SPI Physics Principles

Which of the following describes the amount of refraction that occurs at an interface? a. Bernoulli's law b. Snell's law c. Poiseuille's law d. Law of Reflection

Snell's law Refraction: the redirection of the transmitted sound beam Snell's law describes the angle of transmission at an interface based on the angle of incidence and the propagation speeds of the two media.

Which of the following is described as the ability of an object to resist compression and relates to the hardness of a medium? a. stiffness b. density c. pressure d. inertia

Stiffness Stiffness is also referred to elasticity. Think: ↑ Stiffness ↑ Speed (thumbs UP!) ↓ Density ↑ Speed

In clinical imaging, the wavelength measures between: a. 1 and 10 Hz b. 1540 and 2000 m/s c. 0 and 1 d. 0.1 to 0.8 mm

0.1 to 0.8 mm In clinical imaging, the wavelength measures between 0.1 to 0.8 mm

Which of the following would have the highest propagation speed? a. Air b. Bone c. Soft Tissue d. Water

Bone Bone has the highest propagation speed, at 2000-4000 m/s.

Which of the following is defined as only the active time? a. Duty factor b. Pulse repetition frequency (PRF) c. Period d. Pulse duration

Pulse duration Pulse duration is defined as the active time/"on time" Duty factor is the percentage of time that sound is actually being produced. PRF is the number of cycles of sound produced in 1 second Period is the time it takes for one cycle

Which of the following would be considered ultrasonic? a. 10 Hz b. 12.5 Hz c. 1 MHz d. 200 Hz

1 MHz 1 MHz is considered ultrasonic. (1,000,000 Hz) Ultrasound: greater than 20,000 Hz (20 kHz) Audible: 20-20,000 Hz Infrasound: less than 20 Hz

The typical range of frequency for diagnostic ultrasound imaging is a. 20-20,000 Hz b. 1-20 MHz c. 10-20 Mhz d. 12-100 MHz

1-20 MHz 1-20 Mhz is the typical range of frequency for diagnostic ultrasound imaging.

The duty factor for continuous wave ultrasound is: a. <99% b. 100% c. >20,000 Hz d. 8 Pa

100 % Continuous wave ultrasound has a duty factor of 100%. Continuous wave is always on.

What is the total amount of attenuation that occurs if a 6.0 MHz sound beam travels through a 4 cm of soft tissue? a. 24 dB b. 12 dB c. 6 dB d. None of the above

12 dB If a 6.0 Mhz sound beam travels through a 4 cm of soft tissue, the attenuation is 12 dB. Total Attenuation = (f/2) X Path Length = (6.0 MHz/2) X 4 cm = 3 MHz X 4 cm = 12 dB

If the angle of incidence is 40°, what is the angle of transmission at the interface if medium 1 has a propagation speed of 1320 m/s and medium 2 has a propagation speed of 1700 m/s? a. <40°( b. >40° c. 40° d. Cannot tell the angle of transmission

>40° The angle of transmission is greater than 40° If the propagation speed of medium 2 is less than the propagation speed of medium 1, then the angle of transmission will be less than the angle of incidence. Medium 1 Prop. Speed > Medium 2 Prop. Speed then: Angle of Incidence > Angle of tranmission If the propagation speed of medium 2 is greater than the propagation speed of medium 1, then the angle of transmission will be greater than the angle of incidence. Medium 1 Prop. Speed Angle of Incidence

The major component of attenuation is: a. Scatter b. Absorption c. Transmission d. Refraction

Absorption Absorption is the major component of attenuation Absorption is also a potential source of thermal bioeffects. The three mechanisms of attenuation are absorption, reflection and scattering.

