IAEA International Atomic Energy Agency Radiation Protection in Paediatric Radiology Radiation Protection of Children in Screen Film Radiography L03

IAEAInternational Atomic Energy

Agency

Radiation Protection in Paediatric Radiation Protection in Paediatric RadiologyRadiology

Radiation Protection of Radiation Protection of Children in Screen Film Children in Screen Film

RadiographyRadiographyL03L03

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

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Educational objectives

At the end of the programme, the participantsshould:

•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


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Answer True or False

1. Added filtration will reduce the dose to the patient.

2. Short exposure time is a disadvantage.

3. Proper collimation reduce dose.4. 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


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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


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General recommendations

Key areas in radiation protection in paediatricradiology:

• 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) 2001:229–238)


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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 department’s 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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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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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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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) 2001:229–238


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Dose reduction with added filtration

From: Mooney and Thomas : Dose reduction in a paediatric X-ray department following optimization of radiographic technique, BJR (77) 1998:852-860

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 %


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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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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 <3 years old

• skull imaging <1 year old • in most fluoroscopic imagingCook, V., Imaging, (13) 2001:229–238


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Antiscatter grids

If used for children,Antiscatter grids should have*:

• Grid ratio (r) > 8:1 • Line numbers: >100 cm-1

• Low attenuation intersperse material, such as carbon fibre

Alternative: air gap technique(reduces the effect of scatterwithout dose increase, but theimage is magnified)

*Cook, V., Imaging, (13) 2001:229–238


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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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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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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• >700 speed – constipation transit

abdominal radiographs, follow-up films, e.g. scoliosis and hips, swallowed foreign body,…


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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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Lateral skull radiograph (horizontal beam and

round cone)

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.

Cook, J.V., Imaging, 13 (2001), 229–238


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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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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)

Age

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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1. Added filtration will reduce the dose to the patient.

2. Short exposure time is a disadvantage.

3. Proper collimation reduce dose.4. Shielding of radiosensitive organs is

recommended in paediatric radiography.


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1. True - Filtration absorbs low energy photons that are absorbed in patient’s 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.


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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) 2004:S173-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) 1999:158-162

• Mooney and Thomas : Dose reduction in a paediatric X-ray department following optimization of radiographic technique, BJR (77) 1998:852-860

• Cook, V., Radiation protection and quality assurance in paediatric radiology, Imaging, (13) 2001:229–238.

Documents

IAEA International Atomic Energy Agency Radiation Protection in Paediatric Radiology Radiation Protection of Children in Screen Film Radiography L03