Week 3 // UTZ Interaction and Attenuation Flashcards
also known as tissue interface
acoustic boundaries
position within the tissue where the values of acoustic impedance change
acoustic boundaries
weakening of the sound as it propagates through a medium
attenuation
reduction in amplitude and intensity as sound travels
attenuation
unit of attenuation
decibel
2 factors affecting attenuation
medium
frequency
attenuation that occurs with each centimeter the sound wave travels
attenuation coefficient
for soft tissues, the typical value for attenuation coefficient is ____
0.5 dB/cm
term used to describe the average tissue that makes up the soft tissues of the human body
soft tissue
5 types of attenuation
absorption
reflection
scattering
refraction
divergence
converted to heat
absorption
back to the transducer
reflection
reflected in multiple directions
scattering
redirection of part of the sound beam
refraction
power spread over a large area
divergence
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
The dominant factor contributing to attenuation of ultrasound in soft tissues.
absorption
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
the major interaction of interest for diagnostic ultrasound
reflection
the sound that hits an acoustic interface
incident energy
reflected beam
echo
reflectors can either be
specular
diffuse
reflector that occurs when the boundary is smooth and larger than the beam
specular reflector
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
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
