Ch 1 Intro Flashcards
How many kHz is u/s?
Above 20 kHz (higher than humans can hear)
What is u/s?
-Non invasive way of looking inside human body
-2D/3D anatomic + flow imaging uses u/s
U/s is accomplished by using what technique?
Pulse-echo technique
What is the pulse-echo technique?
-Pulses of sound get sent into the tissues
-Echoes returning from the tissues provide anatomic info
How many pulses per scan line with the pulse-echo technique?
1 pulse = 1 scan line
(therefore, multiple scan lines are used to create an image)
Once the u/s instrument processes the returning echoes, how will it present them?
As visible dots, which form the anatomic image
Are all of the u/s pulses reflected back?
No - most of the original pulses continue on to be reflected from deeper structures
The brightness of the dot corresponds to what?
Echo strength (based on medium acoustic impedance)
The location of the dot corresponds to what?
The echo return time
Strengths of the reflected + transmitted pulses are determined by what?
The impedances of the 2 mediums at the boundary
Explain the variables in the acoustic impedance formula: Z = p x c
Z: acoustic impedance
p: density of medium
c: velocity
(measured in Rayls)
List the 3 types of 2D scan formats?
-Linear
-Sector (phased)
-Combination (curvilinear)
List 4 things about the linear format?
-Closely spaced parallel vertical scan lines
-Pulses travel in same direction
-Different starting points for each subsequent pulse
-Produces rectangular display
List 3 things about the sector format?
-Slice of pie display
-Each pulse originates from same starting point
-Subsequent pulses go out in slightly different directions
List 3 things about the combination (sector + linear) format?
-Pulses originate from different starting points (linear)
-Each pulse travels in a slightly different direction from the previous pulse (sector)
-Curved display
