Transducers Flashcards Preview

Physics > Transducers > Flashcards

Flashcards in Transducers Deck (30):
0

Beam based imaging is what kind of resolution?

lateral resolution

1

Axial resolution is based on what?

SPL - spatial pulse length

2

What were the transducers of the past made of?

single crystal or element

fixed focus

3

How are images formed?

scanning , sweeping and steering of the beam through the tissue

many images - frames within a second

REAL TIME SONOGRAPHY

electronically done

4

Images are called....

frames

5

What are the different types of transducers?

mechanical

annular phased array

linear array (sequenced and phased)

curved array

vector array

6

First transducers were created in the...

1970's

7

What is a mechanical transducer?

MOTOR hooked up to a single piece of PZT

motor moves the ONE singular circular disc shaped crystal

produces a sector shaped image

8

What are the characteristics of the mechanical transducer crystal?

one

circular

fixed focus

9

What kind of image does a mechanical transducer produce?

fan or sector shape

10

What moves the PZT in the mechanical transducer?

the motor - back and forth

11

What kind of focus the mechanical transducer have?

conventional (mechanical, fixed)

fixed focal depth

internal curvature of the PZT

acoustic lens - external focuses the beam

12

How is the mechanical transducer beam steered?

by the motor

also fixed

a defective crystal destroys the entire image - because there is only one

13

What is the annular phased array?

crystal: multiple ring shaped elements

concentric rings: inner - shallow focus, outer - deep focus

multifocus in all planes at all depths

14

What kind of steering do annular arrays have?

mechanical steering

may limit the life due to moving parts

design limits multi capabilities during doppler

15

Annular Phased Array : steering is done ___________, focusing is _________

mechanically

electronic

16

With an annular what happens if you damage one crystal?

dropout

17

What is a modern transducer?

collection of active elements in a single transducer

elements are connected to the WIRE

each element has its own wire

18

What is a linear array?

linear segmental, switched or sequential array

NO beam steering

pulses send down straight lines

finish slide 33

19

which transducer has a large footprint?

linear array

20

Can the image be wider than the linear array transducer?

no

21

What kind of image does a linear array create?

a rectangular

22

How does the linear array work

defective crystal causes band dropout/black line

a few elements (3-10) are fired at the same time in GROUPS

23

What is the difference between early and modern models of linear array?

early- fixed focused - no steering

modern - electronic transmit focusing and receive focusing - electronic steering available

24

What is the linear Phased array?

sector or vector array

adjustable or multi focus

achieved electronically

small footprint

multiple elements each with electronic circuitry

ALL of the elements are fired in various patterns

crystal damage - black line dropout

25

What kind of steering and focus do the linear phased array have?

electronic

26

What is the shape of the image for the linear PHASED array?

sector

pie

vector

flat top

27

how does the linear phased array deal with focus?

curved signals due to the time delays with the phasing tells it to focus

the slopes " " know how to steer the beam

28

what is the beam former?

electronics that create the patterns of slope (steering) and curvature (focus)

incredible short time delays to create these patterns

IN the MACHINE - tells the transducer what to do

**creates the focusing**

29

what is called a channel?

combo of the PZT and the electronic wires