System for transcutaneous monitoring of intracranial pressure

• US 8,784,332 B2
• Filed: 10/04/2012
• Issued: 07/22/2014
• Est. Priority Date: 02/24/2005
• Status: Active Grant

• Current Assignee: Erich W. Wolf II
• Original Assignee: Erich W. Wolf II
• Inventors: Wolf, Erich W. II
• Primary Examiner(s): TOWA, RENE T
• Application Number:
  US13/645,358
• Publication Number:
  US 20130035577A1
• Time in Patent Office: 656 Days
• Field of Search: 600300-301, 600/309, 600433-435, 600/473, 600485-488, 600/561, 600/310, 604/9, 604/164.1, 604/466, 604508-510, 604/528, 604/544, 607/33, 607/60, 737/22
• US Class Current: 600/561
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/0017 transmitting optical signals transmission by light H04B10/00
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/0077 Devices for viewing the surface of the body, e.g. camera, magnifying lens
• CPC Class Codes: A61B 5/0086 using infrared radiation
• CPC Class Codes: A61B 5/031 Intracranial pressure

Abstract

A system for measuring and converting to an observer intelligible form an internal physiological parameter of a patient. The invention allows transcutaneous telemetry of intracranial pressure via a system which includes a patient implanted sensor module and an external processing module, optically coupled to the sensor module via an external coupling module. A sensor within the sensor module transduces the measured pressure and a near infrared emitter transmits the telemetry when interrogated by the external coupling module. A set of tuned inductor-crystal circuits comprised in part of a cylindrical crystal oscillator whose resonant frequency is sensed by a dipper circuit arrangement is provided. Power for the sensor module is derived inductively through rectification of a transcutaneously-applied high-frequency alternating electromagnetic field generated within the external coupling module. A computer within the processing module calculates the physiological parameter from the telemetry signal and represents this data in numerical, graphical, or analog format.

Claims

1. A method of determining an intracranial fluid pressure of an intracranial fluid comprising the steps of:

providing a cylindrical crystal oscillator probe having a transducer crystal and a reference crystal, wherein the transducer crystal is in contact with the intracranial fluid;

providing at least one driver circuit within the cylindrical crystal oscillator probe connected to the transducer crystal and the reference crystal;

exposing the reference crystal to a reference pressure;

exposing the transducer crystal to the intracranial fluid pressure;

exciting the transducer crystal to provide a first radio frequency energy absorption;

exciting the reference crystal to produce a second radio frequency energy absorption;

measuring the first radio frequency energy absorption;

measuring the second radio frequency energy absorption;

comparing the first radio frequency energy absorption and the second radio frequency energy absorption to determine a difference;

determining the intracranial fluid pressure from the difference and the reference pressure;

determining a first resonance frequency from the first radio frequency absorption;

determining a second resonance frequency from the second radio frequency absorption;

determining a calibration slope linearly relating a set of absorption frequencies to a set of pressures;

wherein the step of determining the intracranial fluid pressure includes application of the formula;

P=P₀−

m(f₀−

f₁) where;

 

P=the intracranial fluid pressure;

 

P₀=the reference pressure;

 

m=the calibration slope;

 

f₀=the first resonant frequency; and

,

 

f₁=the second resonant frequency.

2. The method of claim 1 wherein the steps of exciting the transducer crystal and exciting the reference crystal include the steps of:

providing a first coil connected to the reference crystal;

providing a second coil connected to the transducer crystal; and

,

sweeping an oscillating electromagnetic field over the first coil and the second coil to produce at least one frequency absorption null.

3. The method of claim 1 including the further steps of:

providing a memory in the crystal oscillator probe; and

,

storing a set of calibration data in the memory.

4. The method of claim 1 including the further steps of:

providing a memory in the crystal oscillator probe; and

,

storing a set of patient data in the memory.

5. The method of claim 1 wherein the step of measuring the first radio frequency energy absorption further comprises the step of accounting for a protein deposit from the intracranial fluid.

6. The method of claim 5 wherein the step of accounting for a protein deposit further includes the step of:

determining a reported resonant frequency f_r according to the formula;

f_r=f_measured+(f_i−

f_t) where;

fr=the reported resonant frequency;

f_measured=the first resonant frequency;

f_i=an initial resonant frequency; and

,

f_t=a final resonant frequency.

7. The method of claim 6 further including the step of:

recording the initial resonant frequency and a time of inception.

8. A method of determining an intracranial fluid pressure of an intracranial fluid comprising the steps of:

providing a cylindrical crystal oscillator probe having a transducer section and a reference section;

providing at least one driver circuit within the cylindrical crystal oscillator probe connected to the transducer section and the reference section;

exposing the reference section to a reference pressure;

exposing the transducer section to the intracranial fluid pressure;

exciting the transducer section to provide a first radio frequency energy absorption;

exciting the reference section to produce a second radio frequency energy absorption;

measuring the first radio frequency energy absorption;

measuring the second radio frequency energy absorption;

comparing the first radio frequency energy absorption and the second radio frequency energy absorption to determine a difference;

determining the intracranial fluid pressure from the difference and the reference pressure;

determining a first resonance frequency from the first radio frequency absorption;

determining a second resonance frequency from the second radio frequency absorption;

determining a calibration slope linearly relating a set of absorption frequencies to a set of pressures; and

,

wherein the step of determining the intracranial fluid pressure includes application of the formula;

P=P₀−

m(f₀−

f₁) where;

 

P=the intracranial fluid pressure;

 

P₀=the reference pressure;

 

m=the calibration slope;

 

f₀=the first resonant frequency; and

,

 

f₁=the second resonant frequency.

