title: Manually defining regions of interest when quantifying paravertebral muscles fatty infiltration from axial magnetic resonance imaging: a proposed method for the lumbar spine with anatomical cross-reference.
abstract: There is increasing interest in paravertebral muscle composition as a potential prognostic and diagnostic element in lumbar spine health. As a consequence, it is becoming popular to use magnetic resonance imaging (MRI) to examine muscle volume and fatty infiltration in lumbar paravertebral muscles to assess both age-related change and their clinical relevance in low back pain (LBP). A variety of imaging methods exist for both measuring key variables (fat, muscle) and for defining regions of interest, making pooled comparisons between studies difficult and rendering post-production analysis of MRIs confusing. We therefore propose and define a method as an option for use as a standardized MRI procedure for measuring lumbar paravertebral muscle composition, and to stimulate discussion towards establishing consensus for the analysis of skeletal muscle composition amongst clinician researchers.
  
  
  
  In this descriptive methodological study we explain our method by providing an examination of regional lumbar morphology, followed by a detailed description of the proposed technique. Identification of paravertebral muscles and vertebral anatomy includes axial E12 sheet-plastinates from cadaveric material, combined with a series of axial MRIs that encompass sequencing commonly used for investigations of muscle quality (fat-water DIXON, T1-, and T2-weighted) to illustrate regional morphology; these images are shown for L1 and L4 levels to highlight differences in regional morphology. The method for defining regions of interest (ROI) for multifidus (MF), and erector spinae (ES) is then described.
  
  
  
  Our method for defining ROIs for lumbar paravertebral muscles on axial MRIs is outlined and discussed in relation to existing literature. The method provides a foundation for standardising the quantification of muscle quality that particularly centres on examining fatty infiltration and composition. We provide recommendations relating to imaging parameters that should additionally inform a priori decisions when planning studies examining lumbar muscle tissues with MRI.
  
  
  
  We intend this method to provide a platform towards developing and delivering meaningful comparisons between MRI data on lumbar paravertebral muscle quality.
authors.affiliation: Institute for Health Sciences, Zurich University of Applied Sciences, Technikumstrasse 81, Postfach, CH-8401, Winterthur, Switzerland. rebecca.crawford@zhaw.ch.|Faculty of Health Professions, Curtin University, Perth, Australia. rebecca.crawford@zhaw.ch.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Crawford
authors.affiliation: Institute for Health Sciences, Zurich University of Applied Sciences, Technikumstrasse 81, Postfach, CH-8401, Winterthur, Switzerland.|Graduate School of Nursing, Midwifery and Health, Victoria University of Wellington, Wellington, New Zealand.
authors.forename: Jon
authors.initials: J
authors.lastname: Cornwall
authors.affiliation: Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Abbott
authors.affiliation: Institute for Health Sciences, Zurich University of Applied Sciences, Technikumstrasse 81, Postfach, CH-8401, Winterthur, Switzerland.|Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, USA.|School of Health and Rehabilitation Sciences, University of Queensland, Brisbane, Australia.
authors.forename: James M
authors.initials: JM
authors.lastname: Elliott
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000473:pathology; D009929:Organ Size
keywords: Erector spinae; Fat infiltration; Lumbar spine; Magnetic resonance imaging; Manual segmentation; Multifidus; Paravertebral muscles; Region of interest