Chapter 2 Penny Flashcards
the diameter of the piezoelectric element(s) producing the beam
aperture
the transducer with multiple active elements
array
same as real-time ultrasound
automatic scanning
the ability to accurately identify reflectors that are arranged parallel to the ultrasound beam
axial resolution
the damping material of the transducer assembly, which reduces the number of cycles produced in a pulse
backing material
the range of frequencies present within the beam
bandwidth
occurs when in-phase waves meet; the amplitudes of the two waves are added to form one large wave
constructive interference
the ability to differentiate one shade of gray from another
contrast resolution
a synonym for the active element of the transducer, the piezoelectric part of the transducer assembly that produces sound
crystal
the temperature at which an ultrasound transducer will gain its piezoelectric properties, and also the temperature at which a transducer will lose the ability to produce sound if heated again above this temperature
curie point
the transducer commonly referred to as a curvilinear or convex probe
curved sequenced array
the process of reducing the number of cycles of each pulse in order to improve axial resolution
damping
same as backing material; the part of the transducer assembly that reduces the number of cycles produced in a pulse
damping material
the inability to determine the depth of the reflector if the pulses are sent out too fast for them to be timed
depth ambiguity
occurs when out-of-phase waves meet; the amplitude of the resultant wave is smaller than either of the original waves
destructive interference
spreading of the beam that occurs in the far zone
divergence
the piezoelectric part of the transducer assembly that produces sound
element
slice-thickness plane
elevational plane
the resolution in the third dimension of the beam
elevational resolution
the diverging part of the beam distal to the focal point
far zone
the area of the beam with the smallest beam diameter
focal point
the portion of the transducer that is in contact with the patient’s skin
footprint
three-dimensional ultrasound in real-time
4D ultrasound
one complete ultrasound image
frame
the number of frames per second
frame rate
far zone
Fraunhofer zone
the number of cycles per second
frequency
the number of cycles per second
frequency
near zone
Fresnel zone
states that waves are the resultant of the interference of many wavelets produced at the face of the transducer
Huygen’s principle
waves whose peaks and troughs overlap
in-phase
the ability to accurately identify reflectors that are arranged perpendicular to the ultrasound beam
lateral resolution
the man-made ceramic of which many transducer elements are made; abbreviated PZT
lead zirconate titanate
the transducer commonly referred to as the linear probe or transducer
linear sequenced array
the component of the transducer that is used to step down the impedance from that of the element to that of the patient’s skin
matching layer
transducer that acquires real-time volumes using up to 10,000 elements, compared to the 128-512 elements used in a standard 1D array transducer
matrix array transducer
transducers with a motor for steering the beam
mechanical scanheads
the part of the beam between the element and the focal point
near zone
the length of the region from the transducer face to the focal point
near-zone length
waves that are 180 degrees opposite of each other; the peak of one wave overlaps the trough of the other and vice versa
out-of-phase
transducer that uses phasing, or small time differences, to steer and focus the beam
phased-array
the method of focusing and/or steering the beam by applying electrical impulses to the piezoelectric elements with small times differences between shocks
phasing
the ability to convert pressure into electricity and electricity into pressure
piezoelectric
a measure of beam purity; the operating frequency of the transducer divided by the bandwidth
Quality factor
the ability to determine how far away a reflector is so it can be displayed on the screen
range resolution
without range resolution, there is _______.
depth ambiguity
live ultrasound, also known as automatic scanning
real time
the alternatively expand and contract
resonate
created when one or more pulses of sound return from the tissue containing information related to the depth and amplitude of the reflectors
scan lines
slice thickness plane
section thickness plane
the ability of a system to display low-level or weak echoes
sensitivity
the third dimension of the beam
slice-thickness plane
the length of the pulse
spatial pulse length
the ability of the system to distinguish between closely spaced objects; refers to axial, lateral, contrast, and elevational resolution
spatial resolution
allows the user to see width, height, and depth; may also be referred to as volume scanning
3D Ultrasound
ability to display moving structures in real time; also known as frame rate
temporal resolution
any device that converts one form of energy into another; may also refer to the part of the ultrasound machine that produces sound
transducer
component of the backing material
tungsten
the leading edge of a wave which is perpendicular to the direction of the propagating wave; formed as a result of Huygen’s principle
wavefront
a small wave created as a result of Huygen’s principle
wavelet
F0 = c / 2 x thickness
operating frequency
provides insulation and protection from electrical shock
housing
used to transfer electrical signals to and from the transducer
wire
Advantages of Damping
decreases the number of cycles in a pulse
decreases SPL
improves axial resolution
Side effects of Damping
decreases sensitivity of the transducer
increases the bandwidth
reduces the quality factor
Q = Fo / Bandwidth
Quality Factor
Rectangular shaped image
firing is sequenced
electronic steering available
electronically focused
used for vascular and high-resolution imaging
linear sequenced array
curved shaped image
firing is sequenced
electronically focused
used for abdominal, gynecology, and obstetrics imaging
curved sequenced array
vector or sector shaped imahe
electronic phased steering and focus
used for cardiac, abdominal, neonatal imaging, and endocavity transducers
phased array
Synonyms for axial resolution
Longitudinal
Axial
Radial
Range
Depth
Synonyms for lateral resolution
lateral
angular
transverse
azimuthal
SPL = ^n
Spatial Pulse Length
^ = c / f
wavelength
AR = 1/2SPL
axial resolution
at a distance of one near-zone length, the beam diameter is equal to _______ of the diameter of the element
one-half
at a distance of two near zone lengths, the beam diameter again _____ the element diameter
equals
If frequency increases, NZL ______
increases
If NZL increases, divergence in the far field ________
decreases
if aperture increases, NZL _______
increases
if aperture increases, divergence in the far field ______
decreases
FR = PRF / LPF
frame rate
most commonly used man made piezoelectric element
lead zirconate titanate
328 - 365 degrees celcius
curie point
Naturally occuring piezoelectric materials
quartz
tourmaline
the thicker the element, the _______ the frequency
lower
the thinner the element, the ________ the frequency
higher
also known as center or operating frequency
resonating frequency
Resonating frequency medical diagnostic ultrasound transducer
2-15 MHz
composed of epoxy resin loaded with tungsten
backing material
2 methods of sending out scan lines to form an image using real time
mechanical scanning
electronic scanning
Major advantages of mechanical scanheads
inexpensive
small footprint
Major disadvantages of mechanical scanheads
fragile
mechanical elements were easily broken
flat-topped trapezoidal image
vector
all scan lines originate from a common point of origin
sector phased array
3 different ways to create 3D image
freehand
mechanical transducer
electronically
spatial resolution can be divided into four components:
axial, lateral, elevational, contrast
represents time
Temporal Resolution
3 adjustments that can be made to alter frame rate in gray-scale imaging
image depth (PRF)
number of focal zones
number of scan lines per frame or line density
PRF is __________ to frame rate
directly relatedT
The higher the line density, the ______ the temporal resolution
worse
FR = PRF / number of lines per frame
Frame rate
In PW operation, the ___________ is the primary determinant of the resonating frequency of the transducer.
thickness of the element
The diameter of the beam is determined by both the ______ and the ______.
frequency
aperture
Most transducers have better ______ resolution than ______ resolution
axial
lateral
The impedance of the matching layer is ______.
an intermediate value between the transducer element and tissue
If the aperture increases, the near-zone length ______.
remains unchanged
The dimension perpendicular to the scan plane is called ______.
section thickness
Electronic scanning is performed by _____ transducers.
array
