SPI Review Penny & Fox chapter 2
formula for the frequency of the transducer for pulsed-wave operation
Fo= c/2 x slice thickness
formula for quality factor
Q-factor = Fo/bandwidth
tungsten
component of the backing material
scan lines
crated when one or more pulses of sound return from the tissue containing infromation related to the depth and amplitude of the reflectors
3 side effects of damping
decreases sensitivity of the transducer. increases the bandwidth. reduces the quality factor.
3 Advantages to damping
decreases the number of cycles in a pulse. decreases spatial pulse length. improves axial resolution.
real tim
live ultrasoun, also known as automatic scanning
purpose of a crystal
material that produces diagnostic ultrasound; composed of piezoelectric material, most commonly lead zirconate titanate; converts electrical energy into acoustic energy during transmission and acoustic energy into electrical energy during reception
fresnel zone
near zone
constructive interference
occurs when in phase waves meet; the amplitudes of the 2 waves are added to form one large wave
destructive interference
occurs when out-of-phase waves meet; the amplitude of the resultatn wave is smaller thaneither of the original wave
frame
one complete ultrasound image
range resolution
the ability to determine how far away a reflector is so it can be displayed on the screen; withut range resolution there is depth ambiguity
contrast resolution
the ability to differentiate one shade of gray from another
focal point
the area of the beam with the smallest beam diameter
matching layer
the component fo the transducer thaqt is used to step down the impedance from that of the element to that of the patients skin
backing material
the damping material of the transducer assembly, which reduced the number of cycles produced in a pulse
aperature
the diameter of the piezoelectric elements producing the beam
far zone
the diverging part of the beam distal to the focal point
depth ambiguity
the inability to determine the deoth of the reflector if the pulses are sent out too fast for them to be timed
wavefront
the leading edge of a wave which is perpendicular to the direction of the propagation wave; formed as a result of Huygen's principle
spatial pulse length
the length of the pulse
near-zone length
the length of the region from the transducer face to the focal point
lead ziconate titanate
the man-made ceramic of which many transducer elements are made; abbreviated PZT
phasing
the method of focusing and/or steering the beam by applying electrical impulses to the piezoelecgtric elements with small time differences between shocks
frequency
the number of cycles per second
frame rate
the number of frames per second
near zone
the part of the beam between the element and the focal point
element
the piezoelectric part of the transducer assembly that produces sound
footprint
the portion of the transudcer that is in contact with the patient's skin
damping
the process of reducing the number of cycls of each pulse in order to improve axial resolutino
bandwidth
the range of requencies present within the beam
elevational resolution
the resolution in the third dimenion of the beam; the slice-thickness plane
curie point
the temperature at which an ultrasound transducer will gain its piezoelecgtric propertiies, and also the termparture at which a transducer will lose the ability to produce sound if heated again above this temperature
curved sequenced array
the transducer commonly referred to as a curbillinear or convex probe
phased array
the transducer that uses phasing, or small time differences, to steer and focus the beam
array
the transducer with multiple active elements
linear sequenced array
the transudcer commonly referred to as the linear probe of the transducer
slice-thickness plane
third dimenion of the beam
four-dimensional ultrasound
three-dimensional ultrasound in real time
resonate
to alternatively expand and contract
matrix array transducer
transducere that acquires real-time volumes using up to 10,000 elements, compared to the 128 to 512 elements used in standard 1D array transducers
mechanical scanheads
transducers with a motor for steering the beam
purpose of matching layer
used to step down the impedance from that of the element to that of the patient's skin
purpose of wire
used to transfer electrical signals to and from the transducer
out-of-phase
waves that are 180 degrees opposite each other; the peak of one wave overlaps the trough of the other and vice versa
in-phase
waves whose peaks and troughs overlap
Formula for wavelength
speed/frequency
divergence
spreading of the beam that occurs in the far zone
Huygens principle
states that waves are the results of the interference of many wavelets produced at the face of the transducer
sensitivity
the ability of a system to display low-level or weak echoes
spatial resolution
the ability of the system to distinguish between closely spaced objects; refers to axial, lateral, contrast, and elevational resultion
axial resolution
the ability to accurately identify reflectors that are arranged parallel to the ultrasound beam
lateral resolution
the ability to accuratley identify reflectors that are arranged perpendicular to the ultrasound beam
piezoelectric
the ability to convert pressure into elecricity and electricity into pressure
formula for frame rate
FR = PRF/LPF (lines per frame)
synonyms for axial resolution
LARRD longitudinal, axial , range, radial, depth
synonyms for lateral resolution
LATA lateral, angular, transverse, azimuthal
spatial pulse length formula
SPL = # of cycles x wavelength
axial resolution formula
SPL/2
quality factor (Q-factor)
a measure of beam purity; the operating frequency of the transducer divided by the bandwidth
wavelet
a small wave created as a result of Huygen's principel
crystal
a synonym for the active element of the transducer, the piezoeelctric part of the transucer assembly that produces sound
temporal resolution
ability to display moving structures in real time; also known as frame rate
three-dimensional ultrasound
allows the user to see width, height, and depth; may also be referred to as volume scanning
info about curved sequenced arrays
also referred to as a convex, curvilinear, or cuved sequential array. curved-shaped image firing is sequenced electronically focused used for abdominal, gynecology, and obstetrics imaging
info about phased array
also referred to as a sector or vector transducer vector- or sector-shaped image electronic phased steering and phased focusing used for cardiac, abdominal, neonatal imaging, and endocavity transducers
info about linear sequenced array
also reffered to as a linear sequential array or linear array. rectangular-shaped imaghe firing is sequenced electronic steering available electronically focused used for vascular and high-resolution imaging.
transducer
any device that converts one form of energy into another; may also refer to the part of the ultrasound machine that produces sound
characteristics of an ultrasound single-element transducer
at the face of the transducer, the beam diameter is equal to the element diameter at a distance of one near-zone length, the beam diameter is equal to one half of the diameter of the element at a distance of two near-zone lengths, the beam diameter again equals the element diameter
fraunhofer zone
far zone
Relationship between aperture, near zone length, and divergence in the far field
increase aperture= increase NZL= decrease divergence in far field
Summary of the effects of damping on the pulse
increase damping = decrease spatial length = increase bandwidth = decrease Q-factor = better axial resolution
Relationship between frequency, near zone length, and divergence in the far field
increase frequency= increase NZL = decrease in divergence in far field
purpose of housing
provides insulation and protection from electrical shock
damping material
same as backing material; the part of transducer assembly that reduces the number of cycles produced in a pulse
automatic scanning
same as real-time ultrasound
purpose of backing material
shortens the length of the pulse by decreasing the number of cycles in the pulse
synonyms for elevational resolution
slice- or section- thickness plane resolution
elevational plane
slice-thickness plane
section-thickness plane
slick-thickness plane
