Radiation Protection in Paediatric Radiology

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Radiation Protection in Paediatric Radiology

• Radiation Protection of Children in Screen Film
  Radiography

L03
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Educational objectives

• At the end of the programme, the participants
• should
• Become familiar with specific radiation
  protection issues in paediatric radiography
• Identify the features of radiographic imaging
  equipment used in paediatric radiology
• List important operational considerations in
  paediatric radiography
• Discuss important considerations in paediatric
  radiography using mobile X-ray units

3
Answer True or False

• Added filtration will reduce the dose to the
  patient.
• Short exposure time is a disadvantage.
• Proper collimation reduce dose.
• Shielding of radiosensitive organs is recommended
  in paediatric radiography.

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Contents

• Justification in radiography
• Practical optimisation in paediatric radiography
• Equipment related
• Radiographic technique related
• Important consideration for mobile radiography
• Image quality and patient dose

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Introduction

• Children have higher radiation sensitivity than
  adults due to a longer life expectancy
• For children under age of 10, the probability for
  fatal cancer is 2-3 times higher than for whole
  population
• The higher radio-sensitivity of the patients
  should be taken into account

Radiation Protection in Paediatric Radiology
L03.Radiation protection in screen-film
radiography
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Introduction

• Radiologists and radiographers should be
  specifically trained for paediatrics
• A paediatric radiological procedure should be
  individually planned and projections should be
  limited to what is absolutely necessary for a
  diagnosis

Radiation Protection in Paediatric Radiology
L03.Radiation protection in screen-film
radiography
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General recommendations

• Key areas in radiation protection in paediatric
• radiology
• Justification
• Optimisation
• Evaluation of patient dose and image quality
• Do you really need a glossy picture to
• make that diagnosis

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Justification in radiography

• Justification is required for all radiographic
  studies
• Ask referring practitioner, patient, and/or
  family about previous procedures
• Use referral guidelines where appropriate and
  available
• Use alternative approaches, such as ultrasound,
  MRI where appropriate
• Consent, implied or explicit, is required for
  justification
• Include justification in clinical audit

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Justification in radiography

• Referral guidelines for radiological
  examinations
• EUROPEAN COMMISSION, Referral Guidelines for
  Imaging, Luxembourg, Radiation Protection 118,
  Office for Official Publications of the European
  Communities, Luxembourg (2001) and Update (2008)
• THE ROYAL COLLEGE OF RADIOLOGISTS, Making the
  Best use of Clinical Radiology Services (MBUR),
  6th edition, RCR, London (2007)

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Examples of radiography examinations not
routinely indicated

• Skull radiograph in a child with epilepsy
• Skull radiograph in a child with headaches
• Sinus radiograph in a child, under 5 years,
  suspected of having sinusitis
• Cervical spine radiograph in a child with
  torticollis without trauma
• Radiographs of the opposite side for comparison
  in limb injury

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Optimisation in radiography

• Justified studies must be optimised
• Various actions taken contribute to systematic
  dose savings (from a factor of two to ten, with
  the result that their combined effect can
  dramatically reduce dose)
• Sustain good practice through a quality assurance
  and constancy checking program

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Optimisation in radiography

• Selection of equipment
• Influence on patient dose and image quality
• But, good radiographic technique is the main
  factor in improving quality without increasing
  dose

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Practical optimisation measures in radiography (I)

• Have a standard type and number of projections
  for specific indications
• Views in addition to standard should only be
  performed on a case-by-case basis
• Use manual technique selection pending equipment
  developments on small patients or body parts
• Where practical use a long (or the recommended)
  Focus-to-Film Distance

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Practical optimisation measures in radiography
(II)

• Carefully collimate the X-ray beam to area of
  interest, excluding other regions, especially
  gonads, breast, thyroid and eyes
• Use appropriate gonad, thyroid, and breast
  shielding
• Fast film-screen combinations are acceptable for
  the majority of indications
• Antiscatter grid is often unnecessary in children
  do not use grid for abdominal examination in
  patients under age of 3, for skull radiography
  for patients under age of 1 and any fluoroscopy
  examination unless high detail is required (Cook,
  V. Imaging, (13) 2001229238)

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Practical optimisation measures in radiography
(III)

• Use PA projections, where practical, for chest
  and spine radiographs
• Make sure the correct filtration is used to
  reduce entry dose
• Use as high a kVp as is consistent with
  examination requirements
• Consider additional filtration at higher kVp
• Balance the use of a small focal spot size and
  short exposure times

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Practical optimisation measures in radiography
(IV)

• Use of quality assessment, quality assurance and
  audit programs for all aspects of the
  departments work, including film processing and
  justification
• Introduce and use a system that allows patient
  dose be assessed regularly
• Monitor reject rate and the causes (overexposure,
  underexposure, positioning, motion, and
  collimation problems)

