U.S. patent application number 10/446417 was filed with the patent office on 2004-04-08 for curved surgical instruments and method of mapping a curved path for stereotactic surgery.
This patent application is currently assigned to KENT RIDGE DIGITAL LABS. Invention is credited to Nowinski, Wieslaw Lucjan, Poston, Timothy.
Application Number | 20040068172 10/446417 |
Document ID | / |
Family ID | 20429326 |
Filed Date | 2004-04-08 |
United States Patent
Application |
20040068172 |
Kind Code |
A1 |
Nowinski, Wieslaw Lucjan ;
et al. |
April 8, 2004 |
Curved surgical instruments and method of mapping a curved path for
stereotactic surgery
Abstract
The method of mapping a curved path for stereotactic surgery
involves the selection of a helical-shaped path. The first step is
toobtain an accurate image of the pertinent structures of the
patient's internal areas. The image includes the lesion or target
region (15) and potential opening site. Using the image, the
non-target areas (16, 17, 19) surrounding the lesion area (15) are
determined and evaluated for the medical acceptability of passing
through them. A curved path (H) which is substantially helical in
shape is then selected within the image such that the curved path
(H) avoids these non-target areas (16, 17, 19), but intersects the
target region (15) and the opening site. The corresponding surgical
instrument (65) which will be used to follow the path has a rigid
body (H) having a shape which is substantially identical to the
path.
Inventors: |
Nowinski, Wieslaw Lucjan;
(Singapore, SG) ; Poston, Timothy; (Singapore,
SG) |
Correspondence
Address: |
LADAS & PARRY
26 WEST 61ST STREET
NEW YORK
NY
10023
US
|
Assignee: |
KENT RIDGE DIGITAL LABS
|
Family ID: |
20429326 |
Appl. No.: |
10/446417 |
Filed: |
May 28, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10446417 |
May 28, 2003 |
|
|
|
08945474 |
Jul 12, 1999 |
|
|
|
Current U.S.
Class: |
600/407 |
Current CPC
Class: |
A61B 90/11 20160201;
A61B 90/10 20160201; A61B 2034/107 20160201; A61B 2090/0811
20160201; A61B 2034/102 20160201; A61B 90/36 20160201 |
Class at
Publication: |
600/407 |
International
Class: |
A61B 005/05 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 1996 |
SG |
96 06118-9 |
Claims
We claim:
1. A method of mapping a curved path for stereotactic surgery using
a substantially rigid surgical instrument to access an area of a
patient's body comprising: a) obtaining an accurate image of an
area of the body, said image including an opening site and a target
region; b) determining high-risk areas around said target region;
c) selecting a non-linear curve within said image, wherein said
curve is substantially helical in shape; whereby said curve
intersects said target region and said opening site, but not said
high-risk areas, said curve defining the curved path for which a
rigid stereotactic surgical instrument having an identical shape to
said curve will be navigated to said target region.
2. The method as recited in claim 1 wherein the non-linear curve in
said selection step is a helix.
3. The method as recited in claim 1 wherein said image obtaining
step is performed using an imaging technique selected from the
group consisting of: MRI, PET, CAT, plain radiography, SPECT, MEG,
EEG, US, fMRI, angiography, colour doppler, and reference maps of
the body.
4. The method as recited in claim 3 further comprising the steps of
digitizing said image and interfacing said digitized image with a
computer.
5. The method as recited in claim 1 wherein said determining step
and selecting step are performed simultaneously.
6. The method as recited in claim 5 wherein a virtual reality
apparatus is used to execute at least one of the steps.
7. The method as recited in claim 2 wherein said selecting step
includes: a) marking a target point P in said target region; b)
selecting straight line L as a helix axis; and c) tracing a curve
around said line L maintaining a constant radius r and angle
.alpha. with respect to said line L, said curve intersecting said
target point P.
8. The method as recited in claim 7 wherein said selecting step b)
and said tracing step c) are performed substantially
simultaneously.
