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Claims  |
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What is claimed is:
1. In combination with a laser angioplasty system in which a laser catheter
is positioned within a moving vessel and oriented to impinge radiation
upon a selected target site within the vessel, the improvement comprising:
means for defining a cycle representative of repetitive vessel movement;
means for defining the position of the laser catheter relative to the
selected target site during various times of the cycle, and
means for activating the laser catheter at a selected time or times to
impinge laser radiation on the target site during an upcoming cycle or
cycles.
2. The combination of Claim 1 in which the means for defining a cycle
representative of vessel movement defines an aspect of the cardiac cycle.
3. The combination of claim 1 in which the vessel is a coronary artery and
the means for defining a cycle representative of vessel movement defines
an characteristic relative to the coronary artery.
4. The combination of claim 1 wherein the means for defining the cycle
includes electrocardiographic data.
5. The combination of claim 4 wherein the cycle is defined by the QRS
complex.
6. The combination of claim 1 wherein the means for defining the position
of the laser catheter includes at least one imaging system.
7. In combination with a laser angioplasty system for the delivery of laser
energy to atherosclerotic plaque in a vessel and for ablation of the
plaque therein, the combination comprising:
a laser catheter including an actuating mechanism therefore;
first means responsive to an aspect representative of repetitive vessel
movements for defining a time period cycle representative thereof and for
dividing the time period cycle into a variable number of fixed times or
time intervals;
second means responsive to the relative positions of the laser catheter and
the plaque in the vessel for identifying those times or time intervals
during a cycle (or a cardiac cycle) when the laser catheter is aimed at
the plaque and those times or time intervals when it is not, and
computer means responsive to said first means and said second means for
controlling the actuation of the laser catheter during at least one time
or time interval of an upcoming cardiac cycle in which the laser catheter
is oriented to the plaque.
8. The combination of Claim 7 in which the aspect representative of
repetitive vessel movement relates to the cardiac cycle.
9. The combination of claim 7 wherein the first means includes
electrocardiographic data and further includes associated means for
defining a time period represented by the electrocardiogram QRS complex
generated thereby and for defining a plurality of times therebetween.
10. The combination of claim 7 wherein the second means includes image
acquisition and processing means for visually displaying on a CRT images
of the vessel toward which the catheter is oriented and orientation of the
catheter or its aiming mechanism relative to a target area.
11. The combination of claim 10 wherein the second means includes
angiography imaging means.
12. The combination of claim 10 wherein the second means includes
angioscopic imaging means.
13. The combination of claim 7 wherein the second means includes signal
generating means and sensing means for sensing when the catheter is
oriented toward the plaque in the vessel.
14. The combination of claim 13 wherein the second means includes a laser
induced fluorescent signal.
15. The combination of claim 13 wherein the second means includes
ultrasound signal means.
16. The combination of claim 7 wherein the first and second means generate
electrical output signals representative of time and positional data,
respectively.
17. The combination of claim 16 wherein the computer means is
electronically connected to the first and second means and includes
electronic data storage and display means for storing and displaying the
time and positional data at operator command.
18. The combination of claim 17 wherein the computer means further includes
manual data entry means for selecting certain times or time intervals
during which the catheter is oriented toward plaque in the vessel.
19. The combination of claim 18 further including means for automatically
triggering the firing of the laser catheter during the selected time
intervals during an upcoming cycle or cycles.
20. The combination of claim 18 including means for deactivating the laser
catheter.
21. In combination with a medical treatment device in which a treatment
means is positioned within a moving body and oriented toward a selected
site therewithin for effecting treatment thereof, the improvement
comprising:
means for defining a repetitive time cycle representative of body movement;
means for defining the position of the treatment means relative to the
selected site during various times of the time cycle, and
means for activating the treatment means at a selected time or times to
effect treatment of the selected site.
