Radiology - Digital vs Film

Question 1

what types of intra-oral image receptor are used in digital radiography?

Answer 1

phosphor plates

solid state sensor

Question 2

what types of intra-oral image receptors are used in film radiography?

Answer 2

direct action film

indirect action film

Question 3

when is a size 0 image receptor used?

Answer 3

anterior periapicals

Question 4

when is a size 2 image receptor used?

Answer 4

bitewings

posterior periapicals

Question 5

when is a size 4 image receptor used?

Answer 5

occlusals

Question 6

in digital radiography, what colour does the grid square go when few photons are reaching the receptor?

Answer 6

white - value 255

Question 7

what type of image receptor (film or digital) used grid squares/pixels?

Answer 7

digital

Question 8

what is the benefit of a digital radiograph having more grid squares/pixels?

Answer 8

better detail as it has higher resolution

resolution has a limit in terms of being beneficial cliniccally

Question 9

what are the disadvantages using digital receptors?

Answer 9

each image requires storage space which is expensive

Question 10

how many bits (binary digits) do digital radiographs typically use to create an image?

Answer 10

8 bits (binary digits)

= higher the number of bits the more accurate

Question 11

what is the total number of shades of grey used in digital radiographs?

Answer 11

256 shades of grey

Question 12

what is the format for digital images?

Answer 12

DICOM - digital imaging and communications in medicine

Question 13

what software manages digital images?

Answer 13

PACS - picture archiving communications system

Question 14

what is the limitation of PACS?

Answer 14

Hospital PACS is not linked to practices - have to ask for them separately

Question 15

how do we view digital radiographs?

Answer 15

subdued lighting without glare

clean, bright monitor with adequate resolution and contrast

Question 16

describe how digital phosphor plates work.

Answer 16

not connected to a computer

after use the plate is put in a scanner and read to create the final image.

Question 17

describe how the phosphor plate used in digital radiographs create the visible image.

Answer 17

Receptor is exposed to the x-ray beam

Phosphor crystals in receptor are excited by the x-ray energy = latent image

The receptor is taken out of the mouth, taken out of the packet and disinfected

Then it is placed in the scanner

The laser from the scanner excited the phosphor crystals and they emit visible light
= digital image

Question 18

list the types of digital solid state sensors.

Answer 18

CCD

CMOS

Question 19

describe how solid state digital sensors work.

Answer 19

usually wired to a computer (some aren’t)

Latent image is created within the receptor and then also immediately read within the sensor to create an image instantly.

Question 20

how is cross contamination minimised when using intra-oral receptors?

Answer 20

covering them with a single use cover
i.e. adhesive sealed plastic covers or long plastic sleeves for receptors with wires.

receptors disinfected between uses

Question 21

Compare digital phosphor plates to solid state sensors.

Answer 21

PP are thinner and flexible where as SS are bulkier and rigid

PP are wireless whereas SS are usually wired to a computer

PP are sensitive to daylight and have to be kept in a dark container whereas SS dont have any problems with room light control

PP have to be processed in a scanner whereas SS are processed immediately.

PP are delicate whereas SS are more durable and have to be replaced less often.

SS more expensive

Question 22

what are the advantages of digital receptors? (6)

Answer 22

• No need for chemical processing
• Images can be manipulated
• Easy storage and archiving of images
• Easy back-up of images
• Radiographs can be integrated into patients records
• Easy sharing and transfer

Question 23

what are the disadvantages of digital receptors? (5)

Answer 23

• Risk of pixelation = worse resolution compared to film as you can only have a certain number or pixels in a digital radiograph.
• Requires computer monitors for optimal viewing
• Risk of loss /corruption (however this can be overcome by backing the radiographs up)
• If you print these images = poor quality image
• Image enhancement can create misleading images.

Question 24

what is radiographic emulsion (film)?

Answer 24

Silver halide crystals embedded in a gelatin binder

The crystals act as the pixels (that is present in the digital radiograph receptors)

Question 25

what type of image receptor (film or digital) has higher resolution and why?

Answer 25

film is generally higher resolution than digital as the silver bromide crystals are smaller (than pixels)

Question 26

How do the silver halide crystals create the latent image in film radiology?

Answer 26

Become sensitised upon interaction with x-rays (& visible light) - Sensitised crystals are converted to black metallic silver = dark parts of the image - Non-sensitised crystals are removed = light parts of the image

Question 27

What is the role of the lead foil in a film packet?

Answer 27

absorbs excess x-ray photons

Question 28

what is the purpose of the embossed pattern of the lead foil in a film packet?

Answer 28

so that you can detect if the film packet has been placed the wrong way around in the mouth - if it has, the pattern will be superimposed on to the radiograph and it will be pale

Question 29

when are intensifying screens used in film radiology?

Answer 29

extra-orals - too bulky to be used in the mouth

Question 30

what are intensifying screens used in film radiology for?

Answer 30

reduce the radiation dose

Question 31

define film processing

Answer 31

Converts invisible latent image in the emulsion to a visible permanent image

Question 32

list the methods of film processing (3)

Answer 32

Manual Automated Self developing films (less common)

Question 33

list the stages in film processing.

Answer 33

1. Developing - Converts sensitised silver bromide crystals to black metallic silver particles 2. Washing - removes residual developer solution 3. Fixing - removes non-sensitised crystals (allows lighter areas to be seen) and hardens emulsion 4. Washing - removes residual fixer solution 5. Drying - removes water so that film can be handled and stored

Question 34

describe what occurs in wet developing.

Answer 34

Person dips film into different chemicals at precise concentrations and temperatures for specific periods of time. The film is washed after each tank. - This must be carried out in a dark room with red lights and ventilation

Question 35

what are the advantages of automated film processing ? (4)

Answer 35

Faster More controlled Avoids the need for a dark-room Sponge rollers squeeze the solution out of the film instead of washing

Question 36

describe how you prepare the film packet for automated processing.

Answer 36

- Disinfect the surface of the packet - Hold the packet under the hood of the processor unit (to prevent interaction with the daylight) All of these steps one within the automated unit; - Peel back the flap out of the outer wrapper - Fold back the lead foil - Pull back the paper flap - Hold the film by the edges - Insert film into the processor shelf and it passes through the cycle.

Question 37

what are the advantages of self developing film processing (not recommended)?

Answer 37

- No darkroom or processing facilities required | - Faster

Question 38

what are the disadvantages of self developing film processing (not recommended)? (6)

Answer 38

- poorer image quality - Image deteriorates more rapidly over time - No lead foil - Easily bent - Difficult to use in positioning holders - Expensive

Question 39

what issues can arise during the film developing stage?

Answer 39

film not put in the solution for long enough = pale developer solution is too cold = pale developer solution is too dilute = pale developer solution can oxidise and become less effective = pale

Question 40

what issues can arise during the film fixing stage?

Answer 40

• Inadequate fixing = non-sensitised crystals are left behind and the image appears greenish/yellow/milky and becomes brown over time which makes the image harder to see and less diagnostically useful.

Question 41

what issues can arise during the film washing stage?

Answer 41

Developer and fixer solution continues to act if not washed off properly