Summary
A study of skull thickness and resistivity variations over the upper surface was made for an adult human skull. Physical measurements of thickness and qualitative analysis of photographs and CT scans of the skull were performed to determine internal and external features of the skull. Resistivity measurements were made using the four-electrode method and ranged from 1360 to 21400 Ohm-cm with an overall mean of 7560±4130 Ohm-cm. The presence of sutures was found to decrease resistivity substantially. The absence of cancellous bone was found to increase resistivity, particularly for samples from the temporal bone. An inverse relationship between skull thickness and resistivity was determined for trilayer bone (n=12, p<0.001). The results suggest that the skull cannot be considered a uniform layer and that local resistivity variations should be incorporated into realistic geometric and resistive head models to improve resolution in EEC Influences of these variations on head models, methods for determining these variations, and incorporation into realistic head models, are discussed.
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The author would like to acknowledge James V. Sullivan and Paul Fitze of the Precision Instrument Unit of the Biomedical Engineering and Instrumentation Program, National Institutes of Health for their expert drilling of the skull, preparation of the samples, and fabrication of the four-electrode test assembly. The author would like to thank Drs. Michael J. Eckardt and Dan Hommer of the Lab. of Clinical Studies, NIAAA, for their review and comments of the manuscript, and Dr. Stephen Nawrocki, Deptartment of Biology, University of Indianapolis, for sharing his expertise in the study of the human cranium. Preliminary experiments were performed under Dr. Paul Nunez, Department of Biomedical Engineering, Tulane University, New Orleans, LA, supported by NIH grant R01-NS243314.
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Law, S.K. Thickness and resistivity variations over the upper surface of the human skull. Brain Topogr 6, 99–109 (1993). https://doi.org/10.1007/BF01191074
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DOI: https://doi.org/10.1007/BF01191074