Digital Radiography

Question 1

When was digital radiography introduced?

Answer 1

1987

Question 2

Does digital radiography use more or less radiation than conventional?

Answer 2

Less. Sensor is more sensitive to x-rays than conventional film

Exposure times are 50-90% less than what is required for conventional

Question 3

What are the essential equipment components for digital radiography?

Answer 3

x-radiation source, intraoral sensor, computer

Question 4

What is the time frame for exposure that the x-ray source must be adapted to allow?

Answer 4

1/100 of a second

Question 5

What are the digital sensors coated with?

Answer 5

Phosphor

Question 6

What are the three types of sensors that exist? Which is the most commonly used?

Answer 6

1) Charged-coupled devide (CCD)
2) Complementary metal oxide semiconductor/active pixel sensor (CMOS/APS)
3) Charged injection device (CID)

CCD is most commonly used

Question 7

What is a CCD sensor?

Answer 7

Solid-state detector that contains a silicon chip w/ electronic circuit embedded in it. Light sensitive.

Made up of electrons that can be divided and visualized as pixels

Equivalent of a silver crystal used in film.

Question 8

How many pixels in a CCD sensor comprised of? What is its function?

Answer 8

640X480 pixels

Contains 307,200 pixels and functions to sense transmitted light and translate it into an electronic image

Question 9

What is an electronic potential well?

Answer 9

The pixel arrangements

Contain a charge proportional to the # of electrons that reacted within the well

Each well corresponds to a specific area on the linked computer screen

Question 10

What is CMOS/APS?

Answer 10

Another seonsor technology. Difference to CCD is the way in which the pixels are read.
Company that makes them claims 25% better resolution
Also cheaper to manufacture and are more durable than CCD sensors

Question 11

What is the role of the computer in digital radiography?

Answer 11

Responsible for converting the electronic signal into a shade fo gray that is viewed on the monitor.

Pixels are represented numerically by location and level of gray (gray scale resolution)

Allows for manipulation of image to enhance contrast and density without additional exposure to patient

Question 12

What are the two types of digital imaging?

Answer 12

Direct digital imaging

Indirect digital imaging

Question 13

What is direct digital imaging?

Answer 13

Sensor is exposed to radiation and transferred directly to the computer

Question 14

What is indirect digital imaging?

Answer 14

Storage Phosphor Imaging or photo-stimulable phosphor imaging (PSP)

Considered indirect because a scanner is needed to digitize and transfer the image to a computer

Question 15

Describe the PSP plates

Answer 15

Coated in phosphor and flexible like film. Also similar in size, shape and thickness

Image remains on the plate until it is erased. Some scanners will do this

Question 16

Which technique is preferred when using digital sensors?

Answer 16

Paralleling technique because of the dimensional accuracy or images and ease of standardizing such images

Question 17

Advantages of digital imaging

Answer 17

• Superior gray-scale resolution
• Reduced exposure to radiation
• Increased speed of viewing
• Lower equipment and film cost
• Increased efficiency
• Enhancement of diagnostic images
• Effective patient education tool

Question 18

Disadvantages of digital radiography

Answer 18

• High initial set-up costs
• Image quality (debatable as human eyes can only resolve up to a certain point)
• Sensor size (thicker)
• Infection control (cannot sterilize)
• Legal issues (image manitpulation)