Digital Imaging Systems

Question 1

What is the fundamental element of a digital image?

Answer 1

the PIXEL (picture-element)

Question 2

Digital

Answer 2

numeric format of image content and its discreteness

Question 3

What are digital images?

Answer 3

Large collection of individual pixels organized in a matrix of rows and column

Question 4

How is the location of each pixel uniquely identified?

Answer 4

By a row and column coordinate within the image matrix

Question 5

Digital image is made up of a large number or

Answer 5

discrete pixels

Question 6

For every pixel, 2 numbers are recorded. What is the 1st number?

Answer 6

Assigns location

Question 7

For every pixel, 2 numbers are recorded. What is the 2nd number?

Answer 7

Assigns brightness

Question 8

The bigger the pizels, the

Answer 8

less detailed the image

Question 9

The smaller the pixels, the

Answer 9

better the detail

Question 10

At each pixel of an electronic detector, the absorption of xrays generates

Answer 10

a small voltage

Question 11

More xrays generate a

Answer 11

higher voltage

Question 12

At each pixel, the voltage can flucturate between a min and max value and is therefore an

Answer 12

analog signal

Question 13

Production of a digital image requires

Answer 13

Analag to digital conversion

Question 14

ADC (analog to digital conversion) requires what 2 steps?

Answer 14

• Sampling
• Quantization

Question 15

What is sampling in ADC?

Answer 15

Grouping small range of voltage values –> single value

Question 16

What is quantization of ADC?

Answer 16

A sample signal is assigned a value

Question 17

Examples of solid state detectors

Answer 17

CCD/CMOS

Question 18

Smaller pizel size, the _____ spatial resolution

Answer 18

higher

Question 19

Pixel size of solid state detectors

Answer 19

20-70

Question 20

In solid state detectors, charges are proportional to

Answer 20

amount of radiation received

Question 21

In solid state detectors, charges are generated in cells when they are

Answer 21

irradiated

Question 22

In solid state detectors, the charge pattern formed from the individual pixels in matrix represents the

Answer 22

latent image

Question 23

CCD sensors move charge

Answer 23

row by row, pixel by pixel and convert it to voltage at an output anode

Question 24

CMOS sensors convert charge to

Answer 24

voltage inside each pixel

Question 25

Active area of solid state sensors is ______ than the physical size

Answer 25

less

Question 26

What are flat panel detectors used for?

Answer 26

Medical imaging, extra-oral imaging or cone beam

Question 27

Photostimulable phosphor plates (PSP) are plastic plates coated with

Answer 27

Europium dopped barium fluorohalide

Question 28

PSP plates have extremely good contrast resolution due to

Answer 28

high exposure latitude, means longer gray scale

Question 29

What are some advantages of PSP?

Answer 29

- Lower initial cost modality - Easy to use and perform FMX - Cheaper - Great latitude in radiographic exposures

Question 30

What are disadvantages of PSP?

Answer 30

- Scratch easily - Need to insert each plate into indiv barrier - Req erasing after each use - Req scanning of latent image - High cost of a scanner - Lower res

Question 31

What are advantages of digital radiographs?

Answer 31

- Immediate image display - No film and room processing - Dynamic image - Reduced radiation dose (60-80% less) - easy image storage, transferability and communication - Cheaper

Question 32

What are disadvantages of digital radiographs?

Answer 32

- Decreased resolution (11 line pair/mm) - More retakes - Set-up cost - Susceptible to rough handling - Cable attachment - Hygiene - Evolving technology