9. A method of determining an intracranial fluid pressure of an intracranial fluid comprising the steps of:

providing a cylindrical crystal oscillator probe having a transducer section and a reference section;

providing at least one driver circuit within the cylindrical crystal oscillator probe connected to the transducer section and the reference section;

exposing the reference section to a reference pressure;

exposing the transducer section to the intracranial fluid pressure;

exciting the transducer section to provide a first radio frequency energy absorption;

exciting the reference section to produce a second radio frequency energy absorption;

measuring the first radio frequency energy absorption;

measuring the second radio frequency energy absorption;

comparing the first radio frequency energy absorption and the second radio frequency energy absorption to determine a difference;

determining the intracranial fluid pressure from the difference and the reference pressure;

determining a first resonance frequency from the first radio frequency absorption;

determining a second resonance frequency from the second radio frequency absorption;

determining a calibration slope linearly relating a set of absorption frequencies to a set of pressures;

wherein the step of determining the intracranial fluid pressure includes application of the formula;

P=P₀−

m(f₀−

f₁) where;

 

P=the intracranial fluid pressure;

 

P₀=the reference pressure;

 

m=the calibration slope;

 

f₀=the first resonant frequency;

 

f₁=the second resonant frequency;

providing a first coil connected to the reference section;

providing a second coil connected to the transducer section; and

,

sweeping an oscillating electromagnetic field over the first coil and the second coil to produce at least one frequency absorption null.

10. A method of determining an intracranial fluid pressure of an intracranial fluid comprising the steps of:

providing a cylindrical crystal oscillator probe having a transducer section and a reference section;

providing at least one driver circuit within the cylindrical crystal oscillator probe connected to the transducer section and the reference section;

exposing the reference section to a reference pressure;

exposing the transducer section to the intracranial fluid pressure;

exciting the transducer section to provide a first radio frequency energy absorption;

exciting the reference section to produce a second radio frequency energy absorption;

measuring the first radio frequency energy absorption;

measuring the second radio frequency energy absorption;

comparing the first radio frequency energy absorption and the second radio frequency energy absorption to determine a difference;

determining the intracranial fluid pressure from the difference and the reference pressure; and

,

wherein the step of measuring the first radio frequency energy absorption further comprises the step of accounting for a protein deposit from the intracranial fluid.

11. A method of determining an intracranial fluid pressure of an intracranial fluid comprising the steps of:

providing a cylindrical crystal oscillator probe having a transducer section and a reference section;

providing at least one driver circuit within the cylindrical crystal oscillator probe connected to the transducer section and the reference section;

exposing the reference section to a reference pressure;

exposing the transducer section to the intracranial fluid pressure;

exciting the transducer section to provide a first radio frequency energy absorption;

exciting the reference section to produce a second radio frequency energy absorption;

measuring the first radio frequency energy absorption;

measuring the second radio frequency energy absorption;

comparing the first radio frequency energy absorption and the second radio frequency energy absorption to determine a difference;

determining the intracranial fluid pressure from the difference and the reference pressure;

wherein the step of measuring the first radio frequency energy absorption further comprises the step of accounting for a protein deposit from the intracranial fluid; and

,

wherein the step of accounting for a protein deposit further includes the step of;

determining a reported resonant frequency f_r according to the formula;

f_r=f_measured+(f_i−

f_t) where;

fr=the reported resonant frequency;

f_measured=a first resonant frequency;

f_i=an initial resonant frequency; and

,

f_t=a final resonant frequency.

12. A method of determining an intracranial fluid pressure of an intracranial fluid comprising the steps of:

providing a cylindrical crystal oscillator probe having a transducer section and a reference section;

providing at least one driver circuit within the cylindrical crystal oscillator probe connected to the transducer section and the reference section;

exposing the reference section to a reference pressure;

exposing the transducer section to the intracranial fluid pressure;

exciting the transducer section to provide a first radio frequency energy absorption;

exciting the reference section to produce a second radio frequency energy absorption;

measuring the first radio frequency energy absorption;

measuring the second radio frequency energy absorption;

comparing the first radio frequency energy absorption and the second radio frequency energy absorption to determine a difference; and

,

determining the intracranial fluid pressure from the difference and the reference pressure;

wherein the step of measuring the first radio frequency energy absorption further comprises the step of accounting for a protein deposit from the intracranial fluid;

wherein the step of accounting for a protein deposit further includes the step of;

determining a reported resonant frequency f_r according to the formula;

f_r=f_measured+(f_i−

f_t) where;

fr=the reported resonant frequency;

f_measured=a first resonant frequency;

f_i=an initial resonant frequency;

f_t=a final resonant frequency; and

,

further including the step of recording the initial resonant frequency and a time of inception.