Improving neonatal chest radiography: an evaluation of image acquisition techniques, dose and technical quality Maryann Hardy, PhD Professor of Radiography & Imaging Practice Research
Beverly Snaith, PhD Consultant Radiographer in Emergency Care
Background •
Neonatal chest radiography is a frequently performed examination around the world
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Majority of examinations are undertaken in general hospitals rather than specialist paediatric centres.
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The quality of radiographic images has been criticized internationally over the last 20 years
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A number of research studies have been undertaken examining radiographic dose and image quality in neonates but these have been undertaken from the perspective of the radiologist or medical physicist rather than the radiographer.
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No study has overtly considered or systematically explored the image acquisition process and criteria as a fundamental component to high quality examinations
Existing Standards for Neonatal Chest Radiography •
Published in 1996 , adapted and modified to underpin practice internationally
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Based on film technology
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International authorship of doctors (radiologists) and physicists – no radiographer invited to be part of advisory group or authorship.
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Standards focus on generic criteria related to dose reduction and image diagnostic quality from perspective of radiological assessment – Little guidance on how to best acquire a good image.
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Neonatal chest standards based on review of 72 images acquired between 1989-1991
Current suggested best radiographic practice (UK) • Head straight • Arms flexed (to prevent lordosis) and held to side of head (to minimise rotation) • 15⁰ pad beneath neck to promote neck extension and reduce risk of chin overlying chest anatomy • Inconsistent published advice on: o Centring point o Central ray angulation o Immobilisation of lower limbs o Use of lead protection
Problem and Study Aim • A clear gap in the international evidence base exists in relation to: – – – –
Radiographic image acquisition techniques; Radiographic quality assessment criteria; Radiographer knowledge and confidence when working with neonates; Dose assessment measures and reduction approaches when working with digital technology
• This study, supported by an ISRRT research award, aims to begin to address these gaps by: – Undertaking a comprehensive evaluation of image acquisition techniques, dose and technical quality criteria to determine the learning needs of radiographers to improve the quality of neonatal radiography practice; – Developing a practice improvement intervention that could be implemented and evaluated as part of a multidisciplinary programme of work at a later stage.
Method • 2 geographically distinct UK hospital organisations participated in this study and completed a survey of current local practice. • Random selection of 100 chest radiograph examinations was identified at each site – All neonatal chest radiographs (10% at 4th & 8th Rib Level (rotated)
Width variation within >10% at 4th rib and within 10% at 8th rib level (rotation at shoulders)
Width variation within 10% at 4th rib and >10% at 8th rib level (pelvis rotation)
Results: How does head and arm position affect rotation? Head position Unable to ascertain Straight Rotated Total Arm Position Unable to ascertain Advocated position Abducted laterally Extended cranially Extended caudally Asymmetric position Grand Total
Thorax position Rotated Straight Total 39 11 50 47 (30.7%) 13 (27.7%) 60 67 (43.8%) 23 (48.9%) 90 153 47 200 Thorax position Rotated Straight Total 12 4 16 7 (4.6%) 1 (2.1%) 8 39 (25.5%) 14 (29.8%) 53 13 (8.5%) 3 (6.4%) 16 46 (30.1%) 16 (34.0%) 62 36 (23.5%) 9 (19.1%) 45 153 47 200
Results: Collimation European Guidelines (1996)
Results: Collimation • Image annotation – EC guideline maximum limits of collimation drawn on each image • 1cm beyond outer border of widest rib laterally • Cervical trachea (C5) • Lower border of L1
• Compared EC guideline limit to actual exposed area • Determined if area of interest was included within EC guideline limit
Results: Collimation
Results: Collimation
Results: Collimation • 34 images excluded from collimation assessment as autocollimation or receptor edge prevented actual edge of exposed field being determined. • For 1 examination (1/166; 0.6%), relevant anatomy extended beyond EC guideline limit
Area (cm2) Effective Dose received (mSv)
Mean Actual (range) 166.7 (56.7-316.2) 0.017 (0.008-0.062)
Mean EC
Difference (Actual – EC)
129.8
-22.1%
0.015
-10.42%
Results: Centring Point 100 90 80 70
Number
60 50
Actual centre EC centre
40 30 20 10 0 TV2 TV3 TV4 TV5 TV6 TV7 TV8 TV9 TV10 Vertebral level
Results: Image Appearances
Site A 33wks, 1765g, 60kV, 1.25mAs
Site B 33wks, 1780g, 60kV, 1.25mAs
Both images meet EC guideline criteria for image quality when assessed on PACS Difference in appearances related to different post-processing algorithms
Key Findings • There appears to be little evidence to support current advocated radiographic positioning techniques for neonatal chest radiography • EC guidelines remain the international standard even though based on old technology (film/screen) • Inconsistent image acquisition practices exist as a result of lack of local expertise, leadership and practice protocols including knowledge of equipment adaptation • No standard exists for image presentation and clinicians are looking to manufacturers to dictate appearances rather than appearances being driven by clinical needs.
Interim Intervention • We have a lot of data to analyse but in response to initial findings, both clinical sites have requested an interim intervention to improve image quality. • Suggested practice guidance – – – – – – –
Remove artefacts Straight tube Centre to midpoint at level of intermamillary line Arms symetrically abducted or extended caudally Head positioned straight Both knees flexed and supported on pad/roll Collimate to level of shoulder soft tissue outline superiorly and laterally to border of thorax
Evidence of improvement? Pre-intervention training
Post-intervention training
Not perfect but a definite improvement
Conclusion • The findings of this study suggest a large gap in the existing evidence base • We want this study to underpin and inform a revision of international guidelines regarding neonatal chest radiography Maryann Hardy
[email protected]
• Are you interested in joining us?
Bev Snaith
[email protected]
