NZ613148B2 - Apparatus and method of characterising a narrowing in a fluid filled tube - Google Patents
Apparatus and method of characterising a narrowing in a fluid filled tube Download PDFInfo
- Publication number
- NZ613148B2 NZ613148B2 NZ613148A NZ61314812A NZ613148B2 NZ 613148 B2 NZ613148 B2 NZ 613148B2 NZ 613148 A NZ613148 A NZ 613148A NZ 61314812 A NZ61314812 A NZ 61314812A NZ 613148 B2 NZ613148 B2 NZ 613148B2
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- NZ
- New Zealand
- Prior art keywords
- tube
- sensor
- measurement
- probe
- location
- Prior art date
Links
- 239000012530 fluid Substances 0.000 title description 17
- 238000005259 measurement Methods 0.000 abstract description 44
- 239000000523 sample Substances 0.000 abstract description 30
- 200000000009 stenosis Diseases 0.000 abstract description 23
- 230000036262 stenosis Effects 0.000 abstract description 23
- 210000004204 Blood Vessels Anatomy 0.000 abstract description 2
- 238000009530 blood pressure measurement Methods 0.000 description 12
- 238000000034 method Methods 0.000 description 9
- 230000000747 cardiac effect Effects 0.000 description 6
- 210000001367 Arteries Anatomy 0.000 description 5
- 230000001435 haemodynamic Effects 0.000 description 5
- 240000005511 Pisonia aculeata Species 0.000 description 4
- 238000002399 angioplasty Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 239000003550 marker Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 206010020565 Hyperaemia Diseases 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 101710034857 ATIC Proteins 0.000 description 1
- 229920000181 Ethylene propylene rubber Polymers 0.000 description 1
- 230000004872 arterial blood pressure Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000000271 cardiovascular Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 201000000057 coronary stenosis Diseases 0.000 description 1
- 230000001186 cumulative Effects 0.000 description 1
- 238000002059 diagnostic imaging Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000001361 intraarterial administration Methods 0.000 description 1
- 238000010845 search algorithm Methods 0.000 description 1
- 230000000153 supplemental Effects 0.000 description 1
- 238000004450 types of analysis Methods 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/02007—Evaluating blood vessel condition, e.g. elasticity, compliance
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/021—Measuring pressure in heart or blood vessels
- A61B5/0215—Measuring pressure in heart or blood vessels by means inserted into the body
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
- A61B5/107—Measuring physical dimensions, e.g. size of the entire body or parts thereof
- A61B5/1076—Measuring physical dimensions, e.g. size of the entire body or parts thereof for measuring dimensions inside body cavities, e.g. using catheters
Abstract
system and method for characterising a narrowing or stenosis in a blood vessel is disclosed. Assessment or measurement of the constriction is helpful to review the extent and location of the constriction. The system includes a probe (6) having a first measurement sensor (7) to take an instantaneous measurement at different locations along the tube and a mechanism to draw the probe through the tube. Position (D1-3) is measured to provide data (P1-4) relating to the location at which a respective instantaneous measurement is taken by the first measurement sensor. The system may have a further sensor (9) so that two instantaneous measurements are taken, one by the further sensor at a substantially constant location along the tube and another by the first sensor at different locations along the tube. The line or wire between the two sensors is used to draw the probe through the tube to alter the distance between the first sensor and the second sensor. This information is used to calculate a characteristic, such as the instantaneous pressure ratio, of the tube at different locations along the tube which is useful in identifying a location for a stent. s measurement at different locations along the tube and a mechanism to draw the probe through the tube. Position (D1-3) is measured to provide data (P1-4) relating to the location at which a respective instantaneous measurement is taken by the first measurement sensor. The system may have a further sensor (9) so that two instantaneous measurements are taken, one by the further sensor at a substantially constant location along the tube and another by the first sensor at different locations along the tube. The line or wire between the two sensors is used to draw the probe through the tube to alter the distance between the first sensor and the second sensor. This information is used to calculate a characteristic, such as the instantaneous pressure ratio, of the tube at different locations along the tube which is useful in identifying a location for a stent.
Description
Title: Apparatus and method of characterising a narrowing in a fluid filled tube
Field of the invention
This invention relates to an apparatus and method of characterising a
narrowing in a fluid filled tube.
Background to the invention
An example of a fluid filled tube or vessel formed with a constriction or
narrowing is a blood vessel having a is. Assessment or measurement
of the constriction is helpful to review the extent and location of the
constriction.
