An optimal protocol for full-spine radiography

Transcription

1 An optimal protocol for full-spine radiography Poster No.: C-0649 Congress: ECR 2016 Type: Scientific Exhibit Authors: C. Ernst, N. Buls, A. Laumen, E. ASSENOVA, S. Assouti, G Van Gompel, J. de Mey ; Brussels/BE, LEDE/BE, Antwerpen/ 4 BE, Brussel/BE Keywords: Musculoskeletal spine, Pediatric, Radioprotection / Radiation dose, Conventional radiography, Digital radiography, Dosimetry, Radiation safety, Dosimetric comparison DOI: /ecr2016/C-0649 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 18

2 Aims and objectives Scoliosis is defined as a lateral curvature of the spine. Full-spine radiography is the golden standard for identifying and monitoring this disease occurring in approximately 2-4% of children aged six to fourteen (1). Imaging is required to help in the decision regarding treatment by characterizing (2) the type of curve and its severity; to identify possible underlying pathologies; to detect any increase in deformation. Scoliosis patients typically receive multiple radiographs during treatment and follow-up. Average numbers of 22.9 radiographs per patient are reported in literature (3). Owing to the increased radiation sensitivity of children and the numerous follow up images with exposure of the most sensitive organs (thyroid gland, mammary gland and gonads) radiation safety is of particular concern in patients with scoliosis. The purpose of this phantom study was to optimize our standard full-spine radiography protocol with respect to diagnostic quality and radiation dose. Methods and materials Phantom: A phantom study was performed using an adult humanoid Rando Alderson Phantom (The Phantom Laboratory, Greenwich, NY). These phantoms are molded of tissue-equivalent material and are designed within highly sophisticated technological constraints. The phantom is transected-horizontally into 2.5 cm thick slices (Fig. 1). In order to include the effect of a brace, a specific device was manufactured matching the phantom size (T!GO, Wetteren, Belgium)(Fig. 2). Imaging technique and protocol: All full spine radiographs were performed on a full digital X-ray device (Siemens, AXIOM Luminos drf) (Fig. 3). Page 2 of 18

3 The technical parameters of our standard full spine protocol for both in-brace and without brace imaging are: 85 kvp (PA view) or 113 kvp (LAT view), relative dose per puls 1.39, automated exposure control, anti-scatter grid, no additional spectral filter. This standard protocol results in a Dose Area Product (DAP) of µgym² and µgym² for PA (Fig.4) and LAT (Fig.5) views respectively. Optimisation proces The impact of following parameters was assessed: tube potential (kvp), relative dose per pulse, additional filtration (Cu) and anti-scatter grid. The "relative dose per pulse" parameter was altered in technical service mode with cooperation of the manufacturer. Tube potential range: kvp Relative dose per pulse: Additional Cu filtration: mm Cu Anti-scatter grid: present - absent A total of 50 different protocols were investigated: 21 PA views without brace and 13 inbrace; 8 LAT views without brace and 8 LAT in-brace. Diagnostic quality was assessed by a pediatric radiologist (C.E.) and a pediatric orthopedist (A.L.) for following criteria in PA view: bone sharpness, contrast between soft tissue and bone, spine curvature, confidence of Risser grade, visibility of pedicles and processi spinosi. For LAT view, following criteria were assessed: bone sharpness, contrast between soft tissue and bone, spine curvature. Each criterium was graded on a 5 point ordinal scale, ranging from no to high diagnostic confidence. The optimal protocol was defined as having the lowest dose with non-inferior quality compared to our standard protocol. Images for this section: Page 3 of 18

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5 Fig. 1: Rando Alderson Phantom Radiology department, UZ Brussel, Brussel/Belgium 2015 Page 5 of 18

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7 Fig. 2: Customized brace for phantom. Radiology department, UZ Brussel, Brussels/Belgium 2015 Fig. 3: AXIOM Luminos drf, full digital X-ray device Radiology department, UZ Brussel, Brussels/Belgium 2015 Page 7 of 18

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9 Fig. 4: Standard protocol PA view. Radiology Department, UZ Brussel, Brussels/Belgium 2015 Page 9 of 18

