JP2002513601A - Apparatus and method for identifying and characterizing lesions and therapeutic outcomes by analyzing flow disturbances - Google Patents

Abstract

(57) SUMMARY A medical treatment diagnostic system 1 includes a signal analyzer 10 and a pressure sensor device 4 adapted for use in a biological fluid delivery system, such as a vascular system. The system 1 measures flow disturbances found in a blood vessel to determine characteristics of the vessel wall including stenosis, aneurysm, and signs of treatment outcome (inflation of the balloon, dissection or malposition of the stent). The measured flow disturbance is created by blood flow in the area of atherosclerotic occlusion of the blood vessel. The system 1 of the present invention increases the amount of knowledge available to the treating physician about occlusion size and blood flow volume.

Description

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL FIELD [0001] The present invention relates generally to the field of medical diagnostic equipment and therapeutic evaluation, and more particularly to systems for vascular walls and vessels characterizing lesions.

BACKGROUND OF THE INVENTION Vascular disease is often manifested by reduced blood flow due to atherosclerotic occlusion of the blood vessels. For example, obstruction of the coronary arteries that supply blood to the heart muscle is a major cause of heart disease. Invasive procedures to alleviate arterial occlusion, such as bypass surgery and catheter balloon inflation, are nowadays dependent on the characteristics of the occlusion and the estimation of blood flow through the occluded artery. These estimates are based on measurements of occlusion size and / or blood flow. Unfortunately, current methods of measuring occlusion size and blood flow are low resolution, inaccurate, time consuming, require expertise in interpreting results, and are expensive. And the decision whether to use any of the occlusion mitigation methods and whether to use such methods is often based on incomplete information. Evaluation of treatment outcome is also problematic, where both the opening of the occlusion and the stent location must be evaluated.

[0003] Pressure, flow and geometry are often measured in the cardiovascular system3
There are two variables. Recent advances in probe miniaturization, improved probe sensor frequency response, and computerized processing have opened up a whole new range of pressure, flow, and geometry measurements that were not possible before. .

[0004] Typically, physicians first begin with drug therapy, cardiovascular therapy over catheters (T
CT), coronary artery bypass graft (CABG), or no treatment. Atherosclerotic lesions may have different characteristics.
Some lesions exhibit varying degrees of sclerosis, while others have the characteristics of hyperlipidemia or thrombosis. The characteristics of the lesion along with its proximal and peripheral vascular status are key factors in determining the required therapeutic treatment. Recently, TCT
The number of patients devoted to is increasing. TCT begins with an intervening diagnostic procedure (X-ray angiography), followed by medication, CABG or T
The patient is treated by continuing the CT procedure.

[0005] Numerous methods are available today to treat various lesion types. Some of these methods are given below, side by side, from "softer" to "heavier" in relation to their ability to open sclerotic lesions. Percutaneous intraluminal angioplasty (PTCA), "cutting balloon" angioplasty, directional coronary artery aselectomy (DCA), circulating coronary artery aselectomy (RCA), ultrasonic disruption catheter vessel Formation, Intraluminal Extraction Catheter (TEC) Aselect Me, Rotablator
A) Aselective and excimer laser angioplasty (ELCA). Often, within the lesion, to prevent reocclusion of blood vessels (also known as recoil)
A stent is deployed. If the stent is misplaced, it may stop flow and initiate restenosis.

[0006] The characteristics of the lesions, as well as the proximal and peripheral vascular status of the lesions, are used to determine the choice of a medically and economically optimal treatment method or combination of methods.
X-ray angiography has been the primary diagnostic tool in catheter labs. The physician identifies and locates the lesion, assesses the level of occlusion (usually a percentage of diameter), and qualitatively estimates perfusion according to the "thrombolysis in myocardial infarction" (TIMI) grade, which is determined according to the appearance of the controls. An X-ray angiographic image is used. 0, 1, 2, 3 of the TIMI grade, respectively, without perfusion
Represents minimal perfusion, partial perfusion and complete perfusion, respectively.

[0007] More sophisticated diagnostic tools include qualitative coronary x-ray angiography (QCA), intravascular ultrasound (IVUS) intravascular Doppler velocity sensor (IDVS), and intravascular pressure sensor (IPS). QCA is performed in the image area selected by the doctor,
Calculate geometric properties from X-ray angiographic images.

[0008] IVUS provides accurate geometry data on cross-sectional areas and accurate information on the composition and structure of vessel walls. IDVS is based on residual coronary artery flow (CFR).
2.) provide velocity measurements that allow different phases of occlusion to be distinguished according to criteria; IDVS suffers from inaccuracies due to positional errors in the blood vessels. IPS
Provides a pressure measurement that allows discrimination of various degrees of occlusion according to the FFR (residual partial flow) criteria. X-ray angiography and the elaborate techniques discussed above may be employed prior to and after the therapeutic procedure (finally for evaluation of results and determination of corrective action).

[0009] Unfortunately, the elaborate methods discussed above are not commonly used because of their cost and complexity of operation.

SUMMARY OF THE INVENTION The present invention provides a medical treatment and diagnostic system that includes a signal analyzer and a pressure sensor device adapted for use in a fluid delivery system of a living organism, such as the vascular system. The system measures flow disturbances found in the blood vessel to determine characteristics of the vessel wall including stenosis, aneurysm, and signs of treatment outcome (inflation of the balloon, dissection or malposition of the stent). The measured flow disturbance is created by blood flow in the area of atherosclerotic occlusion of the blood vessel. The system of the present invention increases the amount of knowledge available to the treating physician about occlusion size and blood flow volume. When natural blood flow is too low to induce flow disturbances, flow enhancement methods are used to create measurable flow disturbances, ie, vasodilation (blood flow enhancement), controlled saline. A bolus may be used. Known blood rheological properties may be included in the computational procedure. The method can also be used for bypass graft assessment and heart valves. Finally, the invention can be applied to other biological flow conduits, such as the ureter.

It is an object of the present invention to determine flow disturbance characteristics in blood vessels.

It is a further object of the present invention to detect and characterize partial occlusions or aneurysms in blood vessels or tubular conduits through which fluids flow in the body.

An advantage of the present invention is that it measures blood pressure or blood flow velocity values at multiple points in a blood vessel as a function of time.

Another advantage of the present invention is in assessing the outcome of a clinical treatment, such as detecting a full opening of an occlusion or malposition of a stent.

