Image Fusion of Computed Tomographic and Magnetic Resonance Images for the Development of a Three‐dimensional Musculoskeletal Model of the Equine Forelimb

Abstract

Biomechanical models that compute the lengths and forces of muscle-tendon units are broadly applicable to the study of factors that promote injury and the planning and effects of orthopedic surgical procedures in equine athletes. A three-dimensional (3D) generic musculoskeletal model of the equine forelimb comprised of bony segment, muscle-tendon, and ligament information, was developed based on high-resolution computed tomographic (CT) and T1-weighted magnetic resonance (MR) images from an isolated forelimb of a Thoroughbred racehorse. Image fusion was achieved through coregistration of CT and MR images with an image analysis program (Analyze) by adjustment of the relative position and orientation of fiducial markers visible in both modalities until the mutual information between the images was maximized. 3D surfaces of the bones and origin/insertion sites, centroid paths and volumes of the muscle-tendon and ligamentous structures were obtained from the multimodal (CT/MR) images using semiautomated and manual segmentation combined with sagittal and transverse color-cryosection anatomic images obtained from three other cadaveric equine forelimbs. Once bony and soft-tissue structures were reconstructed in the same coordinate system, data were imported to a software package for interactive musculoskeletal modeling (SIMM). The combination of integrated CT and MR acquisitions and anatomical images provided an accurate and efficient means of generating a 3D model of the musculoskeletal structures of an average-sized equine adult horse.

Musculoskeletal modelling of an ostrich (Struthio camelus) pelvic limb: influence of limb orientation on muscular capacity during locomotion

“…Our digitizing procedure, performed in 2002, was simplistic (similar to that of Burkholder & Nichols, 2004), whereas more recent techniques have fused CT and MRI imaging modalities to produce quite accurate and complex 3D musculoskeletal models (e.g., Zarucco et al, 2006; Harrison et al, 2014). Real muscles have complex 3D structure but we have simplified them into basic Hill model muscles of 2D structure.…”

“…The same software (SIMM) or other packages (GaitSym, Anybody, varieties of Adams, etc.) has been used to estimate limb muscle moment arms in other extant species including chimpanzees and other hominins (O’Neill et al, 2013; Holowka & O’Neill, 2013; and references therein), horses (Brown et al, 2003a; Brown et al, 2003b; Zarucco et al, 2006; Harrison et al, 2010), domestic cats (Burkholder & Nichols, 2004), rats (Johnson et al, 2008), emus (Goetz et al, 2008), Alligator and ostriches (Bates & Schachner, 2012), frogs (Kargo & Rome, 2002; Kargo, Nelson & Rome, 2002), cockroaches (Full & Ahn, 1995) and others, in addition to simpler past approaches (e.g., for small mammals, McClearn, 1985). It is not clear which software packages most accurately estimate muscle moment arms, but our comparisons with the data from Bates & Schachner (2012) suggest some advantages of our approach.…”

An Innovative Technique for Displaying Three Dimensional Radiographic Anatomy of Synovial Structures in the Equine Distal Limb

“…3D reconstructions of images produced by computed tomography (CT) and magnetic resonance imaging (MRI) have proven to be valuable tools in furthering our knowledge of internal structures both in the live animal and in cadaver specimens 7–10 . The advantages of these imaging techniques over conventional radiography include enhanced detail of soft tissue structures and greater bone surface information due to cross‐sectional images removing problems caused by superimposition 11,12 .…”

In search of clinical truths: equine and comparative studies of anatomy

“…Three-dimensional models based on CT and MR images have been used extensively; however discrete anatomical structures cannot be delineated (Qiu et al 2004). A combination of integrated CT and MR acquisitions from isolated equine forelimb (Martinelli et al 1997;Zarucco et al 2006), transferred to a computer for 3D dimensional reconstruction and analysis, provided an accurate and efficient means of generating a 3D model of musculoskeletal structures.…”