Module 2 Review key

Question 1

What causes electrons in a cathode ray tube (CRT) to go towards the phosphor?

Answer 1

The electrons have a negative charge and are attracted by the positive anode

Question 2

What is a raster scan?

Answer 2

Scanning from left to right, top to bottom

Question 3

What controls the position of the electron beam in storage CRT?

Answer 3

The charged deflection plates

Question 4

Why was the scan converter such an important step in the development of ultrasound?

Answer 4

Allowed for grey scale

Question 5

Why is an analog scan converter obsolete today?

Answer 5

Less stable than digital with less processing ability

Question 6

How many lines of information are on a standard television?

Answer 6

525 lines

Question 7

Beginning with the electron beam at the top left of the television monitor; describe how television images are formed?

Answer 7

Lines are written from left to right; first the odd then the even

Question 8

Distinguish between operating and program software?

Answer 8

Operating software tells the machine how to behave and the program software is necessary to use the machine

Question 9

Identify some fundamental difference between an analog and digital scan converter

Answer 9

Digital stores numbers and is more stable whereas analog stores a charge and is not permanent

Question 10

Distinguish between an interlaced and progressively scanned image

Answer 10

Interlaced is odd then even and progressive is scanned in order from top to bottom

Question 11

State the five functions typically associated with the receiver and state what each function accomplishes

Answer 11

1. Application: gain
2. Compensation: TGC
3. Compression: Dynamic range
4. Rejection: Eliminates low level echoes
5. Demodulation: compressed of rectification and smoothing to convert the RF signal into a video signal

Question 12

Distinguish between electronic and mechanic damping and state where each is accomplished?

Answer 12

Mechanical damping is the backing material attached to back of the crystal and electronic is from the pulsed that sends the inverse of the original pulse

Question 13

Why is it preferable to digitize the ultrasound echoes as early as possible?

Answer 13

The signal will be more stable

Question 14

Name the parts of the beam former

Answer 14

1. Pulsed
2. Pulse delays
3. T/R switch
4. Amplifier
5. ADC
6. Echo delay
7. Sumer

Question 15

What does the pulsed do?

Answer 15

Creates the pulse to send to the crystal controlling the PRF, signal amplitude and operating frequency

Question 16

What does the pulse delay do?

Answer 16

Controls the steering of the beam and the focus

Question 17

What does the T/R switch do?

Answer 17

Directs the signal into the appropriate direction

Question 18

What does the amplifier do?

Answer 18

Boost the amplitude of the returning signal

Question 19

What does ADC do?

Answer 19

Digitizes the signal for stability

Question 20

What does the Sumer do?

Answer 20

Add the echo information to help form an image

Question 21

Explain the importance of bit depth with regards to contrast resolution

Answer 21

Increasing the bit depth allows for
1. More shades of grey so that the machine can manipulate the dynamic range
2. Improves the contrast between structures with similar echo strengths