A methodology for assessment of a constriction in a fluid filled tube such as a
coronary stenosis is onal flow e (FFR). This technique measures
the drop in pressure at two points along a vessel; see Figure 1 of the
accompanying drawings where e points P1 and P4 identify where
measurements of pressure and flow rate can be taken, under conditions of
maximal achievable hyperemia in a coronary environment. The Pd
measurement comes from a pressure sensor on the wire and the Pa
ement comes from the catheter. A comparison is then made by
expressing the mean distal pressure (Pd), as a proportion of mean proximal
pressure (Pa), n the values are mean Pa and Pd over the entire cardiac
cycle, taken over at least one complete cardiac cycle (but usually an average
of 3 or more beats):
WO 93260 2012/050015
F‘s‘actémmé Fémv fissewe {FFRJ = P;
It is an object of the invention to provide an apparatus and method of profiling
or characterising a narrowing in a fluid filled tube.
One aspect of the present invention provides system for characterising a
narrowing in a fluid filled tube, the system comprising: a probe having a first
measurement sensor to take an instantaneous measurement at different
locations along the tube; a mechanism to draw the probe through the tube; a
position measure to provide location data relating to the location at which a
respective instantaneous measurement is taken by the first ement
sensor; a sor to calculate, from the instantaneous measurements, a
characteristic of the tube at different locations along the tube.
Another aspect of the present invention provides a probe for assessing a
characteristic of a fluid filled tube comprising two measurement sensors
spaced apart by a known distance and a line between the two sensors, the
line being drawable through the tube to alter the known distance between the i
first sensor and the second sensor.
A further aspect of the present invention provides a method of characterising a
ing in a fluid filled tube using a probe having a sensor, comprising:
drawing the probe within the tube along the tube; recording probe sensor
readings at different locations along the tube; and calculating, from the
instantaneous measurements, a teristic of the tube at ent locations
along the tube.
A yet further aspect of the present invention es a probe for assessing a
teristic of a fluid filled tube comprising two measurement sensors and a
line between the two sensors, the line being drawable through the tube to alter
the distance between the first sensor and the second sensor.
Brief description of the drawings
In order that the present invention may be more readily understood,
embodiments of the invention will now be described with reference to the
anying drawings, in which:
FIGURE 1 is a schematic diagram of a series of constrictions in a fluid filled
tube, where P is pressure, R is a ratio of the pressures and D is the distance
between measurements;
FIGURE 2 is a schematic diagram of a system embodying the present
invenflon;
FIGURE 3 is a schematic diagram of part of the system of figure 2 located in a
fluid filled tube;
FIGURE 4 is a plot created using a method embodying the t invention
illustrating the IPR for a length of artery;
FIGURE 5 is a point-by—point constriction intensity map generated following
one embodiment of the t invention and based on the Figure 4 data, in
this example, the point—by—point ment is of a stenosis in an artery,
where Do is the start of a recording, D1 is a point at the start of high stenosis
intensity, 02 is a point at the end of high stenosis intensity and 03 is the end of
the recording;
FIGURE 6 is a plot d using a method embodying the present invention
illustrating the IPR for a length of artery and a likely site for a stent along the
tube between locations D1 and D2;
FIGURE 7 is a plot illustrating the likely effect on the same characteristic, IPR,
on the artery after a hypothetical angioplasty procedure of locating a stent
along the tube between locations D1 and D2 together with a plot of the
ed values of lPR obtained using a method embodying the present
invention; and
FIGURE 8 is a flowchart showing operation of a system embodying the
present invention incorporating a feedback procedure.
FIGURE 9 is a tic diagram of another system embodying the present
invenfion.
Description
This invention provides an apparatus and method of profiling or characterising
a narrowing in a fluid filled tube. The apparatus and method of profiling or
characterising is also useful to characterise or profile a series of narrowings in
a fluid filled tube.
Referring to Figure 2, a system 1 embodying the ion for characterising a
narrowing in a fluid filled tube comprises haemodynamic equipment 2
ing a processor 3, a catheter 4, a motor drive 5 and an intra—arterial
probe 6 such as an arterial pressure wire (WaveWire or Combowire
(Volcano Corp.) or Radi pressure wire (St Jude Medical) with a pressure
measurement transducer or sensor 7 — Le. a device measuring re (P).
Preferably, the probe 6 comprises the wire and the sensor 7 integrated in the
wire. The sensor 7 is shown in situ in Figure 3.
