Comparison of MR sequences for in vivo olfactory bulb volumetry: reproducibility and repeatability of volumetric measurements using 3 Tesla MRI

Transcription

1 Comparison of MR sequences for in vivo olfactory bulb volumetry: reproducibility and repeatability of volumetric measurements using 3 Tesla MRI Poster No.: C-0504 Congress: ECR 2012 Type: Scientific Paper Authors: H. P. Burmeister, P. A. T. Baltzer, C. Moeslein, T. Bitter, H. Gudziol, M. Dietzel, O. Guntinas-Lichius, W. A. Kaiser; Jena/DE Keywords: DOI: Anatomy, Ear / Nose / Throat, Neuroradiology brain, MR, Image manipulation / Reconstruction, Imaging sequences, Observer performance, Statistics, Trauma, Infection, Pathology /ecr2012/C-0504 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 6

2 Purpose A systematic radiologic comparison of MR sequences for in vivo olfactory bulb volumetry (OBV) has not been performed yet. The aim of this study was to compare different sequences for OBV using 3T-MRI evaluating reproducibility, repeatability, and systematic biases. Methods and Materials Twenty-two volunteers underwent 3T-MRI of the frontal skull base in this prospective study. Imaging included constructive interference in steady state (CISS), 3D-SPACE-T2, and 2D-TSE-T2 weighted sequences (Fig. 1). Two observers independently performed 2 OBVs per bulb and sequence. Intra- and inter-observer reliability was assessed by intraclass correlation coefficients (ICC). For evaluation of reproducibility, concordance correlation coefficients (CCC), and for repeatability and systematic biases, Bland-Altman plots were analyzed. Figure 1: Comparison of sequences applied at 3 Tesla for olfactory bulb volumetry (Upper line, a-c) constructive interference in steady state (CISS), (middle line, d-f) 3D-T2 weighted, and (lower line, g-i) 2D-T2 weighted sequence in axial (left column, a+d+g), sagittal (middle column, b+e+h), and coronal planes (right column, c+f+i). All images are from the same volunteer. Areas of left olfactory bulb where volumetry was performed (white hatched areas), image 1a demonstrates an OB during segmentation - the contours are lined using the segmentation tool with a diameter of 1mm just before defining the transitorial zone between the olfactory bulb and tract (blue short arrowhead), left olfactory tract and its transition to the olfactory bulb (green short arrowheads), proper olfactory artery (yellow long arrowheads), accessory vessel at the left antero-lateral pole of the olfactory bulb (red arrows), bilateral artificial gaps in the horizontal lamella of the cribriform plate (orange star) due to the overestimation of cerebrospinal fluid, stair step artifacts (purple lightning symbol + arrows), missing structures (additional question marks). S = superior, I = inferior, A = anterior, P = posterior, R = right, L = left. Images for this section: Page 2 of 6

3 Fig. 1: Comparison of sequences applied at 3 Tesla for olfactory bulb volumetry Page 3 of 6

4 Results ICC-analysis of the specialized observer yielded almost perfect results for intra-observer reliability (CISS=0.94; 3D-T2w=0.85; 2D-T2w=0.93). For the less experienced observer the results were 0.86 (CISS), 0.78 (3D-T2w), and 0.74 (2D-T2w). Inter-observer reliability showed almost perfect agreements for all sequences (0.92, 0.86, and 0.86). The CISS yielded highest values for CCC (0.84), precision (0.85), and accuracy (0.99) (Fig. 2). Bland-Altman plot analyses revealed the lowest repeatability coefficient for 2D-T2w (Fig.3+4). Systematic biases of the 2D-T2w and 3D-T2w compared to CISS were -22.7% and -8.3%, respectively (Fig. 3+4). Figure 2: Systematic bias of compared sequences for olfactory bulb volumetry. Bland-Altman plots of difference of volumetric measurement results (y-axis) against average volumetric measurement results (x-axis), with mean absolute difference (i.e., bias) (continuous line) and 95% limits of agreement (dashed lines) for (A) the comparison of the 2D-T2w and CISS sequence (B) the comparison of the 2D-T2w and 3D-T2w sequence (C) the comparison of the 3D-T2w and CISS sequence. Dash-dotted lines are related with significant regressions in (A) (slope=-0.428, P<0.001) and (B) (slope=-0.309, P=0.005). The regression in (C) is not significant (slope=-0.131, P=0.171). All values are given as absolute values in mm3. Images for this section: Page 4 of 6

5 Fig. 2: CCCs, Interobserver Reliability, and Reproducibility Fig. 3: Systematic bias of compared sequences for olfactory bulb volumetry Fig. 4: Repeatability and Test-retest Reliability Page 5 of 6

6 Conclusion Due to best values for intra- and inter-observer reliability, reproducibility, accuracy, and precision, the CISS sequence is recommended for in vivo OBV purposes. As even less experienced observers achieve almost perfect results, standardized application of the CISS facilitates the assessment of olfactory and neurologic disorders affecting the OB volume and ensures comparability between volumetric studies. References Already published by: Academic Radiology For further references please refer to the following article: Burmeister HP, Baltzer PAT, Moslein C, et al. Reproducibility and repeatability of volumetric measurements for olfactory bulb volumetry: which method is appropriate? An update using 3 tesla MRI. Acad Radiol. 2011;18(7): Personal Information *Corresponding author: Dr. Hartmut Peter Burmeister, Institute of Diagnostic and Interventional Radiology, University Hospital - Friedrich Schiller University Jena, Philosophenweg 3, D Jena, Germany (phone: , doctorbob@hotmail.de). Page 6 of 6