[0015] Yet another advantage is that the present invention can be used for measurement and determination in blood vessels, but for use in any tubular conduit containing a fluid flow, such as urine flow in the urethra. It can be adopted.

In addition, an advantage of the present invention is that it has a pulsating flow through it that can induce a pulsating flow therethrough for measurement and characterization of the interior narrowed by the buildup of water scale, such as a water pipe. There is also its adaptability which can be used for abiotic conduits.

Features of the present invention include features such as maximum turbulence intensity and spectral bandwidth, which may be calculated and reported as absolute terms or the ratio of a parameter value in a diseased area to a parameter value in a non-lesioned area of the same patient. Calculating and reporting the determined flow disturbance parameters.

[0018] A further feature is to calculate and report the ratio of relevant parameters determined in a normal, stress-free state compared to a high stress state, wherein such a high stress state is determined. One condition is vasodilation induced by the infusion of a vasodilator such as papaverine.

Still other features are biological processes that trigger stenosis, plaque growth,
It consists in characterizing the flow disturbances created in the vessel wall to predict lesion growth, including plaque rupture and angiogenesis.

[0020] Objects, advantages and features of the present invention include at least one pressure sensor device adapted to be insertable into a fluid delivery system, and a pressure connected to and generated by the pressure sensor device. Implemented in a system for measuring turbulence in communication with a biological fluid delivery system that includes a signal analyzer that operates on signals. The signal analyzer operates to measure and record the value of the turbulence intensity.

In one embodiment, the system sensor device includes a plurality of pressure sensors, wherein at least one pressure sensor is a wire. In another embodiment, the pressure sensor is a fluid-filled pressure transducer. The pressure sensor device includes a luminal catheter for positioning the fluid-filled pressure transducer in signal communication with the fluid delivery system.

In another embodiment, at least one of the plurality of pressure sensors is connected to a guide wire.

The system signal analyzer includes a computer adapted to measure and record a fluid delivery system pressure signal according to a first software program. The data is then recorded by off-line post-processing.

[0024] The system signal analyzer also includes a second software program, whereby the computer is adapted to determine a value of turbulence intensity in the fluid delivery system. The turbulence intensity value and the associated measurement may be used to determine stenosis characteristics for the fluid delivery system.

The system is a method for measuring flow disturbances in a biological fluid delivery system, the method comprising: at least one pressure sensor device; and operable by the pressure sensor device to receive a pressure signal. Providing a data acquisition system having a signal analyzer connected thereto; inserting and placing a pressure sensor device at a first location in the fluid delivery system; and measuring pressure at the first location. Moving the pressure sensor device to a second position by a predetermined distance; measuring pressure at a second position; repeating the moving and measuring steps to obtain a plurality of positions; Calculating the spectral bandwidth and turbulence intensity for each of the.

The moving, measuring and calculating steps of the method steps are repeated until the data has exactly the measured characteristics of the turbulence intensity.

In addition, the present invention provides a system wherein the computer is adapted by the second program to determine an aneurysm based on a length of the turbulence zone. Such a system is an evaluation tool for identifying malpositioned stents that are detected by pressure (as well as stenosis) and cause flow disturbances. further,
The system is used for localizing drug delivery when the computer is adapted by the second program to determine shear stress in the vasculature.

Furthermore, if blood rheology is known (mainly for viscosity), the flow disturbance parameters may be either manual or automatic, but may be modified to take account of them. Good.

Finally, the identification and quantification of flow disturbances would be useful in diagnosing the nature and assessing the function of the implant, ie, treating and diagnosing heart valves, both prosthetic implants and tissue valves . Flow perturbation identification and quantification may be useful for bypass grafting, especially for treatment and diagnosis by suture evaluation.

The present invention will be more fully understood from the detailed description below, taken in conjunction with the accompanying drawings, in which like components are designated by like reference numerals.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides methods and systems for determining disturbances in blood vessel flow. Such a determination involves detection and characterization of blood vessels related to stenosis. The determination of flow disturbance is based on the occurrence of vortices in the blood vessel, particularly by measuring and determining the spectral bandwidth of the pressure signal in multiple regions of the blood vessel. As determined here, a wider bandwidth means that there is a large stenosis, while a smaller bandwidth means that there is a smaller stenosis.

The present invention provides medical diagnostic methods and systems including a signal analyzer and a pressure sensor device adapted for use in a biological fluid supply system, such as a vascular system. This system measures turbulence within a blood vessel for the purpose of determining characteristics of the vessel wall, including signs of stenosis. The measured turbulence is caused by reduced blood flow within the area of atherosclerotic occlusion of the blood vessel. The system of the present invention increases the amount of knowledge available to treating physicians about the size of the occlusion and the volume of blood flow.

Next, reference is made to FIG. 1, FIG. 2, FIG. 3, and FIG. 1 and 2 show schematic isometric views of a system for lesion identification and determination of lesion severity, maximum flow rate, maximum velocity, shear stress and shear stress time.

This system is configured and operating according to two embodiments (1 and 2) of the present invention. 3 and 4 are schematic functional block diagrams showing details of the system 1 of FIG. 1 and the system 2 of FIG.

The systems 1 and 2 comprise a pressure sensor catheter or guide wire 4 inserted directly into the blood vessel or through a catheter lumen 3 for measuring the pressure in the blood vessel.
Contains. The type of lumen catheter is available from Medtro, Minneapolis, U.S.A.
Guide catheters, such as the Model 8F Archer coronary guide catheter sold by Nic International Vascular, and the Model Sit sold by Bard Cardiology, USA
diagnostic catheters such as the Eseer diagnostic catheter and Biotroni in the United States
k Model Supreme Fast Exchange PTCA sold by GMBH & Co
It may include a balloon catheter, such as a catheter, or other conventional hollow catheter. System 1 and system 2 include at least one sensor 4.

It will be appreciated that a number of pressure sensor arrangements may be envisioned without departing from the scope of the present invention. For example, in one embodiment, systems 1 and 2 include two (4a, 4b) pressure sensor catheters (not shown) that measure pressure in a blood vessel, or a guidewire. Alternatively, when using two pressure sensors,
As shown in FIGS. 1 and 2, a fluid-filled (FF) pressure transducer 31 is also acceptable and included in a system that replaces one of the two pressure sensors 4A or 4B. In such a case, the FF pressure transducer is connected via the distal end of the guiding catheter 3. In an exemplary embodiment, the pressure sensor 4 is of the type sold as a 3F single pressure sensor model SPC-330A or dual pressure catheter SPC-721, commercially available from Millar Instruments, Texas, USA. It is. Other commercial pressure catheters suitable for diagnostic or combined diagnostic / therapeutic purposes are available under the serial number 1 from Radi Medical Systems, Uppsala, Sweden.
2000, or Cardiometrics, California, USA,
Also suitable for the present invention are such as the 0.014 inch guidewire mounted pressure sensor type sold as a Cardiometrics WaveWire pressure guidewire from Endsonics.

