British Journal of Radiology 74 (2001),1032-1040 © 2001 The British Institute of Radiology
Key factors in the optimization of paediatric X-ray practice
J V Cook, MRCP, FRCR1,
J C Kyriou, BSc, MSc2,
A Pettet, DCR, DMU2,
M C Fitzgerald, BSc, MSc2,
K Shah, DCR, DMU1 and
S M Pablot, FRCR1
1Queen Mary's Hospital for Children, The St Helier NHS Trust, Wrythe Lane, Surrey SM5 1AA and 2The Radiological Protection Centre, St George's Hospital, Blackshaw Road, London SW17 0QT, UK
Correspondence: J C Kyriou
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Abstract
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Justification of radiological requests, standardization of procedures and optimization of protection measures are key principles in the protection of individuals exposed to ionizing radiation for diagnostic purposes. Nowhere is this more pertinent than in the imaging of children and, following the recent introduction of the Ionising Radiation (Medical Exposure) Regulations, there is now a regulatory requirement for diagnostic radiology departments to demonstrate compliance with these principles. A study was undertaken to compare all aspects of paediatric radiological practice at two specialist and two non-specialist centres. An initial study involved analysis of nearly 3000 patient doses. The second phase of the project involved assessment of referral criteria, radiographic technique and approximately 100 radiographs at each centre by two consultant paediatric radiologists. While all radiographs were found to be diagnostically acceptable, major differences in technique were evident, reflecting the disparity in experience between staff at the specialist and non-specialist centres. The large number of sub-optimum films encountered at the latter suggests that there is a need for specific training of less experienced radiographic and clinical staff.
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Introduction
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Children can be unco-operative and obstructive when undergoing radiography and often challenge the very technique and ability of the imaging staff within whose custody they have been temporarily placed. In addition, there is substantial evidence to suggest that children are more susceptible to the effects of ionizing radiation than adults, which places an added burden on both radiographer and radiologist to attain the best possible results every time. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) have emphasized that risks from exposure to ionizing radiation are dependent on the age at which exposure occurs, and that exposure during childhood results in a likely two- to three-fold increase in lifetime risk for certain detrimental effects (including solid cancers) compared with that in an adult [1]. Children, therefore, need more careful evaluation with regard to the necessity of examination, and radiographic technique needs to be even more exacting. The European Commission has recognized the need for special treatment of children in the X-ray department, in both the "European guidelines on quality criteria for diagnostic radiographic images in paediatrics" [2] and more recently in the Council Directive 97/43/Euratom [3] on the protection of individuals against the dangers of ionizing radiation. The guidelines suggest examples of good radiographic technique and present useful image quality criteria for a number of common paediatric projections, with the aim of producing high quality images at the lowest possible dose to the patient. A limited number of reference doses based on a European survey are also included. The Council Directive recommends that special consideration be given to diagnostic radiological procedures involving children. Implementation of the directive in the UK through the Ionising Radiation (Medical Exposure) Regulations 2000 (IR(ME)R) [4] now makes this a legal requirement, along with documentation of procedures, justification and authorization of referrals, and adoption of clinical audit.
The aim of our study was to assess and compare all aspects of the paediatric radiographic procedure at two specialist paediatric centres (C1 and C2) and two non-specialist centres (G1 and G2), including radiographic technique, image quality, patient doses and examination frequencies. We also looked at the use of referral criteria and the justification of radiological requests, both crucial components within the optimization process.
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Method
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Referral criteria
There is strong experimental evidence to suggest that a least 20% of radiological examinations undertaken in NHS hospitals are clinically unhelpful [5]. The availability to the referring clinician of good, practical guidelines is an essential first step in the optimization process, as they can help to limit the number of unnecessary exposures. Each centre was asked to provide its referral criteria for the 16 most common paediatric radiological investigations. These were chosen from a study of examination frequency data at C1 (Queen Mary's Hospital for Children, Surrey) and included 14 conventional examinations and two fluoroscopic procedures (Table 1
). The referral criteria from each of the four centres were compared.
Frequency data
The numbers of paediatric chest, abdomen, pelvis and skull examinations were counted at each department during one winter month and one spring month chosen to account for any seasonal variations in frequency owing to climatic conditions. The most recently available census data (1991) were used to calculate the local catchment populations served by each hospital and, hence, the frequency rates at each centre.
