Pulse Wave Operations, Intensity, Attenuation

chapter 4, 5, 6

what are the 5 parameters of pulse wave operation

pulse duration, pulse repetition period, pulse repetition frequency, duty factor, and spatial pulse length

short bursts, or pulses of acoustic energy for every picture

pulsed utrasound

talking time is referred to as

on-time or transmit time

listening time is referred to as

off time

Waves that pulse continuously, no off time

continuous waves

2 components of pulsed ultrasound

on time and off time

the flat black line refers to

listening (off) time

Actual time from the start of a pulse to the end of that pulse

pulse duration

pulse duration is ____ time

on

is pulse duration adjustable

no

what is the typical unit for pulse duration

microseconds

pulse duration is determined by

sound source

is pulse duration fixed or able to be changed

fixed

#cycles/frequency (MHz)=

pulse duration

is equal to the number of cycles in each pulse, multiplied by the period of each cycle

pulse duration

pulse duration is ________ proportional to the number of cycles in a pulse

directly

pulse duration is ________ proportional to the period

directly

pulse duration is ________ proportional to the frequency

inversely

many cycles in a pulse, and cycles with long periods

long duration

few cycles, short periods

short duration

which is better for imaging short or long duration

short duration

why does short duration provide greater accuracy

provides more listening time

the distance that a pulse occupies in space from the start to the end of a pulse

spatial pulse length

units of spatial pulse lengths

millimeters

spatial pulse length is determined by

both sound and medium

is spatial pulse length adjustable

no

= #cycles X wavelength (mm)

SPL

spatial pulse length is ________ proportional to the number of cycles in the pulse

directly

spatial pulse length is ________ proportional to wavelength

directly

spatial pulse length is _________ proportional to frequency

directly

many cycles and a long wavelength make ____ pulse

long

few cycles and short wavelength makes ______ pulse

short

does short or long pulse create more accurate images

short

from the start of one pulse to the start of another

pulse repetiton period

what is the unit for PRP

microseconds

is PRP adjustable

yes

what is PRP determined by

sound (depth)

does the media change the PRP

no

does the frequency change the PRP

no

if you are scanning at a shallow depth is the PRP short or long

short

is you are scanning at a deep depth is the PRP short or long

long

what is increasing when PRP is taken from short to long

the listening time

PRP and depth are _________ related

directly

deep imaging _____ the listening time, and ______ the PRP

increases, increases

how often a pulse is sent

pule repetition frequency

PRF is _______ proportional to depth

inversely

what is the unit for prf

Hz

is prf adjustable

yes

is prf related to frequency

no

if the depth changes from 10cm to 5 cm, how does the prf change

it increases (pulses more frequently)

prf and depth are ______ proportional

inversely

a depth of 2cm has a ____ prf and _____ prp

high, low

prp and prf are _____ related

inversely

the relationship between prp and prf is a _______ relationship

reciprocal

% or fraction of time that the system transmits a pulse

duty factor

what is the typical value for duty factor

0.2-0.5%

what is the duty factor of a continuous wave

1 or 100%

is duty factor adjustable

yes

what changes duty factor

depth

duty factor has a _____ relationship with prf

direct

shallow depth have ______ listening time

less

shallow depth have ___ prp

short

shallow depths have ____ prf

high

shallow depth have ____ duty factor

high

deep depths have ____ listening time

more

deeper depths have ____ prp

long

deeper depth have _____ prf

low

deeper depth have _____ duty factor

low

deeper imaging means you listen _____, pule _____ frequently, and have a ____ duty factor

more, less, lower

cheat sheet

refers to distance or space

spatial

the maximum value

peak

mathematical middle value

average

refers to all time, transmit and receive

temporal

refers only to transmit time

pulsed

power divided by area

intensity

unit for intensity

watts/cm²

T or F: the strength of a sound beam varies

true

T or F: intensity varies over time

true

beam’s intensity at the location where it is maxiumum

spatial peak intensity (Isp)

average intensity across the beam’s entire cross-sectional area

spatial average intensity (Isa)

spatial peak intensity is _____ ______ than the spatial average intensity

always higher

intensity at the instant in time of its maximum value

temporal peak intensity (Itp)

average intensity during the most intense half cycle

Imax

average intensity during pulse duration

Ipa

intensity during entire pulse repetition period

temporal avergae intensity (Ita)

temporal intensities from largest to smallest

Itp, Imax, Ipa, Ita

measured at location where intensty is max. and at instant in time when the most powerful part of the pulse passes

SPTP

measured at the location where intensity is max. averaged over transmit time

SPPA

measured at location where intensity is max. and averaged over all time

SPTA

measured over the entire cross-sectional area, and overall time

SATA

spatial peak, temporal peak

SPTP

spatial average, temporal peak

SATP

spatial peak, temporal average

SPTA

spatial average, temporal average

SATA

spatial peak, pulse average

SPPA

spatial average, pulse average

SAPA

intensities may be reported in various ways with respect to ____ and _____

time and space

the different measurements of intensities are important in the study of 

bioeffects

which is most relevant in terms of bioeffects

SPTA