9. A method of mapping a curved path for stereotactic surgery using
a substantially rigid instrument, said method being aided by a
virtual reality apparatus, said apparatus including a a display
means, and a stylus adapted for allowing a user to interact with
said virtual reality apparatus via said display means, said virtual
reality apparatus adapted for displaying medical images on said
display means and superimposing a helical curve of a selected
radius r and angle .alpha. within said images, said method
comprising: a) displaying an accurate image of an affected area of
a patient's body on said display means, said image including a
target region; b) determining high-risk areas around said target
region; c) pointing said stylus to a point P in said target region;
d) moving said stylus until a helical curve originating from point
P is displayed on said displaying means such that no part of the
helical curve intersects said high-risk areas, said curve defining
the curved path for which a rigid stereotactic surgical instrument
having an identical shape as said curve will be navigated to said
target region.
10. The method as recited in claim 8 further comprising: a)
determining a location for an opening site; b) determining whether
said helical curve intersects the opening site; and c) moving said
stylus and selecting another helical curve until no part of the
helical curve intersects said high-risk areas but intersects said
opening site.
11. A method of mapping a least-invasive curved path for
stereotactic surgery using a substantially rigid instrument
comprising: obtaining an accurate image of an affected area of a
patient's body, said image including a target region and an opening
site; determining high-risk areas around said target region;
assigning a medical acceptability value to each of said high-risk
areas; selecting a plurality of curves within said image wherein
each of said curves is substantially helical in shape, and said
curves intersecting said target region and said opening site;
assigning a medical acceptability value to each of said curves
based on its interaction with said high-risk areas; comparing said
curves based on said medical acceptability value; and choosing a
curve with an optimal value, said curve defining the curved path
for which a rigid stereotactic surgical instrument having an
identical shape as said curve will be navigated to said target
region.
12. The method as recited in claim 11 wherein each of said curves
is helical in shape.
13. A method of mapping a curved path for intracranial stereotactic
surgery using a substantially rigid surgical instrument comprising:
obtaining art accurate image of an affected area of a patient's
intracranial area, said image including a target region and an
opening site; determining high-risk areas around said target
region; selecting a curve within said image wherein said curve is
substantially helical in shape, whereby said curve intersects said
target region and said opening site, but not said high-risk areas,
said curve defining the curved path for which a rigid stereotactic
surgical instrument having an identical shape as said curve will be
navigated to said target region.
14. The method of mapping a curved path for intracranial
stereotactic surgery as recited in claim 13 wherein said curve is
helical in shape.
15. A non-linear surgical instrument for stereotactic surgery
conducted along a curved path comprising: a substantially rigid,
elongated body, said body being substantially helical in shape,
wherein said instrument is adapted for being inserted into a small
opening on a patient's body and navigated precisely along a
selected curved path having substantially same shape as said
instrument to perform a surgical function.
16. The surgical instrument as recited in claim 15 wherein said
rigid body is helical in shape.
17. The surgical instrument as recited in claim 15 further
comprising a monopolar electrode disposed at an end of said rigid
body; a conductor core electrically coupled to said electrode and
disposed inside said rigid body; wherein said rigid body is made of
electrically insulating material; whereby said instrument is
adapted for measuring or delivering electrical signals.
18. The surgical instrument as recited in claim 15 further
comprising a plurality of electrodes of alternating polarity
disposed at an end of said rigid body, said electrodes adapted for
delivering electrical current to a localized area; a protruding
opening for collecting fluid samples disposed at said end; a fluid
channel disposed inside said rigid body leading to said opening;
and a power cable electrically coupled to said electrodes, said
cable disposed inside said rigid body and around said fluid
channel.
19. The surgical instrument as recited in claim 15 wherein said
instrument is a biopsy sampling instrument further comprising a
flexible, withdrawable, and turnable shaft disposed inside said
rigid body; a collection chamber at an end of said shaft, said
chamber adapted for receiving and storing a sample fluid; and a
rotatable window head at an end of said rigid body and over said
collection chamber.
