Edelman Understanding Ultrasound Physics Questions and Answers

True or false. We need one intensity to calculate decibels.

A waves intensity is 2 mW/cm^2. There is a change of +9 dB. What is the final intensity?

If the final intensity of a sound beam is more than the initial intensity, then the gain in dB is ____.

If the initial intensity of a sound beam is less than the final intensity, then the gain in dB is _____.

Name the three components of attenuation.

As the path length increases, the attenuation of ultrasound in soft tissue _______.

Attenuation in lung tissue is [less than, greater than, the same as] attenuation in soft tissue.

Attenuation in bone is _________ attenuation in soft tissue.

Attenuation in air is _______ attenuation in soft tissue.

What are the units of attenuation?

True or False. In a given medium, attenuation is unrelated to the speed of sound.

What is the relationship between ultrasound frequency and the attenuation coefficient in soft tissue?

What are the units of the half value layer thickness?

As frequency decreases, depth of penetration:

As path length increases, the half boundary layer:

Impedance is associated with?

As the path length increases, the attenuation coefficient of ultrasound in soft tissue [increases, decreases, remains the same] _______.

Acoustic impedance= ______x_____.

Two media A and B have the same densities. The speed of sound in medium A is 10% higher than in medium B. Which medium has the higher acoustic impedance?

Impedance is important in ____ at boundaries.

Which is better to use while examining a carotid artery, a 7.5 or 3.0 MHz transducer?

A sound wave with an intensity of 50 W/cm^2 strikes a boundary and is totally reflected. What is the intensity reflection coefficient?

A sound wave with an intensity of 50 W/cm^2 strikes a boundary and is totally reflected. What is the reflected intensity?

A pulse of ultrasound is propagating in soft tissue, such as liver. The pulse strikes a boundary with a different soft tissue at normal incidence. What portion of the intensity is reflected back toward the transducer? Why?

Sound is traveling in a medium and strikes a boundary with normal incidence. If 63% of the waves intensity is reflected back toward the transducer, what percentage is transmitted?

Sound strikes a boundary between two media orthogonally (normal incidence). Although the media are very different, no reflection is created. How can this be?

A pulse of ultrasound is propagating in bone and strikes an interface with soft tissue at 90%. A giant reflection is created. From these facts alone, what can be said about the impedance of bone? What can be said about impedance of soft tissue? What can be said about the differences between the impedances of bone and soft tissue?

Which of the following terms does not belong with the others?

Sound is traveling from bone to soft tissue. The impedances of the media differ significantly, and 90% of the beams intensity is reflected. What percentage of the intensity is transmitted?

Sound that is traveling in Jell-O passes through an interface at 90 degrees and continues to travel in whipped cream. The impedance of Jell-O and whipped cream are nearly identical. What percentage of the intensity is transmitted?

A pulse of ultrasound propagates in soft tissue, such as liver. The pulse strikes a soft tissue-soft tissue interface with oblique incidence. Some of the sound energy is transmitted. To what extent is the transmitted beam refracted?

A sound pulse travels in Medium 1 and strikes an interface with another tissue, Medium 2 at 30 degrees. The angle of transmission is 10 degrees. In which medium does sound travel slowest?

A sound pulse travels in medium 1 and strikes an interface with another tissue, medium 2, at 30 degrees. The angle of transmission is 10 degrees. From these facts, what can be said about the speed of sound in medium 1, the speed of sound in medium 2, and the difference between the speeds of media 1 and 2?

A sound pulse travels in medium 1 and strikes an interface with another tissue, medium 2 at 30 degrees. The angle of transmission is 10 degrees. In which medium is impedance higher?

Sound travels in a medium and orthogonally (normal incidence) strikes a boundary with a different medium. Although sound waves traveling in the media have no vastly different speeds, there is no refraction. How can this be?

A sound wave strikes a boundary with normal incidence. The impedances of the two media are identical. What percentage of the sound wave is refracted?

A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The depth of the reflector is 10 cm in soft tissue. What is the go-return time?

A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 26 microseconds. What is the depth of the reflector?

A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 26 microseconds. What is the total distance that the pulse traveled?

The max 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?

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

The imaging depth during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 5 cm. What happens to pulse repetition period?

A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The imaging depth is 10 cm in soft tissue. What is the max pulse repetition frequency?

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

A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 130 microseconds. What is the max PRF?

You are given 5 substances: backing material, PZT, matching layer, gel, and skin, whose impedances have been measured. Unfortunately, the labels identifying the impedance of each substance have fallen off these materials. There are five labels indicating impedances of 0.8 Mrayls, 1.9 Mrayls, 1.6 Mrayls, 2.0 Mrayls, and 1.0 Mrayls. If the impedance of the backing material is 1.9 Mrayls, what are the impedances for the rest of the substances?

Pulse length is (directly or inversely) related to pulse duration.

Q-factor is (directly or inversely) related to bandwidth.

Pulse duration is (directly or inversely) related to bandwidth.

The sensitivity of transducers that create short duration pulses is likely to be (greater than, less than, or equal to) that of transducers that create long pulses.

All of the following correctly describe an imaging transducer except:

True or False. Shorter duration events (such as dampened pulses) are more likely to be wide bandwidth.

What occurs when PZT crystals temperature is elevated above the Curie point?

True or False. The acoustic impedance of the matching layer is approximately the same as the acoustic impedance of skin.

True or False. Imaging transducers are usually of high rather than low bandwidth.

True or False. A very high Q factor transducer is used more often in diagnostic imaging transducers than a low Q factor?