The systems 1 and 2 also include a signal conditioner 23. A signal conditioner of the type suitable for this purpose is a model TCB-500 controller commercially available from Millar Instruments or Radi Medica of Uppsala.
l Systems Systems RadiPressure Wire interface model PW110. The signal conditioner 23 is operatively connected to the pressure sensor 4 to amplify the pressure sensor signal. The system 1 further includes an analog / digital (A / D) converter 28 connected to a signal conditioner 23 and an FF pressure transducer 31 that receives analog signals therefrom. A type of A / D converter suitable for this purpose is the NIE series multi-function I / O model PCI-MIO-16XE-10 available from National Instruments, Austin, Texas. The signal conditioner 23 depends on the particular type of pressure sensor used and is preferably integrated into the data acquisition card of the computer 20 or omitted altogether.

The system 2 of FIG. 2 also includes a standard cardiac catheterization system 22 that performs the function of a monitoring system. A standard cardiac catheterization system of the type suitable for this purpose is the Nihon Kohden model RMC-1100 available from Nihon Kohden, Tokyo, Japan. The signal conditioner 23 and the FF pressure transducer 31 are directly connected to the monitoring system 22. The system 2 further includes an analog / digital (A / D) converter 28 connected to the output of the monitoring system 22 via a shielded I / O connector box 27. A connection box of the type suitable for this purpose is available from Nation, Austin, Texas.
NI Instruments BSC-2090 or NISCB-68, available from al Instruments.

The systems 1 and 2 also include a signal analyzer 20 connected to the A / D converter 28 and receiving the digitized regulated pressure signal from the A / D converter 28. The signal analyzer 20 preferably includes a computer 25 having a user interface connected to the computer 25 and including a display 21 for displaying text numbers and graphs indicating the results of calculations performed by the computer 25. This computer is designated by the reference numeral 26 and is operatively connected to the computer 25 and is connected to a recording device such as a network storage device or a printer which provides a hard copy of the results for documentation and archiving. A / D converter 28 may be a separate device or may be integrated with a data acquisition computer card installed in computer 25 (not shown). The computer 25 processes the pressure data detected by the pressure sensor 4 and collected by the A / D converter 28 or a data collection card (not shown), and converts the text, numerical value, and / or graph data displayed on the display 21. appear.

The computer 25 of the systems 1 and 2 is adapted by using a data recording program that measures and records intra-vascular pressure data. Proceeding with the measurement procedure calculation of the recorded data, in order to determine a check for a given vessel characteristic,
Requires a second program running on computer 25. In another embodiment, the computers 25 of the systems 1 and 2 are adapted by using an online data recording program to measure and record intra-vascular pressure data in real time. Continue with the measurement procedure.

To fully understand the nature and characteristics of software programs, it is necessary to first review the basic principles of vascular fluid dynamics.

In general, the fluid flow in a straight tube is characterized by a Reynolds number R = ud / ν. Here, u is the average flow velocity, d is the pipe diameter, and ν is the fluid viscosity. For steady state flow through a cylindrical tube, the critical Reynolds number R _cr is in the range of 1500-3000. For pulsating flow, the critical Reynolds number is directly related to the frequency parameter α. Therefore, R _cr = K · α, where K is a constant in the range of 250 to 400, α ² = d ² (ω / ν), and ω is the frequency of the pulsating flow.

If the maximum Reynolds number R _max = u _max d / ν is greater than the critical Reynolds number R _cr , the pulsating flow becomes turbulent, and u _max is the maximum flow velocity in one cycle of the pulsating flow. Therefore,

[0044]

(Equation 1) become.

Therefore, in a blood vessel, the transition from laminar flow to turbulent flow is represented by u _max , flow frequency ω
And blood viscosity ν.

[0046]

(Equation 2) , The flow becomes turbulent. In humans, ω is the heart rate. 6 for 1 minute
In the case of a heartbeat frequency of 0 pulse, ω ≒ 2π (1 / sec). Human blood viscosity is ν ≒ 4 · 10 ⁻⁶ (m ² / sec ² ). Therefore, u _{max is} almost 1
. Above 5 m / sec, the blood flow becomes turbulent. In the case of flow separation, the transition to turbulence in the region downstream of the constriction may occur at a lower Reynolds number.

The maximum velocity of a human artery is approximately 1 m / s. If the maximum velocity of the stenotic area is proportional to the cross-sectional area reduction of the vessel, turbulence for a 30% to 50% percent stenosis level may be expected. Percent stenosis is usually defined as the ratio of the cross-sectional area of the stenotic vessel to the nominal (non-stenotic) cross-sectional area of the vessel. Stenosis in the range of 30-50% usually does not result in significant flow reduction. Percent constriction values of less than approximately 50% result in a transition to turbulence only in the flow separation region downstream of the constriction. The separation area is defined as the area between the flow separation and the flow recombination point.

Downstream of the flow separation point, the turbulence intensity of the pressure increases. Beyond the recombination point,
The generation of turbulence stops, and the turbulence intensity decreases. Analysis of the change in turbulence intensity along the longitudinal axis of the blood vessel makes it possible to estimate the axial position of the separation and recombination points. Therefore, the percent stenosis can be estimated from the length of the isolation region.

Using the pressure signal, the pressure turbulence intensity P _t is

[0050]

(Equation 3) Can be calculated using Here, P is a measured pressure signal,

[0051]

(Equation 4) Is the average pressure calculated from the entire measurement cycle.

In the case of turbulence, ω _max / ω = (R / R _cr ) ^3/4 , where ω _max is the frequency of the minimum vortex and ω is the heartbeat frequency. Therefore, ω _max / ω is

[0053]

(Equation 4) Is proportional to The measurement of ω _max for turbulence is related to the value of u _max within the stenosis. If the minimum diameter of the stenosis, d _min, is determined separately, for example, from separately performed QCA data, the maximum shear stress, τ _max , can be approximated by using the equation for straight tube turbulence.

