Conventional X-ray Equipment

Question 1

Describe the mains isolator switch

Answer 1

Supplies main electrical power
Spring loaded to prevent accidental use

Question 2

Describe the X-ray Generator

Answer 2

Allows selection of kVp, mA and exposure time
2 main components:
Control panel
Transformer assembly

Question 3

Name the 3 different generator types

Answer 3

Single phase
Three phase
High frequency

Question 4

Describe efficiency in relation to generator types

Answer 4

Generator type alters efficiency
Improving efficiency improves beam quality

Question 5

Describe high frequency generators

Answer 5

Small, can be placed in tube housing
Nearly constant potential voltage waveform
Short exposure times possible

Question 6

What does the transformer assembly consist of?

Answer 6

1. Low voltage filament transformer(step down)
2. High voltage transformer (step up)
3. Rectifiers

Question 7

Name the features of the control panel

Answer 7

kVp
mA
Exposure time
Exposure button

Question 8

Describe the X-ray tube structure

Answer 8

Strong - carbon fibre
Easy to clean
Floating tabletop
Allows beam to be centred easily
Incorporates grid, detector and AED

Question 9

Describe beam filtration

Answer 9

Must be aware of area of interest and limit x-ray field
Collimation - limits field to protect patients

Question 10

Describe light beam diaphragm

Answer 10

Provides collimation
Allows visualisation of x-ray beam
Metal plates can be manoeuvred to change collimation
Radiolucent mirror at 45°

Question 11

Describe the benefits of the light beam diaphragm

Answer 11

Visible demonstration of beam
Variety of field shapes
Optimum protection

Question 12

Describe the limitations of the light beam diaphragm

Answer 12

Only rectangular field, may not be best
Problems when light fails or mirror slips

Question 13

Describe the Dose Area Product Meter

Answer 13

Ensures patient dose is recorded
Attached to light beam diaphragm

Question 14

Describe the basic structure and function of Grids

Answer 14

Series of sections of radiopaque material interspaced with radiolucent material
Eliminates scattered radiation

Question 15

Describe Parallel grids

Answer 15

Simplest grids
Lead strips placed parallel

Question 16

Describe a disadvantage to parallel grids

Answer 16

Misalignment gives reduction in beam intensity –> grid cut-off

Question 17

Describe focused grids

Answer 17

Radiopaque strips faced towards midline, match diverging beam
Beam MUST be centred, correct FFD is vital

Question 18

Describe moving grids

Answer 18

Movement blurs grid lines
Reduces scatter

Question 19

Describe the disadvantages to moving grids

Answer 19

Magnification –> increases OFD
Mechanism prone to failure
Could be slight absorption

Question 20

Describe the relation between grid and dose

Answer 20

Grid ratio increases - contrast increases - patient dose increases
Grid ratio decreases - contrast decreases - patient dose decreases

Question 21

Describe the air gap technique

Answer 21

Increasing object to IR distance - gap reduces scatter
Contrast will increase

Question 22

What do AEDs do?

Answer 22

Terminate exposure time
Allows production of images of uniform density

Question 23

Describe the structure of AEDs

Answer 23

Ionising chambers
- Thin parallel plate
- 5mm thickness
Uses 3 chamber configuration

Question 24

What is the function of AEDs?

Answer 24

Measure exposure to receptor
Allow radiographer to not have to set exposure time

Question 25

What are some disadvantages to AEDs

Answer 25

Radiographer doesn't have exposure time control or mAs control Become dependent on AED - use it unnecessarily