INTRAVASCULAR BLOOD FLOW MEASUREMENT USING DIFFERENTIAL PRESSURE PRINCIPLE AND AN EXPANDING FLOW SENSOR

Abstract

A blood flow measurement system for measuring a blood flow quantity such as flow velocity or flow volume inside a blood vessel includes an intravascular blood flow measurement device with a body that comprises an expandable body section. A control unit sequentially provides a size control signal indicative of a respective one of the at least two predetermined expandable sizes to be assumed by the expandable body section. A pressure sensor unit measures respective sequences of blood pressure signals over a measuring time span defined with respect to a heart cycle period. A flow determination unit uses the values of cross sectional area of the expandable body section, the associated pressure signals and a known value of a density of blood, to calculate a value of a blood flow quantity inside the blood vessel based on Bernoulli's law.

Claims

1. An intravascular blood flow measurement device, comprising: a body suitable for placement inside a blood vessel of a living being and extending along a longitudinal direction; an expandable body section of the body, having a longitudinal extension in the longitudinal direction and a cross-sectional area perpendicular to the longitudinal direction that is controllably and reversibly expandable to assume a respective one of at least two different predetermined expanded sizes associated with at least two respective values of an expanded cross sectional area of the expandable body section; a controllable actuator arranged and configured to set the expandable body section to one of the at least two sizes; and a pressure sensor unit comprising at least one pressure sensor arranged on the body within the longitudinal extension of the expandable body section, the pressure sensor unit being configured to provide, for each of at least three values of cross sectional area of the body, including the at least two values of the expanded cross-sectional area of the expandable body section, a respective sequence of pressure signals indicative of a pressure of blood flow in the blood vessel over a predetermined measuring time span defined with respect to a heart cycle period.

2. The intravascular blood flow measurement device of claim 1, wherein the body, including the expandable body section, has a stream-lined shape maintaining a laminar blood flow inside the blood vessel.

3. The intravascular blood flow measurement device of claim 1, wherein the expandable body section comprises an electro-active polymer configured to controllably change its shape or volume in response to receiving an electrical expansion-control signal.

4. The intravascular blood flow measurement device of claim 1, wherein the expandable body section comprises an inflatable balloon configured to controllably change its volume within a volume range, and wherein the controllable actuator is configured to controllably pump a pressurized fluid or gas into or out of the inflatable balloon.

5. The intravascular blood flow measurement device of claim 1, wherein the pressure sensor unit comprises at least two pressure sensors; and at least one of the pressure sensors is arranged on the measuring head body outside the longitudinal extension of the expandable body section.

6. A blood flow measurement system for measuring a blood flow quantity inside a blood vessel of a living being, the flow measurement system comprising: an intravascular blood flow measurement device according to claim 1; a control unit configured to sequentially provide to the controllable actuator a size control signal indicative of a respective one of the at least two predetermined sizes to be assumed by the expandable body section; and a flow determination unit, which is configured to receive the pressure signals provided by the pressure sensor unit and, using the at least three values of cross sectional area of the body, the pressure signals associated with the at least three values of cross sectional area of the body and taken at respective measuring times corresponding to an identical phase of the heart cycle, and a known value of a density of blood, to calculate a value of a blood flow quantity inside the blood vessel.

7. The blood flow measurement system of claim 6, wherein the pressure sensor unit comprises only one pressure sensor; and the control unit is configured to provide to the controllable actuator a size control signal indicative of a respective one of at least three predetermined sizes to be assumed by the expandable body section.

8. The blood flow measurement system of claim 6, wherein the flow determination unit is configured, using Bernoulli's law, the at least three values of cross sectional area of the body, the associated sequences of pressure signals, and a known value of a density of blood, to solve a system of two or more equations, to determine a value of the cross sectional area of the blood vessel (A) and a value of a volume flow velocity (v.sub.0) at a respective value of cross sectional area.

9. The blood flow measurement system of claim 8, wherein the expandable body section is controllably and reversibly expandable to assume at least three different predetermined expanded sizes associated with at least three respective values of an expanded cross sectional area of the expandable body section; the pressure sensor unit is configured to provide, for each of at least four values of cross sectional area of the body, including the at least three values of the expanded cross-sectional area of the expandable body section, the respective sequence of pressure signals; the flow determination unit is further configured to determine, using a predetermined fitting model, calibration curve parameters fitting pressure values determined from the received pressure signals as a function of cross-sectional area of the body and to determine, using the pressure values and the associated values of the cross-sectional area of the body, a fit-error measure, to compare the fit-error measure with a pre-determined error threshold value, and, in case the fit-error measure exceeds the error threshold value, to provide an error output signal indicative thereof.

