Apparatus and method of assessing a narrowing in a fluid filled tube

• US 9,775,524 B2
• Filed: 04/30/2015
• Issued: 10/03/2017
• Est. Priority Date: 01/06/2011
• Status: Active Grant

• Current Assignee: Imperial College of Science Technology & Medicine (Imperial College London), Medsolve Limited
• Original Assignee: Imperial College of Science Technology & Medicine (Imperial College London), Medsolve Limited
• Inventors: Davies, Helen, Davies, Justin
• Primary Examiner(s): Huynh, Phuong
• Application Number:
  US14/701,000
• Publication Number:
  US 20150230714A1
• Time in Patent Office: 887 Days
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/1076 for measuring dimensions inside body cavities, e.g. using catheters A61B3/1005 takes precedence
• CPC Class Codes: A61B 5/6852 Catheters
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

An apparatus and method of assessing a narrowing in a fluid filled tube having a fluid flow pressure wave having a backward-originating pressure component and a forward-originating pressure component without taking a flow velocity measurement, comprising: taking pressure measurements in the tube; separating the pressure components into the backward-originating pressure component and the forward-originating pressure component; identifying a time window when the differential of flow velocity (dU) is minimal or absent; and deriving the backward and forward pressure components for pressure measurements taken in at least the time window.

Claims

1. A method of assessing a narrowing in a blood vessel, the method comprising:

positioning at least one pressure-sensing probe within a blood vessel;

obtaining, with an intravascular processing system having a processor in communication with the at least one pressure-sensing probe, pressure measurements from within the blood vessel using the at least one pressure-sensing probe, the pressure measurements being obtained not during hyperaemia;

identifying, with the intravascular processing system, a wave free period corresponding to a time window when a differential of flow velocity is minimal or absent; and

calculating, with the intravascular processing system, a pressure ratio using the pressure measurements obtained during the wave free period to provide an assessment of a severity of the narrowing in the blood vessel.

2. The method of claim 1, wherein the wave free period is identified heuristically.

3. The method of claim 1, wherein the wave free period is identified based on a characteristic of a pressure waveform of the obtained pressure measurements.

4. The method of claim 1, wherein the wave free period is identified as a certain time window before or after a characteristic of the pressure waveform.

5. The method of claim 1, wherein the wave free period is identified by:

identifying a peak pressure time (t_Pmax);

identifying an end of pressure waveform time (t_Pend); and

specifying the wave free period as a time window between t_Pmax and t_Pend.

6. The method of claim 5, wherein the time window extends from t_Pmax+150 ms to t_Pend−

50 ms.

7. The method of claim 5, wherein the time window is a mid 3/5 window between t_Pmax and t_Pend.

8. The method of claim 1, wherein the wave free period is identified by:

calculating a standard deviation of a pressure ratio of the obtained pressure measurements; and

specifying the wave free period as a time window after a peak pressure time point where the standard deviation is below a predetermined threshold.

9. The method of claim 8, wherein the predetermined threshold is a bottom 10% or less of the calculated standard deviation.

10. The method of claim 8, wherein the time window has a length of at least 100 ms.

11. A system of assessing a narrowing in a blood vessel, the system comprising:

at least one pressure-sensing probe sized and shaped for positioning within the blood vessel; and

a processor in communication, with the at least one pressure-sensing probe, the processor configured to;

receive pressure measurements obtained by the at least one pressure-sensing probe positioned within the blood vessel, the pressure measurements being obtained not during hyperaemia;

identify a wave free period corresponding to a time window when a differential of flow velocity is minimal or absent; and

calculate a pressure ratio using the pressure measurements obtained during the wave free period to provide an assessment of a severity of the narrowing in the blood vessel.

12. The system of claim 11, wherein the processor is configured to identify the wave free period heuristically.

13. The system of claim 11, wherein the processor is configured to identify the wave free period based on a characteristic of a pressure waveform of the obtained pressure measurements.

14. The system of claim 11, wherein the processor is configured to identify the wave free period as a certain time window before or after a characteristic of the pressure waveform.

15. The system of claim 11, wherein the processor is configured to identify the wave free period by:

identifying a peak pressure time (t_Pmax);

identifying an end of pressure waveform time (t_Pend); and

specifying the wave free period as a time window between t_Pmax and t_Pend.

16. The system of claim 15, wherein the time window extends from t_Pmax+150 ms to t_Pend−

50 ms.

17. The system of claim 15, wherein the time window is a mid 3/5 window between t_Pmax and t_Pend.

18. The system of claim 11, wherein the processor is configured to identify the wave free period by:

calculating a standard deviation of a pressure ratio of the obtained pressure measurements; and

specifying the wave free period as a time window after a peak pressure time point where the standard deviation is below a predetermined threshold.

19. The system of claim 18, wherein the predetermined threshold is a bottom 10% or less of the calculated standard deviation.

20. The system of claim 18, wherein the time window has a length of at least 100 ms.