Chapter 1 Flashcards by Amanda Rex McLain

Change in the direction of propagation of a sound wave transmitted across an interface where the speed of sound varies

Refraction

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Angle at which a sound beam strikes the interface b/w two types of tissue

Angle of incidence

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Power per unit area

Intensity

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Special material in the transducer that has the ability to convert electric impulses into sound waves

Crystal

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Propagation of energy that moves back and forth or vibrates at a steady rate

Wave

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Any device that coverts energy from one form to another

Transducer

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Number of cycles per second that a periodic event or function undergoes

Frequency

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Measure of a materials resistance to the propagation of sound; expressed as the product of acoustic velocity of the medium and density of the medium

Acoustic impedance

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Generation of electric signals as the result of an incident sound beam on a material that has piezoelectric properties.

Piezoelectric effect

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Region over which the effective width of the sound beam is within some measure of its width at the focal distance

Focal zone

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Reduction in amplitude and intensity of a sound wave as it propagates through a medium

Attenuation

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Passive force in opposition to another, active force; occurs when tissue exerts pressure against the flow.

Resistance

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Surface forming the boundary between media having different properties

Interface

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Region of increased particle density

Compression

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Distance over which a wave repeats itself during one period of oscillation.

Wavelength

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Refers to the minimum distance between two structures positioned along the axis of the beam where both structures can be visualized as separate objects

Axial resolution

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Rate of energy flow over the entire beam of sound

Power

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Unit used to quantitatively express the ratio of two amplitudes or intensities

Decibel ( dB)

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1,000,000 Hz

Megahertz (MHz)

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Resolution

Ability of the transducer to distinguish between two structures adjacent to one another

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Time interval required for generating the transmitted pulse

Pulse duration

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Sequence of events occurring at regular intervals

Cycle

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Speed of the ultrasound wave; determined by tissue density

Velocity

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Minimum distance between two objects at which they still can be displayed as separate objects

Lateral resolution

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Unit for frequency; equal to one cycle per second

Hertz (Hz)

Field closest to the transducer during formation of the sound beam

Fresnel zone

Angle of incidence at which the sound beam strikes the interface

Angle of reflection

1000 Hz

Kilohertz (kHz)

Field farthest from the transducer during formation of the sound beam

Fraunhofer zone

Thickness of the section in a patient that contributes to echo signals on any one image

Slice thickness

Sound transmitted and received intermittently with one transducer

Pulse wave (PW) Doppler

Ability to compensate for attenuation of the transmittal beam as the sound wave travels through tissue in the body

Time gain compensation (TGC)

Change in frequency of a reflected wave; caused by motion b/w the reflector and the transducers beam

Doppler shift

One transducer continuously transmits sound, and one continuously receives sound; used in high velocity flow patterns

Continuous wave (CW) Doppler

Normal pattern of vessel flow; flow in the center of the vessel is faster than at the edges

Laminar

Rate at which images are updated on the display; dependent on transducer frequency and depth selection

Frame rate

Analysis of the entire frequency spectrum

Spectral analysis

Technical artifact that occurs when the frequency change is so great that it exceeds the sampling view and pulse repetition frequency

Aliasing

In pulse echo instruments, it is the number of pulses launched per second by the transducer

Pulse repetition frequency (PRF)

Ability of the system to accurately depict motion

Temporal resolution

Ratio of the largest to the smallest signals that an instrument or a component of an instrument can respond to without distortion

Dynamic range

In pulsed Doppler, the Doppler signal must be sampled at least twice for each cycle in the wave if Doppler frequencies are to be detected accurately

Nyquist sampling limit

Strength of the ultrasound wave measured in decibels

Amplitude

Measure of strength of the ultrasound signal

Gain

Echo fill-in of the spectral window that is proportional to the severity of stenosis

Spectral broadening

Ultrasound instrumentation that allows the image to be displayed many times per second to achieve a "real-time" image of anatomic structures and their motion patterns

Real time

B-mode scanning technique that permits the brightness of the b-mode dots to be displayed in various shades of gray to represent different echo amplitudes

Gray scale

Amount of change in the returning frequency compared with transmitting frequency when the sound wave hits a moving target such as blood in an artery

Frequency shift

Sample site from which the signal is obtained with pulsed Doppler

Gate

Angle that the reflector path makes with the ultrasound beam; the most accurate velocity is recorded when the beam is parallel to flow

Doppler angle

Acoustics is the study of what?