22. In combination with a medical treatment system for effecting treatment
to a selected site in a body or body part, the combination comprising:
medical treatment means inserting into the body including an actuating
mechanism therefore;
first means responsive to repetition body movements for defining a time
period representative thereof and for dividing the time period into a
variable number of fixed times;
second means responsive to the relative positions of the medical treatment
means and the site in the body for identifying those times or time
intervals during a time period when the treatment means is oriented toward
the site and those times or time intervals when it is not, and
computer means responsive to said first means and said second means for
controlling the actuation of the medical treatment means during at least
one time or time interval of a cycle in which it is oriented toward
selected site during upcoming cycle.
23. A method of timing the actuation of a laser angioplasty catheter
carried in a moving vessel to assure impingement of laser radiation upon
atherosclerotic plaque rather than on the vessel wall, the method
comprising:
inserting the catheter into a vessel and positioning it toward a target
area therein;
establishing a repeating time cycle based on vessel movement, including
discrete times within the cycle;
selecting those discrete times in the cycle during which the catheter
aiming mechanism is aimed at the plaque, and
arranging for the actuation of the laser during at least one of those
determined discrete times in an upcoming cycle.
24. The method of claim 23 in which the step of selecting those times when
aiming is at the plaque includes the use of an image acquisition, storage
and display systems.
25. The method of claim 23 in which the step of selecting those times when
aiming is at the plaque includes the use of sensing means for providing
data that indicates the orientation of the catheter relative to the
plaque.
26. The method of claim 23 in which the step of arranging for actuation of
the catheter includes the use of computer means for correlating the
selecting step with the actuation of the laser.
27. The method of claim 23 wherein the selecting step includes data from a
plurality of modalities, some associated with the catheter per se and some
independent thereof.
28. A method of timing the actuation of a medical treatment system in which
a medical treatment means is inserted into the body and to assure
effecting treatment by the means to a selected site in the body, the
method comprising:
inserting the medical treatment means into the body and positioning it
toward a selected site therein;
establishing a repeating time cycle based on certain body movement,
including discrete times within the cycle;
selecting those discrete times in the cycle during which the medical
treatment means is oriented toward the site and
arranging for the actuation of the medical treatment means during at least
one of those determined discrete times or time intervals during an
upcoming cycle. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The invention relates specifically to laser angioplasty and to improved
methods and apparatus therefor. With this in mind, the invention will be
specifically described with reference to laser systems and methods for
ablating plaque, although it has broader applicability. For example, it is
applicable to the so called hot probe laser approach as described in U.S.
Pat. No. 4,650,024, entitled "Thermorecanalization Catheter and Method for
Use", issued March 31, 1987. In its broader sense the invention relates to
any medical treatment systems and method for effecting treatment to
selected sites in the body in which cyclic or repetitive movement is
involved.
The aiming of laser energy accurately at atherosclerotic plaque within a
vessel, such as a coronary artery, is negatively affected by the
continuous movement of the vessel. This movement is associated with
cardiac contractions, hence relates to phases of the cardiac cycle. As a
result of such movement a laser catheter positioned within a vessel also
undergoes relative movement and may at times be aimed at plaque and at
other times aimed at normal vessel wall.
Mechanical damage to vessels, including wall perforation, continues to be a
major problem with laser angioplasty. The aiming of laser energy
(delivered via a fiberoptic delivery system) is a major task. The
continuous motion of the vessel wall significantly complicates aiming and
delivering of laser energy accurately to the atherosclerotic plaque. The
prior art has treated the movement of coronary arteries and other vessels
as a problem rather than attempting to take advantage of the repetitive
nature of the movement of coronary arteries as displayed from one cardiac
cycle to another.
The present invention relates to a control system for timing the delivery
of laser energy such that it accurately impinges on plaque or other
intended target area.
