Part II Flashcards by Queenie Francisco

Function of the distance to the UTZ machine
Penetration into the deeper tissues [longer it takes, deeper]

Depth

How well did you know this?

Not at all

Perfectly

Volume of returning echo/intensity
The louder the return echo, the brighter [quiter, darker]

Brightness

How well did you know this?

Not at all

Perfectly

-provide energy to crystal
-known as the pulses
-function: control the rate of pulses emitted by the transducer or PRF & provides voltage

Transmitter

How well did you know this?

Not at all

Perfectly

-produces and detects UTZ
-where piezoelectric effect occurs

Transducer

How well did you know this?

Not at all

Perfectly

-range of frequency produced by a given transducer
-if broad - improve CR
-if narrow - speckle

Bandwidth

How well did you know this?

Not at all

Perfectly

-“pressure electricity”

Piezoelectric

How well did you know this?

Not at all

Perfectly

Explain PIEZOELECTRIC EFFECT

Electricity is applied to piezoelectric material → vibrates (expands & contracts) to produce mechanical sound or pressure waves → reflected waves (echoes) go back to transducer, thus converting mechanical back to electrical

How well did you know this?

Not at all

Perfectly

Parts of a transducer

Physical housing
Electrica connections
Piezoelectric Elements
Backing Material
Acoustic Lens
Matching Layers

How well did you know this?

Not at all

Perfectly

Structural support of the transducer that serves as the electrical and acoustic insulator

Physical Housing

How well did you know this?

Not at all

Perfectly

Placed in front & back of crystal
Thin film of Ag and Au

Electrical Connections

How well did you know this?

Not at all

Perfectly

-discovered by Jacques an Pierre (1820)
-mechanical force will induce some material to be electrically polarized

Piezoelectric Element

How well did you know this?

Not at all

Perfectly

Piezoelectric element can be destroyed by exceeding beyond the [..]

Curie Temperature

How well did you know this?

Not at all

Perfectly

Act as an electrode for non conducting piezoelectric element

Thin silver on sides

How well did you know this?

Not at all

Perfectly

Reason for mechanical vibration: [..]

Crystal change in shape/produce sound waves

How well did you know this?

Not at all

Perfectly

Piezoelectric Element
Natural: [..]
Man-made: [..]

Quartz - first material used,
Tourmaline - black mineral/prism crystals in granites and rocks
Rochelle Salt/ Potassium Sodium Tartrate Tetrahydrate
PZT- Lead Zirconate Titanate (also used in ceramic capacitors)
Barium Titanate -piezoelectric material for microphones and transducer
Lead Metaniobate - ceramics

How well did you know this?

Not at all

Perfectly

-used to clean transducer because alcohol disrupts transducer

Ethyleneoxide

How well did you know this?

Not at all

Perfectly

-reduce vibrating
-broadens the bandwidth and shorten the pulses
-improves axial resolution

Backing Material

How well did you know this?

Not at all

Perfectly

Composition of backing material

Tungsten/ rubber in epoxy resin

How well did you know this?

Not at all

Perfectly

Importance of backing material

Eliminate back face vibration
Control vibrations in front face

How well did you know this?

Not at all

Perfectly

-located in front of transducer
-reduce the beam width of the transducer
-improv lateral resolution

Acoustic Lens

How well did you know this?

Not at all

Perfectly

Materials of acoustic lens

Aluminum, Perspex, polystyrene

How well did you know this?

Not at all

Perfectly

-interface between transducer and the tissue
-minimize acoustic impedance differences between the transducer

Matching Layer

How well did you know this?

Not at all

Perfectly

-used between matching layer and patient’s skin to eliminate air pockets that could attenuate and reflect the UTZ beam
-hypoallergenic

Acoustic Coupling Gel

How well did you know this?

Not at all

Perfectly

Types of transducer

Linear Array (Sequential)
Phased Array
Curvilinear Array

How well did you know this?

