3.0 T 심장 MRI를 이용한 아데노신 스트레스 심근 매핑 및 자세 의존적 심장 혈류 분석 = 3.0 T cardiac MR myocardial mapping at adenosine stress and positional dependent cardiac flow assessment

다국어 초록 (Multilingual Abstract)

High-field cardiac magnetic resonance imaging (MRI) enables noninvasive assessment of myocardial tissue characteristics and blood flow in anesthetized small animals; however, adenosine stress mapping and recumbency-dependent flow at 3.0 T remain insufficiently characterized in dogs. This study evaluated stress–rest myocardial mapping and the effects of body position and airway pressure on cardiac index–based flow metrics.
Seven asymptomatic dogs not receiving cardiac medications underwent 3.0 T cardiac MRI under general anesthesia. All seven completed two myocardial mapping sessions (adenosine stress and rest) separated by ≥48 h. During stress, adenosine was infused at 140 μg/kg/min. T1 native, T1 post-contrast , T2, and extracellular volume (ECV) were acquired at basal, mid, and apical short-axis levels. Flow analysis was performed in a separate MRI session in six dogs using 2D phase-contrast imaging at the aortic (AV) and pulmonic valves (PV) in dorsal, right-lateral, and left-lateral recumbency under zero end-expiratory pressure (ZEEP), plus in dorsal recumbency during continuous positive airway pressure (CPAP) of 10 cmH₂O. Mapping and flow indices were analyzed using repeated-measures nonparametric tests (Friedman and Wilcoxon signed-rank; p < 0.05).
Compared with rest, adenosine stress increased global T1 native and T2 by 6.73% and 10.16%, respectively, whereas global T1 post-contrast and ECV did not change significantly. Level-wise, basal T1 native and ECV during stress were higher than mid and apical values, whereas basal T2 at rest was lower than mid and apical levels. Under ZEEP, left- and right-ventricular cardiac indices (LV CI, RV CI) varied with recumbency; mean RV CI in lateral positions was approximately 14–15% higher than in dorsal recumbency, with LV CI showing a similar but smaller effect. RV/LV CI ratios remained relatively stable across positions. In dorsal recumbency, CPAP at 10 cmH₂O reduced LV CI and RV CI by approximately 7–10% relative to ZEEP, without consistent changes in RV/LV CI. MRI-derived AV peak velocities were generally higher, and PV peak velocities lower, than those obtained by Doppler echocardiography, indicating valve- and modality-specific differences in peak-velocity measurements.
At 3.0 T, quantitative cardiac MRI enabled integrated assessment of adenosine stress–rest myocardial mapping and of position- and airway pressure–dependent flow in dogs. Adenosine stress produced measurable increases in T1 and T2, indicating that stress-induced myocardial responses can be quantified without contrast. In addition, level-dependent heterogeneity in mapping indices (T1 native, T2, and ECV) underscores the importance of myocardial sampling level when interpreting stress–rest maps. Phase-contrast flow imaging showed that recumbency and airway pressure modestly but consistently influenced LV CI and RV CI, whereas AV and PV peak velocities differed systematically between MRI and echocardiography. Collectively , these findings provide an integrated tissue–flow framework for high-field veterinary cardiac MRI, clarifying how adenosine stress, recumbency, and airway pressure influence quantitative myocardial and flow metrics and supporting their future clinical application in dogs.

목차 (Table of Contents)

• General Introduction 1
• General Materials and Methods 11
• Part 1 15
• 1. Materials and Methods 15
• 2. Results 28
• 3. Discussion 41
• Part 2 53
• 1. Materials and Methods 53
• 2. Results 61
• 3. Discussion 75
• General Conclusion 88
• References 90
• Appendix 104
• Abstract (In Korean) 116