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Non-Invasive Measurement of Pulsatile Intracranial Pressures Using UltrasoundEarly detection of elevated intracranial pressure (ICP) will aid clinical decision-making for head trauma, brain tumor and other cerebrovascular diseases. Conventional methods, however, require surgical procedures which take time and are accompanied by increased risk of infection. Accordingly we have developed and refined a new ultrasound device to measure skull movements which are known to occur in conjunction with altered ICP. The principle of this device is based upon pulse phase locked loop (PPLL), which enables us to detect changes in distance on the order of microns between an ultrasound transducer on one side of the skull and the opposite inner surface of the cranium. The present study was designed to verify this measurement technique in cadavera. Transcranial distance was increased in steps of 10 mmHg from zero to 50 mmHg by saline infusion into the lateral ventricle of two cadavera. In separate experiments, pulsations of ICP with the amplitudes of zero to 2 mmHg were generated by rhythmic injections of saline using a syringe. When the ICP was stepwise increased from zero to 50 mmHg, transcranial distance increased in proportion with the ICP increase (y=12 x - 76, r=0.938), where y is changes in transcranial distance in microns and x is ICP in mmHg. In the data recorded while ICP pulsations were generated, fast Fourier transform analysis demonstrated that cranial pulsations were clearly associated with ICP pulsations. The results indicate that changes in transcranial distance is linearly correlated with those in ICP, and also that the PPLL device has sufficient sensitivity to detect transcranial pulsations which occur in association with the cardiac cycle. By analyzing the magnitude of cranial pulsations, we may be able to estimate the pressure-volume index in the cranium. As a result, estimates of intracranial compliance may be possible by using the PPLL device. Further studies are necessary in normal subjects and patients.
Document ID
20020039801
Document Type
Conference Paper
Authors
Ueno, Toshiaki (NASA Ames Research Center Moffett Field, CA United States)
Ballard, Richard E. (NASA Ames Research Center Moffett Field, CA United States)
Shuer, Lawrence M. (Stanford Medical Center Stanford, CA United States)
Cantrell, John H. (NASA Langley Research Center Hampton, VA United States)
Cantrell, John H. (NASA Langley Research Center Hampton, VA United States)
Hargens, Alan R. (NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
August 20, 2013
Publication Date
January 1, 1997
Subject Category
Aerospace Medicine
Meeting Information
10th International Symposium of Intercranial Pressure and Neuromonitoring in Brain Injury(Williamsburg, VA)
Funding Number(s)
PROJECT: RTOP 199-26-12-38
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.