[0054]

(Equation 6) In pulsatile flow, the time of the transition from laminar to turbulent flow, a t _r can be determined experimentally. Using the experimentally determined value of the critical Reynolds number R _cr and the separately obtained value of d _min , the critical velocity u _cr is defined as u _cr = R _cr · ν / d _min . Laminar shear stress tau _cr at the time t _cr, shear stress equation for the case of laminar flow

[0055]

(Equation 7) Can be calculated using Where ρ is the blood density. When the maximum velocity is obtained at the time of the maximum turbulence intensity, the differential coefficient dτ / dt becomes (τ _max −τ _cr ) /
Δt, where τ _max is the maximum shear stress, τ _cr is the laminar shear stress, △
t is the time interval between t _cr and the empirically determined point at which the turbulence intensity reaches its maximum value.

In Vitro Experimental Apparatus Next, reference is made to FIG. 5, FIG. 6 and FIG. FIG. 5 is a schematic diagram illustrating an in vitro experimental apparatus configured and operative to determine simulated non-lesional and diseased vessel flow characteristics according to an embodiment of the present invention. FIG. 3 is a schematic functional block diagram showing the functional details of the system, including the device of FIG. 5 and the devices for data collection, analysis and display.

The fluid system 51 of FIG. 5 is a recirculation system that provides a pulsating flow. This system 51 is based on Harvard Apparatus, Mass., USA.
Includes a pulsatile pump 42 model 1421A pulsatile blood pump commercially available from the company.
However, other suitable pulsating pumps can be used. Pump 42 allows control over rate, stroke volume and contraction / non-contraction ratio. Pump 42 recirculates the distilled water from water tank 15 to water tank 14.

The system 51 further includes a flexible tube 43 immersed in a water bath 44 to compensate for the effects of gravity. The flexible tube 43 is made from latex,
It has a length of 0 cm. Flexible tube 43 simulates an artery. Flexible tube 43
Is connected by a Teflon tube to the pulsation pump 42 and other system components.
All tubes of system 51 have an inner diameter of 4 mm. The bypass tube 45 allows for flow control of the system and simulates a flow split between blood vessels. A Windkessel compliance chamber 46 is at the base of the flexible tube 43 to control pressure signal characteristics. Wind Kessel compliance chamber 47 and flow control valve 48 are distal of flexible tube 43 to simulate the impedance of the vessel bed.

The system 51 of FIG. 5 also includes a flow meter 11 connected to the distal end of the flexible tube 43 and a flow meter 12 connected to the bypass tube 45. The flow meters 11 and 12 are appropriately connected to an A / D converter 28. Flow meters 11 and 12 are Model 111 turbine flow meters commercially available from McMillan, Texas, USA. In some cases, Transonic Sys in New York, USA
An ultrasonic flowmeter model T206 available from tems is used.

Next, reference is made to FIG. 6, which is a schematic sectional view showing a part of the fluid system 51 in detail. An artificial stenosis made with a tube 55 inserted into the flexible tube 43 is described.
The tube 55 is made from one piece of Teflon tubing. Inner diameter 52 of artificial stenosis 55
(Not shown) may be manufactured separately and altered by artificial constrictions having various inner diameters.

The pressures include MIKRO-TIP pressure catheters 57, 58 and 59, a model SPR-524 pressure catheter connected to a model TCB-500 controller available from Millar Instruments, Texas, USA. Measured along the flexible tube 43 using a pressure measurement system. The catheters 57, 58 and 59 are inserted into the flexible tube 43 connected to the distal end of the flexible tube 43 via the connector 10. The catheters 57, 58 and 59 include pressure sensors 24A, 24B and 24C for pressure measurement, respectively. The fluid-filled pressure transducer 31 is connected to the system 51 via the distal end of the guiding catheter 3, which is inserted into the flexible tube 43 via the connector 9. The fluid-filled pressure transducer 31 is connected to the system 51 if an additional pressure reading is required or instead of a defined experimental intravascular pressure transducer.

Next, reference is made to FIG. System 41 includes system 51. System 41 is a signal conditioner 23 commercially available from Millar Instruments.
A model TCB-500 controller is also included. Signal conditioner 23 is suitably connected to pressure sensors 24A, 24B and / or 24C to amplify the pressure signal.

Data collection was performed using PC (Pentium 586) with Na, Texas, USA.
The test was performed in combination with an E-series instrument multi-function I / O board 28 model PC-MIO-16E-4, commercially available from Tional. The I / O board is controlled by Labview graphic programming software available from National Instruments, Texas, USA. Pressure and flow data at 10 second intervals are sampled at 5000 Hz,
Displayed on the monitor during the experiment and stored on the hard disk. The analysis was performed using Matl, commercially available from The Math Works, Mass., USA.
Performed off-line using ab version 5 software.

Method of Implementation The method is based on performing pressure measurements at multiple points along a blood vessel in the area of the stenosis. Knowing the pressure versus time at these points allows for the calculation of flow parameters that indicate the presence of flow disturbance due to stenosis, and to obtain parameters that characterize the stenosis.

The general method is shown in the flowchart of FIG. This method can be performed by using two clinical approaches. One scheme uses a single pressure sensor and the second scheme uses two pressure sensors.

In both cases, the following outputs can be obtained:

1. Lesion Identification and Location The location of the stenosis can be determined by inspection (visual or computerized) of variations in the spectral bandwidth and turbulence intensity of the area around the stenosis. Such fluctuations are an indication of the presence of flow disturbances caused by the constriction.

2. Severity of stenosis The separation area is defined as the area between the flow separation point and the flow recombination point. Analysis of the change in turbulence intensity along the longitudinal axis of the blood vessel allows to approximate the axial position of separation points and flow recombination points. Therefore, the percent stenosis can be estimated from the length of the isolation region.

The percent stenosis can also be determined by the maximum in spectral bandwidth and turbulence intensity, as measured in the area around the stenosis.

[0070] 3. Maximum speed (u _max ) The maximum speed is determined using the following equation.

[0071]

(Equation 8) ω: heartbeat frequency _ωmax : minimum vortex frequency ν: blood viscosity K: constant that can be determined experimentally Maximum shear stress (τ _max ) The maximum shear stress is determined using the following equation.

[0072]

(Equation 9) τ _cr is the laminar shear stress The laminar shear stress at time t _cr τ _cr can be calculated using the shear stress equation for the case of laminar flow.

[0073]

(Equation 10) The critical speed u _cr is defined as follows.

U_cr= R_cr・ Ν / d_min  For pulsating flow R_cr= K1 · α K1 is a constant in the range of 250 to 400.

