High Inter-Rater Reliability of Manual Segmentation and Volume-Based Tractography in Healthy and Dystrophic Human Calf Muscle

Abstract

Background: Muscle diffusion tensor imaging (mDTI) is a promising surrogate biomarker in the evaluation of muscular injuries and neuromuscular diseases. Since mDTI metrics are known to vary between different muscles, separation of different muscles is essential to achieve muscle-specific diffusion parameters. The commonly used technique to assess DTI metrics is parameter maps based on manual segmentation (MSB). Other techniques comprise tract-based approaches, which can be performed in a previously defined volume. This so-called volume-based tractography (VBT) may offer a more robust assessment of diffusion metrics and additional information about muscle architecture through tract properties. The purpose of this study was to assess DTI metrics of human calf muscles calculated with two segmentation techniques—MSB and VBT—regarding their inter-rater reliability in healthy and dystrophic calf muscles. Methods: 20 healthy controls and 18 individuals with different neuromuscular diseases underwent an MRI examination in a 3T scanner using a 16-channel Torso XL coil. DTI metrics were assessed in seven calf muscles using MSB and VBT. Coefficients of variation (CV) were calculated for both techniques. MSB and VBT were performed by two independent raters to assess inter-rater reliability by ICC analysis and Bland-Altman plots. Next to analysis of DTI metrics, the same assessments were also performed for tract properties extracted with VBT. Results: For both techniques, low CV were found for healthy controls (≤13%) and neuromuscular diseases (≤17%). Significant differences between methods were found for all diffusion metrics except for λ1. High inter-rater reliability was found for both MSB and VBT (ICC ≥ 0.972). Assessment of tract properties revealed high inter-rater reliability (ICC ≥ 0.974). Conclusions: Both segmentation techniques can be used in the evaluation of DTI metrics in healthy controls and different NMD with low rater dependency and high precision but differ significantly from each other. Our findings underline that the same segmentation protocol must be used to ensure comparability of mDTI data.

Robustness and stability of volume‐based tractography in a multicenter setting

“…Based on the findings and limitations of this study, we recommend using the same imaging and processing protocol. Tractography algorithm and fiber‐tracking stop criteria must be the same, while the influence of different raters appears to be negligible 17,42 . Furthermore, different leg positioning in centers can influence tractography results and those effects should be minimized by using the same positioning devices (i.e., cushions).…”

“…Tractography algorithm and fiber-tracking stop criteria must be the same, while the influence of different raters appears to be negligible. 17,42 Furthermore, different leg positioning in centers can influence tractography results and those effects should be minimized by using the same positioning devices (i.e., cushions). To analyze muscle-specific tract properties and directly correlate these parameters to anatomical findings, whole muscle volume should be measured.…”

Application of diffusion microstructure imaging in musculoskeletal radiology — translation from head to shoulders

“…Due to the highly organized macro-and microstructure, a directional diffusivity similar to that of neuronal axons is found in muscle [5]. As the sizes of myofibrils (1-2 μm) and neuronal axons (0.01 to 10 μm) are in a similar range [6,7], diffusion-based MRI (dMRI) techniques such as diffusion tensor imaging (DTI) may provide additional information on structural and microstructural alterations of skeletal muscle before they become visible on morphologic MRI [8][9][10]. DTI metrics provide insight into the microstructure as they reveal subvoxel information in a mesoscopic approach [11,12].…”