# US 9,775,524 B2 · Apparatus and method of assessing a narrowing in a fluid filled tube > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,775,524 B2 - Document ID: US9775524B2 - Status: Granted - Kind: B2 - Application number: 14/701,000 - Filed: 2015-04-30 - Published: 2015-08-20 - Granted: 2017-10-03 - Earliest claimed: 2011-01-06 - Assignees: Medsolve Limited; Imperial College of Science, Technology and Medicine - Applicants: Imperial College of Science, Technology and Medicine; Medsolve Ltd. - Inventors: Helen Davies; Justin Davies - Web page: https://patentgrep.com/patent/US9775524B2 ## CPC - A61B 5/02007: {Evaluating blood vessel condition, e.g. elasticity, compliance} - A61B 5/02125: {of pulse wave propagation time} - A61B 5/0215: by means inserted into the body - A61B 5/0285: Measuring or recording phase velocity of blood waves - A61B 5/103: Measuring devices for testing the shape, pattern, {colour,} size or movement of the body or parts thereof, for diagnostic purposes (measuring instruments specially adapted for dentistry A61C19/04) - A61B 5/1076: {for measuring dimensions inside body cavities, e.g. using catheters (A61B3/1005 takes precedence)} - A61B 5/7264: {Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems} - A61B 5/7278: {Artificial waveform generation or derivation, e.g. synthesizing signals from measured signals} - A61B 5/026: Measuring blood flow {(A61B3/1233, A61B3/1241 take precedence)} - A61B 5/6852: {Catheters} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## 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 ### Claim 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. ### Claim 2 (depends on 1) The method of claim 1, wherein the wave free period is identified heuristically. ### Claim 3 (depends on 1) 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. ### Claim 4 (depends on 1) 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. ### Claim 5 (depends on 1) The method of claim 1, wherein the wave free period is identified by: identifying a peak pressure time (tPmax); identifying an end of pressure waveform time (tPend); and specifying the wave free period as a time window between tPmax and tPend. ### Claim 6 (depends on 5) The method of claim 5, wherein the time window extends from tPmax+150 ms to tPend−50 ms. ### Claim 7 (depends on 5) The method of claim 5, wherein the time window is a mid 3/5 window between tPmax and tPend. ### Claim 8 (depends on 1) 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. ### Claim 9 (depends on 8) The method of claim 8, wherein the predetermined threshold is a bottom 10% or less of the calculated standard deviation. ### Claim 10 (depends on 8) The method of claim 8, wherein the time window has a length of at least 100 ms. ### Claim 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. ### Claim 12 (depends on 11) The system of claim 11, wherein the processor is configured to identify the wave free period heuristically. ### Claim 13 (depends on 11) 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. ### Claim 14 (depends on 11) 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. ### Claim 15 (depends on 11) The system of claim 11, wherein the processor is configured to identify the wave free period by: identifying a peak pressure time (tPmax); identifying an end of pressure waveform time (tPend); and specifying the wave free period as a time window between tPmax and tPend. ### Claim 16 (depends on 15) The system of claim 15, wherein the time window extends from tPmax+150 ms to tPend−50 ms. ### Claim 17 (depends on 15) The system of claim 15, wherein the time window is a mid 3/5 window between tPmax and tPend. ### Claim 18 (depends on 11) 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. ### Claim 19 (depends on 18) The system of claim 18, wherein the predetermined threshold is a bottom 10% or less of the calculated standard deviation. ### Claim 20 (depends on 18) The system of claim 18, wherein the time window has a length of at least 100 ms.