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Effectiveness of Adjusting Radiographic Technique Parameters on Image Quality in Direct Digital Radiography: a Systematic Review Protocol

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Effectiveness of Adjusting Radiographic Technique Parameters on Image Quality in Direct Digital Radiography: a Systematic Review Protocol SYSTEMATIC REVIEW PROTOCOL Effectiveness of adjusting radiographic technique parameters on image quality in direct digital radiography: a systematic review protocol 1,2 3 2,4 2 Caitlin Steffensen Gregory Trypis Gordon T.W. Mander Zachary Munn 1Philips Australia and New Zealand, Murrarie, Australia, 2Joanna Briggs Institute, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, Australia, 3Department of Medical Imaging, Sunshine Coast University Hospital, Birtinya, Australia, and 4Department of Medical Imaging, Toowoomba Hospital, Toowoomba, Australia ABSTRACT Objective: The purpose of this review is to investigate the effectiveness of adjusting radiographic technique parameters on image quality of projectional radiographs acquired on a direct digital radiography system. Introduction: Projectional radiography performed with direct digital detectors is now commonplace in many medical imaging departments across the world. While the acquisition technology has advanced, it appears that many sites have not optimized their radiographic technique factors for this new technology. The aim of this review is to uncover evidence to support the continued use of these traditional technique parameters or to suggest changes in clinical practice that would produce optimized results. Inclusion criteria: The review will consider studies that include projectional radiographs acquired on a direct digital radiography system of the axial and appendicular skeleton. Only studies that investigate a human subject (living or post-mortem), or an anthropomorphic phantom will be included. Studies that directly investigate the effect of changing a technique parameter on the resultant image quality and the effect on patient dose will be included. Methods: A comprehensive search of both published and unpublished literature will be performed to uncover studies meeting the inclusion criteria. Studies will be screened for inclusion by two reviewers and disagreements resolved through discussion or with a third reviewer. Studies included in final analysis will be critically appraised for methodological quality. Data will be extracted by a single reviewer and checked by the author team for accuracy. Statistical meta-analysis and subgroup analyses will be performed as appropriate, and a Summary of Findings created. Systematic review registration number: PROSPERO CRD42019137806 Keywords Direct digital radiography; image quality; optimization; radiographic technique JBI Database System Rev Implement Rep 2019; 17(10):2165–2173. Introduction image acquisition has shifted from an analog process 3 ver the past 122 years since the discovery of to a digital one. The way projectional radiographs O x-rays, diagnostic imaging has undergone signifi- are acquired, manipulated, stored and viewed has cant evolution.1,2 During this time, the method of advanced, leading to significant changes for all stake- holders.4 Images are now able to be viewed simulta- Correspondence: Caitlin Steffensen, neously by multiple viewers across differing geographic [email protected] locations and stored for almost instantaneous 3 Conflicts of interest: Primary author, CS, is an employee of Philips retrieval. What has remained constant since the incep- Australia and New Zealand. This review will not evaluate the perfor- tion of diagnostic x-ray imaging is the need for appro- mance of different image processing software. It will extract details on priate image quality to provide an accurate diagnosis. detector material for the sole purpose of providing accurate technique The literature acknowledges that dose and image information for the specific detector type (should there be any varia- 5,6 tion dependent on detector material). There will be no ranking/grading quality are directly related. Image quality can be of performance. The other authors declare no conflicts of interest. significantly improved by increasing the exposure DOI: 10.11124/JBISRIR-2017-003888 factors, but this is at the expense of increased JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2165 ©2019 Joanna Briggs Institute. Unauthorized reproduction of this article is prohibited. SYSTEMATIC REVIEW PROTOCOL C. Steffensen et al. radiation dose to the patient.7 Optimization, rather In terms of acquisition, DDR detectors have a than maximization, of image quality in diagnostic wider dynamic range than that of film-screen. The radiography should be the chief goal. An optimized dynamic range, also known as latitude, of an acqui- technique results in the clinical question being effec- sition device refers to the range