Definitions, equations, artifacts

Question 1

Duty Factor

Answer 1

% of time ultrasound is “listening”.
(Pulse Duration) / (Pulse Repetition Period).
Typically ~0.2%. CW is 100%

Question 2

Velocity of ultrasound through tissue

Answer 2

1540 m/s

Question 3

Nyquist limit (formula)

Answer 3

= 1/2 PRF

Question 4

Ultrasound “period”

Answer 4

Time to complete one cycle

Question 5

Shadowing

Answer 5

artifact that results in a hypoechoic signal area behind a highly attenuating structure

Question 6

Enhancement

Answer 6

artifact that results in a hyperintense signal behind a low attenuating structure (like fluid)

Question 7

Grating Lobes

Answer 7

Artifact that results in ghost images of high contrast structures off axis to the sound beam

Question 8

Reverberation

Answer 8

Artifact that results in the placement of echogenic lines, equally spaced apart from each other

Question 9

Refraction

Answer 9

Artifact that results in the misplacement of a structure in an image due to change in direction at non-perpendicular bountires with a difference in tissue impedance

Question 10

Main Bang

Answer 10

Chest wall interface seen in the very near field on TTE. Strong reflectors from transduce and skin interface results in no useful imaging.