10. The blood flow measurement system of claim 9, further comprising a user interface configured to receive the error output signal and, upon receiving the error output signal, to provide output information to a user, the output information being indicative of a blood flow limitation induced by the intravascular blood flow measurement device exceeding a predetermined maximum blood flow limitation amount in the blood vessel.

11. The blood flow measurement system of claim 9, wherein the control unit is configured, in response to receiving the error output signal, to determine and provide to the controllable actuator corrected size control signals indicative of at least two corrected size values within a corrected size value range having a smaller corrected maximum size value in comparison with a maximum size value of the expandable body section set by the control unit before receiving the error output signal.

12. A method for controlling operation of an intravascular blood flow measurement device according to claim 1, the method comprising: sequentially providing to the controllable actuator of the intravascular blood flow measurement device a size control signal indicative of a respective one of at least two predetermined expanded sizes to be assumed by the expandable body section of the body of the intravascular blood flow measurement device; and controlling provision, by a pressure sensor unit which comprises at least one pressure sensor arranged on the body of the intravascular blood flow measurement device within a longitudinal extension of the expandable body section, for each of at least three values of cross sectional area of the body, including the at least two values of the expanded cross-sectional area of the expandable body section, of respective sequence of pressure signals indicative of a pressure of blood flow in the blood vessel over a predetermined measuring time span defined with respect to a heart cycle period.

13. A method for determination of a blood flow quantity inside a blood vessel of a living being, the method comprising: performing the method of claim 12; and calculating a value of a blood flow quantity inside the blood vessel, using the at least three values of cross sectional area of the body, the pressure signals associated with the at least three values of cross sectional area of the body and taken at respective measuring times corresponding to an identical phase of the heart cycle, and a known value of a density of blood.

14. The method of claim 13, wherein calculating a value of a blood flow quantity inside the blood vessel comprises: using Bernoulli's law, the at least three values of cross sectional area of the body, the associated sequences of pressure signals, and a known value of a density of blood, solving a system of two equations, each equation having the form $p_{i} = \frac{v_{0}^{2} .Math.}{2} .Math. (1 - {(\frac{A - A_{0}}{A - A_{2}})}^{2}) + p_{0},$ wherein A.sub.0 is a first of the predetermined values of cross sectional area of the body; A.sub.i is a respective second of the predetermined values of cross sectional area of the body, wherein in the two equations two different predetermined values of cross sectional area are used; A is a value, to be determined, of a cross sectional area of the blood vessel; p.sub.0 is a first pressure value associated with the respective first value of cross sectional area A.sub.0, taken at the respective measuring time corresponding to the identical phase of the heart cycle; p.sub.1 is a second pressure value associated with the respective value of cross sectional area A.sub.i, taken at the respective measuring time corresponding to the identical phase of the heart cycle, wherein in the two equations two different measured values of pressure are used; is the density of the blood; v.sub.0 is the volume flow velocity, to be determined, at the value of cross sectional area A.sub.0 ; wherein the indices 0 and i are arbitrarily allocatable to the different cross sectional area values of the expandable body section and the associated measured pressure values; and wherein determining the blood flow quantity comprises determining a value of a flow rate Q, by calculating
(AA.sub.0)v.sub.0=Q.

15. A computer program comprising executable code for executing a method according to claim 12 when executed by a processor of a computer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0074] In the following drawings:

[0075] FIG. 1A shows an embodiment of a blood flow measurement system for measuring a blood flow quantity inside a blood vessel of a living being using an intravascular blood flow measurement device;

[0076] FIG. 1B shows a cross sectional view of an intravascular blood flow measurement device shown in FIG. 1A, as placed inside a blood vessel;

[0077] FIG. 2A shows the embodiment of a blood flow measurement system using the intravascular blood flow measurement device shown in FIG. 1A being expanded to a larger size;

[0078] FIG. 2B shows a cross sectional view of the intravascular blood flow measurement device shown in FIG. 2A, as placed inside a blood vessel;

[0079] FIG. 3A shows another embodiment of a blood flow measurement system for measuring a blood flow quantity inside a blood vessel of a living being that comprises another embodiment of an intravascular blood flow measurement device;

[0080] FIG. 3B shows a cross sectional view of the intravascular blood flow measurement device shown in FIG. 3A, as placed inside a blood vessel;

[0081] FIG. 4 shows four pressure curves obtained by measuring the pressure of blood flow in a direction perpendicular to the main direction of blood flow over a predetermined time span covering one heart cycle and plotted versus a normalized and shifted heart cycle time.

