intensities?

1. Incident Intensity 2. Reflected Intensity 3. Transmitted Intensity \*All intensities have units of W/cm2. Incident (starting) Int. = Reflected Int. + Transmitted Int.

Acoustic impedance = ___ x \_\_\_.

impedance = density (kg/m³) x propagation speed (m/s)

What is the percentage of the intensity that bounces back when a sound beam strikes the boundary between 2 media?

IRC Intensity Reflection Coefficient

What is the percentage of intensity that passes in the forward direction when the beam strikes an interface between 2 media?

ITC Intensity Transmission Coefficient

In clinical imaging, what percentage of a sound wave's intensity is transmitted at a boundary between 2 soft tissues?

99% or more.

IRC (%) + ITC (%) = ?

100%

The percentage of the incident beam that is reflected is related to what?

The difference in the impedances of the tissues.

With normal incidence, what formula do you use to calculate the IRC?

The value of the ITC ranges from 0% to 100% and is defined by what formula?

ITC (%) = _Transmitted Int_. x 100 Incident Int. OR ITC (%) = 1 - IRC

The angle between the incident sound beam and an imaginary line that is perpendicular to the boundary is called what?

Angle of Incidence.

The angle between the reflected sound beam and the line perpendicular to the boundary is called what?

Angle of Reflection.

Transmission with a bend is called what?

Refraction

How do we identify Medium 1 and Medium 2?

Medium 1 is the medium in which the sound is currently traveling. Medium 2 is the medium into which the sound is entering.

Under what conditions will the transmission angle be greater than the incident angle?

When the speed of Medium 2 is GREATER than the speed of Medium. The transmission angle will be less than the incident angle when the speed of Medium 2 is LESS than the speed of Medium 1.

The maximum imaging depth (depth of view) during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm. What happens to pulse repetition period (PRP)?

PRP is directly related to imaging depth. When imaging depth doubles, PRP doubles.

The maximum imaging depth during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm. What happens to pulse repetition frequency (PRF)?

PRF is inversely related to imaging depth. When imaging depth doubles, PRF is halved.

A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The maximum imaging depth is 7.7 cm. What is the PRF?

77,000 / 7.7 = 10,000 Hz PRF (Hz) = _77,000 cm/s_ imaging depth (cm)

What is the formula for Pulse Repetition Period (PRP)?

PRP (us) = imaging depth (cm) x 13 us/cm ex: When the depth of view is set to 10 cm, PRP is 130 us (10 x 13 us)

What term is used to describe the effects of an ultrasound wave on living tissue?

Biological effects