Α ² = d ² (ω / v) Shear stress derivative (dτ / dt) Assuming that the maximum velocity is obtained at the time of maximum turbulence intensity, the derivative dτ / d
t can be approximated.

Dτ / dt = (τ _max −τ _cr ) / Δt τ _cr is a laminar shear stress.

Δt is the time interval between t _cr (the time that is τ _{cr occurs} ) and the empirically determined point at which the turbulence intensity reaches its maximum value τ _max .

Method 1—Single Pressure Sensor Clinical System Referring now to FIG. 8, which is a cross-sectional view of an artery 30 having an arterial wall 32 and an occlusive stenosis 34. A guiding catheter 3 (or a diagnostic catheter, or any other hollow catheter) is inserted into the vessel of interest. A single guide wire 7 having a pressure sensor 4 at its end is inserted through the catheter and placed at the base point A of the stenosis so that the pressure sensor 4 is located. The catheter, guidewire and pressure sensor are part of the clinical system shown in FIGS.

Data Collection Data is collected by using the clinical system shown in FIG. The steps used to collect the data are as described below. That is, 1. The pressure sensor 4 is inserted into the artery.

2. The pressure sensor 4 is placed in the target area (base point A of the stenosis).

[0081] 3. The pressure at the point A is measured, and then the pressure sensor is moved by a certain distance Δ, and the pressure after the movement is measured.

[0082] 4. Calculate the spectral bandwidth and, for each point (of step 3), calculate the turbulence intensity.

[0083] 5. From the data calculated in step 4, the average of the spectrum bandwidth and the average of the turbulence intensity are calculated. If the difference is large, two more points of data are collected and a new average is calculated. This data will be used as “reference data”.

6 The pressure sensor 4 is again advanced to a new point by a distance Δ (indicated by an arrow with arrows at both ends denoted by Δ in FIG. 9), and the measurement of pressure is performed as disclosed in step 3. Performed (in vitro experiments indicate that the distance Δ required by this method is about 1.5 ÷ 2 cm, but this number may vary slightly in actual arterial stenosis).

[0085] 7. Calculate the spectral bandwidth and turbulence intensity at the new point.

[0086] 8. The value of the turbulence intensity calculated at the new point and the value of the spectral bandwidth are compared with a reference value.

If the calculated values of both these parameters at the new point are close to both the corresponding reference parameter values, the pressure sensor 4 is again advanced by a certain distance.

If the calculated values of both the turbulence intensity and the spectral bandwidth parameter at the new point are greater than the reference value, the pressure sensor 4 returns to the aforementioned point by the distance Δ.

The measurement and calculation process is performed until the calculated values of the turbulence intensity and the spectral bandwidth return to the values measured at a plurality of points initially measured at the base of the stenosis (step 3). Is repeated at successive new points.

Data Analysis and Results When the pressure data is analyzed, turbulence intensity, maximum flow rate, pressure power spectrum and ωmax are obtained. These calculated data are used to determine the value of the location and severity of the stenosis, the maximum velocity, the maximum shear stress and the shear stress time derivative by using the equations and methods described above.

Example 1 Referring now to FIG. 9, there is shown a partial view of the in vitro system shown in FIGS. 5 and 6, modified to take a pressure measurement with a single pressure sensor 24a. It is a schematic diagram. The pressure catheter 3, the guide wires 57 and 58, and their pressure sensors 24b and 24c have been excluded from the system. The dynamic measurement of the pressure pulsation is performed by moving the pressure sensor 24a along points 60 to 71 in FIG. The points 60 to 71 in FIG.
Are located along a common longitudinal axis 72.

With these measurements, the spectral bandwidth and the maximum turbulence intensity are calculated, identifying the location of the stenosis and generating stenosis features such as maximum flow.

The calculated values of the turbulence intensity and the spectral bandwidth of all points are shown as a function of the distance step or as an arbitrary distance along the longitudinal axis of the flexible tube 3 representing the stenosis. .

The location and percentage of the stenosis can be determined visually by the operator of the system, or by computer analysis of the variations in spectral bandwidth and turbulence intensity in the area surrounding the stenosis. Calculated automatically.

Referring now to FIG. 10, there is shown a schematic graph (curve 74) showing the variation in calculated spectral bandwidth as a function of distance from the rigid tube 55 of FIG. The location of the rigid tube is indicated by arrow 73. The vertical axis represents the spectral bandwidth, and the horizontal axis represents the distance along the horizontal axis 72 (FIG. 9) in centimeters. Here, the distance value 0 is equal to the base end 55 of the hard tube 55 which is 2 cm long.
A is arbitrarily selected to correspond to the longitudinal point of A. Positive distance values represent distal points of end 55A, and negative distance values represent base points of end 55A.

Table 1 summarizes the turbulence intensity calculated from the pressure measurement and the calculation result of the spectral bandwidth in the experiment in which the area reduction rate is 44%.

[0097]

[Table 1] It can be seen that no indication of any turbulence is found at the base of the rigid tube 55, which is indicative of a stenosis, nor within that range.

In FIG. 10, a curve 74 is a curve adapted to the point of the calculated value of the spectral bandwidth in Table 1. An increase in the calculated spectral bandwidth value, starting from a distance value of approximately 2 centimeters, indicates that turbulence exists. The value of the spectral bandwidth at and within the base of the rigid tube 55 representing the stenosis is:
About 50 Hz, and the pressure sensor 24A detects the stenosis at the base end 5 of the rigid tube 55.
It does not change much from 5A until it is about 2 centimeters. This type of flow property can be used during the diagnostic process in catheter experiments.

In clinical systems, variations in the value of the spectral bandwidth may result in the physician or the operator of the system either because of their small dimensions or in the limited space of standard X-ray angiography. Because of the resolution, even small stenosis that cannot be detected by X-ray angiography can be detected, located and characterized.

Thus, as shown in FIG. 10 and as evidenced in Table 1, the spectral bandwidth values indicate that there is a flow disturbance distal to the stenosis. As such, the spectral bandwidth value is used to identify areas of stenosis. The above example and FIG. 10 show that the spectral bandwidth due to turbulence occurring distal to the stenosis gives a good indication of the location and characteristics of the stenosis lesion in the artery.

