digital imaging

Question 1

analogue images

Answer 1

• have a continuously varying density across them

Question 2

digital images

Answer 2

• Have discrete pixels with numerical density values

Question 3

digital imaging series

Answer 3

• generation
• processing
• archiving
• presentation

Question 4

types of digital radiography

Answer 4

computed radiography

digital radiography

Question 5

computed radiography

Answer 5

• uses imaging plates which need developing in a processor

Question 6

digital radiography

Answer 6

• acquires an image directly without using a processor

Question 7

main digital image detector functions

Answer 7

• capture - absorbing x-rays
• coupling - linkage between the capture element and converter
• conversion - change of x-ray energy into an electrical signal which can be read

Question 8

advantages of digital radiography

Answer 8

• time-efficient - receive image immediately
• ## reduction of unsharpness - no spread of light

Question 9

advantages of indirect imaging

Answer 9

• can reduce dose/exposure

Question 10

digital imaging (DR)

Answer 10

• Image does not need to be procecessed
• the image is sent to the computer via wireless connection
• the imaging detectors can either be fixed plates in a vertical or table bucky or portable cassettes

Question 11

Selenium drum detector system

Answer 11

• the photoconductor is made of amorphous selenium ( generates an electrical charge
• has a detector drum
• A-D converter - readout process

Question 12

In ….. x-ray energy is converted directly into electrical signal

Answer 12

DDR

Question 13

a simple conversion process of x-rays to electronic signal reduces noise in……

Answer 13

DDR

Question 14

one advantage for ….. is good image resolution

Answer 14

DDR

Question 15

one advantage for… is reduction in patient dose, since x-ray exposure can be reduced

Answer 15

CR

Question 16

…. can give a salt and pepper appearance

Answer 16

CR

Question 17

one advantage of… is amplification of signal

Answer 17

CR

Question 18

one advantage of … is image sharpness

Answer 18

DDR

Question 19

One disadvantage of …. is that the extra energy conversion process produces image noise

Answer 19

CR

Question 20

in…. X-rays first strike a light-producing layer, light is then used to produce an electrical signal in the detector plate

Answer 20

CR

Question 21

Dose creep occurs in …

Answer 21

DDR

Question 22

….. gives a lower dose to the patient

Answer 22

CR

Question 23

…. uses cassettes, containing imaging plates which need processing

Answer 23

CR

Question 24

…. Acquires an image without using a cassette or processor

Answer 24

DDR

Question 25

.......... can be linked via PACS

Answer 25

Both CR and DDR

Question 26

.... is a direct method

Answer 26

DDR

Question 27

.... is an indirect method

Answer 27

CR

Question 28

one disadvantage of .... is that the light spread produces image fuzziness

Answer 28

CR

Question 29

..... has a photoconductor of amorphous selenium

Answer 29

DDR

Question 30

....... has a scintillation crystal made of caesium iodide activated with Thalium

Answer 30

CR

Question 31

a simple conversion process of x-rays to electronic signal reduces spatial blurring in ......

Answer 31

DDR

Question 32

purpose of a photoconductor

Answer 32

- absorbs light and then produces an electrical charge

Question 33

flat-panel detector system

Answer 33

the photoconductor is made of Amorphous selenium uses a TFT Array read-out process.

Question 33

flat-panel detector system

Answer 33

the photoconductor is made of Amorphous selenium uses a TFT Array read-out process.

Question 34

flat-panel detector system

Answer 34

the photoconductor is made of Amorphous selenium uses a TFT Array read-out process.

Question 35

types of Amorphous Selenium DR systems

Answer 35

- selenium drum detector system | - flat-panel detector system

Question 36

indirect DR

Answer 36

- each cell in the detector has a top layer of a scintillation crystal (made of CsI (caesium iodide) activated with thallium - which produces light when hit by x-rays - below this, an amorphous silicon photodiode converts the light into an electric charge

Question 37

types of CCD indirect radiography systems

Answer 37

lens-coupled CCD based system Slot scan CCD based system

Question 38

lens-coupled CCD based system

Answer 38

x-rays are converted into light by the scintillation crystals - light passes through an optical lens and light is received by the charged-couple device

Question 39

Amorphous silicon indirect DR system

Answer 39

x-rays are converted into light by the scintillation crystals - this light is received by the Amorpous silicon photodiode - light energy is converted to electrical energy and is received by the TFT array

Question 40

what is quantum mottle

Answer 40

at very low mAs values, random fluctuations in x-ray intensity beam start to show - image can appear grainy

Question 41

CR system

Answer 41

x-rays hit the first storage phosphor IP and are stored a laser is emitted and hits the second storage phosphor IP a blue light is then emitted and is received by the photomultiplier then the photomultiplier sends this light to an A/D converter where an electrical charge is produced

Question 42

what is image noise

Answer 42

- random fluctuations in signal, due to imperfections in image recording/transfer process

Question 43

sources of noise

Answer 43

- background scatter - detector faults - random electrical fluctuations - quantum mottle