Method and apparatus for determining changes in intracranial pressure utilizing measurement of the circumferential expansion or contraction of a patient's skull

#1. Technical Field of the Invention

#The present invention relates broadly to the field of apparatuses and methods for determining changes in intracranial pressure (“ICP”) by measuring the effects of these changes on a patient's skull.

#2. Related Art and Problem to be Solved

#The features of the invention believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The invention itself, however, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:

#FIG. 1 is a block diagram of an apparatus of the present invention; and

#FIG. 2 is a schematic diagram of one embodiment of a measuring device that can be used in the apparatus of the present invention.

#In describing the embodiments of the present invention, reference will be made herein to FIGS. 1 and 2 of the drawings in which like numerals refer to like features of the invention.

#Referring to FIG. 1, there is shown apparatus 10 of the present invention. Apparatus 10 comprises measurement device 11. In one embodiment, the measurement device can be configured as a CFPPLL described in commonly owned U.S. Pat. No. 5,214,955, the disclosure of which is herein incorporated by reference as if set forth in its entirety. The CFPPLL is shown in FIG. 2 and is briefly described in the ensuing description in order to facilitate understanding of the present invention. The CFPPLL is configured to operate in the “pitch-catch” mode which is described in the aforementioned U.S. Pat. No. 5,214,955. In another embodiment, the measurement device 11 might comprise a variable frequency pulsed phase-locked loop (“VFPPLL”), for example as described in the article by Yost, et al., Fundamental Aspects of Pulse Phase-locked Loop Technology-based Methods for Measurement of Ultrasonic Velocity, J. Acoust. Soc. Am. 91, 1456-1468 (1992), which article is incorporated herein by reference as if set forth in its entirety.

#As shown in FIG. 2, the CFPPLL includes a fixed frequency oscillator 12, such as a phase-stable synthesizer. The fixed frequency oscillator 12 sends its constant frequency output to three different blocks: the logic and timing circuit 14, a buffer amplifier-phase shift circuit 16, and a tone-burst formation gate 18. The logic and timing circuit 14 uses this signal as a clock and counts down to determine the timing on its outputs. One output is the transmit or Tx gate to form the electrical tone burst. The logic and timing circuit 14 also contains a setting so that the operator can set the gate for as many cycles as is desired.