Lecture 12 Flashcards
Sound can ____/______
Converge/diverge
Sound is _______ and is not ______ 0r _______
A mechanical wave
Is not ionizing radiation
Is not electromagnetic
Transducer assembly aka _____ or______
Probe
Scan head
Probe made of (4)
Element, damping material, matching layers, and case
What does transduce mean
Convert one form of energy into another
Converse piezoelectric effect
Turning pulse/echo into voltage
Reverse piezoelectric effect
Turning voltage into pulse/echo
Piezo-electric element aka
Crystale
Adding a voltage causes thickness of ____ to change. This creates a ____
Element
Mechanical wave
1 cycle of alternating voltage —>
2/3 cycles of pulse
Longer alternating voltage ==
Longer pulse (doppler )
Returning echo affects the _____ and this creates a ______
Element
Voltage
What is one of the first natural piezoelectric crystals
Quartz
We now make synthetic crystals with which types of ceramics
Lead
Zirconate
Titanate
Barium
Electric elements are usually made of _____
Lead zirconate titanate
Lead zirconate titanate is aka
PZT
We make PZT piezo electric my
Placing it in a strong magnetic feild at a high temp (350) which realigns its molecular dipoles
When piezo electric elements are heated, what happens
The molecules spread out
When piezo electric elements are polarized, what happens
The dipoles align
piezo electric elements are cooled while in
Magnetic field
What is the curie point
The temp in which the magnetic properties of a solid can be changed
The curies point of PZT is
350 degrees
piezo electric element has a ________ frequency
Natural vibrational frequency
The natural frequency of piezo electric element can also be called (3)
Fundamental freq
Operational freq
Resonance freq
Operating frequency depends on ____
Element
Propogation speed of PZT element
4 mm/us
Thickness of element
Th
0.2-1 mm
2 x th = ______
Wavelength
To get different frequencies we would have to
Change crystals/transducers
In present day systems, they are bit more complex and can uses the _________ to adjust the transducer frequency
Voltage frequency
With pulsed wave we are dealing wiht a ______
Bandwidth
2 or 3 freq on the same element =
Multihertz operation
PRF of voltage also affects PRF of
Pulse
Piezo-electric element is inversely proportional to
Depth
If you need to go farther down you must _______ PRF
Decrease
If PRF is not decrease when trying to go deeper you get
Range ambiguity / echo misplacement
For 2d ultrasound ______ automatically accomodates
Depth