Reference intervals for myocardial T1, T2, and extracellular volume in clinically normal dogs and cats at 3-Tesla magnetic resonance imaging: a single-center study.

Species-specific 3-T cardiac MRI reference intervals now enable objective myocardial tissue characterization in clinical dogs and cats.

This single-center prospective study establishes species-specific reference intervals for myocardial tissue characterization parameters—native T1, native T2, and extracellular volume fraction (ECV)—in clinically normal dogs (n=54) and cats (n=60) using 3-Tesla cardiac MRI (CMRI). All examinations were performed under general anesthesia with ECG gating between 2015 and 2024. Parametric methods were used to derive 95% prediction intervals with 90% confidence intervals around reference limits. In dogs, reference intervals were: native T1 1,057–1,152 ms, native T2 42.0–60.9 ms, and ECV 19.3%–25.7%. In cats, corresponding values were: native T1 1,066–1,172 ms, native T2 34.2–61.6 ms, and ECV 21.8%–30.3%. ECV was calculated using pre- and post-contrast T1 measurements combined with hematocrit values. Notably, age was not a significant predictor of myocardial ECV in either species. The study adapted validated mapping sequences from human CMRI protocols and provides detailed methodology to facilitate reproducibility in both clinical and research settings. These reference intervals are clinically significant because T1 mapping, T2 mapping, and ECV quantification are sensitive markers of myocardial pathology—including fibrosis, edema, and infiltrative disease—that are increasingly important in veterinary cardiology. Establishing normal values enables objective identification of myocardial abnormalities in dogs and cats, supporting early diagnosis and monitoring of conditions such as hypertrophic cardiomyopathy and dilated cardiomyopathy.

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