Pediatric Radiology By Dr. Wambani, J.S. Chief Radiologist Kenyatta National Hospital IAEA RADIOGRAPHERS TRAINING 11TH-16TH July 2011 .ACCRA ,GHANA

Objective To become familiar with the specific devices used in pediatric radiology To know the specific radiation risk concerning children

Contents Description of specific equipment and auxiliary devices used for children Knowledge of appropriate exposure factors in pediatrics Equipment malfunction affecting radiation protection Criteria of acceptability and quality control

Pediatric Equipment Because of their longer life expectancy and their greater sensitivity to radiation, the risk of late radiation effects is greater in children than in adults. In view of this increased radiation risk in younger age, the radiological examination of children (0-15 years) merits special consideration and specific recommendations for pediatric equipment and procedures. Pediatric radiology is a recognised sub-speciality within diagnostic radiology and specific education and training should be obligatory for pediatric radiology practitioners.

Pediatric Equipment (cont) Special Equipment for Pediatric Examinations

Pediatric Equipment (cont)

Pediatric Equipment (cont)

Pediatric Equipment (cont) The basic criteria for x-ray equipment used in pediatric radiology are the same as for general purpose equipment. However, additional performance and design requirements are necessary because of the small size of the patients and the special conditions required for many examinations (such as dealing with movement of a child). These include:- very short, accurate and reproducible exposure times; collimators adjustable to dimensions that may be smaller than some simple general purpose x-ray equipment may provide. The design and appearance of x-ray rooms are also important to improve the co-operation of children.

Pediatric Equipment (cont) Consequently: powerful generators are necessary for the very short time exposure times required (only 12-pulse or medium-high frequency generators should be used to ensure suitable accuracy and reproducibility); where mobile x-ray equipment must be used (although not advisable), medium or high frequency generators are preferred; low x-ray tube voltages should be avoided whenever practicable. Hgher x-ray tube voltages and appropriate additional filtration are recommended;

Pediatric Equipment (cont) a nominal focal spot size of between 0.6 mm and 1.3 mm is desirable; the x-ray beam must be carefully restricted to the area of clinical interest by the use of accurate light beam collimation; additional protective shielding must be adapted to children and available in a range of sizes; low attenuation materials between the x-ray tube focus and the image receptor (e.g. table top, cassette, anti-scatter grid) will contribute to dose reduction;

Pediatric Equipment (cont) In infants and younger children, the use of an anti-scatter grid may not always be necessary. Therefore, anti-scatter grids in pediatric equipment must be easily removed by the operator. Some automatic exposure control (AEC) systems may not function satisfactorily due to the wide range of body thickness and proportion in children. Specially designed pediatric AECs have a small mobile detector for use behind a lead-free cassette.

Pediatric Equipment (cont) Careful manual selection of exposure factors may result in lower radiation doses. The selection of faster intensifying screen-film systems, and image intensifiers with high conversion factors, will result in lower radiation doses. Proper patient positioning and immobilisation are essential: immobilisation devices must be easy to use without stressing the patient.

Malfunctions affecting radiation protection Basically the same as for general x-ray systems but the tests performed and the measuring instruments used shall be adapted to pediatric equipment. Quality control programs are especially important in pediatric radiology services.

Protection principles Justification Optimisation (ALARA) Dose Reference Levels (DRLs) Dose limits

Justification Risks v/s Benefits No practice involving exposures to radiation should be adopted unless it produces sufficient benefit to the exposed individuals or to society to offset the radiation detriment it causes

Optimisation (ALARA) -1 In relation to any particular source within a practice, the magnitude of individual doses, the number of people exposed, and the likelihood of incurring exposures where these are not certain to be received should all be kept As Low As Reasonably Achievable, economic and social factors being taken into account.

Optimisation (ALARA) -2 This procedure should be constrained by restrictions on the doses to individuals (dose constraints), or the risk to individuals in the case of potential exposures (risk constraints), so as to limit the inequity likely to result from the inherent economic and social judgement.

The Dose Limits Continuous exposure at or near the dose limit is considered unacceptable The dose limit should form only part of the system of protection within the As Low As Reasonably Achievable (ALARA) framework

The Dose Limits Natural background exposure ~ 2 to 2.5 mSv per annum is expressly excluded from occupational exposure. There are two exceptions: Air crew uranium mining Medical exposure is expressly excluded There are no dose limits for medical exposures BUT!

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