20. The surgical instrument as recited in claim 15 wherein said
instrument is a needle adapted for extracting material or
delivering medicine or other fluids, further comprising a hollow
core disposed along inside said rigid body; a sharp point at a tip
of said rigid body; and a opening at said tip.
21. The surgical instrument as recited in claim 15 wherein said
instrument is a resection instrument further comprising a flexible,
turnable shaft disposed along inside said rigid body; a resection
wire having a loop, said loop being cable of being in an active and
retracted positions, said loop being outside said shaft in the
active position, and inside said shaft in the retracted
position.
22. The surgical instrument as recited in claim 15 wherein said
instrument is a temporary implant placement instrument further
comprising a tip at an end of said rigid body, said tip having a
material chamber adapted for releasing radiation or drugs through
said tip.
23. The surgical instrument as recited in claim 15 wherein said
instrument is a permanent implant placement instrument further
comprising a core slidably disposed inside said rigid body; a
detachable drug source or device disposed at an end of said rigid
body, such that said drug source or device is detached by advancing
said core.
24. The surgical instrument as recited in claim 15 wherein said
instrument is a cooling or heating instrument for cooling or
heating an isolated area of the patient's body further comprising a
tip disposed at an end of said rigid body; a core inside said rigid
body for delivering heat or cold; and an insulating sheath
surrounding said cable.
25. The surgical instrument as recited in claim 15 wherein said
instrument is a drilling instrument further comprising a rotatable
flexible shaft inside said rigid body; and a rotatable cutting burr
attached to an end of said shaft.
26. The surgical instrument as recited in claim 15 further
comprising a hollow core disposed inside said rigid body adapted
for guiding a flexible guide wire, said rigid body capable of being
removed from the patient's body while leaving said guide wire in
the curved path.
27. The surgical instrument as recited in claim 26 further
comprising a channel inside said rigid body, said channel adapted
for delivering electrical current or biological material in either
direction.
28. The surgical-instrument as recited in claim 15 further
comprising a fixed hand grip disposed at an end of said rigid body;
a turning hand grip pivotally disposed adjacent to said fixed hand
grip; a tool disposed at an end opposite to said fixed and turning
hand grip; and a wire attached of said turning hand grip and said
tool, such that said tool can be opened or closed by rotating said
turning hand grip around a pivot.
29. The surgical instrument as recited in claim 28 wherein said
tool is a pair of scissors.
30. The surgical instrument as recited in claim 28 wherein said
tool is a nibbler.
31. The surgical instrument as recited in claim 28 wherein said
tool is a gripping apparatus.
32. The surgical instrument as recited in claim 28 wherein said
tool is a spreading apparatus.
33. The surgical instrument as recited in claim 15 further
comprising a laser tip disposed at an end of said rigid body, said
laser tip adapted for delivering localized radiation for burning
away unwanted material, separating tissues, and cauterizing
wounds.
34. The surgical instrument as recited in claim 15 wherein said
instrument is a endoscope further comprising a camera at an end of
said rigid body; a optical fiber connection for transmitting and
receiving optical information disposed inside said rigid body and
coupled to said camera; and a means for lighting disposed at said
end.
35. The surgical instrument as recited in claim 15 wherein said
instrument is an ultrasonic aspirator further comprising a
vibrating source at an end of said rigid body adapted for
delivering directed ultrasound for pulverizing tissues; a liquid
insertion tube disposed at said end for making a slurry of said
tissues; an extraction tube for extracting the slurry of tissues; a
fluid channel disposed inside said rigid body for delivering said
slurry of tissues; and a means for delivering power for said
aspirator.
36. The surgical instrument as recited in claim 15 further
comprising a vibrating source at an end of said rigid body adapted
for delivering low level ultrasound for creating detailed image; a
means for delivering power for said vibrating source.