Not at all

Perfectly

-produces beam by firing a subset of the total no of transducer elements as a group -individual beams interact to produce collimated array -f = 4 MHz

Linear Array (Sequential)

Linear Array example part of interests

Breast, thyroid, MSK, Obstetrics, Vessels

-produces a beam from all of the transducer elements fired with fractional time delays in order to steer and focus the beam -f = 2-7.5 MHz

Phased Array

-diverge and allow wider field of view -produce diverging images that originate in a curved arc -f = 3.5 MHz

Curvilinear Array

Curvilinear Array example part of interests

-abdominal and obstetrical scanning -deep lying structures

[utz beam properties] -adjacent to transducer -near field of UTZ beam -used for UTZ imaging

Fresnel Zone

[utz beam properties] -far field -UTZ imaging does not extend to this area

Fraunhofer Zone

-region over which the beam id focused

Focal Zone

Distance from transducer toward focal zone

Focal length

-converging beam profile -adjacent to the transducer face -equal to focal distance -at the end, region for best lateral resolution

Near Field

-diverging beam profile -Fraunhofer Zone -UTZ intensity decrease with distance

Far Field

Crystal relationship with near and far field

CRYSTAL NEAR FIELD FAR FIELD NARROW decrease Increase WIDE increase decrease

Frequency relationship with near and far field

FREQUENCY NEAR FIELD FAR FIELD INCREASE long less DECREASE short more

Types of Resolution

Spatial Resolution Axial/Longitudinal Lateral/Azimuthal Elevation Resolution Contrast Resolution Temporal Resolution

Ability to differentiate two closely situated objects lying along axis of beam

Spatial Resolution

Ability to separate two objects along axis of beam

Axial/Longitudinal Resolution

-resolution in the plane perpendicular to the beam and transducer -determined by slice thickness -transducer directly related to elevation

Elevation/Azimuth Resolution

Ability of imaging system to differentiate between body tissues and display them as different shades of gray

Contrast Resolution

Display events that occur at different times as separated images -frame rate

Temporal Resolution

Detects and amplifies voltage signals from the transducer

Receiver

-ability to compensate for attenuation of the transmitted beam as the sound wave travels through tissues in the body -signals compensate for differences in echo strength

Time Gain Compensation (TGC)

-adapts the dynamic range of backscattered signal intensity (returning echoes/to correspond to the dynamic range of the display

Compression and Remapping of Data

Ratio of the highest to lowest amplitude

Dynamic range

Display UTZ signals depends on the different operational modes CRT, LCD, LED

Image Display

Operational Modes

1. A- Mode 2. B- Mode 3. Real-time 4. M-mode

-Displays depth on the horizontal axis and echo intensity (pulse amplitude) on the vertical axis -Displayed in CRT -Echo, peaks and distance between various structures is measured -Reliable in Axial Resolution

Static Imaging A-mode (Amplitude)

-shows all the tissue travelled of the beam of UTZ scan -2D -appear as black and white images -shown as series of dots in CRT

Static Imaging B-Mode (Brightness)

-display changes in echo amplitude and position with time -eval of rapidly moving structures (cardiac valves, chamber walls) -ultrasonic cardiography -another way of displacing motion -time on the horizontal axis and depth on the vertical axis

Real Time Imaging/Time Mode TM/ M-Mode (Motion)/ Position Mode PM)

-2D, real time, gray scale -image is built by TZ pulses sent down a series of successive line scans -entire image is created 15-60 times per sec

Real Time Imaging B-Mode

He described Doppler Effect

Christian Johann Doppler

-based on Doppler effect -“UTS Stethoscope”

Doppler Mode

-change in a frequency resulting from moving sound source

Doppler Effect

Identification of blood flow vessels

Doppler Ultasound

Explain STATIONARY TARGET (Doppler Effect)

-If reflecting interface is stationary, the backscattered UTS has the same frequency or wavelength as transmitted sound -reflected and transmitted energy as equal

Explain TARGET MOTION towards transducer

-difference in reflected and transmitted frequencies in greater than zero

-use color map to display information based on the detection of frequent shifts from moving targets -determine vessel if artery of vein -shows arterial or venous supply of organ -full of noise, limited sensitivity

Color Flow Doppler Imaging (CD)

BART

Blue away, Red towards

-uses color map to show distribution of the power/amplitude of the Doppler signal -flow direction and velocity info are not provided -noise is reduced with improved sensitivity for flow detection

Power Mode Doppler

-reduces noice and scatter of image -improves spatial resolution

Tissue Harmonic Imaging

-combines images contained by isonating the target from multiple angles -improves contrast -speckle

Spatial Compunding

Part II Flashcards

(64 cards)