[0082] FIG. 5 shows an example of curve fitted using the measured pressure values shown in FIG. 4, and plotted as a function of maximum values of the cross sectional areas of the expandable body section at which they were measured; and

[0083] FIG. 6 shows a flow diagram of an embodiment of a method for controlling operation of an intravascular blood flow measurement device.

[0084] FIG. 7 shows a flow diagram of an embodiment of a method for determination of a blood flow quantity inside a blood vessel of a living being.

DETAILED DESCRIPTION OF EMBODIMENTS

[0085] FIG. 1A shows an embodiment of a blood flow measurement system 100 for measuring a blood flow quantity inside a blood vessel 101 of a living being using an intravascular blood flow measurement device 102. FIG. 1B shows a cross sectional view of the intravascular blood flow measurement device 102, as placed inside the blood vessel 101, having a value of cross sectional area given by A.

[0086] The blood vessel 101 has a cross sectional area value A as explicitly indicated in FIG. 1B by an underlined letter A and indirectly indicated in FIG. 1A by a double arrow labeled A indicating the diameter of the blood vessel.

[0087] The intravascular blood flow measurement device 102 comprises a body 103 suitable for placement inside the blood vessel 101 of a living being and extending along a longitudinal direction L that substantially coincides with a main direction of blood flow if the measurement device is well aligned within the blood vessel.

[0088] The presence of the intravascular blood flow measurement device 102 in the vessel 101 alters a value of blood flow velocity. More specifically, the value of the blood flow velocity at a position P depends on an actual value of the cross sectional area of the intravascular blood flow measurement at the same longitudinal position P. The larger the cross sectional area of the intravascular blood flow measurement, the higher the blood flow velocity at that position, and the lower the pressure exerted by the blood flow on the longitudinal position P.

[0089] The intravascular blood flow measurement device 102 includes a body 103, e.g. a guidewire or a catheter that has fixed cross sectional area values along its longitudinal extension in a distal end section 103.a, a proximal end section 103.b, and in a middle section 103.c: The middle section is located between the distal and proximal end sections. The body 103 comprises an expandable body section 104 arranged at the middle section 103.c. The expandable body section 104 has a cross-sectional area perpendicular to the longitudinal direction that is gradually changing in the longitudinal direction L. Provided that the expandable body section presents a predetermined unexpanded size associated with a value of an unexpanded cross sectional area of the expandable body section in an unexpanded state, the expandable body section is controllably and reversibly expandable to assume a respective one of at least two different predetermined expanded sizes associated with at least two respective values of an expanded cross sectional area of the expandable body section. 104. Therefore, the expandable body section 104 is configured to adopt at least three different sizes, at least two of which are expanded sizes.

[0090] In the present embodiment, the expansion and contraction of the expandable body section 104 is achieved using an electro-active polymer (EAP). EAPs exhibit a change in size or shape when stimulated by a suitable electric drive signal, which herein is also referred to as the electrical expansion-control signal. The electro-active polymer controllably changes its size or shape in response to receiving the electrical expansion-control signal. Suitable EAPs include piezoelectric polymers, electromechanical polymers, relaxor ferroelectric polymers, electrostrictive polymers, dielectric elastomers, liquid crystal elastomers, conjugated polymers, ionic polymer-metal composites, ionic gels, polymer gels, etc.

[0091] In the state shown in FIG. 1A and FIG. 1B, the expandable body section 104 is currently set to a size associated with a value of a cross sectional area of A.sub.0, as explicitly indicated in FIG. 1B and indirectly referred to in FIG. 1A by the diameter of the expandable body section at the position P, which is shown by a double arrow that is also labeled A.sub.0.

[0092] A controllable actuator 106 is arranged and configured to provide a suitable drive voltage to the expandable body section 104 to allow expansion one of the at least three sizes (for example either the unexpanded size or one of the at least two expanded sizes), in response to a corresponding size control signal. The size control signal is provided by the control unit 110.

