digital processing

Question 1

why is digetal better

Answer 1

• improved dynamic range of images (similar to photoshop, can improve brightness, contrast, quality)
• digital processing is very fast
• digital storage, retrieval and transport (PACS) – cant lose the radiograph or mistake it with someone elses

Question 2

how is the image captured

Answer 2

• image is captured with a sensor

- image then transformed into series or binary number (0 and 1)

Question 3

types of sensors that cn be used

Answer 3

• computed radiography (CR)

- CCD (charge coupled device)/ CMOS(complementary metal oxide semi conductor) – similar to mobile phone camera

Question 4

digital radiography how does it work (CCD/CMOS)

Answer 4

• sensor has lots of photodiodes, uses the intermediate step of light production to form image
• or CCD, x ray photons fall onto the phosphor and emit a small flash of light
• the silicon of the receptor acts as a photodiode and converted the light emitted by the phosphor to electrical charge
• the intensity of electrical charge is directly proptional to the light flash which is directly proportional to amount of radiation that fell onto the photodiode
• the charge pattern formed from the pixels in the sensor matric forms the radiographic image

Question 5

resolution is measured by

Answer 5

line pairs per mm

Question 6

what can you do with digital photograpjhy

Answer 6

manipulate the image to increase its diagnosis value

Question 7

problems with digital receptors

Answer 7

1) Laser malfunction
- scan sensor with laser
- one at a time, sequential
- if beam not smooth process can produce dark line/bands

2) Sensor wrong way round/back to front
- easy to spot on film
- white circle (foil) on one side of receptor and not on the other

3) PSP delaminating
- plastic backing with barium fluro… on one side of the slide
- sometimes can start to delaminate
- on the edges of film start to separate
- see white artefact with uneven edge
- sensor need to replaced
4) Bends in PSP
- can over bend film
- can see linear white lines that cross the censor usually along the curvature of the sensor
- adapt to patient mouth
- can get a crack in the phosophor – thin radiopaque line (can be mistken with instruments
- doesn’t have flutes or spirals which endodontic files have