Radiographic technique and image quality
Approximately 100 radiographs from each centre, including samples from each of the 14 conventional investigations, were assessed by two consultant paediatric radiologists from C1. The radiographs were evaluated initially with reference to the quality criteria published in the European guidelines. These concern mainly the visibility of clinical features but do not address all quality or patient protection issues relating to optimization of the image. The European image criteria are available for most common paediatric examinations. Those for the anteroposterior/posteroanterior (AP/PA) chest are shown in Table 2. Additionally, a graded scoring system was developed at C1 to highlight the differences between the four centres, as it was felt that the European criteria would not do this. For instance, the use of patient lead protection, the level and suitability of collimation, the inclusion of unnecessary organs and the presence of the holder's hands on the film were considered in the C1 criteria in addition to the clinical requirements. A 5-point scale enabled the films to be ranked from "undiagnostic" to "excellent" for each criterion. The C1 criteria and the scoring system are shown in Table 3. During the assessment of the radiographs it was also noted whether other films in the X-ray packet were of a better, worse or equal standard to the one under assessment and if the exposure factors had been marked on the film or request form.
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Table 2. Image criteria for the anteroposterior/posteroanterior chest examination from the "European guidelines on quality criteria for diagnostic radiographic images" [2]
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Results
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Referral criteria
C1 had comprehensive and precise referral criteria for all 16 examinations under review as well as for many less common procedures. These included indications, contraindications, and limitations as to the acceptability of a clinician's referral based on experience and seniority, thus minimizing the potential for taking inappropriate or unnecessary examinations. Examples of this areas follows.
(1) ENT referral only for nasal bones performed for injury; not accepted from a casualty officer and not usually performed under the age of 3 years.
(2) Abdominal radiograph only performed following paediatric registrar referral and indicated in the following: loin pain, haematuria, diarrhoea, palpable mass, abdominal distension and suspected inflammatory bowel disease. Requests for abdominal radiographs for constipation would only be accepted from a registrar or above in chronic cases. Some would require pellets for transit time assessment. These latter radiographs were usually performed with high speed screen–film systems and no anti-scatter grid to minimize the dose to the patient.
(3) Skull radiographs for head injury performed only with the following indications: serious scalp laceration/haematoma, clinical signs of a closed fracture, loss of consciousness, amnesia for more than 10 min, foreign body or penetrating injury, disorientation, mental handicap that makes the examination difficult, blood/cerebrospinal fluid from the nose, history of fall greater than 6 feet (or less if concrete floor) and for part of a non-accidental injury survey. Skull radiography requests were the subject of a 6 monthly audit at C1 where the average detection rate varied between 6 fractures and 15 fractures per 100 normal films compared with 1.8% and 2.7% in the literature [6, 7].
There were several examinations that were not performed at C1 unless directly approved by a radiologist. A radiologist was available in the hospital during normal working hours for consultation, and all referrals for complex examinations were vetted by a paediatric radiologist.
C2 also had specific criteria in place for many less common procedures in addition to those for the 16 examinations under review. They included acceptable indications, which were very similar to those at C1. C2, however, did not have a radiologist constantly on site and although the radiographers were very experienced, the clinicians tended to have a dominant role in requesting certain examinations such as abdomen radiographs for abdominal pain or constipation and chest radiographs for chest infection. Consequently, the frequency of abdominal and chest radiographs was higher at C2 than at C1, G1 and G2 (Table 4).
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Table 4. Frequency of common paediatric X-ray examinations over two 1-month periods (May and January) per 100 of the paediatric population (<16 years)
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Neither G1 nor G2 had their own paediatric referral criteria but followed the guidelines published by the Royal College of Radiologists (RCR) in the handbook "Making the best use of a department of clinical radiology" [8]. These guidelines, however, were not always adhered to closely. Probably as a result, the frequency of certain examinations was significantly higher (Table 4
). Radiologists at G1 and G2 stated that they would assess some conditions individually and, unlike C1 and C2, did not have more specific guidelines in place for less routine cases.
Frequency data
Table 4 shows the frequency, over two 1-month periods, of chest, abdomen, pelvis and skull examinations per 100 of the local population at each of the four centres, for the entire paediatric age group (0 –< 16 years). The higher frequency of skull examinations at G1 and G2 reflects the inexperience of the requesting general casualty officers compared with those at the specialist centres. The higher frequency of abdominal radiographs performed at C2 is due to the dominant role of clinicians in the absence of a radiologist, which underlines the importance of having a radiologist always on site during working hours and available for consultation outside these hours, as is the case at C1. The increased frequency of pelvic radiographs at C1 and C2 is not surprising, as they are both tertiary referral centres for orthopaedics and thus see patients from outside their normal catchment areas. However, unlike C1, C2 was unable to offer ultrasound as an alternative to pelvic radiography owing to a lack of suitably qualified ultrasonographers. The relatively low frequency of chest radiographs at G2 is not easily explained but may be due to differences in socioeconomic factors, with C1, C2 and G1 being located in more socially deprived areas.
