Week 3 // UTZ Interaction and Attenuation Flashcards by MA. ANNE JARDINIANO

also known as tissue interface

acoustic boundaries

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position within the tissue where the values of acoustic impedance change

acoustic boundaries

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weakening of the sound as it propagates through a medium

attenuation

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reduction in amplitude and intensity as sound travels

attenuation

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unit of attenuation

decibel

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2 factors affecting attenuation

medium
frequency

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attenuation that occurs with each centimeter the sound wave travels

attenuation coefficient

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for soft tissues, the typical value for attenuation coefficient is ____

0.5 dB/cm

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term used to describe the average tissue that makes up the soft tissues of the human body

soft tissue

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5 types of attenuation

absorption
reflection
scattering
refraction
divergence

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converted to heat

absorption

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back to the transducer

reflection

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reflected in multiple directions

scattering

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redirection of part of the sound beam

refraction

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power spread over a large area

divergence

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Process by which energy in the ultrasound beam is transferred to the propagating medium, where it is transformed into a different form of energy, mostly heat. The medium is said to absorb energy from the beam.

absorption

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The dominant factor contributing to attenuation of ultrasound in soft tissues.

absorption

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Occurs when two large structures of significantly different acoustic impedance form an interface, the interface
becomes a reflector and some of the wave energy is reflected back to the transducer. The energy remaining in the wave is decreased.

reflection

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the major interaction of interest for diagnostic ultrasound

reflection

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the sound that hits an acoustic interface

incident energy

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reflected beam

echo

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reflectors can either be

specular
diffuse

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reflector that occurs when the boundary is smooth and larger than the beam

specular reflector

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reflector that occurs when the reflecting interface is irregular in shape and its dimensions are smaller than the diameter of the ultrasound beam

diffuse reflector

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Occurs when an ultrasound waves strikes a boundary or interface between 2 small structures and the wave is scattered in different directions.

scattering

is responsible for providing the internal texture of organs in the image

scattering

when the scatter in equal in all direction

rayleigh scattering

the change in direction of a sound beam as it enters the medium

refraction

transmission with a bend

refraction

physics of refraction are described by ______ law

physics of refraction are described by SNELL'S LAW

two requirements for refraction to occur

oblique incidence different propagation speed

As a beam of ultrasound travels through it will diverge. This divergence will result in the same power spread over larger area. The intensity of the beam will therefore be reduced.

divergence

converts one form of energy to another from electrical energy to ultrasound energy

transducer

5 compositions of transducer

physical housing electrodes piezoelectric elements backing material impedance matching layer

Contains all the individual components including the crystals, electrodes, matching layer, and backing material.

physical housing

provides structural support and acts as an electrical and acoustic insulator

physical housing

are connected to the UTZ machine which generates the short burst of electrical pulses to excite the crystals

electrodes

outside electrode

grounded electrode

inside electrode

live electrode

transducer element, active element, crystals

piezoelectric element

crystalline materials composed of dipolar molecules

piezoelectric element

naturally occurring material with piezoelectric properties

quartz

man made ceramic, more efficient, better sensitivity and can be easily shaped

lead zirconate titanate

to press

Piezo

Elektron

amber

was described 1880 by Pierre and Jacques Curies

piezoelectricity

Derived from the Greek term Piezo (to press) and Elektron (amber, which is an organic plant resin that was used in early electrical study).

piezoelectricity

States that some materials produced a voltage when deformed by an applied pressure.

piezoelectricity

eliminate the vibrations from the back face and to control the length of vibrations from the face of the crystals

backing/damping material

consists of tungsten powder and plastic or epoxy resin

backing/damping material

sandwiched between the piezoelectric crystal and the patient

matching layer

has acoustic impedance value halfway between that of the crystal and soft tissue

matching layer

Area through which the sound energy emitted from the transducer travels.

ultrasound beam

2 regions of UTZ beam

near field/Fresnel far field/Fraunhofer

Region nearest the transducer face, characterized by a highly collimated beam with more uniform intensity.

near field Fresnel zone

Region farthest from the transducer and characterized by the divergence of the beam with great variation in intensity.

far field Fraunhofer zone

The location where the beam reaches its minimum diameter

focus or focal point

Energy from the transducer that radiates at various angles from the transducer face.

side lobes

the arrangement of crystals within the transducer

array

3 types of electronic array transducer

linear curvilinear/sector phased

refers to the physical size of the part of the ultrasound that contacts the patients

footprint

is the width of the image that is seen on the screen

field of view

array that produces parallel scan lines and has a rectangular field of view

linear array

array that extensively used for vascular, small parts and musculoskeletal applications

linear array

array used to image superficial structures and vessels and therefore operate at frequencies above 4MHz

linear array

Similar to the linear array but the transducer face is formed into a curve (convex in shape) which provides a wide field of view which diverges with depth.

curvilinear/sector array

array that is main application are in abdominal and obstetric scanning

curvilinear/sector array

Transducer designed to enter the body via the vagina, rectum, esophagus or a blood vessel (catheter-mounted type)

invasive transducer

Quartz - _____ Ba. Titanate - ______ PZT-4 - ______ PZT5A - _______

Quartz - 573°C Ba. Titanate - 100°C PZT-4 - 328°C PZT5A - 365°C

is the temperature at which polarization in a crystal is lost

curie point

is a more through cleaning method that often recommended for cleaning endocavitary probes after use

high level disinfection (HLD)

protect probes from contamination and the patient from potential infection

probe covers and sheaths

usually an aqueous gel improves sound transmission into and out of the patient by eliminating air reflection

coupling medium

composition of coupling medium

EDTA Carbomer Propylene glycol Trolamine Distilled Water