[0093] In other embodiments (not shown), where the expansion and contraction of the expandable body section is achieved by using an inflatable balloon, the actuator 106 is configured to change the size by drive a volume expansion, in particular by pumping a pressurized fluid or gas into or out of the inflatable balloon, depending on whether an expansion or reduction of the volume is currently desired.

[0094] In this case, the blood flows inside the blood vessel 101 at the predetermined longitudinal position P with a blood flow velocity given by v.sub.0.

[0095] A pressure sensor unit comprises, in this particular intravascular blood flow measurement device, a single pressure sensor 108 that is arranged on the body 103 within the longitudinal extension 103.c of the expandable body section 104 at a longitudinal position P. The pressure sensor 108 provides, for each of at least three values of cross sectional area of the body (that include the at least two values of the expanded cross-sectional area of the expandable body section), a respective sequence of pressure signals indicative of a pressure of blood flow in the blood vessel over a predetermined measuring time span defined with respect to a heart cycle period. The sequence of pressure signals are then provided to a flow determination unit 112.

[0096] In the following, additional reference will be made to FIGS. 2A and 2B. FIG. 2A shows the blood flow measurement system 100 using the intravascular blood flow measurement device 102 shown in FIG. 1A with an expanded size of the expandable body sections. FIG. 2B in turn shows a cross sectional view of the intravascular blood flow measurement device 102 shown in FIG. 2A, as placed inside a blood vessel having a cross sectional area value of A.

[0097] Thus, FIGS. 2A and 2B show intravascular blood flow measurement device 102 after having been set to a larger maximum cross-sectional value A.sub.i. In this situation, the blood flows inside the blood vessel 101 at the predetermined longitudinal position P with an increased velocity given by v.sub.i, thus creating a pressure drop at position P when compared to the situation described with reference to FIGS. 1A and 1B.

[0098] The flow determination unit 112 is configured to calculate a value of a blood flow quantity Q as it will be explained in the following.

[0099] The calculation of the blood flow is performed by using the at least three values of cross sectional area of the body, including the at least two values of the expanded cross-sectional area of the expandable body section 104, the respective pressure signals associated with these values, taken at respective measuring times corresponding to an identical phase of the heart cycle, and a known value of a density of blood. For this calculation, Bernoulli's law is used.

[0100] Bernoulli's law states that for two different pressure values p.sub.0 and p.sub.i and two corresponding different flow velocities v.sub.0 and v.sub.i the following equation holds:

[00004] $\begin{matrix} p_{0} - p_{i} = \frac{}{2} .Math. (.Math. v_{i}^{2} - v_{0}^{2}) & (5) \end{matrix}$

[0101] Assuming that the three different sizes of the expandable body section are allocated to cross sectional area values of A.sub.0, A.sub.1 and A.sub.2, which result in blood flow velocities at the position P of the pressure sensor having values v.sub.0, v.sub.1 and v.sub.2 respectively, and that the corresponding sequences of pressure signals indicative of a pressure of blood flow in the blood vessel over a predetermined measuring time span defined with respect to a heart cycle period are given by p.sub.0(t), p.sub.1(t) and p.sub.2(t), the value of a blood flow quantity Q can be calculated from one of the following equations:

(AA.sub.0)v.sub.0=(AA.sub.1)v.sub.1=(AA.sub.2)v.sub.2=Q (6)

[0102] In order to solve any of these equations, the value of A and the value of one of the blood flow velocities have to be determined.

[0103] For that, a system of two equations can be obtained from the previous equations:

[00005] $\begin{matrix} p_{1} = \frac{v_{0}^{2} .Math.}{2} .Math. (1 - {(\frac{A - A_{0}}{A - A_{1}})}^{2}) + p_{0} & (7.1) \\ p_{2} = \frac{v_{0}^{2} .Math.}{2} .Math. (1 - {(\frac{A - A_{0}}{A - A_{2}})}^{2}) + p_{0} & (7.2) \end{matrix}$

[0104] This system can be resolved to obtain the values of A and v.sub.0. Alternatively, other sets of values would lead to corresponding systems of equations that would result in values of A and v.sub.1, or A and v.sub.2.

[0105] Once these values are determined, they can be used as an input for the matching equation (6) to obtain the value of the blood flow quantity Q.

[0106] FIG. 3A shows another embodiment of a blood flow measurement system 300 for measuring a blood flow quantity inside a blood vessel 301. The blood flow measurement system 300 comprises another embodiment of an intravascular blood flow measurement device 302. FIG. 3B shows a cross sectional view of the intravascular blood flow measurement device shown in FIG. 3A, as placed inside a blood vessel 301.

