Equine nuclear medicine: Current state of play.

Equine nuclear medicine uses advanced imaging techniques to assess bone health, blood flow, inflammation, and how substances move in horses, especially racehorses and performance horses. This review explores the history, current practices, and emerging technologies like SPECT and PET in this field.

Introduction to Equine Nuclear Medicine

• Equine nuclear medicine provides functional information on biological processes such as bone turnover, blood perfusion, inflammation, and tracer biodistribution in horses.
• It has evolved from simple planar scintigraphy to more advanced imaging methods like Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET), allowing better visualization and quantification.
• This review focuses particularly on the applications of nuclear medicine in performance and racehorses, where detecting subtle injuries and monitoring bone health is critical.

Research Methodology

• The authors conducted a systematic narrative review aligned with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.
• Databases searched included MEDLINE via PubMed, Web of Science Core Collection, and SciQuest, complemented by manual reference checking and citation tracking.
• Inclusion criteria encompassed studies addressing nuclear medicine imaging in horses including technical methods, radiopharmaceutical use, diagnostic and therapeutic applications, dosimetry, radiation safety, and workflow considerations.
• Due to heterogeneity in study populations, imaging modalities, and outcomes, a meta-analysis was not feasible. Instead, a descriptive mapping and narrative synthesis were performed.

Historical Foundations of Equine Nuclear Medicine

• Out of 181 records analyzed, 138 constituted historical and foundational literature.
• These studies predominantly focused on planar scintigraphy for musculoskeletal issues, such as:
  • Detecting changes in bone turnover indicative of injury or stress remodeling.
  • Localizing sources of occult or complex lameness.
  • Assessing stress-related bone injuries in performance and racehorses.
• Key principles emerged including:
  • Importance of correlating imaging findings with clinical signs.
  • Recognition of normal scintigraphic patterns to avoid false positives.
  • Technical standardization to improve reproducibility and reliability.
• Non-skeletal applications and technical factors related to imaging acquisition and interpretation were also covered.

Contemporary Advances and Applications

• Contemporary literature (43 records) highlighted innovations such as:
  • Optimization of scintigraphy parameters to improve image quality and diagnostic accuracy.
  • Quantitative imaging methods to provide objective measurements rather than relying solely on qualitative assessment.
  • Use of Artificial Intelligence (AI) and radiomics to enhance image analysis and interpretation.
  • Integration of newer modalities such as standing SPECT and PET scans, enabling functional imaging of complex anatomical regions while minimizing sedation or anesthesia requirements.
• Specific advances include:
  • Standing SPECT advancement for imaging areas like pelvis, vertebral column, and head with greater detail.
  • Use of PET tracers like 18F-sodium fluoride (18F-NaF) and 18F-fluorodeoxyglucose (18F-FDG) for high-resolution imaging of distal limbs, particularly useful for monitoring lesions and injury progression.
  • Multimodality imaging approaches combining different techniques for comprehensive assessment.

Conclusions and Future Directions

• Equine nuclear medicine has evolved from a planar scintigraphy-based localization tool towards a sophisticated functional imaging discipline.
• Planar scintigraphy remains valuable for general screening of skeletal issues, especially for detecting increased bone turnover or stress injuries.
• SPECT is currently under-utilized but shows significant promise for detailed imaging of complex axial skeletal regions in standing horses, which can aid diagnosis without general anesthesia.
• PET represents the most advanced contemporary technology offering high-resolution, quantitative imaging of distal limbs, critical in performance-horse injury prevention and monitoring.
• Overall, these developments improve the ability to detect, localize, and quantify musculoskeletal and other pathologies, thereby enhancing clinical decision-making and management of equine athletes.