Exam 2 Flashcards
Definition of HVLT
Distance sound travels in tissue that reduces the intensity of sound to 1/2 the original value
Define the 10dB rule
+10dB is number increased by tenfold
-10dB is number decreased by 1/10
10 dB log rule for intensity and power
Define impedance
Acoustic resistance to sound traveling in a medium
Define attenuation
Decrease in intensity, power, and amplitude as sound travels
Define diffuse
Rough irregular or diffusive surfaces that scatter incoming lights/waves in multiple directions
Define specular
Reflecting interfaces with smooth (mirror-like) surface
Define Duty Factor, the abbreviation, and the equation
Percentage or fraction of time that the system transmits a pulse
DF
DF = PD/PRP
Define spatial pulse length, the abbreviation, and the equation
Distance that a pulse occupies in space from the start to the end of a pulse
SPL
SPL = Wavelength x # of cycles
Draw and label parts of a transducer
Look at picture on study guide
What are the consequences of using back material
- Decrease sensitivity
- Wide bandwidth
- Low Q-Factor
What is the equation for BW
What about QF
BW = Max-min
QF = Main frequency/bandwidth
Wha is the Piezoelectric effect
Transmission phase - energy converted to sound
Receiving phase - Reflected sound pulse converted to electric energy
Define intensity
Concentration of energy in a sound beam
Define a multi-frequency transducer
Transducers can produce more then 1 frequency of U/S as long as the frequencies are in the bandwidth of the transducer
Thickness of PZT and its effect on frequency
Thin - Higher frequency
Thick - Lower frequency
Name the regions of a sound beam
Near zone
Focal length/Near zone length/NFL
Focal zone
Far zone/Fraunhofer zone
Define the near zone
Narrowing part
Define the near zone length
Length of the near zone
Define focal zone
Area of relatively high intensity and narrow beam width that extends on either side of the focus
Define the far zone/fraunhofer zone
Diverging part of the beam
What is the equations for PD
PRP?
PRF?
PD = 1/frequency
PRP = 1/PRF
PRF = 1/PRP
What is the equation for axial resolution
AR = Wavelength x # of cycles in a pulse
Define the 13 dB rule
For every 13 us, sound travels 1 cm into the body (“Round trip”)
What is the equation for thickness and frequency
Frequency (MHz) = (Sound speed in PZT (mm/us) /2) x Thickness (mm)
What is the equation for 10 dB
What are the units in intensity and power
10 x log (I/Io)
I = mw/cm^2
P = w/cm^2
What is the angle information of importance and how you figure out the angles of 1 & 2
Speed 1 = Speed 2 - Same material
Speed 1 < Speed 2 - Slow to fast - Large angle
Speed 1 > Speed 2 - Fast to slow - Small angle
What is the purpose/importance of the 1/4 value
Matching layer is 1/4 of the thickness of the wavlenegth to act as a layer of protection
%T + %R = ?
100%
In S.T sound travels to a reflector and comes back in 39 us. How deep is the reflector?
3 cm
T or F:
With certain transducer the systems axial resolution is invariant and there’s nothing you can do to improve it.
True
You have a PRP of 1.2 ms, SPL of 2 mm, and wavelength of 0.4 mm. What is the axial resolution
1 mm
Axial resolution depends on
Wavelength
Where is the highest intensity on a transducer
At the focus
What region from the transducer to the smallest area beam called
Near zone/Fresnal Zone
T or F:
Damping material helps to reduce PRP and given depth
False
T or F:
Period in 3 MHz is > period in 6 MHz
T
In this equation which is the highest value, intermediate value, and the lowest value:
Zm = square root of Ztissue x Ztransducer
Zm - Intermediate value
Ztissue - Lowest value
Ztransducer - Highest value
What does backscatter provides for organs
Much of the tissue texture information about organs
Reflectors are much ____ than the wavelength
Smaller
What is Rayleigh dependent on
Frequency dependent
In non-specular reflectors the amount of scattering will increase with ____ frequencies
Higher
Examples of specular reflectors
Renal capsule
Endometrial and vag stripes
Diaphragm
At specular reflectors the angle of reflection is = to?
Angle of incidence
What is the equation for %R
[Z2 - Z1 / Z2 + Z1] x 100
If you have a DF of 1 what type of wave do you have
Continuous wave
If you have a DF of <1 what type of wave do you have
Pulse wave
Name the characteristics of axial resolution
Determined by SPL
LARRD (Long, range, radial, depth)
Not adjustable
Range 0.1-1mm
Name the characteristics of lateral resolution
Determined by width of sound beam
LATA (Lateral, angular, transverse, Azimuthal)
Lateral resolution = to?
Beam diameter
Color in a scan takes longer due to
Machine needing to “paint” each line
How can you speed up the process of a color scan
Decrease sector
Closer to transducer face = Faster refresh rate
What is the relationship of imaging depth and frame rate
Inversely related
Frame rate is how often a
Complete image is formed by the lines of the ultrasound
What are the units for frame rate
Frames/second or Hz
What are the characteristics of a high Q-Factor
Low Q-Factor?
Long ring, CW, narrow BW, poor AR
Short ring, PW, wide BW, good AR
What is the relationship of the PZT and frequency
Inversely related
Region of the transducer to the focus characterized by fluctuations in ampltiude and intensity from 1 point in the beam to another
Near field
Region of beam starting at focus and extending deeper
Far field
