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Ultrasound Physics
| Question | Answer |
|---|---|
| Longer Distances Create WHAT Attention? | more |
| Shorter distances create WHAT attenuation? | less |
| Higher Frequencies create attenuation? | More |
| Lower Frequencies create WHAT attenuation? | Less |
| 2 Types of organized sound interactions | Specular and Rayleigh |
| 2 Types of Disorganized sound interactions | Diffuse and Scatter |
| What 2 types of sound interactions reflect sound in all directions? | Scatter and Rayleigh |
| What 2 types of sound interactions reflect sound back to the Transducer? | Specular and Diffuse |
| Medium -Amount of Attenuation | water- extremely low fat-low muscle- soft tissue-intermediate blood, urine, biological fluid- low air-very high attenuation bone and lung- extremely high |
| Decibles- Meaning | 3 dB- Double -3 dB- half 10 dB- times 10 -10 dB- 1/10th |
| A thin half value is found w/ WHAT frequency sound? | high |
| A thick high value is found w/ WHAT frequency sound? | low |
| A thin half value is found in a media w/ a WHAT attenuation Rate? | High |
| A thick half value is found in media w/ a WHAT attenuation rate? | low |
| Speeds- Angle of transmission | Speed 2= Speed 1- no refraction, transmission=incident angle.. Speed 2>Speed 1- transmission angle greater than incident angle Speed 1>Speed 2- incident angle greater than transmission angle.. |
| Specular Reflections are well seen when the sound strikes the boundary at WHAT degrees? | 90 degrees |
| Scatter | the redirection of sound in all directions |
| As frequency increases Scatter WHAT? | increases |
| A Red blood cell is an example of what typeof scatter?? | Rayleigh Scatter. |
| Rayleigh Scattering is related to WHAT? | Frequency |
| Attenuation Coefficient | The amount of attenuation per cm. |
| As frequency increases, the attenuation coefficient WHAT? | increases |
| In soft tissue, the Attenuation coefficient is WHAT the transducers frequency? | 1/2 |
| What is the equation for total attenuation? | path length x attenuation coefficient. |
| Is impedance calculated or measured? | Impedance is calculated (density x speed) |
| Impedance Units? | Rayls (2) |
| 4 Other Terms for normal incidence? | Perpendicular, right angle, 90 degrees, orthogonal |
| Incident Intensity? | Intensity of the sound wave at the instant prior to striking a boundary.. |
| Reflected Intensity | Portion of the incident that after striking a boundary changes direction and returns back from where it came.. |
| Intensity Reflection Coefficient | the percentage of the us frequency that bounces back when the sound strikes a boundary. |
| Intensity transmission Coefficient | The percentage of the incident intensity that after striking a boundary continues on in the same general direction that it was originally traveling. |
| IRC+ITC=WHAT % | 100% |
| Intensities are reported in units of WHAT? | w/cm2 |
| When reflected and transmitted intensities are added, the result is the WHAT intensity? | incident |
| Coefficients are reported in WHAT? | Percentages |
| The intensity transmission coefficient of sound is 99.9%, What % of sound is reflected back to the transducer? | 0.1% |
| A sound wave w/ an intensity of 50 w/cm2 strikes a boundary and is totally reflected. What is the reflected intensity? | 50 w/cm2 |
| A sound wave w/ an intensity of 50 w/cm2 strikes a boundary and is totally reflected. What is the intensity reflection coefficient? | 100% |
| W/ normal incidence, reflection only occurs if the 2 media at the boundary have different WHAT? | impedances |
| W/ normal incidence w/ greater impedance differences b/w the 2 media, the IRC WHAT and the amount of reflection. | Increases, Increases.. |
| W/ normal incidence, whatever is not reflected must be WHAT | Transmitted |
| incident intensity= WHAT + WHAT. | reflected + transmitted intensity. |
| Reflection angle= WHAT angle? | Incident. |
| Refraction | transmission w/ a change in direction as sound transmits from one medium to the other.. |
| Can refraction occur w/ normal incidence? | No |
| Refraction requires WHAT 2 THINGS? | different speeds and oblique incidence |
| Snell's Law | A law that describes the physics refraction.. |
| A sound wave strikes a boundary at normal incidence. The impedances of the 2 media are identical. What % of the sound wave is refracted?? | |
| Period | Period= 1/Frequency T=1/F |
| Wavelength | Wavelength=prop. speed/frequency |
| Intensity | I=power(w)/area(cm2) I=P/A |
| Impedance | Impedance=prop. speed x Density Z=Pc |
| SPL | SPL=# of cycles x wavelength Df= PD/PRP |
| PD | # of cycles/Frequency |
| DF | |
| Axial Resolution Definition | measures the ability a system to display2 structures that are very close together when structures are parallel, front to back, to the sound beams main axis. |
| Resolution | refers to accuracy in imaging |
| Lateral Resolution | Measures the ability of a system display 2 structures when the structures are perpendicular, side to side, to the sound beams main axis. |
| Axial Resolution improves w/ WHAT SPL? | shorter |
| Axial resolution improves with WHAT pulse duration? | shorter |
| Axial resolution improves w/ WHAT frequencies? | higher |
| Axial resolution improves w/ WHAT wavelength? | Shorter |
| Axial resolution improves w/ WHAT cycles per pulse? | Fewer |
| Axial resolution improves w/ WHAT numerical values? | lower |
| Axial vs. Lateral | AXIAL Orientation-parallel,front to back,Mneumonic-LARRD, Best W/-short pulse, Changes w/ Depth-no, IN Near Field- short pulse, In Far Field-short pulse,Determined By-pulse length. Lateral Orientation perpendicular,LATA,Chnges @ depth @ focus, |
| Method NAme Type |
Created by:
KJ22