Ultrasound 1

Question 1

What is sound?

Answer 1

The result of mechanical energy producing compression and rarefaction in the form of a wave

Question 2

What’s the unit of frequency?

Answer 2

Hertz - one cycle per second

Question 3

Why does ultrasound differ from normal sound?

Answer 3

> 20 kHz

Question 4

Frequencies of diagnostic sonography:

Answer 4

1 - 20 MHz

Question 5

What did Tom Brown do?

Answer 5

Converted the idea of medical purposes of ultrasound scanning into a practical proposition

Question 6

How does diagnostic ultrasound work?

Answer 6

Short sound pulses are transmitted into the body

Reflection, scattering and absorption result in attenuation in the intensity of sound pulses through matter

Question 7

What does attenuation do?

Answer 7

Limits depth of ultrasound imaging

Question 8

Advantages of ultrasound:

Answer 8

Safe

No ionising radiation

Portable, compact and inexpensive equipment

Question 9

Disadvantages of ultrasound:

Answer 9

Highly operator dependent

Organs obscured by gas (e.g. lung) and structures surrounded by bone do not give clinically useful images

Question 10

What is the ultrasound machine like?

Answer 10

Monitor

US unit

Control panel

Transducers

Data storage device

Question 11

What does the US unit do on ultrasound machine?

Answer 11

Processes signals

Question 12

What do ultrasound transducers do?

Answer 12

Sends an ultrasound

Detects sound and converts it into an electrical signal for diagnosis

Question 13

What are piezoelectric crystals?

Answer 13

Ceramic crystals

Become distorted when echoes return to transducer - generates electric pulse processed into an image

Question 14

What do high-amplitude echoes produce?

Answer 14

Greater crystal deformation - generate larger electronic voltage

Result in brighter pixels on image

Question 15

What images are used because of the significance of high-amplitude echoes?

Answer 15

2D grey-scale images

A.K.A. B-mode images

Question 16

What are linear-array transducers like?

Answer 16

Linear array has a flat superficial surface

Only high-frequency probes used for superficial structures as don’t penetrate deeply

Letter L on image

Question 17

What are curved-array transducers like?

Answer 17

Linear array has a curved convex surface

Letter C on image

Question 18

What’s a phased-array transducer like?

Answer 18

Every element in array participates in formation of each pulse

Smaller - used between ribs

Question 19

What are intraluminal probes like?

Answer 19

Small - various body lumens

Positioned close to organ - allows use of higher frequencies

Higher quality images produced

Question 20

Disadvantages of intraluminal probes:

Answer 20

Limited imaging depth

Question 21

What is A-mode imaging also called?

Answer 21

Amplitude-mode

Question 22

What is A-mode imaging?

Answer 22

Displays echoes acquired in 1 dimension

Echo amplitude displayed along 1 perpendicular axis

Question 23

What is B-mode imaging also called?

Answer 23

Brightness or 2D mode

Question 24

What is B-Mode imaging?

Answer 24

Spike is converted into a dot

Brightness of dot = amplitude of returning signal

Position of dot = depth of returning signal

2D image produced

Question 25

Black images:

Answer 25

Anechoic E.g. fluid, pus

Question 26

Dark grey images:

Answer 26

Hypoechoic E.g. bone, gall stones, metal

Question 27

What does isoechoic mean?

Answer 27

Structure same shade of grey as surrounding tissue

Question 28

What colour images are solid organs usually?

Answer 28

Grey with black inside (where vessels are)

Question 29

What’s colour doppler?

Answer 29

Measures direction and magnitude of Doppler frequency shifts that occur in moving RBCs Produces grey-scale image

Question 30

What’s Power colour Doppler?

Answer 30

Depicts amplitude, or power, of Doppler signals

Question 31

Significance of Power colour Doppler:

Answer 31

Better sensitivity for visualisation of small vessels

Question 32

What’s Pulsed Doppler?

Answer 32

Positions sampling volume (or gate) in a vessel on grey-scale image Displays spectrum of range of blood velocities within gate

Question 33

What is M-mode also called?

Answer 33

Motion mode

Question 34

What is M-mode?

Answer 34

Analyses tissue motion

Question 35

What is 3D ultrasound imaging?

Answer 35

Uses 2D scanner and stack of parallel cross sections 3D images displayed in varying formats

Question 36

What does the gain control do?

Answer 36

Adjusts amplification of returning acoustic signals Optimises US image

Question 37

What does reduced gain produce?

Answer 37

Dark image Detail is masked

Question 38

What does too much gain produce?

Answer 38

White image Detail saturated

Question 39

Why must the US image be properly oriented?

Answer 39

To identify anatomic relations of various structures on the monitor Groove on transducer = orientation marker

Question 40

What is enhancement?

Answer 40

Brighter area in image due to sound passing more easily through a structure

Question 41

What are the US probe manipulation manoeuvres?

Answer 41

Pressure Alignment Rotation Tilt

Question 42

Tilting the probe:

Answer 42

90 degrees to structure of interest

Question 43

What is anistropy?

Answer 43

An artefact encountered - may result in incorrect diagnosis

Question 44

What is the anisotropic effect dependent on?

Answer 44

Angle of ultrasound beam

Question 45

What may the dots on right side of screen correspond to?

Answer 45

1cm intervals on patient - give estimate of depth