Methods of and systems and devices for assessing intracranial pressure non-invasively

• US 20040230124A1
• Filed: 05/12/2003
• Published: 11/18/2004
• Est. Priority Date: 05/12/2003
• Status: Active Grant

• Current Assignee: Steward Research And Specialty Projects Corporation
• Original Assignee: St. Elizabeth'S Medical Center Of Boston, Inc.
• Inventors: Querfurth, Henry W.
• Granted Patent: US 7,122,007 B2
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 3/16 for measuring intraocular pressure, e.g. tonometers
• CPC Class Codes: A61B 5/031 Intracranial pressure
• CPC Class Codes: A61B 8/0808 for diagnosis of the brain

Abstract

A non-invasive method and system for assessing intraocular pressure (ICP) is disclosed. The method comprises the steps of measuring venous outflow pressure (VOP) using a venous ophthalmodynamometer device (vODM); measuring ophthalmic r central retinal arterial blood flow using color Doppler imaging device; and then estimating ICP using venous outflow data from the vODM and pulsatility and/or resistivity relationships derived from the Doppler imaging data. Further disclosed is a novel vODM for measuring VOP in low flow veins.

Claims

27. A non-invasive system for assessing intracranial pressure, the system comprising:

a venous outflow pressure (VOP) measuring device to provide venous outflow pressure (VOP) data;

an ophthalmic or central retinal arterial flow velocity measuring device to provide ophthalmic or central retinal arterial flow velocity data, respectively; and

a device for determining intracranial pressure (ICP) using venous outflow pressure (VOP) data and a characteristic of the ophthalmic or central retinal artery from ophthalmic or central retinal arterial flow velocity data, respectively.

1. A non-invasive method of assessing intracranial pressure, the method comprising the steps:

measuring venous outflow pressure (VOP);

measuring ophthalmic or central retinal arterial blood flow velocity; and

determining intracranial pressure (ICP) using venous outflow pressure (VOP) data and a characteristic of the ophthalmic artery or central retinal artery from ophthalmic or central retinal arterial flow velocity data, respectively.

2. The method as recited in claim 1, wherein the step of measuring venous outflow pressure (VOP) comprises the sub-steps of:

applying a load to a patient'"'"'s orbit incrementally using a loading device;

observing a central retinal vein in the patient'"'"'s orbit; and

recording the load applied to the patient'"'"'s orbit when the central retinal vein is observed to occlude or collapse.

3. The method as recited in claim 2, wherein the sub-step of applying a load to a patient'"'"'s orbit incrementally includes providing a venous ophthalmodynamometer (vODM).

4. The method as recited in claim 3, wherein the sub-step of providing a venous ophthalmodynamometer (vODM) further comprises providing a differential variable reluctance transducer (DVRT), having a loading pressure plate at a distal end thereof, as the loading device, and providing a frequency analyzer, wherein the DVRT is in communication with a frequency analyzer for transmitting loading data for recordation.

5. The method as recited in claim 2, wherein the sub-step of observing a central retinal vein comprises using an ophthalmoscope to observe occlusion of the central retinal vein.

6. The method as recited in claim 2, wherein the sub-step of recording the load applied to the patient'"'"'s orbit comprises transmitting loading data from the loading device to a recordation device.

7. The method as recited in claim 6, wherein the sub-step of recording the load applied to the patient'"'"'s orbit comprises:

transmitting loading data from the loading device to a frequency analyzer; and

providing a device for freezing instantaneous load measurements, wherein the device for freezing instantaneous load measurements is a foot pedal that can be activated manually and that can freeze the load measurement when the central retinal vein collapses.

8. The method as recited in claim 1, wherein the method further comprises the sub-steps of anaesthetizing a patient'"'"'s orbit and dilating a pupil therein pharmacologically before measuring venous outflow pressure (VOP).

9. The method as recited in claim 1, wherein the method further comprises the step of establishing a baseline, resting intraocular pressure (IOP), wherein the baseline, resting intraocular pressure (IOP) can be used to correlate venous outflow pressure (VOP) measurements with intracranial pressure (ICP).

10. The method as recited in claim 9, wherein the step of establishing a baseline, resting intraocular pressure (IOP) is established using a tonometer.

11. The method as recited in claim 1, wherein the step of measuring ophthalmic or central retinal arterial blood flow velocity comprises measuring real-time spectral waveform of blood flow velocity in intracranial arterial vessels.

