A wearable fiber-optoacoustic interface for continuous deep-tissue hemodynamics in MRI environments

Continuous monitoring of arterial waveforms is critical for assessing cardiovascular status in intensive care and intraoperative settings. However, conventional modalities relying on electronics or metallic transducers are strictly incompatible with the strong electromagnetic perturbations in clinical settings, especially magnetic resonance imaging (MRI) suites, creating a blind spot in patient monitoring. Here, we present a fully metal-free, all-fiber optoacoustic system (FOAS) that bridges this gap by integrating focused optical ultrasound generation with ultrasensitive fiber-laser detection in a compact wearable platform. This architecture enables beat-to-beat reconstruction of blood pressure waveforms with high fidelity, preserving morphological features essential for vascular compliance analysis. In-vivo validations, including physiological perturbations (exercise, caffeine) and measurements across 10 healthy volunteers, demonstrated the system's robustness in tracking hemodynamic dynamics and resolving inter-subject waveform variability (e.g., systolic-to-dicrotic notch interval). Crucially, the artifact-free operation was demonstrated inside an active 3 T MRI scanner, confirming superior electromagnetic immunity. This work establishes fiber optoacoustics as a transformative platform for ambulatory hemodynamic monitoring, extending precise cardiovascular profiling into electromagnetically constrained clinical environments.