As a sound wave travels through the human body, the intensity of the sound wave decreases as a result of a. Attenuation b. Absorption c. Scattering d. All of the above

All of the above All of the above - attenuation, absorption, scattering There are three mechanisms of attenuation - absorption, reflection and scattering. Attenuation is the decrease in the amplitude, power and intensity of the sound beam as it travels through tissue (peters/wears out)

The maximum value or minimum value of an acoustic variable minus the equilibrium value of that variable describes the: a. Power b. Intensity c. Duty factor d. Amplitude

Amplitude Amplitude is the maximum or minimum value of an acoustic variable, minus the equilibrium value of that variable.

What is defined as the ability of the ultrasound system to image structures that are positioned parallel to the sound beam as separate structures? a. Transverse resolution b. Parallel resolution c. Axial resolution d. Coronal resolution

Axial resolution Axial resolution is the ability to resolve reflectors that lie parallel to the beam as distinct echoes.

Areas of high pressure and density are referred to as: a. Compressions b. Rarefactions c. Condensations d. Rarefractions

Compressions Compressions are areas of high pressure and density. (High pressure because molecules are compressed/pushed closer) Rarefactions are areas of low pressure and density. Low pressure because molecules are spread wider apart RareFRactions is not even a word....

As imaging depth increases, the pulse repetition frequency (PRF) must: a. Not change b. Increase c. Decrease d. Pulse repetition frequency does not relate to the imaging depth

Decrease As imaging depth increase, pulse repetition frequency (PRF) decreases. ↑ Imaging Depth ↓ PRF PRF will decrease because PRF is the number of ultrasound pulses emitted in 1 second. As you increase depth, you have to send the signal deeper, therefore less US pulses are emitted because it must wait for the echoes to get back to the transducer.

The inertia of the medium describes its: a. Attenuation characteristics b. Stiffness c. Density d. Elasticity

Density The inertia of the medium describes its density Inertia is described by Newton's principle - an object at rest will stay at rest. An object in motion stays in motion, unless acted on by an outside force.

The percentage of time that the ultrasound system is producing pulses of ultrasound describes the a. Pulse repetition period (PRP) b. Pulse duration c. Duty Factor d. Pulse repetition frequency (PRF)

Duty factor Duty factor is the percentage of time the ultrasound system is producing a sound. "On Time" Typically less than 1%

All of the following are true of power EXCEPT: a. As amplitude increases, power remains the same b. Power is proportional to amplitude squared c. Intensity is proportional to power d. Power is measured in milliwatts

EXCEPT: As amplitude increases, power remains the same Think: ↓ Power ↓ Amplitude Power and amplitude are directly related. ✔ Power is proportional to amplitude squared (Power = Amplitude2) ✔Intensity is proportional to power ✔ Power is measured in milliwatts (mW)

All of the following are true of wavelength (λ) EXCEPT: a. It is determined by both the medium and the sound source b. It is equal to the period divided by the frequency c. It is inversely related to frequency d. It is directly related to period

EXCEPT: It is equal to the period divided by the frequency. ✔ Wavelength is determined by both the sound source and the medium ✔ It is inversely related to frequency ✔It is directly related to period

Which of the following is determined by the sound source only? a. Frequency b. Wavelength c. Spatial pulse length d. Propagation speed

Frequency Frequency is determined by sound source only.

The prefix "centi" denotes: a. Thousandths b. Hundredths c. Millions d. Hundreds

Hundredths "Centi" denotes hundredths

As imaging depth increase, pulse repetition period (PRP) a. Remains constant b. Increases c. Decreases d. Doubles

Increases As imaging depth increases, pulse repetition period (PRP) increases ↑ Imaging Depth ↑ PRP Think: increasing the depth means the listening time will be increased cuz it's traveling deeper. Since PRP includes Pulse Duration and Listening Time, they are directly related. PRP is the time from the start of one pulse, to the start of the next pulse. Think: it includes one pulse duration/on time and one "listening"/off time.

