Download Chapter 4 The Construction of an x-ray Unit

Answers to revision questions
Chapter 5: Diagnostic Equipment
1. What are the three controls on the x-ray machine control panel?
This will vary depending on the machine, but is usually kV, mA and time or a
combined setting of mAs.
2. What is the first thing you should check when an x-ray machine is
switched on?
When a machine is first switched on the mains voltage compensator should
be checked when it is not done automatically by the machine. Time should be
taken to ensure that all the controls are displayed accurately and that the
distance is correct.
3. On the x-ray machine, which control governs the length of time the XRays are produced?
Time setting given in seconds or milli seconds controls the exposure time.
This may be linked to the mA and calculated as mAs.
4. Which of the following statements about x-ray machines is false?
a. Portable machines are high power machines capable of
120mA.
b. Some mobile machines are battery powered.
c. The control panel can be some distance from the machine.
d. Fixed machines can be attached to the ceiling by rails.
A is false. Portable machines use lower energy levels and usually work up to
around 100kV levels.
5. What does a generator do?
The generator converts the mains electrical supply into a form that can be
used in the x-ray tube.
6. Why is rectification useful in radiography?
Rectification provides a current that does not fluctuate. Current can be direct
or alternating. Alternating current will fluctuate which is not good for the
production of consistent images.
7. What is a Dose Area Product Meter?
A DAP meter is built into many x-ray machines and will record the dose being
produced within the x-ray tube.
8. What happens in the filament circuit?
The filament circuit provides the energy required to heat the filament within
the cathode.
9. What units are used for measuring the power rating of an x-ray tube?
The power rating of an x-ray tube is measured in kW.
10. What is the source image distance?
The source image distance is also known as the focal film distance or FFD.
This measures the distance between the target of the anode (focus or source)
to the film or digital image receiver.