Comparisons of computed tomography, contrast enhanced computed tomography and standing low-field magnetic resonance imaging in horses with lameness localised to the foot. Part 1: anatomic visualisation scores.
Authors: Vallance S A, Bell R J W, Spriet M, Kass P H, Puchalski S M
Journal: Equine veterinary journal
Summary
# Editorial Summary When investigating foot lameness, equine clinicians must choose between computed tomography (CT), contrast-enhanced CT (CECT) and standing low-field MRI (LFMRI), yet limited evidence has compared how well each modality visualises different anatomical structures. Vallance and colleagues reviewed diagnostic images from 22 lame horses (31 limbs) to directly compare anatomical visualisation scores across all three imaging techniques, assessing 14 key structures within the foot using a four-point grading scale. CT and LFMRI performed similarly for visualising the navicular bone, middle phalanx and collateral ligaments, but LFMRI provided substantially superior visualisation of the distal deep digital flexor tendon, distal sesamoidean impar ligament and joint synovial structures—important findings given that soft-tissue pathology commonly underpins foot lameness; conversely, CT was superior for imaging the proximal and distal phalanges. Contrast enhancement paradoxically worsened visibility of the deep digital flexor tendon and collateral sesamoidean ligament whilst improving synovial visualisation, suggesting contrast protocols warrant careful consideration. These results have clear practical implications: selecting the right imaging modality should depend upon which anatomical structures are suspected to be diseased, with LFMRI favoured for soft-tissue assessment and CT for bone evaluation, rather than assuming one technique provides universal superiority in foot lameness investigation.
Read the full abstract on PubMed
Practical Takeaways
- •Choose LFMRI when soft tissue detail (tendon and ligament quality) is the priority; choose CT when bony detail of the phalanges is critical for diagnosis
- •CT and LFMRI are complementary rather than interchangeable—consider both modalities or select based on the suspected pathology location
- •Contrast enhancement on CT may obscure DDFT detail, so standard CT may be preferable when DDFT evaluation is the clinical question
Key Findings
- •CT and low-field MRI showed similar visibility for navicular bone, middle phalanx, and collateral ligaments, but LFMRI demonstrated superior visualization of distal DDFT and synovial structures
- •Proximal and distal phalanx had significantly lower visibility scores with LFMRI compared to CT
- •Contrast enhancement lowered DDFT visualization but improved distal interphalangeal synovium scores on CT
- •Visualization scores vary substantially by imaging modality and anatomic structure, requiring clinicians to understand each technique's strengths and limitations