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Equipment, practice, dose and image quality

• 1. Generators
• For paediatric examinations, the generator
  should be
• a high frequency
• multi-pulse (converter)
• of sufficient power
• nearly rectangular waveform with minimal
  voltage ripple

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Equipment, practice, dose and image quality

• 2. 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

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Equipment, practice, dose and image quality

• 3. Focal Spot
• Small focal spot
• Improves image quality
• May in some machines increase exposure time and
  motion artefacts
• Choice depends on exposure parameters time, kVp
  and FFD (Focus-to-Film Distance)
• Recommendation focal spot should be 0.6 -1.3mm

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Equipment, practice, dose and image quality

• 4. 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) 2001229238
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Dose reduction with added filtration
Added filtration 0 mm Al 3 mm Al
Examination Mean ESD (?Gy) Reduction
Abdomen AP 10 months (62 kVp) 200 30
Chest AP 10 months (55 kVp) 64 40
Pelvis AP 4 months (50 kVp) 94 51
From Mooney and Thomas Dose reduction in a
paediatric X-ray department following
optimization of radiographic technique, BJR (77)
1998852-860
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Equipment, practice, dose and image quality

• 5. 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

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Equipment, practice, dose and image quality

• 6. 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

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Antiscatter grids

• Antiscatter grid should be removable in
  paediatric equipment
• Remove antiscatter grid for
• abdominal imaging in young children especially lt3
  years old
• skull imaging lt1 year old
• in most fluoroscopic imaging

Cook, V., Imaging, (13) 2001229238
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Antiscatter grids

• If used for children,
• Antiscatter grids should have
• Grid ratio (r) gt 81
• Line numbers gt100 cm-1
• Low attenuation intersperse material, such as
  carbon fibre
• Alternative air gap technique
• (reduces the effect of scatter
• without dose increase, but the
• image is magnified)

Cook, V., Imaging, (13) 2001229238
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Equipment, practice, dose and image quality

• 7. 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

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Automatic Exposure Control

• Specially designed paediatric AEC
• Small mobile detector for use behind a lead-free
  cassette
• Position can be selected with respect to the most
  important region of interest
• This must be done extremely carefully, as even
  minor patient movement may be disastrous

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Equipment, practice, dose and image quality

• 8. 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

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Equipment, practice, dose and image quality

• 9. 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)

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Film-screen systems

• Fast screen-film system
• shorter exposure times (requires a good
  generator)
• reduction in radiation dose and prevention of
  artefacts
• Recommendations
• 200 speed bone
• 400 speed general
• gt700 speed constipation transit abdominal
  radiographs, follow-up films, e.g. scoliosis and
  hips, swallowed foreign body,

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Equipment, practice, dose and image quality

• 10. Collimation
• The most important factor for improving image
  quality whilst also reducing dose
• The most common radiographic fault
• Good collimation/coning is essential to achieve
  better contrast and avoid exposing unnecessarily
  other body parts (dose reduction)
• Body parts outside the region of interest should
  not be in the X-ray field

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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

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Collimation

• Alignment agreement among the collimators,
  radiation beam and the light beam must be
  regularly assessed
• Beyond the neonatal period, the tolerance for
  maximal field size should be less than 2 cm
  greater than the minimal
• In the neonatal period, the tolerance level
  should be reduced to 1.0 cm at each edge
• In paediatric patients, evidence of the field
  limits should be apparent by clear rims of
  unexposed film

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Cook, J.V., Imaging, 13 (2001), 229238
Neonatal anteroposterior supine chest and abdomen
radiograph of newborn all four cone marks
visible, with no extraneous body parts included
and lead masking of the gonads.
Lateral skull radiograph (horizontal beam
and round cone)
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Equipment, practice, dose and image quality

• 11. 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

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Shielding

• For exposures of 60 - 80 kV, maximum gonadal dose
  reduction of about 30 to 40 can be obtained by
  shielding with 0.25 mm lead equivalent rubber
  immediately at the field edge
• However, this is only true when the protection is
  placed correctly at the field edge

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Shielding

• The gonads in "hot examinations", when they lie
  within or close to (nearer than 5 cm) the primary
  beam, should be protected whenever this is
  possible without impairing necessary diagnostic
  information
• It is best to make one's own lead contact shields
  for girls and lead capsules for boys
• Must be available in varied sizes

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Shielding

• With appropriate shielding the absorbed dose in
  the testes can be reduced by up to 95
• In girls, shadow masks within the diaphragm of
  the collimator are as efficient as direct
  shields.
• When shielding of the female gonads is effective,
  the reduction of the absorbed dose in the ovaries
  can be about 50

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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

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Equipment, practice, dose and image quality

• 12. Patient Positioning and Immobilization
• Patient positioning must be exact, whether or not
  the patient co-operates.
• In infants, toddlers and younger children
  immobilization devices, properly applied, must
  ensure that
• the patient does not move
• the beam can be centred correctly
• the film is obtained in the proper projection
• accurate collimation limits the field size
  exclusively to the required area
• shielding of the remainder of the body is
  possible.