The processor 3 analyses and operates on the measurements taken by the
sensor 7. A signal line 8 relays the pressure measurement signal from the
sensor 7 to the processor 3. The signal line 8 is illustrated both as a wired
connection 8 and as a wireless connection 8’ from either the motor drive 5, the
catheter 4 or direct from the transducer 7 — any configuration is available.
The processor 3 operates on the measurements received from the transducer
7 in accordance with a number of algorithms which are discussed in greater
detail below.
The sensor 7 is a pressure measurement sensor but other forms of sensor are
envisaged; flow s, for example. Additionally, a tive sensor for
measuring or ating a thickness of an arterial wall is within the scope of
the ion.
The system 1 may be provided in the following configurations or combination
of configurations, but these are not an exhaustive list of configurations:
i. a stand-alone device incorporating a probe with pressure
measurement capacity in wired connection with a processor
to e on-device analysis;
ii. a device incorporating a probe with pressure measurement
capacity in wireless connection with a processor to provide
is at the processor;
iii. a stand-alone device incorporating a probe with pressure
measurement capacity and a data storage device operable to
record measurement data for real time or subsequent
ication to a processor to e analysis at the
processor (real time and/or off—line); and
iv. a device incorporating a probe with pressure measurement
capacity in wireless connection with a data storage device
operable to record measurement data for real time or
subsequent communication to a processor to provide
is at the processor (real time and/or off-line).
in the c environment where the system 1 is configured as part of
haemodynamic equipment, the system is configured using the processor 3 in
the haemodynamic equipment, such as in McKesson equipment — Horizon
CardiologyTM, a cardiovascular information system (CVIS). The processor can
be configured as supplemental to the haemodynamic ent. Such
configurations are ularly effective for the equipment processor to perform
off-line analysis of the pressure data.
The system 1 can be used in combination with other haemodynamic
equipment, medical imaging equipment and/or ient marker location
equipment.
The system is used for ing or characterising a narrowing in a fluid filled
tube. An example of the use of such a system is in the cardiac environment
when the tube is an artery and the narrowing/restriction/constriction in the tube
is a stenosis.
The basic system components are: the probe 6 having a measurement sensor
7 to take an instantaneous measurement at ent locations along the tube;
the motor drive 5 to draw the probe 6 at a predetermined rate through the
tube; and the processor 3 to calculate, from the taneous measurements,
a characteristic of the tube at different locations along the tube. In this
example a particularly useful measurement to sense is that of pressure as a
pressure drop results following the fluid passing through a restriction.
A profile or ment of a restriction to flow is made by expressing the ratio
of distal to proximal pressures within the tube. This measures the total
2012/050015
restriction to flow across all stenoses along the length of the tube from position
D1 to D3 where the tive pressure measurements are taken and
expressed as a ratio (P4 / P1) either with or without conditions of maximal
hyperaemia.
in addition to calculation of the total restriction to flow along a , it is
possible to calculate the instantaneous pressure drop across an individual
stenosis from the ratios of pressure in segments D distance apart. For
example the ratio of fall in re over distance 03 is:
Instantaneous- Press-1m? ratio {83) = I31
which is approximately identical to the normalised instantaneous pressure
ratio (anR):
, , . f ;
Newmétsad f2:5ta:s-ttaott5 Pressure Rem: {R‘s} = 1 £33
In one example, there are two measurement sensors displaced from one
another — see Figure 3. This system 1 has a further sensor 9 so that two
instantaneous measurements are taken, one by the further sensor 9 at a
substantially constant location along the tube and another by the first sensor 7
at different locations along the tube. The line or wire between the two s
is drawable through the tube to alter the distance between the first sensor and
the second sensor. One sensor (9 in this example) is fixed at the substantially
nt location. The other sensor (7 in this example) moves relative to the
one sensor 9. The “fixed” sensor 9 is located at the end of the catheter 4 from
which the wire 6 carrying the other sensor 7 es. The probe sensor 7
therefore moves relative to the fixed sensor 9. The measurements are
normalised with respect to the measurements taken at the substantially
constant or fixed location.
The normalised instantaneous pressure ratio is more robust, as each distal
value is ised to the proximal aortic pressure, thus making comparisons
along the length of the vessel more reliable as perturbations in te
pressure are minimised.
Systematically moving back along the vessel, at ty U, and logging the
instantaneous measurements alongside the draw distance for the probe create
a pressure ratio (R1, R2, and R3 etc.) for each position (D1, D2, and D3 etc.) as
shown in figure 5. The profiling or assessment of stenosis can be performed
using either the normalised instantaneous pressure ratio or the instantaneous
pressure ratio.
