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Rigid and non-rigid geometrical transformations of a marker-cluster and their impact on bone-pose estimation
T Bonci1, V Camomilla2, R Dumas3
1Department of Movement, Human and Health Sciences, Università degli Studi di Roma ''Foro Italico'', Rome, Italy; Université de Lyon, F-69622 Lyon, France; Université Claude Bernard Lyon 1, Villeurbanne, France; IFSTTAR, UMR_T9406, Laboratoire de Biomécanique et Mécanique des Chocs (LBMC), F-69675 Bron, France; Interuniversity Centre of Bioengineering of the Human Neuromusculoskeletal System, Università degli Studi di Roma "Foro Italico", Rome, Italy.
Soft tissue artefact (STA) in stereophotogrammetry is mainly caused by rigid transformations (RT), not non-rigid transformations (NRT). Understanding this distinction is crucial for improving bone-pose estimation accuracy in biomechanics research.
Area of Science:
- Biomechanics
- Motion analysis
- Medical imaging
Background:
- Stereophotogrammetry with skin markers is vital for bone-pose estimation.
- Soft tissue artefact (STA) can compromise the accuracy of bone-pose estimation.
- STA comprises rigid (RT) and non-rigid (NRT) geometrical transformations.
Purpose of the Study:
- To investigate the impact of both RT and NRT components of STA on bone-pose estimation.
- To compare the propagation of STA components using varying numbers of skin markers.
- To determine which STA component significantly affects pose estimation accuracy.
Main Methods:
- Simulated STA time functions for 12 thigh skin markers using a validated model.
- Generated marker-clusters (4-12 markers) affected by simulated STA.
- Employed Procrustes superimposition to estimate bone-pose and accuracy.
- Assessed pose error with varying NRT energy levels (30-90% of total STA energy).
Main Results:
- Pose error decreased slightly with an increased number of markers in a cluster.
- Pose error was independent of the NRT amplitude.
- Pose error was null when the RT component of STA was removed.
- The RT component was identified as the sole significant contributor to pose estimation inaccuracy.
Conclusions:
- Only the rigid transformation (RT) component of soft tissue artefact (STA) impacts bone-pose estimation accuracy.
- Algorithms designed for STA compensation should prioritize accounting for the RT component.
- Future research should focus on mitigating the effects of RT in motion analysis.
