physics
Card Set Information
Author:
lmarie
ID:
16174
Filename:
physics
Updated:
2010-04-25 22:11:38
Tags:
Period
Folders:
Description:
ARDMS SPI Physics Review
Show Answers:
The effects of the medium upon the sound wave.
Acoustic Propagation Properties
The effects of the sound wave on biologic tissue
Biologic Effects
Sound is what kind of wave?
Mechanical, longitudinal
Period-
Definition?
Determined by?
Changed by sonographer?
The time required to complete a single cycle
determined by--source
changed by sonographer--no
Frequency-
Definition?
Units?
Determined by?
Changed by sonographer?
Definition--The number of certain events that occur in a particular time duration
Units-- per second, hertz, Hz
Determined by--Source
Changed by sonographer--no
Ultrasound Range?
Greater than 20,000Hz, not audible
Audible Sound
20-20,000 Hz
Infrasound?
Less than 20 Hz
Formula for intensity?
I= power/area
I=w/cm
^{2 }
Intensity is proportional to?
Amplitude
^{2}
Formula for wavelength?
wavelength (mm)= prop. speed (mm/us) / frequency (MHz)
Formula for wavelength in soft tissue?
wavelength= 1.54mm/frequency (MHz)
Wavelength is determined by?
Source and Medium
Propagation speed is determined by?
Medium only,
density and stiffness
Propagation Speed formula?
speed= frequency x wavelength
(m/s) =(Hz) x (m)
In-Phase waves interfere how?
Constructively
Pulse duration formula?
PD= number of cycles in pulse x period
or
PD=number of cycles in pulse / frequency
Pulse Repetition Period definition?
The time from the start of one pulse to the start of the next pulse. Includes "on time" and "off time"
PRP
Determined by?
Changed by sonographer?
Determined by-- source
Changed by sonographer--yes
(amount of listening time is determined by image depth)
PRF definition?
The number of pulses that occur in one second
PRP formula?
1/ PRF
PRF formula?
1/ PRP
Depth and PRF are related how?
Inversely proportional
Depth and PRP are related how?
directly proportional
PRP x PRF = ??
1
Duty Factor formula?
DF = PD/PRP x 100
Duty Factor
Definition?
Determined by?
Changed by sonographer?
Definition-- The percentage of time the system is transmitting sound. (% of "on time")
Determined by-- source
changed by sonographer--yes
SPL formula?
SPL= number of cycles x wavelength
SPL determines
resolution?
Axial resolution
PRP, PRF, and DF are all affected by what?
Depth of view
What intensity is most relevant with respect to tissue heating?
SPTA
What is the log of:
a-100?
b-10,000?
a-2
b-4
(count the zeros)