digital radiography

Question 1

80kV, mAs 10
increased to 90 so new mAs is 5

Answer 1

kv-
100- 0.75mAs
80 -3mAs
70 - 6mAs
60 - 12mAs
40 - 48 mAs

Question 1

Digital radiography is split into categories

Answer 1

• computed radiography
• direct digital radiography
• indirect digital radiography
• DDR and IDR are typically included in the same category

Question 2

computed radiography

Answer 2

• cassete based digital radiography
• the cassette protects the imaging plate from light, and handling.
• the imaging plate is the equivalent of the x-ray film from traditional radiography
• the imagining plate consists of many layers
• protective layer
  -phosphor layer
• reflective layer
• conductive layer
  -colour layer
• support layer
  -backing layer (with barcode)

Question 3

How does CR work

Answer 3

• xray photons cause excitation of photons in the phosphor layer, trapping electrons, creating an image
• the cassette is then placed in a processor
• the processor removes the imaging plate from the cassette
• the imagining plate is scanned with a laser, providing energy to release the stored electrons, emitting photons of light.
• photons are detected and digitalised, and then viewed on the computer monitor

Question 4

Digital Radiography

Answer 4

• does not require a cassette
• uses flat panel detectors or charged couple devices which are connect through a wired or wireless connection to a computer
• detectors are split into two categories:
• Direct conversation (DDR) is a one-phase process, converting x-ray energy into an electrical charge and is made - up of a photoconductor and a thin film transistor.

indirect conversion is a two phase process x-ray energy is first converted into light and then into an electrical charge. The FPD is made up of a scintillator, photodiode and TFT. CCDs are made up of a scintillator and CCDs (and sometimes also include an optical lens)

Question 5

CR and DR and Film Based Radiography

Answer 5

Advantages CR/DR
- lower risk of overexposure
-ideal for high workflow
-more efficient

Disadvantages CR/DR
- risk of damaged equipment
-higher cost
- can take a while to develop
- phosphor image plates can be damaged

advantages FBR -
- film screen combos have a higher resolution than digital radiography
- preferred for precise industrial inspections

disadvantages -
-environmental impact
- radiation exposure
-more chemicals -COSHH

Question 6

x- ray cassette layers

Answer 6

protective layer - very thin, tough clear plastic for protection of the phosphor layer

phosphor layer - a layer of photostimulable phosphor that ‘traps’ electrons during exposure

reflective layer - contains light absorbing material and sends light in a forward direction when released in the cassette reader

conductive layer - absorbs and reduces static electricity

colour layer - contains fluorescent materials called phosphors that convert x- ray photons into visible light/ absorbs stimulating light but reflects emitted light

Support layer - ensures proper contact between the imaging plate and cassette and gives it strength

Backing layer - protects the back of the cassette and is a soft polymer

Question 7

Recap

Answer 7

Advances in technology have enable d rapid exposure, processing, and interpretation through CR and Dr

high start - up cost but minimal time required for ongoing maintenance

enables rapid communication between professionals

some concerns regarding routine over - exposure

CR is cassette based

DDR and IDR use flat panel detectors and charged couple detectors to instantaneously produce and image.