If pulse repetition frequency (PRF) increases, then the duty factor: a. Remains constant b. Increases c. Decreases d. Doubles

Increases If PRF increases then the duty factor increases. ↑ PRF ↑ Duty Factor PRF is the number of pulses created by the system in one second. Since duty factor is the fraction of time that the system transmits sound/"on time", Increasing the PRF will cause the Duty Factor to be on longer/increase

When amplitude triples, power ______. a. Doubles b. Triples c. Quadruples d. Increases nine times

Increases nine times If amplitude triples, power increases by nine times. 9 = 3^2 Power = Amplitude2 (think: PA TOO/TWO!)

An increase in pulse repetition frequency would lead to: a. An increase in duty factor b. An increase in pulse duration c. An increase in the number of cycles d. A decrease in resolution

Increasing pulse repetition frequency, increases duty factor. ↑ PRF ↑ Duty Factor Think: increasing the pulse repetition frequency means it needs to be "on" more.

What is essentially equal to the power of a wave divided by the area over which the power is distributed? a. Amplitude b. Power c. Intensity d. Absorption

Intensity Intensity is essentially equal to the power of a wave divided by the area which the power is distributed over.

What is the change in intensity if the power decreases by half? a. Intensity doubles b. Intensity is halved c. Intensity is one-fourth d. Intensity does not change

Intensity is halved If power is halved, intensity is halved Intensity = Power Intensity = Amplitude2 Power = Amplitude2

Density and propagation speed are: a. Inversely related b. Directly related c. Directly proportional d. Unrelated

Inversely related Density and propagation speed are inversely related ↓ Density ↑ Speed

Density is typically measured in: a. Kilograms per centimeter cubed (kg/cm3) b. Millimeters (mm) c. Watts per centimeter squared (W/cm2) d. Pascals (Pa)

Kilograms per centimeter cubed (kg/cm3) Density is measured in kilograms per centimeter cubed (kg/cm3) wavelength/λ, - mm Intensity - W/cm2 Pressure - Pa

Transducers have material within them that, when electronically stimulated, produces ultrasound waves. This is most likely some form of: a. Copperhirm titonize b. Zinconian sulfate c. Lead zirconate titanate d. Barium

Lead zirconate titanate Transducers are made of lead zirconate titanate (aka PZT, crystal, active element, ceramic)

Which of the following would have the lowest propagation speed? a. Water b. Soft Tissue c. Bone d. Lung tissue

Lung tissue Lung tissue, with the propagation speed of 300-1200 m/s Even though air technically has the lowest propagation speed at 300 m/s, it was not one of the choices.

Sound is technically a: a. Transverse and longitudinal wave b. Mechanical and transverse wave c. Mechanical and longitudinal wave d. Nonmechanical and pressure wave

Mechanical and longitudinal wave Sound is a mechanical and longitudinal wave

Which of the following is an appropriate unit of measurements for propagation speed? a. millimeters per microsecond (mm/μs) b. watts per centimeter squared (W/cm2) c. microseconds (μs) d. kilohertz (kHz)

Millimeters per microsecond (mm/μs)

Micro is denoted as: a. Millionth b. Hundredth c. Million d. Billionth

Millionth Micro is denoted as millionth (µ)

Spatial pulse length (SPL) can be calculated by: a. Multiplying the number of cycles times the frequency b. Dividing the period by the frequency c. Multiplying the number of cycles times the wavelength d. Dividing the number of cycles by the wavelength

Multiplying the number of cycles times the wavelength Spatial pulse length equals the number of cycles in the pulse multiplied by the wavelength. SPL = # of cycles X wavelength (λ,) Basically find total length by multiplying how many cycles and length of the cycle

The attenuation coefficient in soft tissue is equal to: a. One half of the operating frequency b. Double the operating frequency c. Frequency times path length d. The total decibels

One the operating frequency Attenuation coefficient = f/2 (one half of the frequency in soft tissue) The attenuation coefficient (in dB/cm) is the rate at which sound is attenuated per unit depth.