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Patient Positioning and Immobilization
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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

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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

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Mobile radiography

• High output converter generators are recommended
• Capacitor discharge systems should be avoided
  (they have significant pre- and post-peak soft
  radiation)
• Appropriate collimation is
• essential to avoid exposing
• organs outside the diagnostic
• area of interest
• Other principles outlined above, should be
  followed with mobile radiography

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Mobile radiography

• Scattered radiation must be managed to reduce
  dose to the patient, parents/guardians and to
  hospital personnel
• The advice of the medical physicist/radiation
  protection officer should be obtained on how best
  to do this.

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Mobile radiography

• Recommendations for Intensive Care Unit
• (Duetting et. al. Pediat. Radiol. 29 158-62
  (1999))
• No additional protection for neighbouring
  premature infants is necessary
• The radiographer should wear a lead apron
• Parents and personnel need not interrupt their
  activities or leave the room during an X-ray
  examination
• When using a horizontal beam, the beam, must be
  directed away from other persons use lead
  shield

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Criteria related to images

• Incorrect positioning is the most frequent cause
  of inadequate image quality in paediatric
  radiographs
• Image criteria for the assessment of adequate
  positioning (symmetry and absence of tilting etc)
  are much more important in paediatric imaging
  than in adults
• A lower level of image quality than in adults may
  be acceptable for certain clinical indications

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Criteria related to images

• Guideline resources
• European Guidelines on Quality Criteria for
  Diagnostic Radiographic Images in Paediatrics
• American College of Radiology

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Quality Criteria List
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Chest-PA/AP projection
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Chest radiography-PA/AP projection
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Typical dose levels in paediatric radiography
Examination ESAK (µGy) ESAK (µGy) ESAK (µGy) ESAK (µGy) ESAK (µGy)
Examination Age Age Age Age Age
Examination 0 1 5 10 15
Abdomen AP 110 340 590 860 2010
Chest PA/AP 60 80 110 70 110
Pelvis AP 170 350 510 650 1300
Skull AP / 600 1250 / /
Skull LAT / 340 580 / /
NATIONAL RADIOLOGICAL PROTECTION BOARD, Doses to
Patient from Medical X Ray Examinations in the
UK 2000 review, NRPB-W14, Chilton (2002).
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ICRP-ISR smart message for paediatrics
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http//rpop.iaea.org/RPoP/RPoP/Content/index.htm
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Summary

• Particular attention should be given to technical
  specifications of X-ray equipment
• Good radiographic technique is the main factor in
  improving quality without increasing dose for
  protocols used in X-ray paediatric radiology
• Justification of practice
• Application of practical optimisation measures in
  radiography

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Answer True or False

• Added filtration will reduce the dose to the
  patient.
• Short exposure time is a disadvantage.
• Proper collimation reduce dose.
• Shielding of radiosensitive organs is recommended
  in paediatric radiography.

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Answer True or False

1. True - Filtration absorbs low energy photons that
   are absorbed in patients skin and superficial
   organs and thus giving contributing to dose but
   not to image formation.
2. False - It prevents motion artefacts and
   unnecessary repetitions.
3. True - Collimation reduces exposed volume, and
   reduces scatter radiation that affects both image
   quality and dose.
4. True - It is especially important for
   radiosensitive organs as breast, gonads and eyes.
   

Radiation Protection in Paediatric Radiology
L03.Radiation protection in screen-film
radiography
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References

• European Guidelines on Quality Criteria for
  Diagnostic Radiographic Images in Paediatrics,
  July 1996. EUR 16261. Available at
  http//www.cordis.lu/fp5-euratom/src/lib_docs.htm
  
• Huda W, Assessment of the problem paediatric
  doses in screen-film and digital radiography,
  Pediatr Radiol 34(Suppl 3) 2004S173-S182
• Duetting,Foerste,Knoch,Darge and Troeger,
  Radiation exposure during chest X-ray
  examinations in a premature intensive care unit
  phantom studies, Pediatr Radiol (29) 1999158-162
• Mooney and Thomas Dose reduction in a
  paediatric X-ray department following
  optimization of radiographic technique, BJR (77)
  1998852-860
• Cook, V., Radiation protection and quality
  assurance in paediatric radiology, Imaging, (13)
  2001229238.