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Ultrasound
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A reduction in the intensity of a sound beam to onehalf of its orignal value is ____ dB?
3dB

A reduction in the intensity of a sound beam to onequarter of its orignal value is _____dB.
6dB

10 dB means that the intensity is reduced to ____ of its orignal value.
Onetenth

dB is a mathematical representation with a ___&___ scale.
logarithmic & relative

True/False. We need one intensity to calculate decibels.
False

A wave's intensity is 2 mW/cw^{2}. There is a change of +9dB. What is final intensity?
16 mW/cm^{2}

Every 3 dB change means that the intensity will ______.
Double

Every 10 dB change means that the intensity will _____________.
Increase ten times

If the final intensity of a sound beam is more than the initial intensity, then the gain in dB is _____. (+ or )
Positive

If the initial intensity of a sound beam is less than the final intensity, then the gain in dB is _______.
Positive

Name the three components of attenuation.
Absorption, reflection & scattering

As the path length increases, the attenuation of ultrasound in soft tissue ________.
increases

Attenuation in lung tissue is [less than, greater than, the same as] attenuation in soft tissue?
greater than

Attenuation in bone is _______ attenuation in soft tissue.
greater than

Attenuation in air is ______ attenuation in soft tissue.
greater than

What are the units of attenuation?
Decibels (dB)

T or F. In a given medium, attenuation is unrelated to speed of sound.
True (Attenuation & propagation speed are unrelated)

What is the relationship between ultrasound frequency and the attenuation coefficient in soft tissure?
In soft tissue, the attenuation coeffiecient in dB per centimeter is approx onehalf of the ultrasonic frequency in MHz.

What are the units of the halfvalue layer thickness?
distance: centimeters

As frequency decreases, depth of penetration _________.
Increases

As path length increases, the half boundary layer ______.
remains the same

Impedence is a characteristic of ______.
Only the medium

As the path length increases, the attenuation coeffiecient of ultrasound in soft tissue [decreases, remains the same, increases]
remains the same

Acoustic impedance = _______x_______
Impedance = density (kg/m^{3}) x propagation speed (m/s)

Two media A and B have the same densities. The speed of sound in medium A is 10% higher than in medium B. Which medium has the higher acoustic impedance?
Medium A's acoustic impedance is higher than medium B's.

Impedance is important in ______ at boundaries.
Reflections

Which is better to use while examining a carotid artery, a 7.5 or 3.0 MHz transducer?
The carotid artery is a superficial structure. A 7.5 MHz transducer is better because the higher frequency transducer produces the better image.

List temporal intensities from largest to smallest.
TP, I_{max,} PA, TA

List temporal intensities from smallest to largest.
TA, PA, I_{max,} TP

Name the many different names for Axial Resolution.
LARRD. (Longitudinal, Axial, Range, Radial, Depth)

Normal incidence is also know as?
PORNN (Perpendicular, Orthogonal, Right angle, Ninety degrees, Normal)

A sound wave with intensity of 50 W/cm^{2} strikes a boundary and is totally reflected. What is the intensity reflection coefficient?
Since the wave is totally reflected, the intensity reflection coefficient is 100%.

A sound wave with intensity of 50 W/cm^{2} strikes a boundary and is totally reflected. What is the intensity reflection coeffiecient?
Since the wave is totally reflected, intensity is 50 w/cm^{2}

What is the formula for reflection with Normal Incidence?
IRC=(Z_{2}Z_{1}) / (Z_{2}+Z_{1}) x 100

What is the formula for transmission with Normal Incidence?
 ITC = 1 IRC
 or ITC = transmitted intensity / incidenct intensity X 100

What is the conservation of energy concerning coefficients?
100%= IRC+ITC

Snell's Law defines what?
refraction

What's the formula for Snell's Law?
Sin (transmission angle) /Sin (incident angle) = Speed of Medium 2/ Speed of Medium 1

A 2 cm deep reflector has a goreturn time of ___microseconds.
26

A 3 cm deep reflector has a goreturn time of ___microseconds.
39

For every 13 microseconds of goreturn time, the object creating the reflection is ___cm deeper in soft tissue.
1 cm

When the depth of view is shallow, the PRP is ______?
short

When depth of view is deep, PRP is ______?
long

What is the PRP when imaging to a depth of 4 cm?
52 microseconds (4x13=52)

If the PRP is 65 microseconds, what is the max imaging depth?
5 cm (13x5=65)