Radiographic technique and image quality
Labelling and numbering of radiographs was accurate at all hospitals. All radiographs that needed to be retrieved at C1 and C2 were found. Not all films could be traced at one of the general hospitals. This highlighted a potential risk of repeat films, but no incidence of this was found. C1 and C2 filed their paediatric film packets separately from adult film packets; G1 and G2 did not. The radiographer's name was always recorded on the film or request form at C1 and C2. This was not always the case at G1 and G2, making audit of quality and feedback to staff more difficult at the non-specialist centres. Exposure factors were always recorded at the children's hospitals but this was not routine at the general hospitals. No follow-up film, however, was found to be of inappropriate density at G1 or G2. Neither of the non-specialist centres used gonad protection frequently. This was partly due to the fact that most of the radiographs (e.g. pelvis) were first examination only and did not warrant gonad protection. The gonad area was frequently coned off on abdominal films and therefore it was not always possible to identify the protection. There were some cases where gonad protection would have been appropriate, but these were small in number. C1 and C2 routinely used gonad and other lead protection where appropriate and C1 had additional coning devices including window protection for hips.
No image was found to be undiagnostic at any of the four centres and all films were of acceptable density. It is assumed that the radiographers involved were all able to identify unacceptable films and reject them. It was not possible, however, to compare reject rates, as only one of the hospitals (C1) performed regular paediatric reject analysis. The reject rate at C1 was 2%.
Figure 1 shows that nearly all the films assessed at each centre satisfied all the image criteria in the European guidelines. Similarly, Vano et al [9] found that in a study of adult chest radiography, there was a high fulfilment of all the European adult chest image criteria [10] by all accepted radiographs and they concluded that stricter application of the criteria was necessary to differentiate between the radiographs. Furthermore, a European trial in which 2000 adult films were assessed by a panel of radiologists found that 86% of image criteria were met for the PA chest image and 96% for the lateral chest image [11]. Although virtually all films satisfied all the criteria in the European guidelines (apart from chest films, which scored lower at G1 and G2), Tables 5 and 6 highlight the areas where major differences in technique were observed between the four centres. Table 5 shows the percentage of films from each centre demonstrating poor technique with regard to radiation protection. Table 6 shows the proportion of films demonstrating excellent technique with regard to patient positioning and visualization of clinical detail. G1 and G2 had a tendency to include the holder's hands or unnecessary patient organs/body parts on films, reflecting the inexperience of the radiographic staff involved. None of the films from C1 or C2 fell into this category. Furthermore, almost all films from C1 and C2 had most or all of the diaphragm marks visible, ensuring that exposure of the child is restricted to the necessary minimum. The marking of exposure factors on the films (or request forms) practised at C1 and C2 provides a useful reference for the taking of subsequent radiographs. This was the exception rather than the rule at the non-specialist centres. The vast majority of films assessed at C1 and C2 displayed a combination of excellent visualization of fine details and minimal rotation or tilting, reflecting the experience of the radiographic staff involved. Most of the films from G1 and G2 failed to meet at least one of these criteria.
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Table 6. Percentage of films displaying excellent radiographic technique with regard to demonstration of clinical information
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A selection of radiographs demonstrating "good" and "bad" technique is shown in Figures 2–5.
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Figure 2. (a) Anteroposterior (AP) chest/abdomen film of a newborn premature boy in the special care baby unit (SCBU). This is an excellent film, perfectly centred over the mid chest region to avoid lordosis, with all four collimation marks present and excluding the gonads, head and limbs. (b) AP chest/abdomen film of a newborn premature boy in the SCBU. The image is well centred over the mid chest region but the presence of extraneous wires and leads obscures some of the anatomical detail. Although all four collimation marks are visible, the gonads are included and are unprotected. (c) AP chest/abdomen film of a newborn premature boy in the SCBU. This film contains several faults, including slight lordosis with the clavicles above the lung apices, absence of all four collimation marks, inclusion of the upper arms and legs and the unprotected gonads, and the presence of a holder's finger (bottom right).
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Figure 3. (a) Anteroposterior (AP) chest radiograph of a term infant in the special care baby unit (SCBU). This is an excellent film displaying ideal positioning, centring and collimation and with all four collimation marks visible. Note the exclusion of the head and upper limbs. (b) AP chest radiograph of a 31 week infant in the SCBU. This poor quality film shows the child rotated to the right and includes a holder's hand, which obscures the right hemi-thorax and lung apices. (c) AP chest radiograph of a 31 week infant in the SCBU. This poor quality film has all four collimation marks missing and includes the head and upper arms.
