Pulse Wave 2

Pulse duration

time that a pulse lasts

Pulse duration formula

period X #of cycles

PRP

time between repeating pulses

PRF

number of pulses transmitted per second

Duty Factor

percentage of time system is on

PD/PRP

SPL

#cyclesXwavelength

line/acoustic line

single path of sound from a pulse

receive line

the returning echo data

display line

the displayed representation of a line

image

a full frame built from multiple acoustic lines

frame time

time required to create one image frame

frame rate

number of images displayed per second

sampling rate

frequency at which pulses are sent/received

Scanned modalities

acquire data over a plane

examples of scanned modalities

2D Bmode, color doppler, 3D/4D imaging

Characteristics of scanned modalities

lower temporal resolution compared to non scanned modalities

Non scanned modalities

acquire data along a single line repeatedly

Examples of non scanned modalities

CW doppler, PW doppler, M-mode, A-mode

Characteristics of non scanned modalities

higher temporal resolution

Deeper imaging depth =

longer PRP

longer PRP=

lower PRF

shallower imaging depth =

shorter PRP

shorter PRP=

higher PRF

frame time depends on

imaging depth and number of acoustic lines

frame rate is the reciprocal of

frame time

higher frame time=

better temporal resolution

Damping

shortens ringdown=shorter SPL=better resolution

more cycles=

longer SPL=poorer axial resolution

bandwidth

range of frequencies over which a transducer operates

shorter pulses =

broader bandwidth

fractional bandwidth

bandwidth divided by the center of frequency

Quality factor formula

Q= operating frequency/ bandwidth

High Q=

narrow bandwidth, long SPL

Low Q=

broad bandwidth, short SPL

Harmonic imaging

technique where the system transmits at a lower fundamental frequency but receives a higher harmonic frequency for improved image quality