1 DECISION 1 (6) REFERENCE LEVELS FOR THE PATIENT S RADIATION EXPOSURE FOR PAEDIATRIC X-RAY EXAMINATIONS

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1 1 DECISION 1 (6) TRANSLATION. ORIGINAL TEXT IN FINNISH. 28 December /310/05 REFERENCE LEVELS FOR THE PATIENT S RADIATION EXPOSURE FOR PAEDIATRIC X-RAY EXAMINATIONS The responsible party's (party running a radiation practice) duty to introduce reference levels for X-ray examinations is laid down in the Decree of the Ministry of Social Affairs and Health on the medical use of radiation (423/2000; Sections 2, 16 and 17). The Decree also prescribes that the reference levels for the most common examinations shall be issued by the Radiation and Nuclear Safety Authority (STUK). This decision issues the reference levels concerning chest radiography, radiography of the paranasal sinuses and voiding cysto-urethrography (micturating cystourethrography). Table 1 presents the reference levels for paranasal sinus imaging (occipito-mental view) as a surface dose (ESD) and as the dose-area product (DAP) for children aged 7 15; the reference levels for voiding cysto-urethrography (micturating cysto-urethrography) are presented as a dose-area product (DAP) separately for children under 1 year and between 1 and 5 years. Figures 1 4 present the reference levels for chest radiography in the AP (or PA) and LAT projections as surface doses (ESD) and dose-area products (DAP) as a function of the patient s thickness. Responsible parties may introduce into practice the reference levels issued by STUK or they may use stricter values of their own. When desired, responsible parties may determine reference levels for their own use for examinations, which have not been given reference levels. This decision is valid as of 1 January Director General Jukka Laaksonen Director Eero Kettunen APPENDIX Instructions: Reference levels for the patient s radiation exposure for paediatric X-ray examinations STUK SÄTEILYTURVAKESKUS STRÅLSÄKERHETSCENTRALEN RADIATION AND NUCLEAR SAFETY AUTHORITY Osoite/Address Laippatie 4, Helsinki Postiosoite / Postal address PL / P.O. Box 14, FI Helsinki, FINLAND Puh. / Tel. (09) , Fax (09) ,

2 2 Table 1. Reference levels for paranasal sinus radiography and voiding cysto-urethrography (micturating cysto-urethrography) for paediatric X-ray examinations. Examination (and imaging projection) Age group (years) DAP (mgy cm 2 ) Reference level ESD (mgy) Radiography of the paranasal sinuses Voiding cystourethrography below

3 3 150 DAP (mgy cm 2 ) Patient thickness (cm) Figure 1. Reference level for dose-area product (DAP) as a function of the patient s thickness for paediatric chest radiography in the AP or PA projections. The equation for the reference level curve: y = e 0.132x.

4 4 0,30 ESD (mgy) 0,20 0,10 0, Patient thickness (cm) Figure 2. Reference level for surface dose (ESD) as a function of the patient s thickness in paediatric chest radiography in the AP or PA projections. The equation for the reference level curve: y = e 0.067x.

5 DAP (mgy cm 2 ) Patient thickness (cm) Figure 3. Reference level for dose-area product (DAP) as a function of the patient s thickness in paediatric chest radiography in the LAT projection. The equation for the reference level curve: y = e 0.083x.

6 6 1,00 0,80 ESD (mgy) 0,60 0,40 0,20 0, Patient thickness (cm) Figure 4. Reference level for surface dose (ESD) as a function of the patient s thickness in paediatric chest radiography in the LAT projection. The equation for the reference level curve: y = e 0.080x.