37. A guide block for a surgical instrument for stereotactic
surgery, said instrument being substantially helical in shape,
comprising a rigid body, a channel disposed in said rigid body,
said channel having an identical shape as said surgical instrument,
said channel adapted for fittingly receiving said surgical
instrument and allowing said instrument to smoothly slide through
said channel without deforming out of shape.
38. The guide block as recited in claim 37 wherein said rigid body
is made of two parts which are mated together.
39. The guide block as recited in claim 38 wherein said parts are
mated by being solidly mounted on a common rigid support.
Description
FIELD OF INVENTION
[0001] This invention relates to the field of stereotactic surgery,
and particularly to curved instruments and method of mapping a
curved path for stereotactic surgery for situations where a
straight path is impossible or would be more invasive or risky than
a curved path.
BACKGROUND OF THE INVENTION
[0002] 1. Nomenclature and Definition of Terms
[0003] Currently, stereotaxis is generally associated with
neurosurgery, and particularly with intracranial surgery. However,
in the following description, the terms "stereotaxis" or
"stereotactic surgery" or "stereotactic surgical procedure" shall
not be used in that limited sense; rather it should be understood
that the term shall be used more generally to distinguish it from
the "conventional" surgical procedures where a large incision is
made in a patient. Hence, the terms "stereotaxis", "stereotactic
surgery", "stereotactic surgical procedure" shall encompass those
clinical procedures where a rigid instrument is inserted into a
small opening and is navigated, by control of the part that remains
outside, to a pre-determined area of a patient's body. However,
frequent references will be made to intracranial surgery as a way
of illustrating the invention and its mode of operation, and
therefore, such references should not be construed as a limitation
on the present invention.
[0004] 2. Description of the Related Art
[0005] Stereotactic surgery (also known as "stereotaxis") is well
known to those skilled in the art. It is a special surgical
procedure for treating an interior portion of a patient, usually
the brain and other intracranial structures, by inserting a rigid
probe into a small opening. In conventional open surgery, the
surgeon makes an incision large enough for the surgeon to see the
path leading to the area of pathology. Stereotaxis, on the other
hand, does not require the surgeon to actually see the entire path,
so a small opening, only big enough to insert the probe, is
required. Hence, stereotactic surgical procedures offer the
advantage of minimizing the damage to the tissues surrounding the
lesion area, and promotes faster recovery of the patient.
[0006] Because a surgeon performing stereotactic surgery does not
directly view the inner portions of the brain, he must be able to
map out a path and note the sensitivity of the tissues surrounding
the damaged area. He must also be able to navigate the probe such
that the position of the probe corresponds exactly with the
designated path. To achieve the necessary control, a number of
apparatus and methods have recently been developed. CAT scan
technology, magnetic resonance imaging (MRI), angiography, digital
subtraction angiography (DSA) and similar diagnostic procedures are
currently used to obtain the visual image of the intracranial area.
Such devices are coupled to apparatus, typically a rigid
helmet-like framework worn on the skull, or (less invasively but
less precisely) markers attached to the skin and `frameless`
guidance system or robot, which precisely positions the probe in
accordance with the visual images.
[0007] Currently, only straight probes are used in stereotaxis.
Hence, only a straight path leading to the selected point can be
used. When choosing a straight path, the surgeon selects a path
which best avoids sensitive areas or other obstructions. If the
path meets a bone, an opening can often be formed by drilling a
hole. But if the selected path meets blood vessels, nerves, or
brain tissues with important brain functions, a different path must
be chosen, or risk causing irreparable damage to the brain.
[0008] Not all areas can be reached via a straight path, however.
Some sites are so well surrounded by important tissues that no
straight path exists where the risk is low. In other situations, a
straight path may exist, but the damaged area may be buried deep
within the brain requiring a penetration through thick layers of
tissues. In still other situations, the path may be confronted by a
hard tissue such as calcified dura mater which the probe is unable
to penetrate. Lesions in such unreachable places may either be
classified as inoperable or be treated using the traditional open
procedure.
