Beam Former - Principle 1

Question 1

Where does scanning, focusing, and apodization occur?

Answer 1

The beam former - specifically the pulser and pulse delays

Question 2

What artifact is reduced via apodization?

Answer 2

Grating lobes/side lobes

Question 3

What part of the beam former generates voltages that drive the transducer?

Answer 3

Pulser - sequencing and phasing are carried out by the pulser and pulse delays

Question 4

How does the sonographer adjust for PRF?

Answer 4

Changing the DEPTH of the image

Question 5

What artifact violates the idea that US assumes that the first pulse sent out is received back to the transducer before the next pulse?

Answer 5

Range Ambiguity

Question 6

Where is the output power/driving voltage produced?

Answer 6

The pulser

Question 7

What is the benefit of having an increased number of “channels” within the transducer?

Answer 7

Allows more precise control of the beam

Question 8

During transmission, the T/R switch opens the path from the pulser to what?

Answer 8

Transducer elements

Question 9

During reception, the T/R switch opens the path from the elements to what?

Answer 9

Reception amplifiers

Question 10

The beam former has how many amplifiers for each channel?

Answer 10

One

Question 11

What do ADC’s convert the analog voltages representing echoes into?

Answer 11

Numbers

Question 12

In what part of the imaging process includes bandpass filtering, amplitude detection, and compression?

Answer 12

Signal processor

Question 13

What rejects frequencies above and below the accepted bandwidth?

Answer 13

Bandpass filter

Question 14

What is amplitude detection also known as?

Answer 14

Demodulation

Question 15

What is the process of decreasing the smallest and largest echo amplitudes to a useable range?

Answer 15

Compression

Question 16

What is higher: display dynamic range or visual dynamic range?

Answer 16

Display DR: which is why we need compression

Question 17

In terms of compression and DR, what setting gives the highest level of contrast resolution?

Answer 17

High compression, low DR

Question 18

What type of resolution is compression important for?

Answer 18

Contrast

Question 19

When is an echo stored in image memory?

Answer 19

When it is converted from A mode to B mode during scan conversion

Question 20

Storing the last several frames acquired before freezing is called?

Answer 20

Cine loop

Question 21

How do we calculate bit depth?

Answer 21

2 ^ n

Question 22

How many shades of grey can an ultrasound unit display?

Answer 22

256

Question 23

Describe acoustic and non-acoustic zoom and if they can be used preprocessing or postprocessing?

Answer 23

Acoustic = write zoom - pre-processing only where new beams are formed in the zoomed display

Non-acoustic = read zoom - NO new sound beams, only magnification of the image

Question 24

What type of resolution is improved using write zoom?

Answer 24

Detail

Question 25

What type of zoom will increase pixel size/stretching of the image?

Answer 25

Read zoom (non-acoustic)

Question 26

What are the three main functions of pre-processing before the image is stored into memory? (Done via image processing)

Answer 26

1. Write (acoustic) zoom
2. Persistence / frame averaging
3. Pixel interpolation

Question 27

What is persistence?

Answer 27

Reduces noise and smoothens the image via frame averaging