SUMMARY OF THE INVENTION
According to this invention the repetitive motion of the walls of the
ventricles (or heart chambers in general) and the motion of associated
vessels during heart cycles is taken advantage of and delivery of laser
energy for ablation of the plaque (or other type of obstruction or target)
is provided only during specific, predetermined times or time intervals
during a cardiac cycle or cycles. Thus, in accordance with this invention
one takes into account the repetitive nature of the movement of the vessel
carrying the laser catheter and uses the repetitive nature of the movement
for timing the firing of the laser only when the laser beam (delivered via
fiberoptic-based catheter) and the plaque or other obstruction or target
are coincident i.e., at times when accurate aiming exists.
In accomplishing this it is necessary to identify, during a number of
consecutive cardiac cycles, those times during the cycle when the laser
catheter is aimed at the target area and not at normal vessel wall. It can
be seen that during certain times of such a cycle repetitive movement of
the vessel will bring the atherosclerotic lesion i.e., a target area into
a position where the laser energy will impinge on it. Therefore, the laser
energy delivery during such time or time intervals will be safer and will
significantly diminish probability of vessel wall perforation.
Consequently, the movement of the vessel is no longer treated as a problem
but rather the motion is taken advantage of by timing its cyclic movement
and selecting or defining those times or time intervals when the laser
energy is coincident with respect to the targeted area, for firing the
laser.
More specifically, with the proposed invention, after initially positioning
and aiming the distal end of fiberoptic-based laser catheter at a target
area such as plaque or some other obstruction or target area within the
vessel, the entire cardiac cycle is artificially divided into a number of
fixed time intervals, as determined by the physician-operator. For the
purpose of establishing a cardiac cycle, the QRS complex from an
electrocardiogram may be used to establish the beginning and end points of
a repetitive cycle to be used. During a plurality of times within such a
cycle an image or signal indicative of the position of the distal end of a
laser catheter, relative to the target, may be obtained during each of
those times. Such an image or signal (more than one may be involved and
used) are stored, preferably in an electronic storage media such as a
digital memory or video tape, for later review and use.
Images may include fluoroscopic or angiographic (both radiographic) images
and or images from a fiberoptic angioscope. Signals may be also obtained
from an ultrasound transducer mounted at the distal tip of a laser
catheter. Also, laser induced fluorescence signals (plaque and normal
vessel walls fluoresce differently in response to a laser radiation) may
be used alone or simultaneously with other signals and/or images
throughout any predetermined number of cardiac cycles.
All such data may be stored electronically for subsequent review by a
physician-operator of the system. After sufficient data has been
accumulated in the storage medium the images and signals may be reviewed
frame by frame. It is preferable to review at the same time all images and
signals which were obtained at the same time in the cycle. Window type
presentation of multiple images and signals on one screen is also
preferable. The review is not done in real time but at a speed convenient
for the physician-operator. The review of the collected data allows the
physician-operator to determine those times of the cycle during which the
laser catheter is accurately aimed at the target area. Through the use of
a microcomputer or other computer means, appropriate programming may then
be placed into operation to control the firing of the laser catheter for
delivery of laser radiation during upcoming cardiac cycles and only during
those times or time intervals when it has been determined that the laser
beam is aimed directly at or coincident with the target area.
In a simple system only one image or signal may be utilized to verify
aiming. However, in a more sophisticated system, wherein one or more
images and/or signals are stored for review, all of the images and signals
which have been obtained simultaneously from several sources during given
times of a cycle may be used to confirm the accurate or inaccurate aiming
of the laser catheter at the target area.
Agreement concerning aiming between different sources of data confirms for
the physician-operator those time intervals of the cycle when it is safe
to activate the laser for ablating the target area. Trains of ablative
laser pulses throughout these safe times or time intervals, which may be
one time or time interval of one cycle or several cycles or several times
or time intervals extending over a number of cycles may be utilized. Such
a system of aiming verification will provide improved operation of a laser
angioplasty system and is most preferred.
As indicated above, the QRS complex of an ECG may be used for establishing
a cycle representative of the vessel movement and is preferred. However,
other sources for establishing representative cycles may be used such as
the blood pressure in the aorta, blood flow in the cardiac ventricle or
aorta or an artificial pacing cycle may be established with the pacing
pulse used as a reference.
