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Radiology & Radiography > Digital Imaging > Flashcards

Digital Imaging Flashcards

1
Q

What are the advanatges of digital x ray imaging?

A

Negates the need for chemical processing
*reduces processing errors
Enhancement of the imagine obtained

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2
Q

What is resolution?

A

Counting the number of pixels in a given linear unit

Measured in lp/mm

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3
Q

How are images produced?

A

outputting pixels in lines

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4
Q

What is the resoltuion of a conventional film?

A

22lp/mm

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5
Q

What colour are pixels in a digital image?

A

Grey

They are assigned a shade of grey depending on the amount of radiation reaching the sensor

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6
Q

T/F

The Digitial imaging receptor film based?

A

False

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7
Q

What are the advanatges of digital imaging?

A 
Lower radation dose (40-80%) reduction
Elmination of film processing
Sensors maybe re used
Manipulation so image can be improved
Stored on computer
Images can be transmitted electrically
Subtraction techniques may be used
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8
Q

What type of receptors are used in digital imaging?

A

Digital which can be either direct action or indirect action

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9
Q

What type of image does a direct action rimage receptor produce?

A

Instant image

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10
Q

What type of image does an indirect image recpetor produce?

A

image needs to be processed in a laser scanner

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11
Q

How does Direct Digitial imagine work?

A

this used a charged couple device (CCD) or a CMOS complimentary metal oxide semiconductor

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12
Q

What are CCD’s? What are the advantages and diasadvantes?

A

A photodiode absorbs photons and produces charge representing pixels
Converts light into electrons
Expensive to manufacture as they have to transport charge across the chip without distortion

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13
Q

What kind of image to CCD’s produce?

A

High quality and low noise

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14
Q

How do CMOS work?

A

Convert light to an electrical charge and then process into electrical signals

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15
Q

WHat are the features ofCMOS?

A

Lowe power
Easter to manufacture same Process as microprocessors
Cheap or manufacture
Light sensitivity lower than CCD
Image noisier than CCD
Active area small compared to size of sensor
More flexible since each pixel can be read individually

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16
Q

How do wireless sensors work?

A

They use radio frequency transmission

17
Q

What method do Phostimuable Phosphor plates use?

A

They are a method of indirect digital imaging

18
Q

What type of plate is used in the PSPs?

A

Plastic plate Coated with a phosphor material which is sensitive to X-rays

19
Q

What does the phosorh plate to with the X-ray energy?

A

It stores it

20
Q

How is the image generated in the PSP?

A

Indirect

The PSP plate is then placed in a laser reader which releases the photon energy as light

21
Q

What are the advantages of PSP over CCD?

A

Larger variety of imaging areas
No bulky connecting cable
Slimmer imaging plate
Variations in exposure potentially correctable
More unform response across plate
Trasmission cable from CCD may cause noise

22
Q

What are the disadvantages of PSP?

A

Plates must be processed within 8 hours
Requires separate processing therefore adds timing
Need to ensure plate is cleared before re using
Careful handling to prevent scratches

23
Q

How can you manipulate digital images?

A

Altering brightness by lowering or raising all grey levels together

24
Q

How can you change the contrast of the image?

A

Altering the contrast multiplies or divides all the grey level numbers by the same amount so that the relative grey level ratios are maintained

25
Q

How do the CCD vs PSP vS film compare with their diagnostic abilities?

A

Caries: same
Periapical: same
Endo files visualisation: same

26
Q

What are the advantages if digital imaging?

A 
Lower radiation dose (by 40-80% for IO dose)
Elimination of processing 
Sensors maybe re used
Manipulation to improve image 
Computerised storage 
Electrical transmission of images
Maybe used with subtraction techniques
27
Q

What are the disadvantages of digital imaging?

A 
Cost
Cross infection 
Bulky rigid sensors
Physical damage to sensors 
Limitation in the size of sensors 
Physical damage to wire onnCCD
Some CCD show distortion around edges of image 
Images maybe manipulated
28
Q

How many line pairs per mm can the human eye resolve?

A

8 without magnification

29
Q

What is the resolution of current dental systems ?

A

6-22lp/mm

30
Q

What is the resolution depansstnt upon?

A

Pixel size

Decreasing the pixel size gives better image

31
Q

How many shades of grey in a typical digital image?

A

256

32
Q

T/F conventional films can be scanned and made into a digital image?

A

T

Radiology & Radiography (11 decks)

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