In an in vitro system, the correct position of the sensor 24A can be directly measured. When the preferred embodiment of the present invention is adapted to perform similar measurements in vitro, the position of the tip of the pressure catheter can be determined at the same time that the x-ray angiography data is collected. This positioning is performed with respect to a single known point of the measurement, and the position of all subsequent measurement points can then be calculated from the known distance increment Δ.

Method 2-Dual Pressure Sensor Clinical System Referring now to FIG. 11, a cross-sectional view of an artery 30 having an arterial wall 32 and an occlusive stenosis 34. A guiding catheter 3 (or a diagnostic catheter, or any other hollow catheter) is inserted into the vessel of interest. Two guidewires 6 and 7 having pressure sensors 4A and 4B at their ends are inserted through the guide catheter, one pressure sensor 4A being located at the base point A of the stenosis and another pressure sensor. 4B is positioned to be located at the distal point B of the stenosis. The two pressure sensors are connected to a signal conditioner 23 as shown in FIGS.

FIG. 11A shows another version of this clinical system. The pressure sensor 4A located at the base point A of the stenosis has been replaced by a fluid-filled catheter connected at its outer end to a pressure transducer that calculates the base pressure of the stenosis. A single guidewire 6 having a pressure sensor at its end 4B is inserted through the fluid-filled catheter and the pressure sensor 4B is positioned such that it is located at the distal point B of the stenosis.

Data Collection Pressure measurements are taken simultaneously by two pressure sensors. One pressure sensor at the base of the stenosis calculates the pressure in the laminar flow zone at a fixed point at the base of the stenosis. The other pressure sensor, located distal to the stenosis, is moved in a downstream direction to measure pressure at multiple points along the blood vessel distal to the stenosis. The measurement and calculation process is repeated again, as shown in Example 1.

Analysis of Data When the pressure data is analyzed, turbulence intensity, maximum flow rate, pressure power spectrum and ωmax are obtained. These calculated data are used to determine the value of the location and severity of the stenosis, the maximum velocity, the maximum shear stress and the shear stress time derivative by using the equations and methods described above.

Example 2 Measurement of pressure pulsations was performed using the in vitro system shown in FIGS. At this time, the two pressure sensors 24a and 24b were located on the upstream and downstream sides of the hard tube 55, respectively. The blood vessel was modeled by a flow of distilled water in a flexible tube 43 having an inner diameter of 4 millimeters. The pressure sensor 24A was located at the base one centimeter from the rigid tube. Pressure sensor 24B was located distal to the rigid tube. The flow rate is calculated for each measurement according to the following formula.
It was calculated from the pressure data of the pressure sensors 24A and 24B.

[0107]

[Equation 11] Here, A ₀ is the normal cross-sectional area of the flexible tube 43.

[0108] A _s is a cross-sectional area represented by the inner diameter of the rigid pipe portion 55.

ΔP is the difference between the pressures calculated by the pressure sensors 24A and 24B across the rigid tube representing the stenosis.

Θ indicates the concentration of water.

The constant K _t = 1.52.

The power spectrum of turbulence intensity _Pt and pressure was analyzed for each measurement. The pressure turbulence intensity _Pt is

[0113]

(Equation 12) Is defined as Here, P is a measured pressure signal,

[0114]

(Equation 13) Is the average pressure calculated from the entire measurement period (10 seconds).

Reference is now made to FIG. 12, which is raw pressure data in a typical measurement. This measurement is performed using a rigid tube 55 whose inner area is reduced by 94%. The vertical axis represents pressure in mmHg, and the horizontal axis represents time in seconds. Curve 75 represents the pressure measured (by sensor 24A) at the base of the rigid tube. Curve 76 represents the pressure measured (by 24B) distal to the rigid tube.

Reference is now made to FIGS. 13 and 14, which show curves 7 of FIG. 12, respectively.
FIG. 7 is a graph showing turbulence intensity calculated from raw pressure data of Nos. 5 and 76. FIG.
3 and FIG. 14 represent the turbulence intensity _Pt (in%), and the abscissa represents time (in seconds). Curve 77 in FIG. 13 represents the turbulence intensity calculated from the raw data of curve 75 in FIG. Curve 78 in FIG. 14 represents the turbulence intensity calculated from the raw data of curve 76 in FIG.

FIGS. 15 and 16 show pressure power spectra calculated from the raw pressure data of the curves 75 and 76 in FIG. 12, respectively. The curve 79 in FIG.
1 represents the power spectrum of the pressure calculated from the raw data of the curve 75 of FIG.
The curve 83 of FIG. 6 represents the power spectrum of the pressure calculated from the raw data of the curve 76 of FIG. Here, the vertical axis of FIGS. 15 and 16 is a logarithmic scale.

[0118] The power spectrum of FIG. 16, by representing on semilogarithmic scale, the signal is approximated by two straight lines 80 and 81 intersecting at 82 points representing the frequency omega _{ma x} are produced.

The lines 80 and 81 were manually fitted to the curve 83, but these lines were achieved by known statistical procedures such as least mean squares or by any other suitable method Can be done. The flow rate and its maximum value are calculated from the measured pressure data.

Table 2 summarizes the results of various flow level analyzes performed on the same stenosis (area reduction ratio, 94%).

In another example, the method is performed by using a single transducer moving from point A to point B, which enters the ECG or fill fluid. Transducer metrology turbulence has a high bandwidth (at least 500 Hz). For example, to calculate hemodynamic parameters, it is necessary to apply pressure simultaneously at points A and B at rest and to dilate blood vessels. At points A and B, the pressure at rest is measured, but not simultaneously. Point A or B
While measuring the pressure at a point, time synchronization is achieved by applying the idea that the ECG signal is stable. Therefore, by synchronizing the ECG signals, it is possible to synchronize the pressure signals at points A and B. Synchronization is achieved by applying Algorithm 2 with an ECG signal used instead of the fluid filling pressure signal. In the state where the blood vessel is expanded, it is possible to measure the pressure only at point B (at the downstream side). The dilation of the vessel wall during dilation is negligible at the base point A of the stenosis. Simultaneous pressures at points A and B when the vessel is dilated are calculated.

[0122]

[Table 2] Here, Lb is the distance between the pressure sensor 24B and the distal end of the rigid tube 55 representing stenosis.

As can be seen from the results in Table 2, the turbulence intensity and ω _max change according to the flow rate. The data shown in Table 2 is calculated at the maximum intensity of turbulence. Turbulence intensity, omega _{ma x,} and maximum relationships suggested between flow rate represents a serious stenosis (94%). The flow rate is dependent on the size of the constriction (type), by knowing the turbulence intensity and omega _{ma x,} it is possible to determine the type of stenosis.