DESCRIPTION OF THE DRAWING
The present invention will be apparent from the detailed description
provided herein taken in conjunction with the accompanying drawing in
which:
FIG. 1 is a block diagram, showing the construction of a hardware
embodiment of the invention;
FIG. 2 is a representation of an electrocardiogram showing deflections
resulting from atrial and ventricular electrical activity. The QRS complex
is due to excitation of the ventricle and is used according to the
invention to establish a repeatable time cycle, and
FIG. 3 is a flowchart showing the operation of the overall system.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In its preferred form, this invention will be practiced in combination with
the laser catheter described in copending application Ser. No. 066,937,
entitled Laser Angioplasty and filed June 25, 1987. That application is
assigned to the same assignee as in this application. Its contents are
incorporated herein by reference. The following description of the subject
invention refers particularly to an overall system and method and not to
any particular catheter construction.
FIG. 1 shows an embodiment of the invention. In the Figure a computer
system 10 includes computer hardware 12 and software program means 14.
Hardware 12 includes storage means (not shown). Also connected to computer
10 are a display CRT 18 and a user input device such as a keyboard, mouse,
light pen or joy stick arrangement or others 20. The storage means is
constructed and arranged such that signals, such as electrocardiogram data
including QRS complex time points or other cardiac cycle time points, may
be used to trigger acquisition and/or storage of images and other data
concerning the relative positions of the laser catheter and a target area
in a vessel or chamber carrying the laser catheter. The images and other
data may be generated by one or more various means 24 and 26 and are
introduced into the storage means hardware.
Storage and digital image subsequent processing may be accomplished by a
system such as the Trapix 5500 digital image processor available from
Recognition Concepts Inc., 341 Skiway, P.O. Box 8510, Incline Village,
Nev., 89450. Another imaging system known as View 2000 is available from a
company known as Virtual Imaging, 725 Kieffer Rd., Sunnyvale, Calif.
94086.
The various positional data means indicated at 24 and 26 may take various
forms. For example, one of these may take the form of an imaging system in
which an image showing the relative positions of the laser catheter and
the target area may be generated angiographically, including utilization
of Digital subtraction Angioplasty (DSA) if necessary, or angioscopically
and stored in the storage means for display on CRT 18. From such images
one can determine if the laser catheter is accurately aimed at selected
target area.
In addition to or in lieu of actual images, various sensing arrangements
which generate a signal indicative of a positional relationship of the
laser vis-a-vis the target area may also be used with the present
invention. As already indicated, the fluorescence effect exhibited by
plaque is different than the fluorescence effect exhibited by a vessel
wall, the florescence being in response to impinging low level radiation.
See the abstract of a presentation entitled Fiberoptic Laser-Induced
Fluorescence Detection of Atherosclerosis and Plaque Ablation; Potential
for Laser Angioplasty Guidance". by Decklebaum, Stetz, Lam, Clubb,
Cutruzzola, Cabin and Long given at the American Heart Association in
Dallas, Tex. and abstracted as paper #27 (II-7) in the Part 2, Volume 74,
Number 4, October 1986, Manograph Number 124, Circulation Supplements,
Abstracts from the 59th Scientific Sessons, American Heart Association.
Also from the same sessions, see Abstract #25 (II-7) entitled "Detection
of Atherosclerotic Places and Characterization or Arterial wall Structure
by Laser Induced Fluorescence" by Sartori; Bossaler, Weilbacher, Henry and
Roberts and see Abstract #26 (II-7) entitled " Laser Induced Placue
Atherolvsis with Tetracycline" by Abela, Barbieu, Roxey and Conti. In
accordance with this invention a sensing means responsive to such
flourescence may be included in the system, the particular type of the
fluorescence being indicative of when the catheter is on target and when
it is not.
Likewise, a data signal may be generated by means of an ultrasound
tranducer which may be mounted on the distal end of the laser catheter.
