Physics

Front 1

Curie temperature

Back 1

the temperature at which the PZT is polarized, 365̊, do not autoclave, do not heat above Curie temp.

Front 2

Piezoelectric effect

Back 2

describes the property of certain materials to create a voltage when they are mechanically deformed. This happens upon reception of the beam.

Front 3

Matching Layer

Back 3

decreases reflections at the PZT/skin boundary, thereby increasing the percentage of transmitted sound between the active element and the skin. ¼ wavelength thick

Front 4

Passband

Back 4

the range of frequencies which equipment is designed to handle, relates to the bandwidth.

Front 5

Q factor

Back 5

unitless, mechanical coefficient, assesses axial resolution and bandwidth.

Front 6

Low Q Factor

Back 6

Short pulse, high damping, improved axial resolution, desirable in PW, most energy is lost during first few vibrations (cycles), seen with broad bandwidth.

Front 7

High Q Factor

Back 7

Longer pulse, low damping, poorer axial resolution, stores energy in crystal, rings for a long time, seen with narrow bandwidth.

Front 8

Bandwidth

Back 8

range or difference between the highest and lowest frequencies in the pulse, imaging probes: are identified as short pulse, wide bandwidth
other probes: no backing material, long pulse, narrow bandwidth.

Front 9

Pulse length

Back 9

the distance that a pulse occupies in space from the start to the end of a pulse. The length of the “on time”, has units of distance

Front 10

Resonant Frequency

Back 10

“natural frequency”, determined by element thickness, aka operating frequency, dominant frequency.

Front 11

Central Frequency

Back 11

frequency with highest amplitude, should be near or equal to the resonant frequency

Front 12

Nominal Frequency

Back 12

“named frequency” should be near resonant frequency, 3.5 MHz vs. 3.55 MHz

Front 13

Axial Resolution

Back 13

parallel to the beam, minimum separation of 2 targets, limited by SPL, uniform along beam, SPL/2,
SPL= ƛ*N
-TX frequency, bandwidth, damping.

Front 14

Damping

Back 14

AKA: backing, insulation. Supports the element, absorbs sound
made of araldite, epoxy and tungsten powder.
Rapid energy removal, reduces pulse length, increases frequencies range, used in PW TX.
Reduces TX sensitivity, 2 types Passive and Dynamic.

Front 15

Lateral Resolution

Back 15

perpendicular to beam axis, minimum separation of 2 targets, limited by bandwidth, varies along beam,

Front 16

Matching Layer

Back 16

intermediate Z value, between TX and tissue, reduces reflection, improves transmission, ¼ wavelength, reinforces resonant frequency, shortens SPL, increases sensitivity
may be multi-layer, broadens frequency bandwidth, increases sensitivity, improves image quality, shortens SPL.

Front 17

Huygen’s Principle

Back 17

summation of wave patterns generated by many individual point sourses.

Front 18

Coefficient (like k, l, etc.)

Back 18

Transmission coefficient-indicates amount of electrical energy converted to acoustical energy “H”
Reception Coefficient- amount of returning acoustic energy that is converted to electrical energy “G”
Coupling Coefficient- Convert electrical stimuli into US energy and convert received US energy into electrical energy.