Exam 3 review

Question 1

Pre-Processing

Answer 1

Takes place before scan conversion and cannot be changed on data that has been stored in the internal system

TGC, receiver, beam former, console, transducer

Question 2

Scan converter

Answer 2

Where most work is done

A-mode to B-mode, memory, cine loop

Question 3

Post-Processing

Answer 3

Takes place after scan conversion and can be changed after the data has been stored in the internal system

Display, Storage (PACS), measurement, and printing

Question 4

Dynamic range

Answer 4

number of available choices, method of reporting the extent to which a signal can vary and still be accurately measured.

Measured in Decibels

When too large, it’s compressed, information is lost

Question 5

The Receiver

Answer 5

Amplification, compensation, compression, demodulation, and rejection

Question 6

Amplification

Answer 6

The process of multiplying the received signal to make the signal larger

Question 7

Compensation

Answer 7

Preformed by TGC and overall gain

Question 8

Compression

Answer 8

Signal is compressed so the ratio of max and minimum signals is reduced

Question 9

Demodulation

Answer 9

Takes any signal below the baseline and flips it so it’s above the baseline then smoothes the signals out

Question 10

Rejection

Answer 10

Any signals below a threshold are eliminated as too weak to be of any value

Question 11

A-mode

Answer 11

Amplitude mode, shows amplitude and time(or depth)

Question 12

B-mode

Answer 12

Brightness mode

Question 13

M-mode

Answer 13

Motion mode, typically used in cardiac imaging, non scanned modality.

Question 14

Analog vs. Digital

Answer 14

For ultrasound, signals must be in digital form like a computer

Question 15

Binary

Answer 15

Expressed in 0’s and 1’s, on and off time

Question 16

Signal to noise ratio

Answer 16

no noise= high signal to noise ratio
Machine averages images to increase SNR and gives a clearer image
Good for ultrasound

Question 17

Pixel

Answer 17

Picture element

Question 18

1.5D transducers

Answer 18

Can produce 2D images and improves elevation resolution

Question 19

2D transducers

Answer 19

Can produce 3D and 4D images and improves elevation resolution

Question 20

Edge enhancement

Answer 20

optimizes images on their edges, similar to spatial averaging

Question 21

Spatial averaging

Answer 21

The averaging of pixels to create a smoother image

Question 22

Spatial resolution

Answer 22

2D “in space”

Pixel size, # of bits, pixel density, lateral resolution, line density all affect spatial resolution

Question 23

Contrast resolution

Answer 23

Shades of grey

High contrast, low contrast resolution= small # shades (bits)
Low contrast, high contrast resolution= large # shades (bits)

Question 24

Grey scale map assignment

Answer 24

Digital # in scan converter, takes amplitude and assigns shades of grey to each number

Question 25

Read magnification

Answer 25

“Magnifying glass”

If image quality is poor, read magnification will be poor as well

Question 26

Write magnification

Answer 26

Optimizes and rescans in better detail

“Microscope”

Question 27

Multiple transmit focus

Answer 27

Composite of multiple transmits in the same line, each with a different focus

Advantages: improved lateral resolution
Disadvantages: degraded temporal resolution and banding noise artifact

Question 28

Dynamic receive focus

Answer 28

Changing the receive focus depending on the depth of the returning reflection, does not change temporal resolution

2 methods:
changing the active window (aperture) of the transducer
changing the delay profile

Question 29

Parallel processing

Answer 29

A wider transmit beam is sent, the receive beam is broken into two or more parallel groups which are processed simultaneously

Advantages: does not degrade temporal resolution

Question 30

Interpolation

Answer 30

A process of filling in the gaps for regions of the image where a scan line did not exist, especially in the far field with sector images

Question 31

Averaging techniques

Answer 31

When more than 1 acoustic line is added together, true signals will add constructively, all averaging techniques improve SNR

Question 32

Spatial compounding (sono CT, cross beam)

Answer 32

One acoustic line is scanned at different angles and then added together

Advantages: improvement in SNR, reduction of artifacts due to specular reflection
Disadvantages: short duration events might be averaged out

Question 33

Image persistance

Answer 33

Averaging is done by frame count and/or weighting, there is no angle change

Disadvantage: short duration events can be averaged out

Question 34

Spatial averaging

Answer 34

An averaging technique at the pixel level, not at frame level.
Averaging pixels results in a reduction in dropout signals or noise

Question 35

Frequency compounding

Answer 35

Averaging multiple images using different frequencies, done as a parallel process and needs a wide broadband for multiple frequencies

Advantages: does not degrade temporal resolution, improves image texture

Question 36

Panoramic imaging

Answer 36

Moving the transducer across the patient to build up a 2D image over time

Advantages: the extended field of view can potentially display a whole organ

Question 37

Adaptive processing (auto optimize, iScan, NTEQ)

Answer 37

The system automatically adapts or controls the system settings depending on the signals it is receiving

Advantages: could result in better scans
Disadvantages: the system assumptions might not be appropriate for the scan