A reduction in the intensity of a sound beam to one-half of its orignal value is ____ dB?
-3dB
A reduction in the intensity of a sound beam to one-quarter of its orignal value is _____dB.
-6dB
-10 dB means that the intensity is reduced to ____ of its orignal value.
One-tenth
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/cw2. There is a change of +9dB. What is final intensity?
16 mW/cm2
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 one-half of the ultrasonic frequency in MHz.
What are the units of the half-value 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/m3) 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, Imax, PA, TA
List temporal intensities from smallest to largest.
TA, PA, Imax, TP
Name the many different names for Axial Resolution.
