Term
| 7 parameters of ultrasound: |
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Definition
1. Frequency
2. Period
3. Wavelength
4. Propagation speed
5. Amplitude
6. Power
7. Intensity |
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Term
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Definition
| Pulse repetition frequency: the number of pulses/sec |
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Term
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Definition
| Pulse repetition period: the time from start of one pulse to the start of the next |
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Term
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Definition
| Duty factor: the proportion of time the transducer is actually vibrating to produce ultrasound |
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Term
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Definition
| Spacial pulse length: the distance of one pulse |
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Term
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Definition
| The length of time of the pulse itself from the beginning to the end of the group of cycles |
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
cycles per pulse • λ
remember: λ=c/f
m/cycle |
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Term
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Definition
# cycles per pulse • period
or
# cycles per pulse/frequency |
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Term
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Definition
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Term
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Definition
| Study of effects of exposure of body to signals used in diagnostic testing, such as US, X-ray, MRI, ect. |
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Term
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Definition
| creation of little spaces due to movement of particles |
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Term
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Definition
| energy dissipated as ultrasound travels through the tissue |
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Term
DF
Time or space?
Range?
DF= |
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Definition
Duty Factor
Time
0-1 or 0-100%
PD/PRP |
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Term
BUC
Time or space?
Range?
BUC= |
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Definition
Beam-uniformity Coefficient
Space
1 or greater (lower the number, the greater the uniformity of intensity)
SP/SA |
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Term
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Definition
| represents the range of frequencies in the signal created by the transducer, the number of frequencies produced. |
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Term
| What is the relationship of bandwidth and the damping of crystals? |
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Definition
| Damping produces a shorter pulse. This is good for resolution but produces wider bandwidth. |
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Term
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Definition
Quality Factor
Index of how clean and efficient the signal is--ratio of center frequency to bandwidth
fo/BW |
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Term
| Is QF for diagnostic US usually high or low? Why? |
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Definition
| Low, because we need short pulses for good resolution. |
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Term
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Definition
power/unit area
W/m2 or mW/cm2 |
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Term
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Definition
SPTP
SPTA
SATP
SATA
SPPA
SAPA
Im |
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Term
| What is the highest type of intensity measurement? |
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Definition
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Term
| What is the lowest type of intensity measurement? |
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Definition
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Term
| What intensity measurement best predicts tissue heating? |
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Definition
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Term
| What is upper limit of safe exposure? (unfocused, focused) |
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Definition
AIUM found no bad effects with unfocused beam at
100 mW/cm2, and with focused beam at 1 W/cm2 |
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Term
| Im intensity: where on high/low scale? |
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Definition
| 2nd because it measures the intensity of the highest 1/2 cycle |
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Term
| What is the relationship between amplitude and intensity? |
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Definition
Intensity increases with the square of the amplitude.
Double amplitude: 4X intensity
Cut amplitude in half: 1/4 intensity
Triple amplitude: 9X intensity
Cut amplitude to 1/3: 1/9 intensity
etc... |
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Term
| Converting PA to TA and vice versa: |
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Definition
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Term
| Converting SP to SA and vice versa: |
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Definition
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Term
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Definition
| Unit of comparison between 2 parameters to express changes in amplitude, intensity, sound pressure levels and range of gray scale |
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Term
If intensity changes from
1 W/cm2 to 1,000 W/cm2 |
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Definition
dB = 10 (log I2/I1)
= 10 (log 1,000/1) = 10 x (log 1000)
= 10 (log 103) (Log of 103 is 3)
= 10 (3)
= 30 dB intensity increase |
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Term
| If intensity increases from 10 W/cm2 to 10,000 W/cm2 |
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Definition
dB = 10 (log I2/I1)
= 10 (log 10,000/10)
= 10 (log 103) (Log of 103 is 3)
= 10 (3)
= 30 dB |
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Term
| Intensity drops from 1,000 W/cm2 to 1 W/cm2 |
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Definition
dB = 10 (log I2/I1)
= 10 (log 1/1,000)
= 10 (log 10-3)
[Log of 10-3 is -3]
= 10 (-3)
= -30 dB intensity decrease |
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Term
If there is an increase of 30 dB,
and the result is 1,000 mW/cm2,
what is the initial intensity? |
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Definition
30 dB = increase of 1,000x
So initial intensity must be
1 mW/cm2 |
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Term
| what do you call an increase of decibels? |
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Definition
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Term
| What do you call a decrease of decibels? |
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Definition
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Term
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Definition
dB = 10 log I2/I1
I1 is original intensity
I2 is changed intensity |
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Term
| What is the difference between a specular reflector and a scatterer? |
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Definition
| Specular: Large, flat reflector ≥1/4 the wavelength Scatterer: Very small reflector or larger but irregular surface <1/4 the wavelength (can also be heterogeneous medium) |
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Term
| What happens to the likelihood of scattering if the frequency is increased? |
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Definition
| The higher the frequency, the more likelihood of scattering. |
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Term
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Definition
| Loss of intensity, loss of signal strength. |
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Term
| What are the three causes of attenuation of ultrasound in tissue? |
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Definition
| reflection, scattering, absorption |
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Term
| What is the attenuation coefficient for soft tissue? |
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Definition
0.5 dB/cm/MHz
(remember 0.5•cm•MHz) |
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Term
| What is half-intensity depth (HID)? |
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Definition
Always 3dB of attenuation
or
-3dB |
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Term
| HID: what happens when frequency changes? |
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Definition
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Term
| If frequency is increased, what happens to scattering? |
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Definition
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Term
What creates an echo?
What makes a strong echo?
What makes a weak echo? |
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Definition
ΔZ
Bigger Z means more reflection: stronger echo
Small Z means less reflection: weaker echo |
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Term
| What is acoustic impedance? |
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Definition
| Indicates how much sound pressure is generated by the vibration of molecules of a particular acoustic medium at a given frequency. |
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Term
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Definition
| unit of acoustic impedance |
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Term
| Whose law governs what happens to transmission of beams with non-normal incidence? |
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Definition
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Term
| The angle of incidence = the angle of __________ |
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Definition
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Term
| What is normal incidence? |
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Definition
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Term
| What do you call an angle other than normal incidence? |
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Definition
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Term
| What do you call an angle other than normal incidence? |
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Definition
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Term
| What two conditions must be present for refraction to occur? |
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Definition
| not normal incidence and 2 different propagation speeds |
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Term
| Rules for oblique angles of transmission: |
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Definition
1. If V2 > V1, then θt > θi
2. If V2 < V1, then θt < θi |
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Term
| What happens to the transmitted angle if the second medium has a faster propagation speed than the first? |
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Definition
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Term
| What happens to the transmitted angle if the second medium has a slower propagation speed than the first? |
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Definition
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