Effects of 1-MHz Ultrasound on Epaxial Muscle Temperature in Horses.
Authors: Adair Henry S, Levine David
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: Effects of 1-MHz Ultrasound on Epaxial Muscle Temperature in Horses Therapeutic ultrasound is increasingly used in equine practice to promote tissue healing and reduce muscle tension, yet evidence supporting its thermal effects at clinically relevant tissue depths remains limited. Henry and Levine investigated temperature changes in the epaxial muscles of ten healthy mares during 1.0-MHz ultrasound treatments at two intensities (1.0 and 2.0 W/cm²), with needle thermistors placed at 1, 3, and 5 cm depths to capture a realistic picture of heat penetration during routine treatment. Over the 10-minute treatment period, the higher intensity (2.0 W/cm²) produced substantially greater temperature rises at superficial (2.48°C at 1 cm) and deeper layers (1.95°C at 5 cm), whilst paradoxically showing minimal heating at the intermediate 3 cm depth (1.24°C)—a finding suggesting preferential absorption patterns that warrant further investigation. For practitioners, these results indicate that ultrasound intensity selection significantly influences therapeutic heating, with lower intensities producing more modest but still meaningful temperature increases, and that heating effects are not simply a function of increasing depth. Understanding these tissue-specific thermal profiles enables more informed decision-making about treatment parameters when addressing different epaxial pathologies, though additional research examining the relationship between these temperature changes and functional clinical outcomes would strengthen the evidence base for routine application.
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Practical Takeaways
- •1-MHz ultrasound at 2.0 W/cm² produces significantly greater tissue heating than 1.0 W/cm², so intensity selection should match clinical goals for depth of treatment effect
- •Clipped epaxial muscles show greatest heating at superficial depths; consider depth of target pathology when selecting treatment parameters
- •The non-linear heat distribution with depth (higher at 5 cm than 3 cm) suggests complex tissue interactions that warrant caution when treating deep structures
Key Findings
- •At 1.0 W/cm² intensity, temperature increases were 1.55°C at 1 cm depth, 1.18°C at 3 cm, and 1.29°C at 5 cm after 10 minutes of treatment
- •At 2.0 W/cm² intensity, temperature increases were 2.48°C at 1 cm depth, 1.24°C at 3 cm, and 1.95°C at 5 cm after 10 minutes
- •Greatest heating effect occurred at the shallowest depth (1.0 cm) with higher ultrasound intensity
- •Heating at 5 cm depth exceeded that at 3 cm depth, suggesting non-uniform heat distribution with depth