Example 3 Pressure pulsations are measured by using the two pressure sensors 24a and 24b by the in vitro system shown in FIGS. The pressure sensor 24a is located two centimeters from the base of the rigid tube and upstream of the rigid tube 55. The pressure sensor 24b has a base at the distal end of the rigid tube portion 55 of 0.5.
It is progressively moved from a point located centimeters to a point 3 centimeters away from the distal end of the rigid tube 55. The blood vessel was modeled by a flow of distilled water in a flexible tube 43 having an inner diameter of 4 millimeters. After each step, the pressure was measured by two pressure sensors.

This procedure was repeated three times using three different rigid tubes (55) with different inner diameters representing different levels of stenosis.

For each measurement, the frequency ω _max was calculated from the pressure data of the pressure sensor 24b.

Table 3 summarizes the results of analyzing this series of simultaneous pressure measurements performed on different sized stenoses (93.75%, 86%, 43.75% area reduction). .

[0128]

[Table 3] Here, Lb is the distance between the pressure sensor 24B and the distal end of the rigid tube 55 representing stenosis.

As can be seen from the results in Table 3, ω _max and turbulence intensity change according to the size of the stenosis. The suggested relationship between ω _max , turbulence intensity, and reduced area of the vessel represents three levels of stenosis. Since ω _max and turbulence intensity depend on the size of the stenosis, knowing these levels can determine the type of stenosis and determine the proportion of stenosis severity.

Certain features and sub-combinations thereof may be used without association with other features or sub-combinations thereof without departing from the scope of the claims herein. Good. Although preferred embodiments and applications of the present invention have been described herein, it is to be understood that the objects and features of the invention are limited only as set forth in the claims appended hereto. Will be apparent to those skilled in the art.

Example 4 Pressure pulsations were measured by placing two pressure sensors 24a and 24b upstream and downstream of a rigid tube 55 by using the in vitro system shown in FIGS. You. The blood vessel was modeled by a flow of 40% glycerin solution in a flexible tube 43 having an inner diameter of 4 millimeters. The pressure sensor 24A was placed at the base 2 cm in a rigid tube. The pressure sensor 24B was placed at a point one or two centimeters from the distal end of the rigid tube.
For each measurement, the flow rate was measured by the system flow meter and the power spectrum of the pressure was analyzed.

Referring now to FIG. 17, FIG. 18, and FIG. 19, FIG. 17 is an example of a single measurement result obtained by a series of measurements. FIG. 17 is a graph showing raw pressure data in a typical measurement. Measurements were taken on a solid tube 55 with 94% internal area reduction.
Was performed using The vertical axis represents pressure in mmHg, and the horizontal axis represents time in seconds. Curve 85 shows the pressure measured (by sensor 24A) at the base of the rigid tube. Curve 86 shows the pressure measured (by sensor 24B) distal to the rigid tube.

FIGS. 18 and 19 are graphs respectively showing the power spectra of the pressure calculated from the raw pressure data of the curves 85 and 86 in FIG. The curve 87 in FIG. 18 represents the power spectrum of the pressure calculated from the raw data of the curve 85 in FIG. 17, and the curve 88 of FIG. 19 represents the power spectrum of the pressure calculated from the raw data of the curve 86 in FIG. Represents. Here, the vertical axis in FIGS. 18 and 19 is a logarithmic scale.

[0134] The power spectrum of FIG. 19, by representing on semilogarithmic scale, the signal is approximated by the frequency omega _{ma x} intersect at 91 points representing in which two straight lines 89 and 90 are produced.

The lines 89 and 90 were manually fitted to the curve 88 by a rule of thumb, but these lines could be fitted by known statistical procedures such as least mean squares or by any other suitable method. Can be achieved by the method.

Table 4 summarizes the results of the analysis of various flow levels performed on different stenosis (area reduction ratio, 94% and 75%).

[0137]

[Table 4] Here, Lb is the distance between the pressure sensor 24B and the distal end of the rigid tube 55 representing stenosis.

The purpose of these test examples is to demonstrate the presence of the effects of fluid disturbances caused by stenosis in fluids having a viscosity value almost similar to that of blood and the ability to detect it. . As can be seen from the results in Table 4, flow disturbances were detected distal to the stenosis for medium severity stenosis types (94% and 75%). For low flow levels (approximately 100 ml / sec), the degree of disturbance is light,
For higher flow levels, the degree of disturbance will be severe. 100ml /
No disturbance was detected for flow rates less than a second. Above spelled out omega _{m ax,} also the relationship that has been suggested between maximum flow and constriction of the levels, using distilled water are shown related to glycerol. The use of a glycerin solution shows a damping effect that only in more severe stenosis above normal physiological levels and higher flow levels will flow delays occur to occur. This means that an artificial increase in flow rate occurs in the clinical system. One common method already used in the field is to use a dilatation of blood vessels that can increase the flow rate sufficiently to detect flow disturbances.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a system for lesion identification, lesion severity, maximum flow rate, maximum velocity, shear stress and shear stress time determination, etc., guided, configured and operating in accordance with a preferred embodiment of the present invention. FIG.

FIG. 2 illustrates a system for lesion identification and lesion identification, determination of lesion severity, maximum flow rate, maximum velocity, shear stress and shear stress time guided, configured and operating in accordance with another preferred embodiment of the present invention. FIG. 3 is a schematic isometric view.

FIG. 3 is a schematic functional block diagram showing details of a system 1 of FIG. 1;

FIG. 4 is a schematic functional block diagram showing details of a system 1 of FIG. 2;

FIG. 5 is a schematic isometric view of an in vitro system constructed and operating in accordance with a preferred embodiment of the present invention.

FIG. 6 is a schematic detailed view of the in vitro tubing system 51 of FIG.

FIG. 7 is a schematic diagram of an in vitro system with its control and monitoring devices.

FIG. 8 is a detailed schematic diagram of a clinical system that uses a single pressure sensor to indicate the initial position of the sensor in a blood vessel.

FIG. 9 is a detailed schematic diagram of the clinical system shown in FIG. 8 during an operation;

FIG. 10 is a schematic graph showing the variation of the calculated spectral bandwidth value as a function of distance from the rigid tube of FIG. 9;

FIG. 11 is a detailed schematic diagram of a clinical system using two pressure sensors.

FIG. 11A uses a fluid-filled pressure sensor to replace the base pressure sensor of FIG. 11,
2 shows another version of one clinical system.

