1. Radiation protection for paediatric patients
IAEA Regional Training Course on Radiation Protection of patients for Radiographers, Accra, Ghana, July 2011
Radiation protection for paediatric patients 1

2. Why Talk about radiation protection during radiological procedures in Children
The number of imaging tests using ionizing radiation
are increasing around the world !!! And….
Children are of special concern in radiation protection:
Higher radiation sensitivity
Longer life expectancy
Identical settings provide higher organ doses than in adults
More susceptible to radiation damage
Radiation Protection in Paediatric Radiology L01. Why talk about radiation protection in paediatric radiology

3. Radiation Protection of Children in Screen Film Radiography
Part No...., Module No....Lesson No
Module title
Radiation Protection of Children in Screen Film Radiography
Generators
For paediatric examinations, the generator should be:
a high frequency
multi-pulse (converter)
of sufficient power
nearly rectangular waveform with minimal voltage ripple
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

4. Equipment, practice, dose and image quality
Part No...., Module No....Lesson No
Module title
Equipment, practice, dose and image quality
Exposure time
When children are uncooperative they may need immobilization
They have faster heart and respiratory rates
Short exposure times improve quality without increasing dose
Only possible with powerful generators and accurate exposure time switches
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

5. Equipment, practice, dose and image quality
Part No...., Module No....Lesson No
Module title
Equipment, practice, dose and image quality
Additional filtration
Additional filtration may lead to dose reduction
0.1 mm of Cu in addition to 2.5 mm of Al*
reduce ESAK by 20%
barely noticeable reduction in image quality
Some modern systems can automatically insert either 0.1mm or 0.2 mm Cu depending on the examination
*Cook, V., Imaging, (13) 2001:229–238
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

6. Equipment, practice, dose and image quality
Part No...., Module No....Lesson No
Module title
Equipment, practice, dose and image quality
Exposure factors
Increased kVp (reduced mAs):
Greater penetration and less absorption
Reduced patient dose for a constant film density
Neonatal chest:
Minimum 60kVp: less contrast but better assessment of lung parenchyma
Lower kVp if looking for bone detail
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

7. Equipment, practice, dose and image quality
Part No...., Module No....Lesson No
Module title
Equipment, practice, dose and image quality
Antiscatter grid
Often unnecessary in children because smaller irradiated volume (and mass) results in less scattered radiation.
Limited improvement in image quality but increased dose of ~50% with the use of antiscatter grids
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

8. Equipment, practice, dose and image quality
Part No...., Module No....Lesson No
Module title
Equipment, practice, dose and image quality
Automatic Exposure Control (AEC)
Generally not appropriate for small children
Sensors (size and geometry) are normally designed for adult patients
AEC use may be associated with the use of the grid (where the grid is not removable), which is frequently unnecessary
AEC should have specific technical requirements for paediatrics
If not appropriate or available, carefully applied exposure charts are preferred
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

9. Equipment, practice, dose and image quality
Part No...., Module No....Lesson No
Module title
Equipment, practice, dose and image quality
Focus-to-film distance (FFD)
Longer focus-to-film distances
Smaller skin dose
Combined with a small object-to-film distance, results in less magnification (less geometric distortion) and improved quality
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

10. Equipment, practice, dose and image quality
Part No...., Module No....Lesson No
Module title
Equipment, practice, dose and image quality
Image receptors
Fast screen-film combinations have advantages (reduction of dose) and limitations (reduced resolution)
Low-absorbing materials in cassettes, tables, etc., are specially important in paediatric radiology (carbon fibre)
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

11. Part No...., Module No....Lesson No
Module title
Collimation
Require a basic knowledge of paediatric pathology
Lung fields extremely large in congestive heart failure & emphysematous pulmonary diseases
Diaphragm, high in intestinal meteorism, chronic obstruction or digestive diseases
Beam-limiting devices automatically adjusting the field size to the full size of the cassette are inappropriate for children
Minimal deviation from the radiation and light beam may have large effects in relation to the usually small field of interest - check light beam diaphragm regularly
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

12. Equipment, practice, dose and image quality
Part No...., Module No....Lesson No
Module title
Equipment, practice, dose and image quality
Shielding
Standard equipment of lead-rubber shielding of the body in the immediate proximity of the diagnostic field
Special shielding has to be added for certain examinations to protect against external scattered and extra-focal radiation
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

13. Part No...., Module No....Lesson No
Module title
Shielding
The eyes should be shielded for X-ray examinations involving high absorbed doses in the eyes, e.g., for conventional tomography of the petrous bone, when patient cooperation permits
The absorbed dose in the eyes can be reduced by 50% - 70%
In any radiography of the skull the use of PA-projection rather than the AP-projection can reduce the absorbed dose in the eyes by 95%
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography 13
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