7 INSTRUCTIONS 1 (3) 28 December 2005 REFERENCE LEVELS FOR THE PATIENT S RADIATION EXPOSURE FOR X-RAY EXAMINATIONS OF CHILDREN Definition of reference level Using reference levels Reference level refers to a pre-determined radiation dose level that is not expected to be exceeded during a procedure that is performed on a normal-size patient according to good treatment practice. Reference levels can be used to detect X-ray equipment and functions that cause higher than normal radiation exposure. The reference levels are not intended for use in limiting the radiation exposure of individual patients; instead, they are used to compare the average radiation exposure of a group of patients selected in the manner described below to the radiation exposure caused by an examination or procedure that follows good practice. A guide published by the Commission of the European Union explains the use of the reference levels [1]. The fact that the dose level exceeds the reference level does not necessarily mean that the examination has been performed poorly. Using radiation exposure above the reference levels may be justified in specific cases, such as when a higher image quality is required. On the other hand, the fact that the reference levels are not exceeded does not mean that the examination is optimised in terms of radiation safety; it should nevertheless be considered whether radiation exposure can be reduced further. The guide published by the Radiation and Nuclear Safety Authority [2] can be used to assist in the optimisation of paediatric X-ray examinations. Determining radiation exposure Radiation exposure shall be measured or calculatory assessed at least once every three years. The guide published by STUK [3] provides instructions concerning the determination of patient exposure due to X-ray examinations and its comparison with the reference levels. Exposure is determined for the examination types performed with each examination stand, using at least one imaging projection and at least one dose quantity (ESD, DAP) for which a good practice reference level for children has been provided. The radiation exposure shall be determined and compared to the reference level again if any changes are made in the examination practices or equipment that may affect radiation exposure. The aim is to determine radiation exposure for a group of at least ten patients per each reference level. Furthermore, it must be verified at least once a year that the radiation exposure has not essentially changed. The verification shall be done at each examination stand and at least with one imaging projection of one examination type that is performed with the examination stand in question and for which a reference level has been provided. For STUK SÄTEILYTURVAKESKUS STRÅLSÄKERHETSCENTRALEN RADIATION AND NUCLEAR SAFETY AUTHORITY Address Laippatie 4, Helsinki Postal address P.O. Box 14, FI Helsinki Tel Fax

8 2 Chest radiography example, comparing the exposure parameters to previous values and using the results from technical quality assurance constitutes sufficient verification. The reference level for paediatric chest radiography is provided as a diagram (reference level curve) where the reference level is presented as a function of the patient s thickness. In addition to the radiation exposure, for lung imaging, the thickness of the patient is also determined at the centre axle of the radiation beam in the imaging projection (AP, PA or LAT). For example, the reference level curve can be used as a printed image; the radiation doses are marked in the image according to the patient s thickness and compared to the reference level curve. If there are more dots above the reference level curve than below it, this indicates that the reference level has been exceeded (Figure 1a) and the deviations from the reference level curve must be examined in more detail. The comparison to the reference level curve can also be performed by means of calculation (such as a spreadsheet) by comparing the curve fitted to the patient doses determined by the responsible party (exponential or linear fitment, for example) to the reference level curve (Figure 1b). If the fitted curve is above the reference level curve, this indicates that the reference level has been exceeded. STUK s website has a table available for download that indicates the reference level as a function of the patient s thickness. This can be utilised when using the reference level curve in calculations. (a) (b) Figure 1. An example of using the reference level curve in chest radiography. The reference level curve is printed and the radiation doses for patients of different sizes (black dots) are marked in the image (Figure 1a). This indicates that the reference level has been exceeded when there are more dots above the reference level curve than below it. Figure 1(b) has an example of a calculatory method where a curve is fitted to the hospital s patient doses (dash line). Since the fitted curve is above the reference level curve, the reference level is seen to have been exceeded.

9 3 Paranasal sinus radiography For paranasal sinus radiography, the reference level is provided for children aged 7 15 both as a surface dose (ESD) and as the dose-area product (DAP). The aim is to determine radiation exposure for a group of at least ten patients per each age group. The average radiation exposure is calculated for this group and is compared to the reference level for the age group. Voiding cysto-urethrography (micturating cysto-urethrography) For voiding cysto-urethrography, the reference level is provided separately for children less than 1 years old and children aged 1 5. For cysto-uretography, the dose-area product (DAP) is determined for the entire examination, including the radiation exposure due to fluoroscopy and separately taken X-ray images. The aim is to determine radiation exposure for a group of at least ten patients per each age group. The average radiation exposure is calculated for this group and is compared to the reference level for the age group. Results assessment and corrective actions The radiation exposure information is recorded and is systematically compared to the reference levels. If the reference level is found to be exceeded, the causes are analysed and corrective actions are taken if necessary in order to reduce the radiation exposure of the patients. Decisions concerning reference levels are available on STUK s website ( BIBLIOGRAPHIC REFERENCES [1] Commission of the European Union. Guidance on diagnostic reference levels (DRLs) for medical exposures. Radiation protection 109. European Communities. Luxembourg, [2] STUK tiedottaa 1/2005. Lasten röntgentutkimusohjeisto (X-ray examination guidelines for children). Helsinki, [3] STUK tiedottaa 1/2004. Röntgentutkimuksesta potilaalle aiheutuvan säteilyaltistuksen määrittäminen (Determining the radiation exposure for a patient, caused by an X-ray examination). Helsinki, 2004.