exam 2 review

Question 1

Pulse duration equation

Answer 1

PD (time)= Period (time) * # cycles

Question 2

Spatial pulse length equation

Answer 2

SPL (distance)= Wavelength(distance) * # cycles

Question 3

Frame Time equation

Answer 3

Frame Time= PRP (time) * # lines

Question 4

Frame time equation with color

Answer 4

Frame Time= PRP * #lines/packet * #packets/frame

Question 5

Frame Time on steroids equation

Answer 5

Frame Time= 13 ms/cm * ID * #lines/packet * #packets/frame * #foci

Question 6

Frame rate and Frame time

Answer 6

Reciprocal

FR*FT=1

Question 7

Pulse repetition period and pulse repetition frequency

Answer 7

Reciprocal

PRP*PRF=1

Question 8

Pulse repetition period equation

Answer 8

PRP= 13 ms/cm * ID

Question 9

Duty Factor equation

Answer 9

DT (%)= PD/PRP * 100

Question 10

Bandwidth equation

Answer 10

BW= F(max) - F(min)
BW= 1/PD

Question 11

Pulsed Wave equation

Answer 11

F(o)=Crystal/2*thickness

F(o)= operating frequency

Question 12

Continuous wave equation

Answer 12

F(o)= drive voltage frequency

Question 13

Beam width equation

Answer 13

D/2 @ the focus

D @ 2X the focus

Question 14

Near zone length equation

Answer 14

D(2)*F(o)/6

OR
D(2)/4y

Question 15

Beam divergence

Answer 15

1.85/D*f(o)

Question 16

Longitudinal resolution

Answer 16

SPL/2

Question 17

Lateral resolution

Answer 17

Beam width in the lateral plane

Question 18

Elevation resolution

Answer 18

Beam width in elevation plane

Question 19

Transducers convert one form of ____ into another.

Answer 19

Energy

Question 20

Piezoelectric effect

Answer 20

Describes the property of certain materials to create a voltage when they are mechanically deformed or when pressure is applied

Question 21

Transducer construction

Answer 21

1. Backing material
2. Piezoelectric crystal(s)
3. Matching layer

Question 22

Importance of matching layer and gel

Answer 22

They decrease the reflection at the piezoelectric crystal and skin boundary and increase the percentage of transmitted sound

Question 23

Band width definition

Answer 23

range of frequencies in the pulse

Question 24

Beam divergence definition

Answer 24

Describes the gradual spread of the ultrasound beam in the far field.

less divergence= larger diameter, higher frequency
more divergence= small diameter, lower frequency

Question 25

Axial Resolution

Answer 25

Ability of a system to display two structures that are very close together when the structures are parallel to the sound beams main axis Determined by the pulse length (shorter pulses have better resolution) Synonyms= longitudinal, range, radial, or depth resolution

Question 26

Better axial resolution

Answer 26

1. shorter spatial pulse length 2. shorter pulse duration 3. higher frequencies

Question 27

Lateral resolution

Answer 27

Ability to distinctly identify two structures that are very close together when they are side by side or perpendicular to the sound beams main axis Determined by the width of the sound beam (narrower beams have better resolution) Synonyms= angular, transverse, or azimuthal

Question 28

Matching layer function

Answer 28

* Located in front of the Piezoelectric crystals at the face of the transducer * Increases efficiency of sound energy transfer between active element and body * Protects the active element * One quarter wavelength thick

Question 29

Backing material function

Answer 29

* Bonded to the back of the active element * Reduces the ringing of the PZT * Dampens emitted sound pulse (enhances axial resolution)

Question 30

Continuous wave transducer frequency

Answer 30

The frequency is equal to the frequency of the electrical signal

Question 31

Pulsed wave transducer frequency

Answer 31

Determined by Speed of sound in the PZT and thickness of the PZT

Question 32

Beam shape characteristics

Answer 32

1. focus 2. near zone 3. focal length/near zone length 4. far zone 5. focal zone

Question 33

Focus (Focal point)

Answer 33

The location where the beam is the narrowest beam shape=1/2 the width of the beam as it leaves the transducer

Question 34

Near zone (fresnel zone)

Answer 34

Region from the transducer to the focus The beam gradually narrows or converges within the near zone Beam shape= 1/2 the width of the active element

Question 35

Focal length (focal depth or near zone length)

Answer 35

The distance from the transducer to the focus

Question 36

Far zone (far field, Fraunhofer zone)

Answer 36

Region that starts at the focus and extends deeper The beam will diverge/spread out Beam shape= @ beginning of far zone, beam is 1/2 as wide as the transducer. @ deeper depths, the beam is wider

Question 37

Focal zone

Answer 37

Region around the focus where the beam is relatively narrow

Question 38

Shallow focus

Answer 38

* smaller diameter PZT | * lower frequency

Question 39

Deep focus

Answer 39

* larger diameter PZT | * higher frequency

Question 40

What part of the beam gives the best focus?

Answer 40

Near zone, right before the natural focus

Question 41

Frame rate

Answer 41

Ability to create numerous frames each second Determined by speed of sound in a medium and imaging depth

Question 42

Pulse duration

Answer 42

actual time from start of a pulse to the end of the pulse Determined by sound source only Cannot be adjusted by the sonographer Values= 0.3-2 microseconds

Question 43

Spatial pulse length

Answer 43

the distance that a pulse occupies in space from start to finish determined by the sound source and the medium Cannot be adjusted by the sonographer Values (in soft tissue)= 0.1-1 mm

Question 44

Pulse repetition period

Answer 44

the time from the start of one pulse to the start of the next pulse determined by the sound source and the imaging depth Can be adjusted by the sonographer Values= 100 microseconds-1 millisecond

Question 45

Pulse repetition frequency

Answer 45

number of pulses that a system transmits into the body each second determined by sound source and imaging depth Can be adjusted by the sonographer Values= 1,000-10,000 Hz

Question 46

Duty factor

Answer 46

percentage of fraction of time that the system transmits a pulse determined by sound source only Can be adjusted by the sonographer Values= 0.2-0.5%