[0107] FIG. 3A shows an intravascular blood flow measurement device 302 that closely resembles the embodiment of FIGS. 1 and 2. The following description focuses on features distinguishing the present embodiment from that described earlier. The intravascular blood flow measurement device 302 comprises a pressure sensor unit 308 comprising two pressure sensors 308.1 and 308.2. The pressure sensor 308.1 is arranged on the body 302 within the longitudinal extension of the expandable body section 304, whereas pressure sensor 310.2 is arranged on the body 302 outside the longitudinal extension of the expandable body section 304. The size of the expandable body section is set by the controllable actuator 306 in response to a corresponding size control signal provided by the control unit 310.

[0108] The flow determination unit 312 receives sequences of pressure signals from pressure detectors 308.1 and 308.2, and is also configured to determine the value of the blood flow quantity inside the blood vessel 102.

[0109] The expandable body section 304 is controllably and reversibly expandable to assume a respective one of at least two different predetermined sizes associated with at least two respective values of a cross sectional area of the expandable body section. The two different predetermined sized can be one non-expanded size and an expanded size or two expanded sizes. The controllable actuator 306 is configured to set the expandable body section to one of the at least two sizes. The pressure sensor unit 308 is configured to provide, for each of at least three values of cross sectional area of the body 302, a respective sequence of pressure signals indicative of a pressure of blood flow in the blood vessel over a predetermined measuring time span defined with respect to a heart cycle period. In the present case, two of the sequences are provided by pressure sensor unit 308.1 at two different associated sizes of the expandable body section 304, whereas the third sequence is provided by sensor 308.2 at a fixed size associated with the cross sectional area value of the body outside the longitudinal extension and given by A.sub.0.

[0110] The intravascular blood flow measurement device 302 thus simultaneously provides two pressure signals obtained at two different longitudinal positions of the measuring head body that have different cross sectional area values (A.sub.0 and A.sub.i in FIG. 3B). The intravascular blood flow measurement device 302 is therefore more robust against variations between heart cycles, since two sequences of pressure values can be provided simultaneously to the flow determination unit.

[0111] The intravascular blood flow measurement device 302 forms, with the control unit 310 and the flow determination unit 312, a particular embodiment of a blood flow measurement system for measuring a blood flow quantity Q or the blood flow velocity vo according to eq. 1-3.

[0112] In operation, particular care has to be taken that the device itself does not limit blood flow. In some blood flow measurement systems, therefore, the evaluation unit is further configured to support safe operation. This can be done using a specific evaluation involving a determination of a fit-error measure. This evaluation is based on using the expandable body section assuming at least three different predetermined expanded sizes.

[0113] Details will be explained in the following with reference to FIGS. 4 and 5. FIG. 4 shows four curves p.sub.0(t), p.sub.1(t), p.sub.2(t) and p.sub.3(t), obtained by measuring the pressure of blood flow in a blood vessel over a predetermined time span covering one heart cycle and plotted versus a normalized and shifted heart cycle time. Each curved is measured while the expandable body section has been set to adopt a different size, given by a value of a maximum cross sectional area at a predetermined longitudinal position of the measuring head body. According to Bernoulli's law, the curves measured at a higher cross-sectional value of the expandable body section show lower pressure values for any given relative time within a heart cycle (e.g. t.sub.c) than those of the curves measured at lower cross-sectional area values.

[0114] The value of flow rate can be obtained by fitting the pressure values obtained at an identical normalized heart cycle time t.sub.c, as it is shown in FIG. 5. FIG. 5 shows an example of a fitted curved according to eq. 4 and using the values p.sub.i(t.sub.c) (for i=0, 1, 2, and 3) shown in FIG. 4 that are plotted versus the cross sectional area value of the expandable body section at which they were measured (A.sub.i, for i=0, 1 2, and 3). The values of the cross sectional area A of the vessel, and of the flow velocity v.sub.0 are thus obtained and can be further used to calculate the flow rate Q according to eq. (6).

[0115] In terms of safe operation, the inventors have recognized that the general form of equations (7.1) or (7.2), given by equation (3) will only fit four or more pairs (p.sub.i, A.sub.i) of cross-sectional area and measured pressure if the flow of blood is not limited by the presence of the intravascular blood flow measurement device. Therefore, a quality value of the fit, such as, but not limited to the mean squared error, can be used as an indicator for measurement error.

