The History Of Ultrasound And Physics Flashcards by Black RoSe

What is active sonar?

‘Ping’

Reflection of sound waves

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What is passive sonar?

Just listening

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What is acoustic impedance?

Density, stiffness and speed of sound.

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Where does reflection of sound occur?

Occurs at boundaries of impedance

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Does sound travel in a vacuum?

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What four qualities of the transmitting medium influence sound transmission?

Density
Stiffness
Acoustic Impedance
Speed of sound

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Do waves carry energy or matter?

Energy

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How do sound waves propagate?

Sound waves propagate by compression and rarefaction of molecules in space.

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What is sound frequency?

The number of cycles of compression and rarefaction in a sound wave per second (Hz)

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What is the definition of the wavelength of sound?

The distance travelled in one second.

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What is the definition of spatial pulse length?

Cycle length multiplied by number of cycles per pulse.

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What is spatial pulse length a determinant of?

It’s a determinant of axial (in line of beam) resolution (1/2 SPL)

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What is the duty factor percentage?

The time spent generating pulse (usually 1% - while 99% of the time is spent listening for signal return).

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What is the definition of pulse repetition frequency?

The number of pulses (send/listen cycles) sent per second.

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What is pulse repetition frequency dependent on?

Speed of sound

- Target depth

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Which has better depth penetration…

Lower or higher frequency?

Lower frequency

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Which has better resolution…

Lower or higher frequency?

Higher frequency

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Is the speed of sound through a transmitting material affected by frequency?

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Is the speed of sound through a transmitting material affected by wavelength?

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Is the speed of sound through a transmitting material affected by stiffness of the material?

Yes

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Does the speed of sound through a transmitting material increase or decrease with increased stiffness of the material?

Increases

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Is the speed of sound through a transmitting material affected by density of the material?

Yes

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Does the speed of sound through a transmitting material increase or decrease with increased density of the material?

Decreases

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Is the speed of sound constant for a given tissue?

Yes

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What is the propagation velocity of sound through bone?

4080

What is the propagation velocity of sound through muscle?

1580

What is the propagation velocity of sound through liver?

1550

What is the propagation velocity of sound through soft tissue (average)?

1540

What is the propagation velocity of sound through kidney?

1560

What is the propagation velocity of sound through blood?

1570

What is the propagation velocity of sound through fat?

1450

What is the propagation velocity of sound through water?

1480

What is the propagation velocity of sound through air?

330

Is there an echo if two tissues have the same acoustic impedance?

Is there an echo if two tissues have similar acoustic impedance?

Weak echo

Is there an echo if two tissues have very different acoustic impedances?

Strong echo

Do most tissues have a heterogeneous or homogeneous acoustic impedance?

Heterogeneous impedance

Does homogeneous medium reflect sound?

What kind of echo does a cyst have?

No echo (anechoic)

What is reflection of sound?

Redirection of a portion of a sound beam back at the interface of tissues of unequal acoustic impedance.

The greater the difference in impedance, the _______ the reflection.

Greater

What are the two categories of reflection?

- Specular (mirror like e.g. diaphragm) | - Diffuse (soft tissue e.g. neck ultrasound)

What is specular reflection dependent on?

Angle of incidence

In diffuse reflection are the adjacent structures smaller or larger than wavelength?

Smaller

What does A-mode of thyroid stand for?

Amplitude (strength of echo)

Is A-Mode one dimensional or two dimensional?

One dimensional

Is B-Mode one dimensional or two dimensional?

Two dimensional

When was A-Mode used? | Years

1960's

When was B-Mode used? | Years

Mid 1960s

Is the 'Halo Sign' an indicator of a benign or malignant nodule?

Benign

Microcalcifications... Benign or malignant?

Malignant

Name four reflection artifacts.

- Shadowing and enhancement - Edge artifact - Reverberation artifact - Comet tail artifact

Name one refraction artifact.

Phantom image

What is the propagation artifact due to?

Displacement due to differences in speed of sound.

What causes shadowing?

When sound passes through a strong attenuator.

Which one is lateral... Sternohyoid or sternothyroid?

Sternothyroid

Which one is medial... Sternohyoid or sternothyroid?

Sternohyoid

Enhancement is seen behind cysts. True or false?

True

Eggshell calcification - what kind of artifact is it?

Reflection artifact

Comet tail artifact is also called...

Ring down artifact

What is refraction?

Bending of wave at an interface when angle of incidence is not 90 degrees.

What is the degree of refraction proportional to?

The difference between the speed of sound in each tissue.

What may happen when a refracting object exists in the path of the US beam?

A second 'ghost' image may appears.

What three things does attenuation of acoustic energy result from?

- Reflection - Scatter - Absorption

What is attenuation dependent on?

Frequency

Do higher or lower frequencies have greater attenuation?

Higher frequencies

What gives greater depth of imaging? Higher or lower frequencies?

Lower frequencies

What artifacts occur due to attenuation?

- Shadowing | - Enhancement

Resolution: Lateral...

Side to side

Resolution: Azimuthal...

Up-down

Resolution: Axial...

Distance from transducer

What determines lateral and azimuthal resolution?

Focused beam width

What is the Fresnal Zone?

Near field

What is the Fraunhofer Zone?

Far field

Where is the area of maximal narrowing?

Focal zone

What happens to intensity in the far field?

Intensity is fairly uniform

What happens to intensity in the near field?

Large variations of intensity

What is the far field also called?

Fraunhofer Zone

What is the near field also called?

Fresnel Zone

What determines axial resolution?

Pulse duration

What is axial resolution =

1/2 x Spatial Pulse Length

What is the spatial pulse length?

Numbers of cycles in the pulses x wavelength

Does axial resolution increase with increasing or decreasing frequency?

Increasing frequency

Is the depth of the focal zone adjustable?

Yes

What frequency (higher or lower) do you use if you want to better visualize superficial structures?

Higher

What frequency (higher or lower) do you use if you want to better visualize deep structures?

Lower

What does a transducer do?

Converts one form of energy to another.

What is the Piezoelectric Effect?

Property of some crystals to emit electricity when compressed.

What are the three types of transducers?

- Linear Array - Curved Array - Phase Array

Multiple crystals in a linear array allow real time scanning with a stationary transducer. True or false?

True

Advances in Technology - Signal Processing. Two types of image enhancement?

- Noise reduction | - Edge sharpening

Advances in Technology - Signal Processing. Two results of CT and MRI reconstruction algorithms...

- Beam steering | - Spatial compounding

At higher power tissue will reverberate and produce harmonics of the original frequency. True or false?

True

What does tissue harmonic imaging involve?

Selective detection of second harmonic.

Selective detection of harmonic leads to increased contrast. True or false?

True

Name two advantages of tissue harmonic imaging.

- Increased conspicuity | - Improved signal to noise for deeper structures

What algorithm does panoramic image reconstruction (extended field of view) use?

'Pattern Matching' Algorithm

The gain can be adjusted on the ultrasound machine. True or false?

True

What is time gain compensation?

Multiple channels corresponding to depth

Can the focal zones on an ultrasound machine be adjusted?

Yes

What two parameters are focal zones on an ultrasound machine adjusted by?

- Depth | - Number

Where are images from ultrasound machine usually stored? | Name three

- Hard drive - CD - DVD

What two formats are images stored in?

- TIFF | - JPG

What two things is resolution dependent on?

- Frequency | - Beam focal width

What are the items to consider when selecting an ultrasound system? (6 items)

- Resolution and image clarity - Portability - Doppler capability - Storage capacity - Speed - Ease of connection of peripheral devices

The History Of Ultrasound And Physics Flashcards

(105 cards)