Pressure is typically expressed in: a. Frequency (Hz) b. Pascals (Pa) c. Decibles (dB) d. Kilograms per centimeter cubed (kg/cm3)

Pascals (Pa)

What is pressure measured in? a. feet, inches, centimeters, miles b. Pascals or pounds per square inch c. kilograms per centimeter cubed d. hertz, kilohertz or megahertz

Pascals or pounds per square inch Pressure is measured in Pascals (Pa) or pounds per square inch.

If only the density of a medium is increased, then the: a. Propagation speed will increase b. Propagation speed will decrease c. Propagation speed will stay the same d. None of the above

Propagation speed will decrease If density is increased, propagation speed will decrease. ↓ Density ↑ Speed ↑ Stiffness ↑ Speed (thumbs UP!)

Which of the following is defined as the number of ultrasound pulses emitted in 1 second? a. Pulse repetition period (PRP) b. Duty Factor c. Pulse repetition frequency (PRF) d. Spatial pulse length (SPL)

Pulse repetition frequency (PRF) Pulse repetition frequency (PRF) is the number of ultrasound pulses emitted in 1 second. Think: how frequently is US pulses emitted per second is PRF

What is defined as the beginning of one pulse to the beginning of the next pulse, and therefore includes both the "on" and "off" time? a. Pulse repetition period b. Pulse duration c. Duty factor d. Pulse repetition frequency

Pulse repetition period Pulse repetition period is the time from the start of one pulse to the start of the next pulse. Includes both the "on" and "off" time.

The portion of the sound beam where the molecules are pulled apart describes an area of: a. Compression b. Rarefaction c. Refraction d. Amplitude

Rarefaction In rarefaction, molecules in the cycle are spread wider apart Compression: molecules are pushed closer together/compressed. Area of high pressure and density. Rarefaction: molecules are spread wider. Area of low pressure and density.

Damping of the sound beam: a. Reduces the spatial pulse length (SPL) b. Increases the spatial pulse length (SPL) c. Increases the pulse duration d. Has no impact on spatial pulse length or pulse duration

Reduces the spatial pulse length (SPL) Damping of the sound beam reduces the spatial pulse length. Think: SPL can be controlled with damping/backing material. Damping reduces the SPL by reducing the number of cycles of each pulse. Damping reduces SPL and PD, which improves the axial resolution. Think: shorter SPLs mean shorter PDs, resulting in better axial resolution and improves image quality.

The change in the direction of the original sound wave that occurs when sound interacts with two different tissue types that have a different propagation speed is referred to as: a. Wavelength b. Scattering c. Refraction d. Absorption

Refraction Refraction is a change in direction when sound transmits from one medium to another. Transmission with a bend that requires an oblique incidence and different propagation speeds.

All of the following are true of stiffness EXCEPT: a. It is defined as the ability of an object to resist compression b. Stiffness and propagation speed are indirectly associated c. Increasing stiffness increases propagation speed d. Stiffness may also be referred to as elasticity

Stiffness and propagation speed are indirectly associated True for stiffness, EXCEPT stiffness and propagation speed are indirectly associated. Also remember:↑ Stiffness ↑ Speed(thumbs UP!) ↓ Density ↑ Speed

All of the following relate to the strength of the sound wave EXCEPT: a. Amplitude b. Wavelength c. Intensity d. Power

Wavelength Wavelength DOES NOT relate to the strength of the sound wave. Think: Sound parameters are API: amplitude, power, intensity

Which of the following is determined by the sound source and medium? a. Propagation speed b. Frequency c. Period d. Wavelength

Wavelength Wavelength is determined by the sound source and medium

Which of the following is described as the distance over which one cycle occurs? a. Pulse duration b. Duty Factor c. Period d. Wavelength

Wavelength Wavelength is distance over which one cycle occurs, or the distance from the beginning of one cycle to the end of the same cycle. Remember, it asks for distance over which one cycle occurs.