Term
What is an every day example of a logarithmic scale? 

Definition
The Richter scale which measures the strength of earthquakes. 


Term
What are the 3 processes that contribute to attenuation? 

Definition
1. Reflection
2. Scattering
3. Absorption



Term
What are the 2 types of reflection? 

Definition
1. Specular
2. Diffuse (backscatter)



Term
What is the special form of scattering that occurs when the structure's dimensions are much smaller than the beam's wavelength? 

Definition


Term
True or False? Rayleigh scattering increases dramatically with increasing freguency. 

Definition
True
Rayleigh scattering ȣ Frequency ^{4}



Term
What is the significance of attenuation in diagnostic sonography? 

Definition
Higher frequency sound attenuates more and is less capable of traveling to substantial depths. 


Term
Attenuation is determined by what 2 factors? 

Definition
1. Path length
2. Frequency of sound
Total Attenuation (dB) =
Atten. Coef. (dB/cm) x Distance (cm) 


Term
Distance and attenuation are related how? 

Definition
Directly.
↑ Distance = ↑ Atteuation



Term
Frequency and attenuation are related how? 

Definition
Directly.
↑ Frequency = ↑ Attenuation



Term
What are the 2 intensities that decibels require? 

Definition
1. Reference (the starting level)
2. The actual level at the time of measurement.



Term
Absorption is related to frequency how? 

Definition
Directly.
↑ Frequency = ↑ Absorption



Term
What occurs when ultrasonic energy is converted into another energy form, such as heat? 

Definition


Term
What is the number of decibels of attenuation that occurs when sound travels 1 cm? 

Definition
Attenuation coefficient.
Atten. Coef. (dB/cm) = F (Mhz)
2



Term
What is the advantage of describing sound weakening with an attenuation coefficient? 

Definition
Its value (dB/cm) remains constant, regardless of how far the sound travels. 


Term
Put the following Media in order from lowest attenuation to highest:
1. bone & lung
2. fat
3. air
4. muscle
5. soft tissue
6. water
7. biologic fluids (blood, urine) 

Definition
1. water
2. biologic fluids (blood, urine)
3. fat
4. soft tissue
5. muscle
6. bone & lung
7. air



Term
On what 2 factors does the halflayer value depend? 

Definition
1. Medium
2. Frequency of sound



Term
What is the acoustic resistance to sound traveling in a medium? 

Definition
Impedance.
Impedance (rayls) = Density (kg/m^{3}) x C (m/s)



Term
Of the 3 types of angles, which ones are oblique? 

Definition
Acute (< 90^{o})
&
Obtuse (>90^{o})



Term
Perpendicular, Orthogonal, Right Angle, & 90^{o} are all names for what? 

Definition


Term
What are the 3 types of intensities? 

Definition
1. Incident Intensity
2. Reflected Intensity
3. Transmitted Intensity
*All intensities have units of W/cm^{2}.
Incident (starting) Int. =
Reflected Int. + Transmitted Int. 


Term
What is the percentage of the intensity that bounces back when a sound beam strikes the boundary between 2 media? 

Definition
IRC
Intensity Reflection Coefficient



Term
What is the percentage of intensity that passes in the forward direction when the beam strikes an interface between 2 media? 

Definition
ITC
Intensity Transmission Coefficient



Term
In clinical imaging, what percentage of a sound wave's intensity is transmitted at a boundary between 2 soft tissues? 

Definition


Term

Definition


Term
The percentage of the incident beam that is reflected is related to what? 

Definition
The difference in the impedances of the tissues. 


Term
With normal incidence, what formula do you use to calculate the IRC? 

Definition
¯Z_{2}  Z_{1}¯ ^{2}
 Z_{2} + Z_{1}  X 100
¯ ¯



Term
What is the percentage of the intensity that continues to move forward when the beam reaches a boundary between 2 media? 

Definition
ITC
Intensity Transmission Coeffcient 


Term
The value of the ITC ranges from 0% to 100% and is defined by what formula? 

Definition
ITC (%) = Transmitted Int. x 100
Incident Int.
OR
ITC (%) = 1  IRC



Term
Which incidence, normal or oblique, can reflections occur even when the impedances of the 2 media are indentical? 

Definition


Term
What are the 2 physical principles that always apply to reflection with oblique incidence? 

Definition
1. Conservation of energy.
2. Reflection Angle = Incident Angle 


Term
What law states that the sum of the percentage of sound reflected and the percentage of sound transmitted must equal 100%? 

Definition
The law of conservation of energy.
Reflection Coef. + Transmission Coef. = 100% 


Term
The angle between the incident sound beam and an imaginary line that is perpendicular to the boundary is called what? 

Definition


Term
The angle between the reflected sound beam and the line perpendicular to the boundary is called what? 

Definition


Term
Transmission with a bend is called what? 

Definition


Term
What 2 conditions must be met for refraction to occur? 

Definition
1. Oblique incidence.
2. Different propagation speeds of the 2 media. 


Term
What is Snell's Law of refraction? 

Definition
Transmission Angle = Speed of Medium 2
Incident Angle Speed of Medium 1 


Term
How do we identify Medium 1 and Medium 2? 

Definition
Medium 1 is the medium in which the sound is currently traveling.
Medium 2 is the medium into which the sound is entering. 


Term
Under what conditions will the transmission angle be greater than the incident angle? 

Definition
When the speed of Medium 2 is GREATER than the speed of Medium.
The transmission angle will be less than the incident angle when the speed of Medium 2 is LESS than the speed of Medium 1. 