See the abstract of a presentation entitled "Continuous On-Line Assessment
of Coronary Angioplasty with a Doppler Tipped Balloon Dilatation Catheter"
by Sibley, Bulle, Baxley, Dean and Whitlow given at the same Scientific
Sessions above-identified and abstracted as #1828 (II-459). Such data may
also be stored for later review and use. Ultrasound image or images can be
reconstructed from such signals or data.
With constructions such as those described above, after initially
positioning a laser catheter in a vessel and aiming it at a target area,
positional images and data and/or signals as described above generated by
various modalities are obtained at predetermined times throughout any
desired number of cardiac cycles. Such a cardiac cycle is shown in the
electrocardiogram of FIG. 2 wherein the repeating cycle is defined by time
between QRS complex R.sub.1 -R.sub.2 of an ECG. In the cycle illustrated,
a plurality of time points t.sub.1 . . . t.sub.n represent the times
during which the images and/or signals are generated to determine whether
the laser catheter is accurately aimed at the target area or not.
Simultaneous collection of various positional images, data and/or signal
by various modalities (whether carried by the catheter or independently
operative means) such as 24 and 26 may be taken at each point of time
t.sub.l . . . t.sub.n for storage (on electronic memory means such as
video tape or optical disc, etc.). Then, all of these images and data may
be recalled and reviewed frame by frame preferably with simultanteous
review of images and data from different imaging and data or signal
sources obtained at the same time in the cardiac cycle.
This review is not done in real time but at a speed convenient for the
physician-operator 28. Any number of cardiac cycles and number of times or
time points per cycle may be selected by the physician-operator. The
review of this data allows the physician-operator to determine those time
or time intervals of the cycle during which the laser catheter is reliably
and consistently aimed at the target area.
Then and only then, computerized control of the laser actuating mechanism
30 may be set through input device 20 to energize or trigger the laser or
allow the laser beam to enter the shooting optical fiber of the laser
catheter during those times or time intervals of the upcoming cycle when
the catheter is reliably aimed at the target area.
If any abnormal pattern of cardiac activity is observed by the
physician-operator or identified by computerized control system, the
operator or the computerized control system is arranged to automatically
block delivery of ablating laser radiation.
FIG. 3 shows a program flow chart for the operations performed by the
hardware shown in FIG. 1. FIG. 3 represents the various steps involved in
selecting times during which to actuate the laser or otherwise allow laser
radiation to impinge on a target area. The first step in this process
occurs at 32 when the QRS time points are generated. 32 represents the
step in which the time period cycle between two consecutive QRS complex
points R.sub.1 -R.sub.2 are determined. The next step is indicated at 33
in which the time period R.sub.1 -R.sub.2 is divided into a number of
times t and n number of images or data signals are obtained and stored
from one or more instruments which the physician-operator selects for each
of the time intervals t.sub.1 to t.sub.n during one cycle. During next
step 34, the images or data readings obtained in step 33 are displayed on
the CRT in operator selected format. Step 36 indicates the point at which
it is determined if plaque or other suitable target is present. Step 38
indicates a decision point in which the operator must decide whether the
laser is accurately aimed during one or more of the times or time
intervals. If the laser is not aimed at the plaque during one or more of
the time intervals, step 40 is executed, which involves adjusting the
catheter position and returning steps 32-38. If the operator determines
that the laser is aimed at plaque or the like during one or more time
intervals, step 42 is performed. Step 42 consists of the operator
selecting the particular time or time interval during which to fire the
laser in an upcoming cycle or cycles and inputting this time or time
intervals and the number of cycles into the computer. The last step
indicated at 44 is triggering the laser actuation mechanism which either
activates the laser itself or allows the laser beam to enter the laser
catheter.
From the foregoing description it will be seen in accordance with this
invention that the safe firing of a laser catheter in an angioplasty
system may be accomplished. Preferably this is done by using various
modalities associated with the catheter and independent of it to generate
positional data and confirm the adequacy of the aiming or the need to
adjust same.
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Description |
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