In one e, the predetermined rate of draw through the tube of the probe
is a known and preferably constant speed. The draw is a known velocity draw
to allow instantaneous pressure measurements to be taken as the probe is
being drawn along the tube, for those measurements to be recorded as
pressure measurements and for a pressure ratio to be calculated for each
position of the probe along the tube.
The motor drive 5 is controlled, ably by the processor 3, to draw the
probe 6 back toward the catheter 4. The control may involve use of a
feedback loop.
The atic assessment of pressure along a vessel is med by
withdrawing the pressure sensor, at velocity U. Pressure is recorded at each
location. It is le to minimise error and to speed up the acquisition phase
by using a feedback loop. in this feedback loop, the sensor is positioned in the
tube, and then attached to the variable speed motor drive, or stepper motor.
After sampling for a period of X seconds to establish a baseline for the
PCT/G32012/050015
measurements being taken and characteristics calculated, in this case NlPR
or IPR mean and standard deviation moving averages, the motor drive
commences pullback of the probe at velocity U. ng can also be over a
fraction or specific time point of a beat.
Using high sampling frequencies and an appropriate sensor with a suitable
frequency response, the pullback velocity U can be made faster by looking at
a partial cardiac cycle in a single beat over a known ce.
Pressure measurements are fed to the sor in the control console, and
IFR or anR is calculated. This live pressure is compared t the moving
average mean and standard deviation for the proceeding n beats, in a cardiac
environment. if the live pressure data falls within the tolerance threshold, the
motor continue with the pullback. If however the live pressure data falls
outside of the tolerance old, the motor is paused and further
measurements of pressure are made. Once pressure ement falls
within the nce threshold the motor continues with the pullback. A serial
assessment or profile is created by this method. The feedback loop e
is illustrated in Figure 6.
in another example, the draw is stepped through the tube with at least one
instantaneous measurement being taken at each location along the tube. The
probe is then drawn through the tube for a predetermined distance, stopped
and then another at least one instantaneous ement is taken at the next
location and so on. Preferably but not necessarily, the predetermined distance
is a constant distance.
Each instantaneous measurement is logged as being at a respective location
or with respect to a draw distance.
An alternative system embodying the invention has a position sensor fitted
which monitors the position of the pressure sensor wire whilst being pulled
back through the tube. In this way, each distance point/position/Iocation
would be linked or cross-referenced to a specific pressure measurement.
ically, the position sensor monitors the guide wire holding the re
sensor.
Referring now to figure 9 r embodiment of the system is described
which may operate with or t a motor drive 5. in the embodiments shown
in figure 2, the system relies upon the motor to operate in a known way to
determine the distance x along the line 6 to the sensor 7. Other mechanisms
for determining the distance x to the sensor from a known point, usually on the
catheter, may be used to take measurements at different known positions of x.
In a purely manual version of the system, the line 6 may be drawn back
through the catheter 4 manually and gs on the line 6 in the form of
physical indicia can convey the ce x to the user. The system takes the
position measure by reading the markings or marker on the probe. The
marker may be a visible indicator read by a laser position indicator.
A semi-automatic version of the system can use a manually drawn line 6
through the catheter 4 and a combination of i) an RF reader 10 positioned
preferably at the head of the catheter 4 from which the line 6 projects a
distance x out of the er 4 and ii) multiple RF tags 11 positioned along the
line 6. The line 6 is provided with a series of equispaced passive RF tags 11
each having an individual identifier which is read when in close (if not only
ate) proximity to the reader 10. in one embodiment, the RF tag reader
is in a coincident position with the second sensor 9 mounted at the head of
the catheter 4. Coincidence of these two elements is not essential. More than
one RF tag reader 10 can be used on the catheter.
A lookup table stored locally or in the processor 3 takes the read information
from the reader 10 and identifies the tag adjacent the reader 10 for example
as tag 110 and identifies from the lookup table that tag 110 which is positioned
at the reader 10 is a distance x away from the sensor 7 along the line 6
meaning that the sensor 7 is at known position P12 The line is then drawn
through until another RF tag 11 is read by the reader 10 at which point that tag
is identified, its position is known as being at the reader 10 and the distance
from that tag to the sensor 7 is also known so the position of the sensor 7 is
known. This process is repeated and tags 11 are identified, the sensor 7
on is identified as known and at least one measurement is taken at the
known position.
