title: A novel diffusion-tensor MRI approach for skeletal muscle fascicle length measurements.
abstract: Musculoskeletal (dys-)function relies for a large part on muscle architecture which can be obtained using Diffusion-Tensor MRI (DT-MRI) and fiber tractography. However, reconstructed tracts often continue along the tendon or aponeurosis when using conventional methods, thus overestimating fascicle lengths. In this study, we propose a new method for semiautomatic segmentation of tendinous tissue using tract density (TD). We investigated the feasibility and repeatability of this method to quantify the mean fascicle length per muscle. Additionally, we examined whether the method facilitates measuring changes in fascicle length of lower leg muscles with different foot positions. Five healthy subjects underwent two DT-MRI scans of the right lower leg, with the foot in 15° dorsiflexion, neutral, and 30° plantarflexion positions. Repeatability of fascicle length measurements was assessed using Bland-Altman analysis. Changes in fascicle lengths between the foot positions were tested using a repeated multivariate analysis of variance (MANOVA). Bland-Altman analysis showed good agreement between repeated measurements. The coefficients of variation in neutral position were 8.3, 16.7, 11.2, and 10.4% for soleus (SOL), fibularis longus (FL), extensor digitorum longus (EDL), and tibialis anterior (TA), respectively. The plantarflexors (SOL and FL) showed significant increase in fascicle length from plantarflexion to dorsiflexion, whereas the dorsiflexors (EDL and TA) exhibited a significant decrease. The use of a tract density for semiautomatic segmentation of tendinous structures provides more accurate estimates of the mean fascicle length than traditional fiber tractography methods. The method shows moderate to good repeatability and allows for quantification of changes in fascicle lengths due to passive stretch.
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands j.oudeman@amc.uva.nl.
authors.forename: Jos
authors.initials: J
authors.lastname: Oudeman
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands.|Orthopedic Research Lab, Radboud UMC, Nijmegen, the Netherlands.|Biomedical NMR, Eindhoven University of Technology, Eindhoven, the Netherlands.
authors.forename: Valentina
authors.initials: V
authors.lastname: Mazzoli
authors.affiliation: Orthopedic Research Lab, Radboud UMC, Nijmegen, the Netherlands.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Marra
authors.affiliation: Biomedical NMR, Eindhoven University of Technology, Eindhoven, the Netherlands.
authors.forename: Klaas
authors.initials: K
authors.lastname: Nicolay
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Mario
authors.initials: M
authors.lastname: Maas
authors.affiliation: Orthopedic Research Lab, Radboud UMC, Nijmegen, the Netherlands.|Laboratory of Biomechanical Engineering, University of Twente, Enschede, the Netherlands.
authors.forename: Nico
authors.initials: N
authors.lastname: Verdonschot
authors.affiliation: Orthopedic Research Lab, Radboud UMC, Nijmegen, the Netherlands.|Laboratory of Biomechanical Engineering, University of Twente, Enschede, the Netherlands.
authors.forename: Andre M
authors.initials: AM
authors.lastname: Sprengers
authors.affiliation: Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Aart J
authors.initials: AJ
authors.lastname: Nederveen
authors.affiliation: Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Gustav J
authors.initials: GJ
authors.lastname: Strijkers
authors.affiliation: Department of Radiology, University Medical Center, Utrecht, the Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: Froeling
mesh_terms: D000328:Adult; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D035002:Lower Extremity; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D015203:Reproducibility of Results; D013710:Tendons / Q000033:anatomy & histology; D055815:Young Adult
keywords: 
  MRI
  ; DT‐MRI; fascicle length; fibertracking; segmentation; skeletal muscles