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Evaluation of Microvascular Flow Imaging and Power Doppler Ultrasonography in an Equine Model of Induced Superficial Digital Flexor Tendonitis.
Abstract: Superficial digital flexor tendon (SDFT) injuries are common in athletic horses and are associated with prolonged healing and high reinjury rates. Conventional ultrasonography provides structural information but limited physiologic assessment. This study compared microvascular imaging (MVI) and Power Doppler (PD) for evaluating vascular changes in a collagenase-induced equine SDFT injury model and assessed the effect of scanning technique on vascular signal detection. Eight adult Thoroughbred horses underwent bilateral collagenase-induced SDFT injury, with one forelimb randomly assigned to intralesional autologous protein solution treatment and the contralateral limb receiving intralesional saline. Ultrasonographic examinations were performed at baseline and Weeks 0, 2, 4, 8, and 12 post-injury. Longitudinal and transverse MVI and PD images were evaluated using semiquantitative vascularity scores and quantitative vascularity ratios. Mixed-effects Poisson regression accounted for repeated measures and assessed effects of imaging modality, time, scanning plane, weight-bearing (WB) stance, stand-off use, and observer experience. MVI detected higher vascularity than PD at all post-injury time points (2.04 [95% confidence intervals-CI: 1.73-2.34] vs. 0.87 [0.64-1.10]) with peak vascularity at Week 2 followed by gradual decline during healing. Quantitative vascularity ratios mirrored semiquantitative findings. Longitudinal imaging yielded greater vascular detection than transverse imaging for both techniques (1.97 [95% CI: 1.72-2.22] vs. 0.92 [0.69-1.15]), whereas WB status and stand-off pad use had no statistical significant effect. Observer experience influenced vascularity scores but not temporal trends. These findings demonstrate MVI detects more intratendinous vascularity than PD during SDFT injury and healing, and support its use as a complementary tool for monitoring equine tendinopathy.
© 2026 The Author(s). Veterinary Radiology & Ultrasound published by Wiley Periodicals LLC on behalf of American College of Veterinary Radiology.
Publication Date: 2026-07-29 PubMed ID: 42522440DOI: 10.1111/vru.70226Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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Overview
- This study evaluates two ultrasound imaging techniques—Microvascular Flow Imaging (MVI) and Power Doppler (PD)—to detect blood flow changes during tendon injury and healing in horses, specifically in the superficial digital flexor tendon (SDFT).
- The research compares the effectiveness of these imaging methods in an experimentally induced tendon injury model and examines the influence of scanning techniques and other factors on vascular signal detection.
Background and Importance
- The superficial digital flexor tendon (SDFT) is frequently injured in athletic horses, leading to long healing times and a high risk of re-injury.
- Traditional ultrasonography provides detailed structural images of the tendon but offers limited information on physiological changes like blood flow and vascularity during injury and healing.
- Evaluating blood flow within injured tendons is important because vascular changes can indicate inflammatory activity and tissue repair processes.
Goals of the Study
- To compare two ultrasound techniques—Microvascular Flow Imaging (MVI) and Power Doppler (PD)—for their ability to detect changes in blood flow within an injured equine SDFT.
- To assess how different scanning approaches (longitudinal vs. transverse views) and factors such as standing position, use of a stand-off pad, and observer experience influence the detection of vascular signals.
- To monitor vascular changes across multiple time points during the injury and healing process over 12 weeks.
Methodology
- Subjects: Eight adult Thoroughbred horses underwent bilateral collagenase-induced injury in their SDFTs, mimicking tendonitis.
- Treatments: One forelimb of each horse received an intralesional autologous protein solution intended as treatment; the contralateral forelimb received saline as a control.
- Imaging Schedule: Ultrasound examinations using both MVI and PD were conducted at baseline (pre-injury) and at Weeks 0, 2, 4, 8, and 12 post-injury.
- Imaging Planes: Both longitudinal (along the length of the tendon) and transverse (cross-sectional) views were obtained for each technique.
- Measurements:
- Semiquantitative vascularity scores: A scoring system to grade the amount of blood flow signal visible.
- Quantitative vascularity ratios: Numerical metrics quantifying the ratio of vascularized area to total area in images.
- Statistical Analysis: Mixed-effects Poisson regression was used to handle repeated measures within the same horses, assessing effects of imaging modality, timing, scanning plane, whether horse was weight-bearing, use of stand-off pad, and observer experience.
Key Findings
- MVI detects significantly more vascularity than PD: Across all post-injury time points, MVI showed approximately double the vascularity signal compared to PD (mean vascularity score 2.04 vs. 0.87).
- Temporal pattern of vascularity: Both qualitative and quantitative measures showed vascularity peaking at Week 2 after injury, followed by a gradual decline as healing progressed through Week 12.
- Effect of scanning plane: Longitudinal imaging consistently yielded higher vascular detection than transverse imaging for both MVI and PD, likely due to better visualizing the lengthwise blood vessels.
- Effect of weight-bearing and stand-off pad: Neither the horse’s stance (weight-bearing vs. not) nor the use of a stand-off pad (device placed between the ultrasound probe and skin to improve imaging) had a statistically significant effect on vascular detection.
- Observer experience: More experienced observers assigned higher vascularity scores overall, indicating some subjectivity, but this did not change the overall trend of vascular changes over time.
Implications and Conclusions
- MVI is a more sensitive ultrasound technique than PD for detecting blood flow within injured equine tendons, offering better visualization of microvascular changes during injury and repair.
- The ability to detect subtle vascular changes at multiple time points provides valuable physiological information that complements structural imaging, potentially aiding in injury assessment, monitoring healing progress, and evaluating treatment effects.
- The preference for longitudinal imaging planes suggests best practices for tendon vascular imaging protocols to maximize sensitivity.
- The study supports the use of MVI as a complementary diagnostic tool for equine tendinopathy and could translate to enhanced clinical management of tendon injuries in horses.
Limitations and Future Directions
- The study was conducted on an experimentally induced tendon injury model, which might not fully replicate naturally occurring injuries.
- The sample size was relatively small (eight horses), so larger studies may be needed to confirm findings.
- Variability due to observer experience suggests further standardization or training may improve consistency in vascularity scoring.
- Future research could evaluate how MVI-guided monitoring influences treatment decisions and clinical outcomes in equine athletes.
Cite This Article
APA
Garcia-Collao MR, Ortved K, Stefanovski D, Christensen JL, Underwood C.
(2026).
Evaluation of Microvascular Flow Imaging and Power Doppler Ultrasonography in an Equine Model of Induced Superficial Digital Flexor Tendonitis.
Vet Radiol Ultrasound, 67(5), e70226.
https://doi.org/10.1111/vru.70226 Publication
Researcher Affiliations
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
- Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
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