14. Patient Positioning and Immobilization
Part No...., Module No....Lesson No
Module title
Patient Positioning and Immobilization
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

15. Patient Positioning and Immobilization
Part No...., Module No....Lesson No
Module title
Patient Positioning and Immobilization
Immobilization devices must be easy to use
Their usefulness should be explained to the accompanying parent(s)
Radiological staff members should only hold a patient under exceptional circumstances
Even in quite young children the time allocation for an examination must include the time to explain the procedure not only to the parents but also to the child
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

16. Part No...., Module No....Lesson No
Module title
Mobile radiography
Mobile radiography is valuable on occasions when it is impossible for the patient to come to the radiology department
It can result in
poorer quality images
unnecessary staff and patient exposures
Where practicable, X-ray examinations should be carried out with fixed units in an imaging department
Mobile units should only be used with those who cannot safely be moved to such a unit
Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

17. Radiation Protection of Children in Digital Radiography
Part No...., Module No....Lesson No
Module title
Radiation Protection of Children in Digital Radiography
Accurate collimation
Dose parameter monitoring
Avoid use of grid
Increase FSD
Shielding sensitive organs
Use manual settings
Reprocess-rather than repeat non
diagnostic images
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology 17

18. Part No...., Module No....Lesson No
Module title
Radiation Protection of Children in Fluoroscopy and Interventional Radiology
Optimization
Positioning, collimation, selection of optimised exposure factors are essential in fluoroscopy.
Use “Child Size” protocol and lowest dose protocol possible for patient size, frame rate, and length of run
A removable grid should be available, and normally only used with children > 8 years.
Acknowledge fluoroscopy timing alerts during procedure
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology 18

19. Equipment, Practice, Dose and Image Quality
Part No...., Module No....Lesson No
Module title
Equipment, Practice, Dose and Image Quality
Focus-to-Skin Distance
The patient should be positioned as close as possible to the image intensifier
The X-ray tube should be as far away as possible from the patient’s table in order to avoid excessive skin dose
Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

20. Part No...., Module No....Lesson No
Module title
The image intensifier/detector should be placed as close to the patient as possible
(< 5 cm) for better image quality and reduced dose (undercoach systems)
Bad practice
Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

21. Equipment, Practice, Dose and Image Quality
Anti-scatter Grid
Anti-scatter grid should be removable in pediatric equipment, particularly fluoroscopic systems
No grid is recommended for small children resulting in a dose reduction up to 50%
Magnification
Magnification should be avoided unless necessary
Using a field of view of less than 12 cm may result in four times the dose of a 25 cm diameter field.
Digital radiography allows post-processing magnification with no increase in dose
Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

22. Magnification
Changing from a large field of view to an increased magnification increases the exposure required by the image intensifier tube
The absorbed dose to tissues within the beam is also increased
Example:
Field of view, diameter 25 cm
Dose rate= 0.3 mGy/s
Field of view, diameter 17 cm
Dose rate = 0.6 mGy/s
Field or view, diameter 12 cm
Dose rate = 1.23 mGy/s.
Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

23. Equipment, Practice, Dose and Image Quality
Exposure factors
Low tube potential (50–60 kV) fluoroscopy provides better demonstration of low to moderate contrast examinations,
e.g. those with iodinated contrast medium (200–300 mmol) or dilute barium (100 mg %)
In combination with heavy tube filtration (0.25 mm copper), can improve quality and reduce dose
Tube current and beam on time are directly proportional to dose
Tapiovaara MJ et.al., Phys Med Biol (2):537-59
Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

24. Equipment, practice, dose and image quality
Filtration
Additional tube filtration may allow dose reductions
0.1mm Cu should be incorporated into all modern systems used in a paediatric setting
Dose reduction by 20% without affecting image quality
Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

25. Equipment, Practice, Dose and Image Quality
Automatic Brightness Control
Specific kV/mA dose rate curves for automatic brightness control (ABC) should be used in fluoroscopic systems for children
An ABC giving a pre-set controlled tube potential (kV) and variable tube current (mA) and allowing ‘‘dose hold’’ is preferred
Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy

26. Equipment, Practice, Dose and Image Quality
Pulsed Fluoroscopy
All new equipment should have pulsed fluoroscopy
Variable pulse rates are possible
Grid controlled pulsed fluoroscopy X-ray tubes: allows very short exposures with very little soft radiation
The lowest pulse rate will usually produce the lowest dose, depending on whether there is a compensatory increase in tube current (mA) to maintain quality
Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy 26