FIG. 12 is a graph showing typical raw pressure data as measured in an in vitro system using two pressure sensors.

FIG. 13 is a graph showing turbulence intensity calculated from the unused pressure data of curve 75 in FIG.

14 is a graph showing turbulence intensity calculated from the unused pressure data of curve 76 in FIG.

FIG. 15 is a graph showing a pressure power spectrum calculated from the unused pressure data of curve 75 of FIG.

FIG. 16 is a graph showing a pressure force spectrum calculated from the unused pressure data of curve 76 of FIG.

FIG. 17 is a graph showing typical measured raw pressure data as measured in an in vitro system using two pressure sensors and a glycerin solution.

18 is a graph showing a pressure force spectrum calculated from the curve 85 and the unused pressure data of FIG.

19 is a graph showing a pressure force spectrum calculated from the curve 86 and the unused pressure data of FIG.

FIG.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR , BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS , JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZA, ZW Tel Aviv, A Delim Street 5/4 (72) Inventor Noskowix, Simon Henry Israel 44444 Kufa Saba, Herzl Street 22/22 (72) Inventor Barak, Chien Israel , 73142, Shiyoham, Bareckett Street, 18 (72) Inventor, Otenberg, Michael 40300 Kufa Jona, Israel, Hargeneb Street 60/2 F term (reference) 4C017 AA07 AA 08 AA11 AC03 BC01 BC11

Claims (36)

[Claims] 1. A system for measuring flow disturbances in a biological fluid delivery system, comprising: at least one pressure sensor device adapted to be inserted into the fluid delivery system; and And a signal analyzer operable on the pressure signal generated by the pressure sensor device, the signal analyzer operative to measure and record the value of the turbulence intensity. , A system for measuring flow disturbances. 2. The system of claim 1, wherein said at least one pressure sensor device includes a plurality of pressure sensors. 3. At least one of the plurality of pressure sensors is a fluid-filled pressure transducer, and the at least one pressure sensor device is for positioning the fluid-filled pressure transducer in signal communication with the fluid delivery system. 3. The system of claim 2, comprising a lumen catheter. 4. The system according to claim 2, wherein at least one of the plurality of pressure sensors is connected to a guide wire. 5. The system of claim 4, wherein the at least one pressure sensor device includes a signal conditioner operably connected to the pressure sensor. 6. The system of claim 1, wherein said signal analyzer includes a digital-to-analog converter connected to said at least one pressure sensor device. 7. The signal analyzer according to claim 1, wherein said signal analyzer is an analog-to-analog converter connected to said signal conditioner.
The system of claim 5, including a digital converter. 8. The system of claim 1, wherein the signal analyzer includes a computer adapted to measure and record a pressure signal of the fluid delivery system with a first software program. 9. The signal analyzer includes a second software program,
The system of claim 1, wherein the computer is adapted to determine a value of turbulence intensity in the fluid delivery system. 10. The system of claim 9, wherein the computer is adapted by the second program to determine a stenosis value based on the turbulence intensity value. 11. The system of claim 9, wherein the computer is adapted by the second program to determine a flow frequency ω _max in a region of turbulence. 12. The system of claim 11, wherein the computer is adapted by the second program to determine a value of a stenosis based on a frequency of disturbance of the flow. 13. The system of claim 9, wherein the computer is adapted to determine a length of the turbulence zone according to the second program. 14. The system of claim 13, wherein the computer is adapted by the second program to determine a value of a stenosis based on a length of the turbulence zone. 15. The fluid delivery system is a vasculature and the computer is adapted by the second program to determine a value of a stenosis based on a flow frequency in a target blood vessel. 10. The system according to 9. 16. The fluid delivery system is a vasculature, and the computer is adapted to determine, by the second program, a value of stenosis based on a value of turbulence intensity along a target blood vessel. 10. The system of claim 9, wherein the system is configured. 17. The system of claim 9, wherein the fluid delivery system is a vasculature, and wherein the computer is adapted to determine a maximum velocity in the vasculature according to the second program. . 18. The system of claim 9, wherein the fluid delivery system is a vasculature, and wherein the computer is adapted to determine the shear stress in the vasculature according to the second program. . 19. The fluid delivery system is a vasculature, and the computer determines, by the second program, a shear stress time derivative that indicates a risk of plaque fragility in the vasculature. 10. The system according to claim 9, adapted for: 20. A method for measuring turbulence in a biological fluid delivery system, comprising: at least one pressure sensor device; and a signal operably connected to the pressure sensor to receive a pressure signal. Providing a data collection system having an analyzer; inserting and positioning the pressure sensor device at a first location in the fluid delivery system; measuring pressure at the first location; Moving the pressure sensor device to a second position by a predetermined distance; measuring pressure at the second position; repeating the movement and measurement steps to obtain a plurality of positions; Calculating the spectral bandwidth and turbulence intensity for each of the turbulent flows. . 21. The method of claim 20, further comprising calculating an average spectral bandwidth and an average turbulence intensity. 22. The method of claim 21, further comprising determining whether additional position measurements are required, and measuring pressure at at least one additional position. 23. The method of claim 22, wherein said determining comprises checking for high data variance. 24. The method of claim 22, further comprising calculating spectral bandwidth and turbulence intensity for the additional location. 25. The method of claim 24, further comprising comparing the spectral bandwidth and turbulence intensity values of the additional locations to the averaged values. 26. The method of claim 25, further comprising determining whether a further position is to be measured and repeating the measuring, calculating and comparing steps for the further position. 27. The method of claim 26, further comprising determining whether the measurement should be repeated. 28. The method of claim 27, wherein said moving and measuring steps are repeated. 29. The method of claim 1, comprising using the turbulence intensity value to determine the severity of a stenosis. 30. The method of claim 1, comprising using the value of ω _max to determine the severity of the stenosis. 31. The method of claim 1, comprising determining the severity of the stenosis by the length of the turbulence zone. 32. The method of claim 1, wherein the pressure measurement is in a blood vessel, and the method includes determining a location of a stenosis using a turbulence intensity value along a target blood vessel.
The method described in. 33. The method of claim 1, wherein the pressure measurement is in a blood vessel, and the method includes determining a location of a stenosis using a value of ω _max along a target blood vessel.
The method described in. 34. The method of claim 19, comprising determining a maximum speed. 35. The method of claim 1, comprising determining a shear stress. 36. The method of claim 1, comprising determining a shear stress time derivative.