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11 Fig. 5: Standard Protocol LAT view. Radiology Department, UZ Brussel, Brussels/Belgium 2015 Page 11 of 18

12 Results Radiation dose For the PA and LAT view protocols the DAP varied from 14.3 µgym² to µgym² and from 53.0 µgym² to µgym² respectively. The presence of the anti-scatter grid increased dose by 132%, the use of a 0.3 mm Cu filter decreased dose by 65%. The use of 102 kvp in PA view increased dose by 42%. The presence of a brace increased dose by 11%. Image quality For all criteria in PA view we did not observe a difference in score's between protocols, with exception of the visibility of the processus spinosus during absence of the anti-scatter grid. When no grid was present the reported image quality was reduced by one point. The presence or absence of a brace did not had an influence on image quality. The lowest dose PA protocol which still yielded non-inferior quality was identified as 85 kvp, 0.87 relative dose per pulse, with grid, 0.3 mm Cu resulting in a DAP of 44.7 µgym² (Fig.6). For LAT view we did not observe a difference in score's between protocols. Consequently, we selected the protocol with the lowest dose. This was identified as 113 kvp, 1.09 dose per pulse, with grid, 0.3 mm Cu resulting in a DAP of µgym² (Fig.7). PA view Standard protocol Lowered dose Slot-scanning protocol system (2) Dynamic flatpanel detector (2) (±20.6) 42.2 (±11.7) LAT view n.a. n.a. Table 1 Dose area product (DAP) in µgym² for our standard and optimized PA view protocol compared to literature data for a 12-year-old child (2). Little information is available concerning radiation dosimetry for full-spine radiography in literature. Yoon et al reported DAP values for 50 adult patients (4). Compared to our Page 12 of 18

13 results, the mean DAP values were very high: µgym² and µgym² for AP and LAT views respectively. Yvert et al evaluated AP view doses with a flat panel detector and slot scanning system for 12-year-old children and reported comparable values with the dose of our optimised protocol (Table 1). Considering our adult humanoid patient model, we believe actual pediatric patient doses will probably be lower due their smaller posture. Our reported values therefore probably represent the upper DAP values for a pediatric patient group. This needs to be further investigated in a clinical study. Images for this section: Page 13 of 18

14 Fig. 6: Standard (left) and lowered dose (right) protocol PA view. Radiology department, UZ Brussel, Brussels/Belgium Page 14 of 18

15 Fig. 7: Standard (left) and lowered dose (right) protocol LAT view. Page 15 of 18

16 Radiology department, UZ Brussel, Brussels/Belgium Page 16 of 18

17 Conclusion According to this phantom study an optimal protocol for a whole-spine radiograph was identified with anti-scatter grid and filtration. With this protocol radiation dose was reduced by approximately 70% for PA view and 30% for LAT view radiographs. Personal information Caroline Ernst, MD, department of Radiology, UZ Brussel, Brussels, Belgium; Caroline.Ernst@uzbrussel.be Nico Buls, Phd, Department of Radiology, UZ Brussel, Brussels, Belgium; Nico.Buls@uzbrussel.be Armand Laumen, MD, Department of Orthopedics, UZ Brussel, Brussels, Belgium; Armand.Laumen@uzbrussel.be References Knott P, Pappo E, Cameron M, et all. Sosort 2012 concensus paper: reducing x-ray exposure in patients with scoliosis. Scoliosis 2014, 9:4; Yvert M, Diallo A, Bessou P, et all. Radiography of scoliosis: comparative dose levels and image quality between a dynamic flat-palel detector and a slot-scanning device (EOS system. Diagnostic and interventional Imaging (2015), Ronckers C, Land C, Miller J, et all. Cancer mortality among woman frequently exposed to radiographic examinations for spinal disorders. Radiat Res 2010, 174(1):83-90 Yoon SW, Gyunggi-Do. Evaluation of Effective Dose of the Patient in Whole Spine Scanography, Based on Automatic Image Pasting Method for Digital Radiography. ECR-2014, Page 17 of 18

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