27. Equipment, Practice, Dose and Image Quality
Part No...., Module No....Lesson No
Module title
Equipment, Practice, Dose and Image Quality
Shielding
Use lead gonad protection whenever possible
Repeating an examination due to overuse of shielding is poor practice
Lead apron, into beam path – reduce light output from the II – System will automatically increase amount of X-rays to achieve same light output as before!! => Increase patient dose - BEWARE
Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy 27
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

28. Part No...., Module No....Lesson No
Module title
Mobile Fluoroscopy
Mobile C-Arms should have the option of removing the anti-scatter grid
Particular attention should be given to collimation, fluoroscopic time and displayed KAP measurements
Trained staff should operate C-arms especially in pressure environments such as theatres
Radiation Protection in Paediatric Radiology L05. Radiation protection in fluoroscopy
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

29. Radiation Protection of Children During Computed Tomography
Part No...., Module No....Lesson No
Module title
Radiation Protection of Children During Computed Tomography
One size does not fit all...
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology 29

30. Equipment, Protocol, Dose and Image Quality
Part No...., Module No....Lesson No
Module title
Equipment, Protocol, Dose and Image Quality
Spiral or helical scanning is preferable in paediatrics as an entire volume is image
Short tube rotation times reduce movement artefacts and provide more detailed cardiac imaging
Immobilization devices vs sedation
PA scout image
Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology

31. Equipment, Protocol, Dose and Image Quality
Image thickness:
Should be chosen depending on the size of the child and the application
Use maximal acquisition collimation (assuming this would result in scanning at lower mA) appropriate for specific diagnosis
Narrow collimation in MSCT and 1 mm slices on some SDCT result in a higher dose (increase in mAs to maintain image quality)
Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

32. Equipment, Protocol, Dose and Image Quality
Pitch:
SDCT: a pitch factor 1.5 is recommended for most examinations
25% reduction in dose compared with using a pitch of 1
MDCT: reduction in dose due to greater pitch may not be achieved
tube current (mA) can be automatically adjusted to keep the dose and noise the same
Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

33. Equipment, Protocol, Dose and Image Quality
Tube potential (kVp)
There are few advantages to using a high tube potential (kV).
Without a reduction in tube current (mA) this leads to a significantly higher dose.
100 kVp or 80 kVp is usually adequate for children.
Lowering of kVp enhances contrast
Be aware that images with high noise, even if they do not look very crisp, may provide the diagnostic information.
Lower tube current (mA): Should be used. High tube current is required only when there is a need for high image detail ( in low contrast settings)
Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

34. Equipment, Protocol, Dose and Image Quality
Gantry Tilt
A straight gantry results in irradiation of a smaller volume of tissue compared with a tilted gantry and is recommended.
Exception: tilt is used to avoid unnecessary exposure of sensitive tissues, e.g. in brain CT for avoiding the orbits.
Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

35. Equipment, Protocol, Dose and Image Quality
Scan Length
Scan the minimum length required and be restrictive in defining upper and lower limits.
Optimise scan parameters for volume coverage by using representative volume sample(s) when the entire volume is not needed (by sequential scans with gaps) to reduce dose-length product
Vock and Wolf , Dose Optimization and Reconstruction in CT of children, in Radiation Dose from Adult and Paediatric MDCT, Springer, 2007
Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

36. Shielding
The bismuth eye shield is simple to place and covers only the eye
In-plane shields are associated with greater image noise and streak artifacts. However, shields reduce radiation dose. Automatic exposure control did not increase radiation dose when using a shield.
Karla et al, Korean J Radiol. 10:156-63, 2009
This adult patient has a 3 layer bismuth latex eye shield in place. While artefact is seen into the globe, no artefact is transmitted into the brain. Standoff pads can reduce surface artefact
Hopper KD, et al, Am J Neuroradiol 22:1194–1198,2001
Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography

37. Example of successful story I
Arch and Frush, AJR 2008;191:611–617:
Since 2001, kVp and mA settings, two principal parameters determining radiation dose, have decreased significantly for paediatric body MDCT
It is a reasonable assumption that these changes are due to efforts to increase awareness about the risks of radiation
Paediatric chest CT
Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 37

38. Example of successful story II
Wallace, et al. Proceedings of IRPA 12, Buenos Aires, 2008, FP0227:
Eight paediatric hospitals
Training and seminars on optimisation
Dose reduction greater than 50%
Radiation Protection in Paediatric Radiology L06. Radiation protection in computed tomography 38

39. Part No...., Module No....Lesson No
Module title
Radiation Protection in Paediatric Radiology L07. Radiation protection in interventional radiology 39
IAEA Post Graduate Educational Course in Radiation Protection in Pediatric Radiology 39

40. THANK YOU!
Radiation Protection in Paediatric Radiology L01. Why talk about radiation protection during radiological procedures in children