Part 1 - important (notes) Flashcards
Infrasound
<20 Hz
Audible Sound
20 - 20,000 Hz
Ultrasonic
> 20,000 to 20 Khz
Diagnostic ultrasound
2 to 15 Mhz
Time to complete one cycle
Unchanged by monographer
Sec/usec
Determined by : Source
Period
of cycles/ sec (affects ———-penetration & axial res)
Unchanged by monographer
Hertz
Determined by: source
Frequency
Rate work is performed
Unchanged by monographer
watts
Determined by Source
Power
Concentration of energy in a sound beam
Changed by sonographer
watts/cm^2
Determined by source
Intensity
Length/distance of single cycle
mm,cm
Changed by sonographer
Determined by source & Medium
wavelength
Rate sound travels in a medium
Unchanged by sonographer
m/sec
determined by : medium
prop speed
Amplitude , Power & Intensity are all related how ?
Direct
Period & Frequency are related how
Inverse
Power & area are related how
Inverse
Wavelength & frequency are related how
Inverse
Stiffness & Speed are related how
Direct
Speed & Density are related how
Inverse
Frequency , speed, intensity and power are related how
UNRELATED
3 bigness parameters changed by the output power
Amplitude
Power
Intensity
Intensity equation
Power/Area
Wavelength equation
Propagation Speed/Frequency
Soft tissue / wavelength equation
1.54 mm / Frequency
Speed equation
Frequency x wavelength
The speed in Air is
330 m/s
The speed in lung is
500 m/s
The speed in fat is
1450 m/s
The speed in Soft tissue/ Blood is
1540 m/s
The speed in tendon is …
1850 m/s
The speed of bone is
3500 m/s
Start of a pulse to the end of that pulse
Not changed by soon
Usec
Determined by - source
Pulse duration
Start of pulse to start of next pulse (on & off time)
Changed by sono
M/sec
Determined by source
PRP
of cycles per second
Changed by sono
1/sec Hz
Determined by source
PRF
% or fraction of time system transmits
Changed by sono
No units
Determined by source
Duty Factor
length / distance a pulse occupies
Not changed by sono
mm/ cm
Determined by source & Medim
SPL
These parameters are changed by depth of view ..
PRP, PRF, Duty factor
PRP and imaging depth are related how
Direct
PRF & Imaging depth are related how
Inverse
Duty Factor & imaging depth are related how
Inverse
PRP & PRF are related how
Inverse
PRF & duty factor are related how
Direct proportional
- Listening time (increase)
- PRP (increase)
- PRF (decrease)
- Duty Factor (decrease)
Deep imaging
- Listening time (decreases)
- PRP (decreases)
- PRF (increases)
- Duty factor (increases)
Shallow imaging
Equation for pulse duration
of cycles x period
Equation 2 for PD
of cycles in a pulse / frequency
SPL equation
of cycles x wavelength
Duty factor equation
Pulse duration/ PRP x 100
Largest value intensity
SPTP
Smallest value intensity
SATA
related to bio effects intensity
SPTA
beam coefficient uniformity
SP/SA
largest to smallest order of intensities
SPTP > Im > SPPA > SPTA > SATA
Which of the following intensities change with maximum imaging depth ?
SPTA or SATA
Decrease of intensity, power & amplitude as wave travels through body
unrelated to propagation speed
Attentuation
Longer distance , higher frequency
More attenuation
Short distance, lower frequency
Less attenuation
Water has what type of attenuation
Extremely low
Blood,urine,biologic fluids has what type of attenuation
Low
Fat have what type of attenuation
Low
Soft tissue has what type of attenuation
Intermediate
Muscle has what type of attenuation
Higher
Bone & lung have what type of attenuation
Even higher
Air has what type of attenuation
Extremely high
High frequency sound, and medium with high attenuation
Thin half value
Low frequency sound, Media with low attenuation
Thick half value
Depends on these two factors & is directly related to them
- Frequency
- Distance of a wave (path length)
Attenuation in ST
What components contribute to attenuation
- absorption
- reflection
- scattering
Sound energy converts to heat
Absorption
Strikes a boundary & returns to the transducer
Reflection
Specular reflection
smooth reflector
Diffuse/backscatter
rough & disorganized , random
Boundary of media are irregular & redirected in all directions
Scattering
uniformly, omni direction, example red blood cell
Rayleigh scattering
Attenuation coefficient equation
Frequency / 2
Soft tissue attuen equation
0.5 dB / frequency
Total attenuation equation
Attenuation coefficient x distance
- Normal incident
- Different Impedance
What occurs?
Reflection
- Oblique incidence
- Different prop speeds
What occurs?
Refraction
Transmitted & reflected intensity = ?
Incident intensity
This law deals w/ refraction
Snells law
If speed 2 = Speed 1
No refraction, transmission angle = incident angle
If speed 2 is greater than speed 1
Transmission angle greater than incident angle
If speed 2 is less than speed 2
Transmission angle is less than incident angle