CODE OF SAFE PRACTICE FOR THE USE OF X-RAYS IN PODIATRY
Office of Radiation Safety P O Box 3877
Revised June 2010
? Office of Radiation Safety
Ministry of Health
Published with the permission of the Director-General of Health
1 INTRODUCTION 1
2 PROTECTION OF THE PATIENT 1
2.1 Clinical and administrative aspects 1
2.2 Protection of the gonads 2
3 PROTECTION OF PERSONNEL 3
3.1 Protection of non-radiation personnel 3
3.2 Protection of operator at the x-ray controls 4
3.3 Protection from exposure to the useful x-ray beam
while holding patients or image receptors in position
during radiography 4
4 X-RAY EQUIPMENT 5
4.1 Appropriate x-ray equipment 5
4.2 Efficient performance of x-ray machines 6
4.3 Light beam diaphragm 7
4.4 Filtration in the x-ray beam 7
4.5 Source-skin distance 8
4.6 X-ray exposure device 8
4.7 Leakage radiation 9
4.8 X-ray films and intensifying screens 9
4.9 X-ray film processing 10
5 ORGANISATION AND ADMINISTRATION OF
RADIATION PROTECTION 10
5.1 Personnel monitoring 10
5.2 Radiation protection surveillance 11
5.3 Dose limits for occupational exposure 11 6 RADIATION PROTECTION LEGISLATION AND
RESPONSIBILITIES OF LICENSEES 12
6.1 Radiation Protection Act 1965 12 7 BIBLIOGRAPHY 14
1.1 The purpose of this Code is to provide criteria for working procedures, x-ray equipment and protective materials necessary for the use of x-rays in podiatric diagnosis according to currently accepted standards of safety. Conformity with this Code may be taken as a primary indication of compliance with radiation protection legislation.
1.2 A copy of this Code is provided to all licensees in podiatric radiography. Licensees shall provide free and convenient access to this Code to all persons using x-ray equipment under their control.
1.3 This Code is compatible with the Recommendations of the International Commission on Radiological Protection (ICRP). Relevant ICRP publications are listed in the bibliography.
1.4 Throughout this Code, measures which are considered necessary for the achievement of satisfactory protection are denoted by the imperative shall and
those which are desirable protective measures by should.
2 PROTECTION OF THE PATIENT
2.1 Clinical and administrative aspects
2.1.1 A basic principle of protection in diagnostic radiology is that an x-ray examination should not be performed unless the benefits accruing to the patient outweigh any radiation risks. Judgement of whether benefits outweigh risks may reasonably be possible in cases where the potential radiation injury is the result of acute excessive doses where the effects are observed in the short term. However, the estimates of risks of delayed injury, such as carcinogenesis, resulting from chronic exposure at the low radiation dose levels typical of most diagnostic radiology are derived from epidemiological studies and can be expressed only on a statistical basis. The simpler question of whether the x-ray examination is necessary for adequate diagnosis should always be examined. In many cases
examinations may routinely be requested to exclude the possibility of unexpected causes or conditions and not be based on clear-cut clinical indications. Implicitly the diagnosis provided by podiatric radiography determines subsequent patient management. If management is expected to be unaffected by the result of an x-ray examination then the need for the examination may be questioned.
2.1.2 Radiological evidence has demonstrated that certain tissues such as the red marrow, gonads, breast (female), lungs, thyroid and bone surfaces may be particularly sensitive to radiation. The total effect of a given dose depends significantly also on the extent of irradiation of other tissues. An expression of the total effect delivered in a diagnostic x-ray examination is the Effective Dose Equivalent, H, which is the sum of the doses to the above specified E
organs and other organs, weighted according to their relative radiosensitivities. For podiatric radiography the effective dose equivalent will be lower than for most diagnostic x-ray procedures because only the bone surfaces amongst the specified organs are included, and no other organs of significant radiosensitivity.
The effective dose equivalent would increase considerably if in any podiatric procedure the x-ray beam were directed towards the lower abdominal region. The longer life expectancy of children results in a greater potential for the manifestation of possible deleterious effects of radiation. Children may also be more radiosensitive. Therefore particular attention should be given to minimising doses to children and indeed, whether the examination is essential. 2.1.3 The useful x-ray beam should be restricted to the area of clinical
interest and shall be collimated to within the cross section of the x-ray film cassette.
2.1.4 Some methods of dose reduction (such as minimising areas of x-ray fields on the patient) also cause improvement of image quality. However, many dose reduction methods act to the detriment of image quality (eg, use of high-speed rather than par-speed screens decreases doses but increases graininess in the image). A compromise between the opposing objectives to minimise doses and to produce good quality images, must therefore eventually be reached.
2.2 Protection of the gonads
2.2.1 Irradiation of the testes and ovaries shall be minimised.
2.2.2 As far as it is possible the useful x-ray bean shall not be directed
towards the pelvic and lower abdominal regions of patients. Where a special angulation is needed which would not comply with this requirement, a leaded apron or other suitable shield shall be draped over the pelvis of the patient or
Note: Compared with the amounts of radiation reaching the foetus or ovaries in the case of direct useful beam irradiation of the abdomen, the scattered radiation reaching these organs during irradiation of other parts of the body is small. This is particularly true when only the feet and ankles are irradiated.
3 PROTECTION OF PERSONNEL
3.1 Protection of non-radiation personnel
3.1.1 Persons who are not radiation workers but who work in, or frequent, the podiatric clinic shall not be exposed to more than 100 µGy/week, and should
not be exposed to more than 20 µGy/week.
3.1.2 The walls, floors, ceiling and other material constructions of podiatry