12. The method as recited in claim 11, wherein the step of measuring real-time spectral waveform of blood flow velocity in intracranial arterial vessels comprises the sub-steps of:

providing a color Doppler imaging (CDI) device, wherein the CDI comprises a Doppler probe and a spectral analyzer;

applying the Doppler probe to at least one of a patient'"'"'s closed eyelids;

using a first ultrasound signal from the Doppler probe to provide an orbital scan image of at least one of a patient'"'"'s orbits to identify an optic nerve head in said at least one of a patient'"'"'s orbits;

using a second ultrasound signal from the Doppler probe to provide a real time, spatially visualized color Doppler image to observe anterograde arterial blood flow and direction in at least one artery of said at least one of a patient'"'"'s orbits; and

using a third ultrasonic signal from the Doppler probe to provide a pulsed wave, ultrasonic signal of arterial blood flow velocity and direction at a specific location of said at least one patient'"'"'s orbits.

13. The method as recited in claim 12, wherein the step of using a second ultrasound signal from the Doppler probe to identify anterograde arterial blood flow identifies anterograde arterial blood flow in at least one of a central retinal artery, an ophthalmic artery, and a posterior ciliary artery.

14. The method as recited in claim 12, wherein the step of measuring real time spectral waveform of blood flow velocity in intracranial vessels further comprises the sub-steps of:

providing a display means for displaying the orbital scan image in two dimensions;

identifying a vessel region in said orbital scan image; and

measuring anterograde arterial blood flow and direction in said vessel region using the third ultrasound signal.

15. The method as recited in claim 14, wherein the sub-step of identifying a vessel region in said orbital scan image comprise identifying a vessel region in said orbital scan image using a cursor window of an input/output device.

16. The method as recited in claim 1, where in the step of determining intracranial pressure (ICP) comprises the sub-step of determining a pulsatility characteristic of the ophthalmic artery or central retinal artery from the ophthalmic or central retinal arterial flow velocity data, respectively.

17. The method as recited in claim 16, wherein the sub-step of determining a pulsatility characteristic of the ophthalmic or central retinal artery comprises providing a system integration device to determine arterial blood flow parameters.

18. The method as recited in claim 17, wherein the step of providing a system integration device to determine arterial blood flow parameters comprises providing a system integration device that can calculate at least one of peak systolic velocity (PSV), end diastolic velocity (EDV), and mean arterial velocity (MAV) from measured ophthalmic or central retinal arterial flow velocity data.

19. The method as recited in claim 18, wherein the sub-step of determining a pulsatility characteristic of the ophthalmic or central retinal artery further comprises calculating Gosling'"'"'s pulsatility index (GPI) in accordance with the following mathematical formula:

GPI=(PSV−

EDV)/MAV.

20. The method as recited in claim 19, wherein the step of determining intracranial pressure (ICP) using a relationship between venous outflow pressure (VOP) data and a pulsatility characteristic of the ophthalmic or central retinal artery further comprises calculating ICP using the following mathematical formula:

21. The method as recited in claim 1, where in the step of determining intracranial pressure (ICP) comprises the sub-step of determining a resistivity characteristic of the ophthalmic or central retinal artery from the ophthalmic or central retinal arterial flow velocity data, respectively.

22. The method as recited in claim 21, wherein the sub-step of determining a resistivity characteristic of the ophthalmic or central retinal artery comprises providing a system integration device to determine arterial blood flow parameters.

23. The method as recited in claim 22, wherein the step of providing a system integration device to determine arterial blood flow parameters comprises providing a system integration device that can calculate at least one of peak systolic velocity (PSV), end diastolic velocity (EDV), and mean arterial velocity (MAV) from measured ophthalmic or central retinal arterial flow velocity data.

24. The method as recited in claim 23, wherein the sub-step of determining the resistivity characteristic of the ophthalmic or central retinal artery further comprises calculating Pourcelot'"'"'s resistive index (PRI) in accordance with the following mathematical formula:

PRI=(PSV−

EDV)/PSV.

25. The method as recited in claim 24, wherein the step of determining intracranial pressure (ICP) using a relationship between venous outflow pressure (VOP) data and a resistivity characteristic of the ophthalmic or central retinal artery further comprises calculating ICP using the following mathematical formula:

26. The method as recited in claim 1, wherein the intracranial pressure assessed is at least one of an absolute intracranial pressure and a change in intracranial pressure.

28. The system as recited in claim 27, wherein the measuring venous outflow pressure (VOP) measuring device comprises a venous ophthalmodynamometer (vODM) in combination with a device for observing collapse of one or more retinal veins in a patient'"'"'s orbit.

29. The system as recited in claim 28, wherein the device for observing collapse of one or more retinal veins in a patient'"'"'s orbit is an ophthalmoscope.

30. The system as recited in claim 28, wherein the venous ophthalmodynamometer (vODM) comprises:

a differential variable reluctance transducer (DVRT) that can be used to apply a recordable, incremental load to a patient'"'"'s orbit; and

a frequency analyzer that is in communication with the DVRT for receiving said recordable loading data for recordation.

