Beyond Time Is Brain: The Time, Tissue, and Systems Framework for Acute Stroke.

Acute ischaemic stroke care has long been guided by the maxim "time is brain," yet outcome variability suggests that clock time alone is insufficient. We propose the Time, Tissue, and Systems (TTS) framework, a quantitative model integrating temporal progression, tissue vulnerability, and health-system performance. Biological injury is conceptualized as accelerated neuronal loss scaled by tissue phenotype and systems friction, and clinical decision-making is reframed as net utility optimization. Illustrative modeling across four archetypal stroke profiles demonstrates how identical clock times yield divergent biological and functional trajectories. The TTS framework provides a coherent structure for precision stroke care, aligning biological time with system time.