The document discusses quality control procedures for x-ray imaging systems. It describes the purpose of quality control as achieving high quality images with minimal radiation exposure while ensuring patient and staff safety and legal compliance. The document then outlines the different stages of quality control checks for x-ray systems - critical examination, acceptance testing, commissioning, and routine performance testing. Key parameters that are checked during quality control include beam alignment and collimation, radiation output levels, total beam filtration, exposure timer accuracy, and leakage radiation. Radiation safety topics like pregnancy radiation risks and cancer risks are also summarized.

1. Quality Control
Lecture #6

2. Quality Control (QC)
• The purpose of QC is to achieve high quality images with the
least amount of radiation.
• Quality Control is a part of Quality Assurance program.
• Quality Assurance program
A programme for the systematic monitoring and evaluation of
the various aspects of a project, service or facility to ensure
that standards of quality are being met.
• Can identify equipment status
• Ensures patient (and staff) safety
• Ensures legal compliance

3. The life cycle of X-ray imaging systems
• There are essentially four
stages of checks that are
applicable to X-ray imaging
systems:
• Critical examination
• Acceptance
• Commissioning
• Routine performance
testing

4. The Critical Examination(CRIEX)
• The installer is required to perform a critical examination of any new
installation.
• The purpose of the ‘CRIEX’ is to ensure all safety features and warning
devices work correctly
• Also includes tube leakage, total filtration, etc
• Primarily related to radiation protection features that affect staff and
visitors, but some impact on patient safety too
• Employer must not allow the equipment to go into clinical service
until the results of the CRIEX are satisfactory

5. Acceptance testing
• Verify that the contractor has supplied all the equipment specified
and has performed adequate tests to demonstrate specified
requirements are met
• Mechanical and electrical safety checks also required.
• Frequency:
• To be performed once only when new machine is installed

6. Commissioning
• Commissioning Testing
• Intensive testing that confirms the protective setup of equipment and its
functionality performed by a representative of the employer (usually Medical
Physics).
• To ensure the equipment is ready for clinical use, and to establish baseline
values against which routine QA can be compared.
• Commissioning tests may need to be repeated during the life of the
system if any major maintenance is started e.g. new X-ray tube
• New baselines may need to be established.

7. Routine testing
• Regular tests throughout the lifetime of the equipment
• Looking for changes in performance that indicates fixing action is
required
• Generally, routine are a subset of the commissioning tests

8. X ray radiation Safety

9. GENERAL RADIATION INFORMATION
 Ionizing radiation
 can cause chemical changes in biological tissue.
 can lead to cell death, cell transformation, and damage which can not be
repaired.
 very serious injuries have resulted from the use of x-ray equipment. large
doses of radiation have caused painful burns and permanent injuries to
workers.

10. Serious Injuries
 People are not able to sense radiation.
 Even very large doses of radiation can not be felt.
 Just because there was no sensation at the time the dose is received,
does not mean you are safe.
 Serious injury can result for radiation exposure.
 It is up to the individual x-ray user to ensure that they are trained,
follow all cautions, and use all x-ray equipment safely.

11. Sources of Exposure
• The primary beam(high energy radiation)
• Leakage of primary beam through cracks in shielding,
• Penetration of primary beam through shutters, collimators, beam stops, etc.
• Secondary emission (fluorescence)
• from a sample or shielding material
• Radiation generated by rectifiers in the high voltage power supply of
older units.

12. Exposure to Ionizing Radiation
Exposure to Ionizing Radiation causes two types of effects
 Deterministic Effects:
 A minimum threshold dose must be gained for the effect to occur.
 Examples include skin reddening (erythema), and sterility.
 Stochastic Effects:
 The effect may (potentially) occur following any amount of exposure
 There is no threshold.
 Examples include cancer and genetic defects.
 Radiation Safety Goals is to
 Eliminate the deterministic effects
 Reduce incidence of Stochastic effects

13. LIMITING YOUR EXPOSURE
Three basic methods for reducing exposure of workers to X-rays:
 Minimize exposure time
 Maximize distance from the X-ray tube
 Doubling your distance from the X-ray tube reduces your exposure by a factor
of four
 Use shielding.

14. Parameters to be checked
• Beam Alignment and Collimator Accuracy
• Radiation output and linearity of mR/mAs versus kV (Large and small
Fields )
• Assessment of Total Beam Filtration (HVL)
• Accuracy and constancy of Exposure Timer
• Leakage Radiation from X-Ray tube

15. Beam Alignment and Collimator Accuracy
Beam Alignment Test Tool
Small hole
X-ray Tube
Test Tool

16. Beam Alignment and Collimator Accuracy
• Improper central ray alignment will
distort a radiographic image.
• When used with the Collimator
Test Tool, this device provides a
simple means of determining if the
X-ray beam is perpendicular to the
image receptor and centered with
respect to the light field.

17. Constancy of Radiation output and linearity of
mR/mAs versus kV2
• Constancy of Radiation output and linearity of mR/mAs versus kV2
(Small & Large focus)
• Victoreen Kv Meter
• Displays kVp maximum
• kVp average
• kVp effective
• dose and time
• Set mAs=20 for LF & 10 for SF
X-ray Tube
Table top
Measure kVp & Output
R a d i a t i o n b e a m

18. Assessment of Total Beam Filtration / (HVL)
• HVL(Half Value Layer):
• The most frequently used factor for describing
both the penetrating ability and the penetration
through specific objects.
• Defined: thickness of material penetrated by one
half of the radiation
• Unit: mm or cm
• Filtration:
• Attenuation of photon according to their Energy
( simply the ability to get rid of unnecessary
radiation)

19. Assessment of Total Beam Filtration / (HVL)
X-ray Tube
Table top
Measure
Output only
Put Aluminum
Shield with
different
thickness 1,2,3,4
mm

20. Assessment of Total Beam Filtration / (HVL)
AL mm Output (+ 2)Xi/X2
0 112.1
1 83
2 65.2
3 57.1
4 49.1 0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1.10
0 1 2 3 4 5
x/xi
Al mm
HVL=3.0 mm (acceptable limit > 2.5 mm Al)

21. Leakage Radiation from X-Ray tube
• Rarely done.
• Typically for very old units.
• To test if there is any leakage of radiation from the x-ray tube.

22. Pregnancy Radiation Risk
• Radiation causes harm through the excitation created by X-ray
photons striking atoms which may either
• disrupt the molecule directly
• or create a free radical, which is capable of reacting with other biologic
molecules.
• The developing CNS is most frequently affected after high levels of
radiation in utero, with common defects being mental retardation
and microcephaly.
• Malignancy can also result, with the most common radiation-induced
cancer being childhood leukemia.

23. Pregnancy Radiation Risk
• For counseling purposes, know that
• at doses < 5 rem(Roentgen equivalent man)
• no proven effects on the fetus
• extrapolation from higher doses suggests that the risk is 0.5-1%/rem for
radiation induced congenital defects.
• The natural occurrence of congenital defects is approximately 5%.
• Radiation effects on the fetus are cumulative throughout the
pregnancy.

24. Risk for Cancer
• The probability of developing radiation-induced carcinogenesis
increases with radiation dose, but the severity of the malignancy is
independent of the radiation dose.
• Leukemia = Most Common