31. The system as recited in claim 30, wherein the venous ophthalmodynamometer (vODM) further comprises:

a device for freezing instantaneous load measurements that is in communication with the frequency analyzer, whereby activation of the device will freeze an instantaneous load measurement value at the instant that the retinal vein collapses so that said frozen value can be recorded by the frequency analyzer.

32. The system as recited in claim 27, wherein the system further comprises a device for establishing a baseline, resting intraocular pressure (IOP) so that the baseline, resting intraocular pressure (IOP) can be used to correlate venous outflow pressure (VOP) measurements with intracranial pressure (ICP).

33. The system as recited in claim 32, wherein the device for establishing a baseline, resting intraocular pressure (IOP) is a tonometer.

34. The system as recited in claim 27, wherein the ophthalmic or central retinal arterial flow velocity measuring device comprises a color Doppler imagining (CDI) device, wherein the CDI device further comprises a Doppler probe and a spectral analyzer;

wherein the Doppler probe can be applied to at least one of a patient'"'"'s closed eyelids and a first ultrasound signal from said Doppler probe can provide an orbital scan image of said at least one of a patient'"'"'s orbits to identify an optic nerve head of said orbit and a second ultrasound signal from said Doppler probe can provide a visual image of anterograde arterial blood flow in at least one artery of the patient'"'"'s orbit to identify a vessel region to measure arterial blood flow velocity; and

a third ultrasonic signal from said Doppler probe can provide continuous arterial blood flow velocity data at the identified vessel region.

35. The system as recited in claim 34, wherein the spectral analyzer comprises:

a display device for displaying the orbital scan image in two dimensions;

an input/output device for identifyng the vessel region in said orbital scan image using the second ultrasound signal.

36. The system as recited in claim 27, wherein the device for determining a characteristic of the ophthalmic or central retinal artery comprises at least one of a system integration device and a microprocessor in combination with a system integration device.

37. The system as recited in claim 36, wherein the said at least one of a system integration device and a microprocessor in combination with a system integration device can calculate at least one of peak systolic velocity (PSV), end diastolic velocity (EDV), and mean arterial velocity (MAV) from measured ophthalmic or central retinal arterial blood flow velocity data.

38. The system as recited in claim 37, wherein said at least one of a system integration device and a microprocessor in combination with a system integration device can further calculate Gosling'"'"'s pulsatility index (GPI) in accordance with the following mathematical formula:

GPI=(PSV−

EDV)/MAV.

39. The system as recited in claim 38, wherein the device for determining intracranial pressure (ICP) using a relationship between venous outflow pressure (VOP) data and a pulsatility characteristic of the ophthalmic or central retinal artery includes means for calculating ICP using the following mathematical formula:

40. The system as recited in claim 37, wherein said at least one of a system integration device and a microprocessor in combination with a system integration device can further calculate Pourcelot'"'"'s resistive index (PRI) in accordance with the following mathematical formula:

PRI=(PSV−

EDV)/PSV.

41. The system as recited in claim 40, wherein the device for determining intracranial pressure (ICP) using a relationship between venous outflow pressure (VOP) data and a resistivity characteristic of the ophthalmic artery includes means for calculating ICP using the following mathematical formula:

41-1. The system as recited in claim 27, wherein the intracranial pressure assessed is at least one of an absolute intracranial pressure and a change in intracranial pressure.

42. A non-invasive device for measuring venous occlusion pressure (VOP) in a patient'"'"'s orbit, the device comprising:

a displacement transducer for applying pressure to a lateral sclera of the patient'"'"'s orbit incrementally, the transducer further comprising;

a probe portion that includes a compression spring and an induction mechanism,

a plunger that is structured and arranged coaxial to the probe portion, wherein at least some portion of the plunger is disposed inside the probe portion and is, further, in communication with the compression spring, and

a removable pressure plate for applying incremental pressure to the patient'"'"'s lateral sclera that is structured and arranged at a distal end of the plunger transducer,

wherein as pressure is applied to the lateral sclera of the patient'"'"'s orbit, the plunger displaces so as to compress the compression spring in the probe portion, which induces a current commensurate with the magnitude of displacement in the induction mechanism; and

a frequency analyzer that is in communication with the displacement transducer, wherein current induced by displacement of the plunger is output to the frequency analyzer as an output signal, which output signal can be processed by said frequency analyzer to provide venous occlusion pressure (VOP) data.

43. The device as recited in claim 42, wherein the device further comprises a foot pedal that is in communication with the frequency analyzer, wherein, when activated, the foot pedal transmits a signal to said frequency analyzer causing said frequency analyzer to freeze, record, and store the instantaneous venous occlusion pressure (VOP) data.

44. The device as recited in claim 42, wherein the frequency analyzer is in communication with at least one of an internal or an external microprocessor, the internal or external microprocessor comprising a central processing unit, one or more input/output devices, and at least one of random access memory, read-only memory, and cache memory.