1. FRCR: Physics Lectures Diagnostic Radiology
Quality Assurance (QA) of radiographic systems
Dr Tim Wood
Clinical Scientist

2. Overview What is QA? The life cycle of X-ray imaging systems
The critical examination
Acceptance testing
Commissioning
Routine performance testing
IPEM Report 91
Recommended tests by modality – a whistle stop tour
The role of Medical Physics in Diagnostic Radiology

3. What is QA? Quality as·sur·ance
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
Merriam-Webster's Medical Dictionary, © 2007 Merriam-Webster, Inc.

4. What is QA?
It is a requirement under the Ionising Radiations Regulations 1999 (Reg. 32(3)-(4)) to…
‘… make arrangements for a suitable quality assurance programme to be provided in respect of the equipment or apparatus for the purpose of ensuring that it remains capable of restricting so far as is reasonably practicable exposure to the extent that this is compatible with the intended clinical purpose or research objective.’

5. What is QA? Regulation 32 also requires;
Adequate testing before entering clinical service (commissioning)
Adequate testing at appropriate intervals and after any major maintenance procedure (routine)
Measurements at suitable intervals to enable assessment of representative doses to persons undergoing medical exposures

6. What is QA?
The regulations use lots of vague terms like ‘suitable’, ‘adequate’ and ‘appropriate’
Deliberate due to range of equipment the regulations have to cover
The ‘Approved Code of Practice’ gives slightly more detail
Depends on the nature and range of equipment in use
The QA programme should specify the frequency of any testing and appropriate actions levels
In establishing these levels the employer should take into account guidance established by relevant professional bodies about criteria of acceptability

7. What is QA?
In devising the QA programme, pay special attention to equipment for;
Children
Health screening programmes
High dose procedures, such as interventional radiology, CT or radiotherapy
The employer should consult their RPA when devising the QA programme
Note QA, does not just cover the equipment, but also procedures, etc (as required under IR(ME)R)

8. The life cycle of X-ray imaging systems
There are essentially four stages of checks applicable to X-ray imaging systems;
Critical examination
Acceptance
Commissioning
Routine performance testing
Maintenance is vital throughout

9. The life cycle of X-ray imaging systems

10. The Critical Examination
Under IRR 99 Reg 31(2), the installer is required to perform a critical examination of any new installation
The purpose of the ‘critex’ 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 critex are satisfactory

11. Acceptance testing
Verify that the contractor has supplied all the equipment specified and has performed adequate tests to demonstrate specified requirements are met
May be a simple check list
Mechanical and electrical safety checks also required

12. Commissioning
Set of tests 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 undertaken e.g. new X-ray tube
New baselines may need to be established

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

14. IPEM Report 91
The Institute of Physics and Engineering in Medicine (IPEM) produce a series of reports related to medical equipment QA
The most useful for Diagnostic Radiology is IPEM Report 91
Recommended standards for the routine performance testing of diagnostic X-ray imaging systems (2005)
Relates primarily to imaging performance and radiation safety checks

15. IPEM Report 91
The report is split into chapters on different modalities
Each chapter starts with a summary table of;
The physical parameter to be tested
Frequency – varies from daily to three yearly
Priority – level 1 is essential for ‘good practice’; level 2 is not essential, but considered ‘best practice’
Level of expertise required – level A applies to frequent and relatively basic tests performed by Radiographers; level B tests are less frequent, but require greater expertise and more complex equipment (Medical Physics tests)
Action levels – split into ‘Remedial’ and ‘Suspension’ (see later)

16. IPEM Report 91
Each test is then described briefly, with appropriate references to other documents, such as the IPEM Report 32 series
These are a series of reports that give much greater detail on the method for testing systems e.g. X-ray tubes and generators, fluoroscopy, CT, etc

17. IPEM Report 91 Remedial Level:
A level of performance at which remedial action is required, but the unit may continue to be used in the mean-time
The action will be based on a risk assessment of the equipments performance and the risk arising should it continue to be used
Following assessment, a timescale must be agreed and restrictions on its use followed

18. IPEM Report 91 Suspension Level:
A level of performance at which it is recommended the equipment is removed from clinical use immediately
Not all tests have suspension levels set due to the subjective nature of the test e.g. image quality

19. IPEM Report 91 IPEM 91 also emphasises that;
A senior radiography or other suitable person should be appointed to supervise the QA programme
Time should be allocated to staff and equipment for testing
All QA tests should be documented as part of the QA programme – may be required as evidence presented to the HSE inspectors
Results and remedial actions must be followed up promptly
Test equipment should be available and within calibration (annual recalibration usually required for dosemeters)

20. A whistle stop tour of IPEM 91

21. X-ray tubes and generators (Chapter 3)
Level A
X-ray/light beam alignment and centring
Light beam/bucky centring
Field size calibration
Distances and scales
Radiation output repeatability and reproducibility (small range of settings)

22. X-ray tubes and generators (Chapter 3)
Level B
Radiation output repeatability and reproducibility (larger range of settings)
Exposure time
Tube potential

23. Film/screen radiography, processors and AECs (Chapter 4)
Level A
Developer temperature, fog, film speed, contrast index, replenishment, pH, silver content
Intensifying screens and darkroom checks
AEC guard timer and resulting film OD

24. Film/screen radiography, processors and AECs (Chapter 4)
Level B
Only AEC tests
Consistency between chambers
Repeatability and reproducibility
Receptor dose