[0116] In some embodiments, the blood flow measurement system 300 further comprises a user interface 314 that receives the error output signal and, upon receiving the error output signal, to provide output information to a user. The output information indicates that a blood flow limitation currently induced by the intravascular blood flow measurement device exceeds a predetermined maximum blood flow limitation amount in the blood vessel and thus allows adjusting the settings. Such adjustment can be made by manual control or automatically.

[0117] FIG. 6 shows a flow diagram of an embodiment of a method 600 for controlling operation of an intravascular blood flow measurement device. The method comprises a step 602 in which a size control signal indicative of a respective one of at least two predetermined expanded sizes to be assumed by the expandable body section of the body of the intravascular blood flow measurement device is sequentially provided to the controllable actuator of the intravascular blood flow measurement device. The method also comprises a step 604 in which a provision of sequence of pressure signals by a pressure sensor unit is controlled. The pressure sensor unit comprises at least one pressure sensor arranged on the body of the intravascular blood flow measurement device within a longitudinal extension of the expandable body section. The sequences of pressure signals are provided for each of at least three values of cross sectional area of the body, including the at least two values of the expanded cross-sectional area of the expandable body section. The sequences of pressure signals are indicative of a respective blood flow in the blood vessel over a predetermined measuring time span defined with respect to a heart cycle period.

[0118] FIG. 7 shows a flow diagram of a method 700 for determination of a blood flow quantity inside a blood vessel of a living being.

[0119] The method comprises performing the method 600 for controlling operation of an intravascular blood flow measurement device. Furthermore, the method 700 includes a step 702 in which a value of a blood flow quantity inside the blood vessel is calculated. For this calculation, the at least three values of cross sectional area of the body, the pressure signals associated with the at least three values of cross sectional area of the body and taken at respective measuring times corresponding to an identical phase of the heart cycle, and a known value of a density of blood are used.

[0120] Additionally, in particular embodiments of the method 700, step 702 includes using Bernoulli's law, the at least three values of cross sectional area of the body, the associated sequences of pressure signals, and a known value of a density of blood, solving a system of two equations having the form

[00006] $p_{i} = \frac{v_{0}^{2} .Math.}{2} .Math. (1 - {(\frac{A - A_{0}}{A - A_{i}})}^{2}) + p_{0}$

and determining the blood flow quantity Q by calculating

(AA.sub.0)v.sub.0=Q

or any equivalent equation using a given value of the cross sectional area of the expandable body section and the respective value of the blood flood velocity.

[0121] In summary, thus, a blood flow measurement system for measuring a blood flow quantity inside a blood vessel includes an intravascular blood flow measurement device with a body that comprises an expandable body section. A control unit sequentially provides a size control signal indicative of a respective one of the at least two predetermined expandable sizes to be assumed by the expandable body section. A pressure sensor unit measures respective sequences of blood pressure signals over a measuring time span defined with respect to a heart cycle period. A flow determination unit uses the values of cross sectional area of the expandable body section, the associated pressure signals and a known value of a density of blood, to calculate a value of a blood flow quantity inside the blood vessel based on Bernoulli's law.

[0122] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0123] In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality.

[0124] A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0125] Any reference signs in the claims should not be construed as limiting the scope.

INTRAVASCULAR BLOOD FLOW MEASUREMENT USING DIFFERENTIAL PRESSURE PRINCIPLE AND AN EXPANDING FLOW SENSOR

Inventors

Cpc classification

Classification Explorer

A61B5/0285

HUMAN NECESSITIES

Classification Explorer

A61B5/02035

HUMAN NECESSITIES

Classification Explorer

A61B5/027

HUMAN NECESSITIES

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A61B5/6853

HUMAN NECESSITIES

Classification Explorer

A61B5/0215

HUMAN NECESSITIES

Classification Explorer

A61B5/02158

HUMAN NECESSITIES

Classification Explorer

A61M2025/0002

HUMAN NECESSITIES

International classification

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A61B5/0215

HUMAN NECESSITIES

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A61B5/027

HUMAN NECESSITIES

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A61B5/00

HUMAN NECESSITIES

Classification Explorer

A61B5/02

HUMAN NECESSITIES

Classification Explorer

A61B5/0285

HUMAN NECESSITIES

Abstract

Claims

Description