What are the 3 variables of the range equation?
- Time
- Distance
- Speed
What is the time from a pulse being sent to a pulse being recieved called?
Time of flight.
When is time of flight short? in superficial or deep structures?
Superfical.
The time-of-flight is directly related to what?
Depth.
What is the range equation?
Depth (mm)=(1.54 mm/usec x time-of-flight (us))/2
For every 13us of time-of-flight, the object creating the reflection is how much deeper?
1cm
What is the reflectors depth if a pulses time-of-flight is 26 us?
2 cm deep.
How do you find period?
1/f
How do you find the frequency?
1/t
What is PRP?
It is the time from the start of one pulse to the start of the next pulse.
When the depth of view is shallow, what type of PRP would it have?
Short.
When the depth of view is deep, what does it PRP look like?
Long.
What is the equation for PRP?
PRP=imaging depth (cm) x 13us/cm
What is PRP directly related to?
Maximum imaging depth.
When the depth of view is shallow, how is the PRF?
High.
When the depth of view is deep, PRF is like?
Low.
What is the equation for PRF?
PRF (Hz)= 77,000 cm/s/image depth (cm)
PRF is inversely related to what?
Imaging depth.
What is “duty factor”?
It counts how long a pulse is on duty.
What is the equation of Duty Factor?
DF %=(Pulse duration/PRP) x 100
What are the advantages of a Pencil probe/Pedof probe?
- Sensitive
- Inexpensive
- Inexpensive electronics necessary
What are the disadvantages of the Pencil probe/Pedof probe?
- No image
- Manual steering
- Fixed focus for transmiting and receiving.
Describe a Mechanical transducer: single element
- First generation (static scanners)
- Mechanical steering-single element.
What are the advantages to a mechanical transducer: single element?
- 2D image
- Wide field
What are the disadvantages to a Mechanical transucer: single element?
- No steering
- Fixed transmitig and recieving focus.
- Parts wear out/break,
- Motion artifacts
What are the advantages to a Mechanical transducer: Annular array?
- 2D
- Variable focus (lateral, elevation)
- Wide field
What are the disavantages to a Mechanical transducer: Annular array?
- Motion artifact
- Parts wear out
- Limited temporal resolution
What are the advantages of a Linear Switched Array?
- 2D
- Electronic switches
- Wide field.
What are the disadvantages of the Linear Switched Array?
- No steering
- Fixed focus (lateral, elevation)
What is the Linear Phased Array associated with?
Hugen’s principle.
What are the advantages of the Linear Phased Array?
- 2D image
- Electronic pulsed sequencing
- Variable focus (lateral)
- Steering.
What are the disadvantages of the Linear Phased Array?
- Expensive
- Fixed focus (elevation)
What are the advantages of the Sector Phased Array?
- Viable focus in lateral
- Has a small footprint which aids in intercostal access.
- 2D
What are the disadvantages to a Sector Phased Array?
- Fixed elevation focus
- Expensive
- No steering in elevation direction.
What are 4 other types of transducers?
- Transesophogeal
- transrectal
- Intravascular
- Waterpath-standoff
What 4 things can cause damage to transducers?
- Heat
- Dropping
- Delamination
- Cable damage
How does heat damage the transducers?
It causes:
- Adhesive failure
- Depolarization
How does dropping damage the transucer?
It causes:
- Cracking case
- Electrical exposure
- Loss of probe sensitivity
How does delamination damage the transducer?
It causes:
- Caustic solvents
- Loss of probe sensitivity
How does cable damage, damage the transducer?
It causes:
- System degradation
- Loss of probe sensitivity.
What is frame rate also known as?
Frame frequency.
What is the time it takes to shoot one image called?
“frame time”
What is the equation for Frame Rate?
FR=1/FT
What is the equation for line time?
LT=13us/cm x depth cm
What is the equation for frame time?
FT= Line time x # of lines.
What does color add to frame time?
It adds a “packet”
What is the equation for packet time?
PT=( Line time x # lines repeated )/packet.
What happens to the frame frequency and temporal resolution if the frame time increases?
They both decreases.
What are 3 ways to impove frame rate?
- Decrease depth
- Turn off color
- Decrease width of color box.
What does decreasing the width of the color box do?
It reduces amount of times a packet has to shoot.
What does the transmitter/pulser do?
It turns electropotential energy into PZT then into pressure and vice versa.
What does the transmitter/pulser sensitivity aid it?
Detecting the weakest signal.
Increased power transmitted and intensity results in?
Improved sensitivity.
What happens if you increase the power?
It increases exposure to patient.
What is power porpotional to?
- Intensity
- Amplitude (brightness)
Gain is _____
Power.
What is the equation for gain?
Gain=20 Log Amax/Amin
What is the “signal-to-noise” ratio?
It is a comparison of meaningful information (signal) in an image, compared to the amount of contamination (noise).
When is the signal much stronger than the noise AND the image is of high quality?
When the signal-to-noise ratio is high.
When is the signal strength closer to the the strength of noise? The image will contain a larger amount of visible contamination.
When the signal-to-noise ratio is low.
What does increased power do to the signal-to-noise ratio?
It increases the signal-to-noise ratio.
What does the beam former do?
- It creates appropriate phase delays to transmitted signal.
- Applies appropriate phase delays to recieved signal.
What are 3 characteristics of a beam former?
- Stable
- Programmable
- Accepts large bandwidth
What is apodization?
It is when the beam former adjust electrical spike voltages to reduce lobe artifacts.
What does apodization do to lobes?
It decreases lobes.
What is the most important thing to remember of a reciever?
Reciever functions do not affect exposure to patients.
What are the 5 functions of the reciever?
- Amplification
- Compensation
- Compression
- Demodulation
- Rejection
What does a recievers amplification do?
- It raises strength of attenuated reflections
- Strength increases equally for all reflections
What does a recievers compensation do?
- It corrects for attenuation as depth increases
What is a function that can be used for compensation?
- TGC
- DGC
- TDC
What does a recievers compression do?
- It maintains “relative” difference in reflection.
- Considers limitations of viewer (shades of grey)
What does a recievers demodulation do ?
- It changes signal into suitable form for monitor
- Rectification→Flips
- Smoothing→Simplifies the echo
What does a recievers reject do?
- Removes :
- Low-level reflections
- Non-meaningful information/noise
What are 6 different types of imagining modes?
- A-Mode
- B-Mode
- C-Mode
- M-Mode
- Real-time
- Grey scale
What is A-Mode?
- Amplitude
- it is mainly used in opthamology.
What is M-Mode?
- Motion
- Used in echo.
What is C-Mode?
- Constant
- Doppler and color.
What is the equation for dynamic range?
dB=20 Log10Amax/Amin
How many dB is in US?
100
How many dB in the human eye?
36 dB (shades of grey)