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Figure 4. Anteroposterior hips radiograph of 3-year-old girl. This film demonstrates ideal collimation and the use of specially developed window lead protection necessary for girls.
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Figure 5. Anteroposterior skull radiograph of 3-month-old boy. This film demonstrates perfect positioning and centring as well as the use of a circular collimator.
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Conclusion and discussion
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The first and perhaps most important step in optimization of the radiological/radiographic process is justification of the radiological request. In this regard, it was encouraging to note that all four centres had referral guidelines in place. The two specialist centres had developed their own very specific referral criteria and the non-specialist centres had implemented the more general RCR guidelines. However, in the latter case, the RCR guidelines were not always strictly adhered to and there was no specific referral criteria in place for less routine examinations. This was reflected in the increased frequency of certain examinations (e.g. skull radiographs) at G1 and G2.
None of the films assessed was undiagnostic and more than 90% satisfied all the European image criteria. However, the criteria did not address all the quality issues and it was felt that the non-specialist centres produced films that were of sufficient diagnostic quality but could be improved in other ways. In particular, there was a tendency at these centres to include unnecessary patient organs and holder's hands on the film owing to inadequate collimation. In addition, these films often displayed inferior technique with regard to patient positioning, as demonstrated by the frequencly of rotated and tilted images. There was a tendency, however, for the specialist centres to produce films of unnecessarily high quality, probably because of the perceived expectations placed upon them as tertiary referral centres. This was reflected in the results of the initial dosimetry survey [12], which indicated a three- to four-fold difference in the entrance surface dose (ESD) for those examinations (e.g. abdomen and pelvis in children under 5 years of age) where both C1 and C2 routinely used an anti-scatter grid to produce aesthetically pleasing images of unnecessarily high quality at an increased dose. The use of the anti-scatter grid at C1 has since been reviewed and is now restricted to the largest children where the loss of image contrast would otherwise make the film undiagnostic. A number of other dose reduction measures have been introduced at C1, including the use of fast screen–film systems (400–800 speed depending on the procedure), the use of increased tube potentials and the permanent addition of 0.1 mm copper filtration on both static conventional and fluoroscopic tubes (but not on the neonatal unit mobiles where the associated loss of image contrast was considered to be too great). Reductions in patient ESDs of over 50% have consequently been achieved at C1 without a noticeable compromise in the diagnostic content of the images. This demonstrates the value of self-audit and critical review in highlighting areas where methods can improve that otherwise may not have been evident. The priority at C1 now is to produce films that are of acceptable rather than maximum quality.
The lack of expertise amongst the radiographic staff at the non-specialist centres was reflected in the number of suboptimal films from G1 and G2. This lends support to the suggestion that every X-ray department should assign responsibility for paediatric imaging to a core group comprising, for instance, a specially trained radiographer and a radiologist with an interest in paediatrics. Furthermore, it should be possible for other radiographic staff to obtain advice from this group on all aspects of paediatric imaging outside normal working hours. A variety of radiographic aids such as shaped sponges, sandbags and blankets for positioning and restraining, as well as various beam-shaping devices should be available in all departments, even where paediatric imaging is relatively infrequent. Many of these devices can be simple and inexpensive to acquire or make, but if used properly can prove to be very effective in gaining the trust and co-operation of the younger patient.
A book of "best practice" based on current methods at C1 has been published by the authors [13] and includes full referral criteria for 18 examinations, examples of good radiographic technique, a selection of child-friendly aids and restraining devices, and suggested exposure factors with corresponding ESDs, dose–area products and effective doses. The ESDs in the book are derived from optimized exposure techniques based on the available equipment at C1 and have been adopted by the National Radiological Protection Board as "achievable doses" [14]. The booklet also includes the film scoring system described here and is intended to be used as a template by other departments, especially those that do not specialize in paediatric imaging. All departments, whether specialist or otherwise, can benefit from self-audit and a re-evaluation of their procedures where necessary. Clinical audit is now a regulatory requirement following the adoption of the European Council Directive 97/43 Euratom [3] through the implementation in the UK of IR(ME)R 2000 [4], which places a responsibility on all X-ray departments to pay special attention to paediatric imaging. This can be achieved in part through the adoption of the practices identified and discussed here.
Received for publication February 27, 2001.
Revision received June 1, 2001.
Accepted for publication July 6, 2001.
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References
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Top
Abstract
Introduction
) and other (
) examinations.