transducer frequency is ___ proportional to penetration and directly proportional to
resolution - ANSWER inversely
name three things that are inversely proportional to transmitted frequency -
ANSWER beam width, spatial pulse length and pulse duration
,Annular array - ANSWER 5 concentric ring shaped piezoelectric elements that
produces a cylindrical beam (sector shaped image)
requires mechanical steering
with an annular phased array outer elements image ___. Central elements image
____. - ANSWER outer - image deeper structures
inner elements- superficial structures
sequential linear array - ANSWER AKA switch array
200 rectangle elements across face of transducer
parallel acoustic lines are transmitted sequentially
uses mechanical focusing (curved lense or crystal)*
what transducer has the same field of view in near and far fields ( no trapezoid FOV)
- ANSWER switched array (sequential linear array)
linear phased array - ANSWER contains 200 elements
elements fired at varied times to allow for electronic focusing & beam steering
phasing creates trapezoidal FOV
curved sequential array - ANSWER similar construction & function as a sequential
linear array
no beam steering
blunted sector FOV
Requires mechanical focusing
curved linear phased array - ANSWER AKA
curvilinear array or convex array
contains a large number of linearly arranged piezoelectric elements (120-250)
sequentially pulsed transducer elements
produced blunted/ curved sector image with a larger near field footprint
uses electronic focusing & steering
sector phased array - ANSWER small footprint with a large number of linearly
arranged rectangular piezoelectric elements
triangle shape created by electronic steering
vector array - ANSWER combine sequenced linear array and phased array
techniques to provide a trapezoidal image. larger footprint than phased array
Harmonic imaging - ANSWER a low frequency beam is transmitted into the patient
but the system displays the received information as double the frequency
5mhz transmitted = 10 MHz displayed
what does harmonic imaging allow - ANSWER deeper penetration with lower
transmitted frequency and improved lateral resolution with increased received
frequency
, harmonic imaging has what sized beam width? - ANSWER provides a narrow beam
width to reduce side lobe/grating lobe artifact
what is axial resolution and what does it improve with? - ANSWER ability to resolve
two separate structures that lie parallel to the ultrasound beam
improves with higher transducer frequency, wider bandwidths and shorter pulse
lengths
lateral resolution and what does it improve with - ANSWER ability to resolve two
separate structures that lie perpendicular to one another
improves with higher frequency, beam focusing, wider bandwidths and more
superficial structures
contrast resolution - ANSWER ability to differentiate two structures with varied
echogenicity
compression will change the contrast resolution of the image
increasing compression and the dynamic range will - ANSWER allow more shades
of gray - increased contrast resolution
educational resolution - ANSWER AKA slice thickness resolution
improves with thinner image slices
most difficult to adjust
what improves elevational resolution - ANSWER increased transducer frequency &
focusing
temporal resolution - ANSWER the ability to detect that an object has moved over
time
a decreased temporal resolution causes the image to lag
how to improve temporal resolution - ANSWER decreased focal zones
smaller field of view
decreased imaging depth
decreased line density
external/mechanical focusing - ANSWER lens placed inside the transducer in front
of the element to focus the beam before it exits the transducer
internal or electronic focusing - ANSWER varied timing of the pulser voltage used
to vary the firing of elements in an array
used to steer the beam, helps to visualize needles during procedures
Hard copy storage - ANSWER any kind of film
thermal paper
Kodak glossy printers
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