of exposure values tively answered, while not imposing a radiation dose over which it is able to produce an adequate image.13 to the patient that is higher than necessary.8 By Direct digital radiography detectors do not require utilizing an optimized technique, radiographers are tight control of exposure factors in order to produce able to ensure that their commitment to keeping an image of diagnostic quality, as was the case in film doses ‘‘as low as reasonably achievable’’ is met, imaging, due to their wide dynamic range.12 Another while not compromising the diagnostic quality of advantage of the wide dynamic range of the DDR the examination. detector is their ability to represent structures of In the literature, digital radiography is used as an varying attenuation in a single image.3 In terms of umbrella term for images that are acquired through image display, digital radiography images are able to any mechanism that transforms the incident photon be manipulated after their creation by way of post- into an electrical charge.9 Under this definition, processing. Optimal contrast and brightness is no digital radiography is comprised of both computed longer reliant on the use of a specific film-screen radiography (CR) and direct digital radiography combination or set of radiographic technique (DDR).3 Direct digital radiography systems acquire parameters.10 images by converting the incident x-ray energy into a Digital radiography technology has given rise to digital signal almost instantaneously,6 skipping the many avenues for dose reduction; no longer bound intermediary storage step that is associated with by a certain exposure requirement for optimal image CR.10 The detector used in DDR systems acts as quality, the new limiting factor is image noise.14,15 both the acquisition and conversion device, whereas a There are a number of sources that are responsible CR system has a separate acquisition device (the for image noise,16 yet regardless of its origin, all photostimulable phosphor plate) and conversion noise leads to degradation of image quality. Noise is device (the processor). In a DDR system, the mecha- the result of statistical fluctuations in signal intensity nism by which the energy is transformed into a digital received by the detector, and is represented in the signal depends on the type of detector used, and this is resultant image as fluctuations in brightness, leading the method by which DDR systems are classified.3 to a mottled appearance.5,17 Visual appreciation of This review will focus only on the optimization of image noise is very subjective18 and what constitutes radiographic technique parameters for DDR. an acceptable level of noise depends on both the Common across all imaging modalities, not just preference of the observer and on the clinical ques- DDR, is the need for appropriate image quality for tion being asked.12,19 diagnosis. When considering the term ‘‘image qual- Image quality research in medical imaging is ity’’, it is important to make the distinction between performed using a variety of methods, one or a a visually appealing image and an image of adequate combination of test objects, phantoms, and clinically quality. An image of ‘‘adequate’’ quality can effec- acquired images.7 Test objects measure a specific tively answer the clinical question posed,7 regardless quality of an imaging system under ideal conditions, of whether the image is visually appealing to the but it is difficult to link these results to performance reader or not. Adequate image quality in analog in clinical use.7 Imaging phantoms used for research imaging revolved around obtaining images with fall into one of two broad categories: geometric or optimal contrast and density.4 Image contrast and anthropomorphic. Geometric phantoms consist pri- density were almost solely dependent on exposure marily of geometric shapes, whereas anthropomor- technique and film-screen combination factors cho- phic phantoms are designed to be analogous to sen prior to acquisition.11,12 As the radiographic film human tissue and accurately represent the anatomi- acted as both the acquisition and display medium, cal structure of the body.20 As images of test objects there were limited means of altering the image alone are unable to be directly linked to clinical appearance after exposure.10 The transition from performance,7 only studies using phantoms and/or analog to digital imaging saw the decoupling of clinically acquired images will be included for the acquisition and display mediums.4 this review. JBI Database of Systematic Reviews and Implementation Reports ß 2019 THE JOANNA BRIGGS INSTITUTE 2166 ©2019 Joanna Briggs Institute. Unauthorized reproduction of this article is prohibited. SYSTEMATIC REVIEW PROTOCOL C. Steffensen et al. Subjective and objective measures of image qual- Reviews and Implementation Reports, and the ity exist, summarized well
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