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Intracranial bleed monitor

A feasibility study to see if brain movement can be detected by ultrasound pulse Doppler is reported. The experimental setup includes a digital Doppler sampling system capable of processing 120 sample gates simultaneously (1 kHz PRF, 14 bit A/D, and 2 MHz carrier frequency with variable pulse length), and a special "headframe" (Marc 500) for holding an ultrasound probe stationary relative to the skull. Brain motions attributed to the cardiac and breathing cycle are clearly discernable with this device. Motions in which a systolic waveform are prominent span as much as 200 microns excursion distances or as little as 10-20 microns. Motions are reported with the contralateral skull as a fixed reference. These motions demonstrate the required sensitivity of an ultrasound device for detection of brain movement associated with very slow intracranial bleeding.