25. CR and DR (Chapters 5 and 6)
Level A:
Detector dose indicator monitoring
Uniformity
Condition of image plates (CR only)
Low contrast sensitivity
Limiting spatial resolution

26. CR and DR (Chapters 5 and 6)
Level B: (in conjunction with IPEM 32 Part VII)
DDI repeatability and reproducibility
Measured uniformity
Threshold contrast detail detectability
Erasure cycle efficiency (CR only)
Limiting spatial resolution
Scaling errors
Dark noise
Modulation transfer function (MTF)
Normalised noise power spectrum (NNPS)
AEC tests

27. Image display (Chapter 7)
Film viewers
Level A – general condition
Level B – luminance, uniformity, variation between viewers, room illumination
Monitors
Level A – general condition, greyscale and resolution with test patterns
Level B – DICOM greyscale calibration, test patterns, uniformity, variation between monitors, room illumination

28. Mammography (Chapter 8)
See also IPEM Report 89 ‘The commissioning and routine testing of mammographic X-ray systems’ and the latest NHSBSP reports
NHSBSP Equipment Report 0604 for full field digital testing
Lots of testing required!
Radiographer testing daily, weekly, monthly
Physics testing every 6 months

29. Mammography (Chapter 8)
Example tests include;
Processing, where applicable
AEC
Limiting spatial resolution
Image quality with test phantoms
MGD to standard breast
X-ray beam alignment
Compression force
kV accuracy (specific calibrations)
Uniformity
Radiation output repeatability/reproducibility
And much more…

30. Dental Radiography (Chapter 9)
Processing tests
Temperature, solutions, step-wedge, light proofing
X-ray/detector tests
Tube voltage, exposure time, collimation, dose at collimator tip for IO, DAP for OPG, detector condition, clinical image quality compared with reference

31. Fluoroscopy (Chapter 10)
Level A
Dose rate reproducibility under ABC/AEC
Display monitor setup
Limiting spatial resolution
Threshold contrast
Radiation/image field size

32. Fluoroscopy (Chapter 10)
Level B
Dose rate at the entrance surface of a phantom under ABC/AEC
Dose rate at the input face of the detector under ABC/AEC
Limiting spatial resolution
Threshold contrast

33. Fluorography (Chapter 11)
Level A
Dose per image under AEC
Limiting spatial resolution
Threshold contrast

34. Fluorography (Chapter 11)
Level B
Dose per image at the input face of the detector under AEC
Limiting spatial resolution
Threshold contrast
Dynamic range

35. Patient dose measurements (Chapter 13)
Perform dose audits and/or QA measurements
Individual radiographic exposures
Entrance surface dose or DAP > Diagnostic Reference Levels (DRLs)
Complete examinations
DAP > DRLs
Mammography
MGD to standard breast >2.5 mGy per film
MGD to patients >3.5 mGy per film
Dental Radiography
IO dose at collimator tip > DRL
OPG dose > DRL
Fluoroscopy
Dose at entrance surface of phantom > 50 mGy/min
DAP > DRL

36. CT (Chapter 12)
Craig to cover…

37. QA is important because…
Can identify equipment deterioration
Can be used to achieve ALARP
Ensures patient (and staff) safety
Ensures legislative compliance
Final thought…
Although it’s not your responsibility to check equipment, you should ensure that the X-ray sets you use have been checked for your own safety, as well as the patient’s

38. The role of Medical Physics in Diagnostic RadiologyQA
Level B tests
Advising on QA programme and monitoring performance
Radiation protection and physics advice (RPA/MPE)
Ensuring compliance with relevant regulations e.g. risk assessments, controlled areas, dose monitoring, etc
IRR and IR(ME)R audits – make sure we’re ready if the inspector calls!
New installations shielding, testing, etc
Notification of incidents to the CQC, HSE, EA, Police, etc
Education
FRCR, Update Training, etc

39. The role of Medical Physics in Diagnostic Radiology
Optimisation
We aren’t just here to interfere and police the regulations!
Significant part of the Radiation Physics groups work is looking at how we can get the most out of our X-ray imaging systems
Rely on feedback and co-operation from Radiology to ensure we are optimising exposures
We’re here to help…

40. Recent publications
A Beavis, J Saunderson, J Ward , WE-G-BRA-06: Calibrating an Ionisation Chamber: Gaining Experience Using a Dosimetry ‘flight Simulator’, Med. Phys. 39, 3970 (2012)
CS Moore, G Avery, S Balcam, L Needler, A Swift, AW Beavis, JR Saunderson , Use of a digitally reconstructed radiograph based computer simulation for the optimisation of chest radiographic techniques for computed radiography imaging systems , Br J Radiol 2012;85 e630-e639
TJ Wood, AW Davis, CS Moore, AW Beavis & JR Saunderson , Validation of a Large-Scale Audit Technique for CT Dose Optimisation , Radiat Prot Dosimetry (2012) 150(4):
CS Moore, GP Liney, AW Beavis, JR Saunderson, A method to produce and validate a digitally reconstructed radiograph-based computer simulation for optimisation of chest radiographs acquired with a computed radiography imaging system, British Journal of Radiology, 84 (2011),
ML Wilson, WP Colley & AW Beavis , The effect of the carbon fibre insert for the Varian Exact™ couch on the attenuation and build-up of high energy photon beams, Journal of Radiotherapy in Practice (2011) 10, 77-83

41. Current Projects Further development of our dose audit software
CT AEC optimisation with a custom built phantom
Development of a high skin dose reporting system for interventional procedures
Development of a new test object for routine image quality assessment in digital mammography
And many more…