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EXAM 1 STUDY PREP
Doppler Sonography & Advanced Hemodynamics
| Question | Answer |
|---|---|
| What is the relationship between a sound wave's period and its frequency? | The period and frequency are inversely related |
| What is the period of a sound wave? | The time to complete one cycle |
| Sound is a traveling variation in quantities called ? variables. | Acoustic |
| According to the "Three Decibel Rule," what happens to the output intensity when it is decreased by 6 dB? | Decreases by a factor of 4 |
| Audible Frequency Range | 20 Hz - 20 kHz |
| Infrasound Frequency Range | 0 Hz - <20 Hz |
| Ultrasonic Frequency Range | 20 kHz - 20 MHz |
| Diagnostic Imaging Frequency Range | 2 Mhz - 12 MHz |
| What are areas of low pressure in a sound wave? | Rarefactions |
| Intensity | Acoustic pressure per square inch of tissue |
| Power | Energy passing through a cross-sectional area per second |
| Amplitude | Acoustic pressure in a sound wave |
| What type of energy is present in a sound wave? | Mechanical |
| Which statement best describes the "3 Decibel Rule?" | Increasing output intensity by three decibels doubles the output intensity at the transducer and vice versa |
| If the frequency in soft tissues is doubled, propagation speed is? | Unchanged |
| What happens to the speed of sound in a medium when the density of the medium increases? | Decreases |
| Calculate the wavelength of a 4 MHz ultrasound beam that is passing through soft tissue | 0.385 mm |
| What two major factors determine the speed of sound through a medium? | Density and compressibility |
| How is sound wave energy transmitted through a material medium? | Pressure waves |
| If the wavelength is 2mm and the frequency is doubled, the wavelength becomes ? mm. | 1 |
| What happens to the wavelength if the frequency is doubled? | The wavelength is halved |
| Which of the following has the highest propagation speeds? | Bone |
| What is the frequency of a sound wave? | The number of complete cycles the wave completes per second |
| How does wavelength affect spatial (image) resolution? | Shorter wavelengths improve image detail |
| Period decreases while ? increases | Frequency |
| Which acoustic variable is most often used to describe the strength, or magnitude, of a sound wave? | Change in pressure |
| What determines the speed (or velocity) of an ultrasound wave? | Medium |
| The wavelength of a 7 MHz ultrasound in soft tissues is ? mm. | 0.22 |
| Which factor determines the amount of interference (constructive or destructive) between two sound waves? | Phase Relationship |
| What is the formula for the speed of sound (C) through soft tissue? | C = frequency x wavelength |
| Wavelength is equal to ? divided by ?. | Propagation speed, frequency |
| What is the average velocity of an ultrasound wave propagating through soft tissue? | 1540 meters/second |
| An increase in frequency will cause a ? in the cycle period. | Decrease |
| What is the relationship between a sound wave's intensity and its pressure amplitude? | Intensity is proportional to amplitude squared |
| What does an Intensity Reflection Coefficiency of 0.25 tell us? | 25% of the intensity is attenuated at an interface and 75% is transmitted through an interface |
| An increase in frequency will cause an increase in what parameter? | Attenuation |
| True or False: Liver parenchyma is an example of a specular reflector | False |
| What does Snell's Law predict? | Amount of sound beam refraction |
| For specular reflectors, the angle of reflection is equal to the? | Angle of incidence |
| What happens to the intensity reflection coefficient and echo intensity as the acoustic impedance mismatch increases? | As the acoustic impedance mismath increases, the reflection coefficient increases as well as the echo intensity |
| Which term best describes the reduction in a sound wave's amplitude as it propagates through tissue? | Attenuation |
| What is the attenuation rate for soft tissue? | 0.5 dB/cm/MHz |
| With perpendicular incidence, the reflected intensity depends on the? | Impedance difference |
| Which term best describes bending of the sound beam as it passes through an interface at non-perpendicular incidence? | Refraction |
| What two factors must be present before refraction of a sound wave can occur at an interface? | Non-perpendicular beam incidence & different speeds of sound at the interface |
| What term is used to describe the maximum variation in an acoustic variable? | Amplitude |
| What two parameters must be known for proper echo display? | Reflection coefficient and transmission coefficient |
| Ampltiude and intensity are indicators of sound? | Strength |
| What factor determines how much of an incident sound wave is reflected back and how much is transmitted? | Impedance |
| Which of the following tissues has the highest attenuation rate? | Bone |
| Intensity is proportional to ? squared | Amplitude |
| True or False: No reflection will occur with perpendicular incidence if the media impedances are equal | True |
| For soft tissues, the attenuation coefficient at 5 MHz is approximately | 2.5 dB/cm |
| What process causes high-frequency ultrasound waves to have less depth penetration than low-frequency ultrasound waves? | Increased attenuation of higher frequencies |
Created by:
marissagirl