Generating, propagating, and receiving sound waves

Ultrasound is defined as sound frequencies beyond the upper limits of human hearing, that is, greater than how much?

20 kHz

Name three pioneers who made a significant contribution to ultrasound

Augustine Fresnel(wave optics), Christian Johann Doppler (Doppler effect), Curie brothers (piezoelectricity), Richard Cushman (B-mode)

The terms --------------,-------------, and ---------------- have all been used to describe an image technique by which soft tissue structures of the body are visualized by recording the returning reflection of ultrasonic waves directed into the body

Ultrasound, ultrasonography, and diagnostic medical ultrasound

The term that applies to the ultrasound evaluation of cardiac structures is what

Echocardiography

One who performs ultrasound studies and gathers diagnostic data under the direct or indirect supervision of a physician is a

Sonographer

List the qualities of a good sonographer

Good physical health, dedication, communication, perseverance, intellectual curiosity, quick and analytical mind, ability to conceptualize 2d images into 3d images

As a ceramic element vibrates, it periodically presses against and pulls away from the adjacent medium with resultant particle -------------- and ----––--------- in the medium.

Compression, rarefaction

A propagation of energy that moves back and forth or vibrates as a a steady rate is a

Wave

A transducer converts –-––------------ energy into –-––––---------energy.

Electrical, mechanical

The time required to produce each cycle depends on the --------------- of the transducer.

Frequency

The distance b/w two peaks over a period of time is the

Wavelength

Wavelength is inversely related to frequency, which means that the higher the frequency, the -------------- the wavelength.

Shorter

As frequencies become higher, the pulse duration ---------------, yielding a decrease in the depth of field.

Decreases

The rate at which energy is transmitted is referred to as the

Power

Power per unit area is defined as

Intensity

If you double the power, the intensity --------------------.

Doubles

The piezoelectric effect was first described by the ---------------- brothers in 1880.

Curie

Air filled structures, such as lungs and the stomach , or gas- filled structures, such as bowel, ----------------- sound transmission.

Impede

Bone conducts sound at a ----------------- speed than soft tissue

Faster

Normal transmission of sound through soft tissue travels at --------- m/sec.

1540

Acoustic impedance is the product of the ------------------------ in a medium and the density of that medium.

Velocity of sound

The angle of reflection is equal to the

Angle of incidence

If specular reflectors are aligned ------------------- to the direction of the transmitted pulse, they reflect sound directly back to the active crystal elements in the transducer and produce a strong signal.

Perpendicular

The sum of acoustic energy losses resulting from absorption, scattering, and reflection is the

Attenuation

Minimum reflector separation along the sound path required to produce separate echoes

Axial resolution

What resolution is the ability to produce separate echoes perpendicular to the sound; it is affected by transducer diameter and focusing

Lateral resolution

Lateral resolution is determined by what

Beam width

What resolution refers to the ability to resolve objects that are the same distance from the transducer but are located perpendicular to the plane of imaging.

Azimuthal resolution

Identify 3 criteria that determine the type of transducer selected for a particular exam

Size of patient, examination, amount of fatty and muscular tissue

The number of pulses launched per second is the

Pulse repetition frequency

If the gain is set to -------------------, artifactual echo noise will be displayed throughout the image.

High

A one-dimensional image displaying the amplitude strength of returning echo signals along the vertical axis and the time (distance) along the horizontal axis is produced by what

Amplitude modulation

The intensity (amplitude) of an echo attained by varying the brightness of a dot to correspond to echo strength is displayed by what method

Brightness modulation method

The condition of assigning each level of amplitude a particular shade of gray is referred to as the what

Gray scale

What mode displays time along the horizontal axis and depth along the vertical axis to depict movement, especially in cardiac structures

Motion mode

A dynamic presentation of multiple image frames per second over selected areas of the body is provided by what imaging

Real time imaging

With pulsed Doppler, for accurate detection of Doppler frequencies, the Doppler signal must be sampled at least how many times for each cycle in the wave

Twice

When the Nyquist limit is exceeded, an artifact called what occurs

Aliasing

1856-1906 piezoelectric effect

Curie brothers

"Doppler effect" 1803-1853

Christian johann Doppler

Theory of wave optics, and wave diffraction

Augustine fresnel (1788-1827)

B-mode ultrasonography, pan scanner (1957)

Richard Cushman

M-mode motion display (1954)

Hertz and Edler

Obstetric contact compound scanner (1910-1987)

Tom Brown and dr. Ian Donald