Extended Data Fig. 6: Doppler spectra acquired from all transcranial windows by using different mechanical indices and thermal indices.

As the mechanical index and thermal index decrease, the signal quality correspondingly declines. The optimal mechanical indices and thermal indices were chosen to be as low as reasonably achievable during blood flow monitoring, balancing safety and signal quality. For the temporal and suboccipital windows, the optimal mechanical index and thermal index were around 0.3; for the orbital window, we selected mechanical index around 0.13 and thermal index around 0.08; and for the submandibular window, the ideal mechanical index and thermal index were approximately 0.2 and 0.11, respectively. Importantly, these thresholds could be subject to individual variations due to physiological and anatomical differences. The spectra share the same scale bars. MI, mechanical index. TIC, cranium thermal index. TIS, soft tissue thermal index.