Los valores y la educación

— The skill profile of the radiographic staff: Are any staff members highly trained paediatric radiographers? Do staff rotation patterns in the area cause the skill profile to vary, e.g. normal working hours versus nights, weekends or holidays?

— Whether examination protocols for all possible age groups are in existence for the examinations that need to be performed; and whether these protocols are routinely used by staff.

— A dose audit will only be successful if carried out with the full cooperation of clinical and technical staff. Staff operating the equipment, and those responsible for clinical governance in the area, should be included in planning discussions, and should receive the results of the dose audit.

— The maximum recommended period of time for data collection is 3–6 months. (This does not prevent a further extension of the audit being carried out at a later date, following analysis of the initial data.) Motivation will be lost if the time period is too long. Too short a measurement period will not result in an adequate amount of data.

— Generic work-sheets (examples are provided in the Annex) should be adapted for local equipment and protocols. It is essential that staff completing work-sheets understand fully what is required and what the varying parameter descriptors mean¹⁹. It should be noted that examination names and other terminology vary from country to country.

— The collection of dosimetric data from DICOM structured reports associated with a patient examination is very appealing as it provides a rapid method of collecting data. however, additional knowledge may be necessary to convert the DICOM data to established dosimetric forms, and not all manufacturers currently make full use of the available DICOM structures. Required patient data, if restricted to the age of the patient, may limit the analysis of such data in the paediatric setting. In this case, supplementary patient size data (such as height and weight) may need to be gathered manually. As new DICOM data fields become available, this process will be simplified.

— A paediatric dose audit can be a complex and lengthy task that covers a wide range of parameters in order to be valid. It is not always possible to be completely prescriptive in outlining audit techniques, as these may be influenced by local factors.

19 In practice, it may be advisable to convert some of the standard nomenclature used here to more common local terms, e.g. mAs instead of PIt, as has been done in the ‘clinical’

forms in the Annex.

3.3. SELECTION OF PATIENTS

Reference [3] makes no recommendations regarding the number or various sizes of patients required for data collection. however, the sample size should be large enough to avoid statistical fluctuations caused by a small number of patients.

Variation in measured doses can be particularly large if the sample contains a wide range of patient sizes. For paediatric dosimetry data collection, the sample size may well be limited by the available number of paediatric examinations.

There are at least two data collection approaches that can be used to assist in this situation:

(a) using defined age bands to allow the averaging of dose data within each band;

(b) Analysing the data as a function of patient size or age (see Section 4.3.5).

A combination of these approaches may also be employed.

If data are being collected for defined age bands, a minimum of 20 patients per age group is recommended for a full audit. When patients are not grouped, ideally the patient sizes should be equally distributed with a sample size sufficient to provide a good statistical analysis of the patient dose with respect to patient age or size. For more complex examinations, or if there are no standard paediatric protocols in place²⁰, there are likely to be large fluctuations in dose, even for patients that are nominally the same size. In this case, patient sample size should be increased to 40–50 patients per age group if possible.

3.4. SELECTION OF PATIENT EXAMINATIONS

Examinations that are commonly performed on paediatric patients may vary in different countries. It is important to audit those examinations that have the highest potential dose and/or frequency, based on the practice in the local radiology facility. The most common examinations may vary with patient age group. Examinations with standard protocols are preferred. Suggested examinations for inclusion in an audit are given in Table 7; however, this list should be supplemented by local procedures if alternative high frequency or high dose examinations are performed.

20 Particularly when there is a high staff turnover.

TABLE 7. SuGGESTED EXAMINATIONS FOR PATIENT DOSE AuDIT

Modality Examination Typical field size^a (cm × cm)

1 year old 5 year old 10 year old General

radiography Chest AP (supine) Chest PA (erect) Abdomen AP Pelvis AP

16 × 13 17 × 14 15 × 17 15 × 10

18 × 17 20 × 19 21 × 15 21 × 15

21 × 23 23 × 26 26 × 19 26 × 19 Fluoroscopy Voiding/micturating cystourethrogram

Contrast swallow

Contrast meal (upper gastrointestinal tract) Contrast enema (lower gastrointestinal tract)

11 × 11 9 × 13 8 × 14

b

12 × 12 11 × 15 13 × 15

b

14 × 14 12 × 17

b b

Computed

tomography^c head (brain protocol) Thorax

high resolution thorax Abdomen

Pelvis

— — —

a Based on data from the Australia and united Kingdom. however, large individual variations from these values are common.

b No data available.

c Trunk examinations may be combined depending on local protocols. Clinical indications should always be recorded, as these may have given rise to large dose differences for examination of the same body area.

note: AP: anteroposterior; PA: posteroanterior.

3.5. AFTER AN AuDIT

It is important that the audit loop be ‘closed’ after the collection of data.

The results need to be analysed and reported to the audited department to allow optimization of protection for the examination to begin. This should be followed by a follow-up audit. An initial narrow scope for an audit, for example, analysis of doses for one particular examination or age group with a defined end point rather than all examinations, equipment and modalities at once, usually results in a more immediate improvement in radiation safety for the patient. An important caveat is that patient radiation dose cannot be considered in isolation, and an assessment of image quality should be included when interpreting the results of a dose audit.