Ch.7 Range Equation Flashcards
Ultrasound systems determine reflector depth by measuring a pulses’s what?
time-of-flight with a very accurate stopwatch
Go-Return Time or Time-of-Flight
is the elapsed time from pulse creation to pulse reception
When a reflector is located superficially, the time from pulse creation to reception is ?
Whereas trips to and from the deeper reflectors?
brief
require more time
Time-of-Flight is directly related to?
how deep a sound pulse travels
Greater distances ______ the time-of-flight ; Lesser distances ______ the time-of-flight.
prolong
shorten
what is the average speed of sound in soft tissue that is programmed in ultrasound systems?
1.54 mm/us
State the equation to calculate the depth of a reflector using the go-return time
depth (mm) = 1.54 mm/us x go-return time (us) / 2
When one reflector is twice as deep as another reflector, the pulse’s time-of-flight is ?
twice as long for the deeper reflector
13-Microsecond Rule
for every 13 us of go-return time, the object creating the reflection is 1 cm deeper in the body
The 13-Microsecond rule ALWAYS applies when ?
sound travels thru soft tissue
A pulse travels to the reflector and back to the transducer, the total distance that a pulse travels is?
twice the reflector depth
Time of Flight Reflector depth Total depth
13 us
26 us
Reflector depth Total depth
1cm 2 cm
2cm (13x2=26) 4 cm
Time of Flight Reflector depth Total depth travelled
39 us
52 us
130 us
Reflector depth Total depth
3 cm 6 cm
4 cm 8 cm
10 cm 20 cm
PRP is altered when the system’s maximum imaging depth is adjusted.
When the depth of view is shallow the PRP is ______ .
When the depth of view is deep, the PRP is _______ .
short
long
What is the formula for calculating the PRP when given the imaging depth and 13 us rule?
PRP (us) = imaging depth (cm) x 13 us/cm