Preferably, the RF tags 11 are aced along the line 6 but they need not
be equispaced as their positions along the line 6 relative to the sensor 7 is the
only essential data to be associated with each tag. This essential data need
not be present at the time the measurements are taken. Measurements can
be taken and logged against each RF tag identifier and then subsequently the
line can be measured to provide the relative on information for each tag
and then that position information is associated with the measurement taken at
each tag.
Preferably, the RF tags 11 are passive RF tags. The RF tags 11 could be
active RF tags powered by a conductor in the line 6.
Examples of the ion allow a serial assessment of pressure ratio along a
vessel. A rate of change of re or a rate of change of pressure ratio is
further calculated to provide a measure of stenosis intensity. The rate of
change in pressure or stenosis intensity at any position is ated as
which can be plotted as a point-by—point stenosis intensity map as shown in
Figure 4.
sts t-t’ttea’tstfiy =
A systematic assessment is made at rate U over time t, (known velocity
example) so it is possible to ate the withdrawal distance and thus the
physiological stenosis length. in this example, this is the length ) a
segment which has the greatest physiological impact. The characteristic of
the tube or further characteristics derived from the characteristic of the tube
can be ed and thresholded. This process can be automated using a
search algorithm which looks for points at which the IPR or anR s a
given threshold (in this example D1 and D2).
physiciagécai stenosis Magi}; = :93 — i),
The characteristics and/or derived characteristics are used to assess or profile
the tube to identify the length and/or location of a ing of the tube along
the tube length. The use of thresholding techniques for the various
characteristics and/or derived characteristics identifies regions of the tube
where the thresholds are exceeded allowing fication and locating of
stenosis and their length.
An example of a derived characteristic of the tube is the cumulative burden on
the tube caused by a narrowing in the tube. It is possible to calculate the
individual stenosis burden or is occlusive value (with time points D1 start
of a stenosis, and D2 end of a stenosis):
fittstazrttartea'tss sfertssts banter: = f EPR
sism instantanemm stenosis burden = g1 MP}?
and total stenosis burden (over time points Do to 03) for the entire vessel,
ne-mmiésad taméf 5?- masts harder = f it! FR
l angioplasty assessment is enabled by examples of the present
invention. Referring to Figure 6, a systematic assessment approach is d
and the measured profile is displayed. The segment of tube to which a stent
or other angioplasty is to be applied (having a high stenosis grade (D1—D2)) has
its profile characteristic estimated with the stent d and then subtracted
away on an individual segment basis to give a compensated profile as shown
in Figure 7. It is therefore possible to assess the effects of angioplasty on IPR
of anR prior to treatment.
Virtuai nglfiu
.g}: ;2: ipgfia.“ g: + -R..._.5§&
Eff-raise} niPR‘I)G,Am m niFflgwgs + fimPR‘ne...m
Where Do is distance=0, D1 the distance at the start of the high stenosis grade,
and Dz the distance at the end of the high stenosis grade.
Such virtual assessment or profiling ofa tube or stenosis in a tube using
either IPR or anR allows the effects of removing a stenosis to be assessed
prior to performing the procedure itself.
There are particular needs in the cardiac environment for simplified equipment
having the smallest possible int (or being the least invasive requiring the
smallest possible entry site) so the provision of a known position probe to
assess or profile stenoses along the length of the tube represents a significant
technical advance in that field.
When used in this specification and claims, the terms "comprises" and
"comprising" and variations thereof mean that the ed features, steps or
integers are included. The terms are not to be interpreted to exclude the
presence of other features, steps or components.
The features disclosed in the foregoing description, or the following claims, or
the accompanying gs, expressed in their specific forms or in terms of a
means for performing the disclosed on, or a method or process for
attaining the disclosed result, as appropriate, may, separately, or in any
ation of such es, be utilised for realising the invention in diverse
forms thereof.
WHAT I/WE
Claims (1)
- CLAIM
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1100136.9 | 2011-01-06 | ||
GBGB1100136.9A GB201100136D0 (en) | 2011-01-06 | 2011-01-06 | Apparatus and method of characterising a narrowing in a filled tube |
PCT/GB2012/050015 WO2012093260A1 (en) | 2011-01-06 | 2012-01-06 | Apparatus and method of characterising a narrowing in a fluid filled tube |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ613148A NZ613148A (en) | 2015-10-30 |
NZ613148B2 true NZ613148B2 (en) | 2016-02-02 |
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