Lecture 22 Part 2

Question 1

Aliasing depends

Answer 1

Nyguist limit

Question 2

Nyquist limit is =

Answer 2

Half the PFR

Question 3

Higher velocities are ________ alias

Answer 3

More likely to alias

Question 4

Aliasing will often show within a ______ is PRF is set too _____

Answer 4

stenosis

low

Question 5

Areas will show aliasing highlights areas

Answer 5

Of highest velocity

This is using it for good

Question 6

Gain

Answer 6

Just like 2D we can amplify the returning echo voltages e

We want wall to wall filling

Question 7

Priority aka

Answer 7

Echo write priorite

Question 8

Priority is

Answer 8

The gray scale vs colour threshol

Question 9

Echoes ______ cut off amplitude will show as colour

Answer 9

Below

Stronger echoes show as grayscale

Question 10

Any movements in the tissue will produce

Answer 10

Doppler shifted colour

(Tissue vibration, vessel movement)

Aka clutter

Question 11

Clutter has ______ velocities

Answer 11

Lower

Question 12

____ will eliminate clutter, as it sets a _______

Answer 12

Wall filter

Cut off point

Question 13

What does wall filter do

Answer 13

Filters out noise -> non useful info

Keeps the useful signal

Question 14

Arterial speed tend to be _______ than venous speeds

Answer 14

Higher

Question 15

If you increase PRF too much it can result in

Answer 15

Echo misplacement

Question 16

Can increase the PRF to help with

Answer 16

Aliasing

Question 17

Tortuous vessels may look like

Answer 17

Flow reversal

Aliasing

Question 18

Higher freq are used for doppler leading to higher ______

Answer 18

Attenuation

Question 19

A _____ patient may be difficult to get a good signal on

Answer 19

Larger

Question 20

Power doppler

Answer 20

Determined by concentration of moving RBCs

Question 21

We can display just power but shows only _____ of flow

Doesnt show _____

Answer 21

Presence

Velocity, direction, flow character info

Question 22

Pros of power doppler

Answer 22

Increased sensitivity by small flow and small or deep vessles

Angle dependent
No aliasing

Question 23

Cons of power doppler

Answer 23

No speed/ cannot quantify
No direction
No flow character to assess stenosis

Question 24

Duplex scanning

Answer 24

We update between doppler and gray scale -

Transducer does one at a time but is simultaneous in the way it rapidly switched between the two