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Radiation Protection in Paediatric Radiology

Radiation Protection in Paediatric Radiology. Radiation Protection of Children in Screen Film Radiography. L03. Educational objectives. At the end of the programme, the participants should: Become familiar with specific radiation protection issues in paediatric radiography

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Radiation Protection in Paediatric Radiology

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  1. Radiation Protection in Paediatric Radiology Radiation Protection of Children in Screen Film Radiography L03

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

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

  4. Contents • Justification in radiography • Practical optimisation in paediatric radiography • Equipment related • Radiographic technique related • Important consideration for mobile radiography • Image quality and patient dose Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  5. 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 5

  6. 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 6

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

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

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

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

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

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

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

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

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

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

  17. 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 Equipment, practice, dose and image quality Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  18. 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 Equipment, practice, dose and image quality Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  19. 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 Equipment, practice, dose and image quality Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  20. 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 canautomatically insert either 0.1mm or 0.2 mm Cu depending on the examination Equipment, practice, dose and image quality *Cook, V., Imaging, (13) 2001:229–238 Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

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

  22. 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 Equipment, practice, dose and image quality Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  23. 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 Equipment, practice, dose and image quality Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  24. 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 imaging Antiscatter grids Cook, V., Imaging, (13) 2001:229–238 Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  25. 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 scatter without dose increase, but the image is magnified) Antiscatter grids *Cook, V., Imaging, (13) 2001:229–238 Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  26. 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 oravailable, carefully applied exposure charts are preferred Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

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

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

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

  30. 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,… Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

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

  32. 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

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

  34. Cook, J.V., Imaging, 13 (2001), 229–238 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) Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

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

  36. 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 Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography 36

  37. 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 Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography 37

  38. 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% Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography 38

  39. 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 39

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

  41. Patient Positioning and Immobilization Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  42. 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 Patient Positioning and Immobilization Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  43. 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

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

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

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

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

  48. Criteria related to images Guideline resources: • European Guidelines on Quality Criteria for Diagnostic Radiographic Images in Paediatrics • American College of Radiology Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  49. Quality Criteria List Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography

  50. Chest-PA/AP projection Radiation Protection in Paediatric Radiology L03.Radiation protection in screen-film radiography 50

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