Difference in signal-to-noise-ratio (SNR) from vertical to horizontal scanner position using a 0,25 Tesla Weightbearing

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1 Difference in signal-to-noise-ratio (SNR) from vertical to horizontal scanner position using a 0,25 Tesla Weightbearing scanner Poster No.: C-0672 Congress: ECR 2014 Type: Scientific Exhibit Authors: F. H. Mortensen 1, J. S. Bovin 2, J. D. Nybing 3, M. Boesen 4, R. Bouert 5 ; 1 København NV/DK, 2 Herlev/DK, 3 Copenhagen/DK, 4 DK, 5 Frederiksberg/DK Keywords: DOI: MR physics, MR, Technical aspects, Experimental investigations, Physics, Image registration /ecr2014/C-0672 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 14

2 Aims and objectives One obvious advantage with a weight-bearing MRI scanner is the possibility to visualise positional dependent pathology, which might be difficult to diagnose in conventional supine MRI scanners. In example supine and weight-bearing MRI of the lumbar spine, permits the study of pathophysiological changes of the bony and soft tissue structures induced by weight-bearing, thus allowing MR images of the lumbar spine to be obtained in positions that usually generate clinical symptoms(fig1.). In selected cases, weightbearing MRI of the spine has proven to be the better choice when demonstrating clinically relevant pathology[1][2]. Fig. 1: Figure 1 [3] Effects of gravity on the intervertebral disc, when scanning in weight bearing position compared to supine position References: In this study we have investigated if there is any difference in the signal-to-noise-ratio (SNR) between the weight bearing (vertical) and supine (horizontal) scanner positions using a tilting 0.25 Tesla G-Scan (Esaote, Genova, Italy, hardware release 3). Page 2 of 14

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4 Images for this section: Fig. 1: Figure 1 [3] Effects of gravity on the intervertebral disc, when scanning in weight bearing position compared to supine position Page 4 of 14

5 Methods and materials Method: A fluid phantom with an aqueous solution of 5 mm NiCl2 and 55 mm of NaCl was scanned in order to measure SNR in both horizontal (0 degrees) and vertical scanner position (90 degrees). To ensure comparable results, the exact same sagittal T2-weighted turbo spin echo sequence (Table1) using the lumbar coil was performed three times in both the horizontal and vertical scanner positions. Table 1: Scan parameters with the scanner in horizontal (0 degrees) and vertical (90 degrees) position References: Røntgenafdelingen, Bispebjerg Hospital - København NV/DK Five region of interest (ROI s) was drawn within the phantom and four in the background, using a DICOM compatible software (Osirix, viewer software version 4.1.1, (Fig. 2). Page 5 of 14

6 Fig. 2: Five region of interest (ROI s) was drawn within the phantom and four in the background. References: Røntgenafdelingen, Bispebjerg Hospital - København NV/DK The mean signal and the standard deviation of the noise was extracted from the ROI's, and SNR for both scanner positions was calculated using the following equation[4]: Mean Signal SNR = 0.66 * Average of noise region standard deviation Statistical significant difference, between the two obtained average SNR's were compared, using a paired T-test with a 95 % confidence level[5]. Materials: Water phantom, filled with an aqueous solution of 5 mm NiCl2 and 55 mm of NaCl, 0.25 Tesla G-Scan (Esaote, Genova, Italy) hardware release 3, lumbar coil, Osirix-Viewer software version 4.1.1, TSE T2 sequence (TR: 3280, TE:125 Slice thickness 4mm, gab 0.4mm) Page 6 of 14

7 Images for this section: Table 1: Scan parameters with the scanner in horizontal (0 degrees) and vertical (90 degrees) position Røntgenafdelingen, Bispebjerg Hospital - København NV/DK Fig. 2: Five region of interest (ROI s) was drawn within the phantom and four in the background. Røntgenafdelingen, Bispebjerg Hospital - København NV/DK Page 7 of 14

8 Results The average SNR in horizontal position was 97,8 (table 2), and the average SNR in vertical position was 56,4 (table 3) with a statistical significant difference in SNR (p<0,05) corresponding to a 42,3% reduction in SNR, when scanning in the verticall position(fig.3.). Table 2: SNR when scanning in horizontal position. References: Røntgenafdelingen, Bispebjerg Hospital - København NV/DK Table 3: SNR when scanning in vertical position References: Røntgenafdelingen, Bispebjerg Hospital - København NV/DK Page 8 of 14

9 Fig. 3: Signal to noise ratio with the scanner in horizontal (0 degrees) and vertical (90 degrees) position References: Røntgenafdelingen, Bispebjerg Hospital - København NV/DK Page 9 of 14

10 Images for this section: Table 2: SNR when scanning in horizontal position. Røntgenafdelingen, Bispebjerg Hospital - København NV/DK Table 3: SNR when scanning in vertical position Røntgenafdelingen, Bispebjerg Hospital - København NV/DK Page 10 of 14

11 Fig. 3: Signal to noise ratio with the scanner in horizontal (0 degrees) and vertical (90 degrees) position Røntgenafdelingen, Bispebjerg Hospital - København NV/DK Page 11 of 14

12 Conclusion In conclusion we found a statistical significant difference in SNR when comparing the horizontal and vertical scanner positions. This should be taken into consideration, when designing scanning protocols for both clinical workflow and research projects. SNR is the most important image quality factor[6], if the SNR is too low, the details of the structure may be obscured by image noise[4]. Thus our findings support the use of the supine position to describe the tissue properties where a high SNR is warranted, and the weightbaring position to the describe the delta changes of the anatomical bony and softtissue structures[1][7] Page 12 of 14

13 Personal information The study was made equally by Frederik Hvid Mortesen and Jonas Sterup Bovin During parts of the study Frederik Hvid Mortensen and Jonas Sterup Bovin, was students at: Metropolitan University College, and we would like to thank the staff at Metropolitan University College for the help during the study. We would also like to thank the staff of the department of radiology Bispabjerg and Frederiksberg hospitals for helping to obtain the images and the OAK foundation for donating the scanner Page 13 of 14

14 References 1. Mauch, Frieder, et al Changes in the Lumbar Spine of Athletes From Supine to the True-Standing Position in Magnetic Resonace Imaging. Spine. vol. 35, no Jinkins, J.R., et al Upright, Weight-Bearing Dynamic-Kinetic MRI of the spine: initial results. European Radiology, 15: pid=713&keepthis=true&tb_iframe=true&height=500&width=800 (billede) 4. McRobbie, Donald W, et al MRI From picture to Proton. New York : Cambridge University Press, Blom-Hanssen, Jesper Statstik for praktikere. Gylling : Ingeniøren bøger, Westbrook, Catherine, Roth, Carolyn Kaut and Talbot, John MRI in Practice. Chichester : John Wiley & Sons Ltd., Hiasawa, Yoichiro, et al. 2007, Postural Changes of the Dural Sac in the Lumbar Spines of Asymptomatic Individuals Using Positional Stand-Up Magnetic Resonance Imaging. Spine vol. 32, no 4, E136-E140 Page 14 of 14