[0009] In some of these situations, a curved path may better avoid
the obstructions or sensitive tissues, and reach the intended area
with lower risk to the patient. However, at the present, only
straight devices are in use, which can follow only a straight path,
unless they are allowed to move sideways and create a sheet of
damage. To make only a line of damage, the body of the device must
slide along the path pierced by the tip. For most curved
instruments, however, such sliding movement along a designated
curved path is difficult or impossible.
[0010] Hence, in light of these shortcomings, it would be desirable
to have curved surgical instruments and a method of mapping a
corresponding curved path which will not cause significant damage
to the surrounding tissue, and which will allow a stereotactic
procedure to become a viable option in a greater number of
cases.
SUMMARY OF THE INVENTION
[0011] The method of mapping a curved path for stereotactic surgery
involves the selection of a helical-shaped path. The first step is
to obtain an accurate image of the pertinent structures of the
patient's internal areas. The image includes the target region and
a potential opening site. Using the image, the non-target or
high-risk areas surrounding the target region are determined and
evaluated for the medical acceptability of passing through them. A
curved path which is substantially helical in shape is then
selected within the image such that the curve avoids these regions.
The corresponding surgical instrument which will be used to follow
the selected curved path has a rigid body having a shape which is
substantially identical to the path.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows the region of the brain accessible by a
straight probe through a single hole in the skull.
[0013] FIG. 2 shows the region of the brain accessible by curved
probes through a single hole in the skull.
[0014] FIG. 3 is an image of the brain having a lesion located deep
inside the brain, and curved access to it.
[0015] FIG. 4 is an image of the brain having a lesion near the
cerebral cortex, in a region where cortex penetration is
dangerous.
[0016] FIG. 5 is an image of the brain having a lesion closely
beneath the folded cortex, where a curved probe meets less tissue
than a straight one.
[0017] FIG. 6 is an image of the placement of drug or radiation
sources at multiple sites in a lesion, which would require two
straight penetrations but only one curved one.
[0018] FIG. 7 is an image of the brain requiring biopsy at multiple
sites, which would require two entry points for straight access but
only one for curved access.
[0019] FIG. 8 shows biopsy access in more than one direction to the
same lesion through a single hole, by curved paths.
[0020] FIG. 9 shows the geometrical form of a helix.
[0021] FIG. 10A shows a restraining block, in two parts, through
which a rigid helical instrument can pass only by sliding along the
helix defining the hole in the block.
[0022] FIG. 10B shows the restraining block of FIG. 10A where the
two parts are mated into one piece.
[0023] FIG. 11 shows a pair of restraining blocks through which a
rigid helical instrument can pass only by sliding along the helix
defining the holes in the blocks.
[0024] FIG. 12 shows a helical instrument being robot-guided along
a helical path.
[0025] FIG. 13 shows a helical instrument being hand-guided through
flexible tissue, where the user is assumed to have a continuously
updated image of its position.
[0026] FIG. 14 is a mathematical diagram illustrating the formation
of a helix using a virtual reality apparatus.
[0027] FIG. 15 is a mathematical diagram illustrating the
determination of a helix by two end points, an intermediate point
and the degree of twist.
[0028] FIG. 16 is a mathematical diagram illustrating the
determination of a helix by an end point, the direction of meeting
it, another point, and the degree of twist.
[0029] FIG. 17 is a mathematical diagram illustrating the
determination of a helix by two end ends and an intermediate
point.
[0030] FIG. 18 is a mathematical diagram illustrating the
determination of a helix by the settings of a mathematically
modeled stereotactic frame.
[0031] FIG. 19 shows a rigid helical monopolar electrode.
[0032] FIG. 19A is a cross-sectional view of the electrode in FIG.
19.
[0033] FIG. 20 shows a rigid helical bipolar electrode.
[0034] FIG. 21A is a perspective view of a helical biopsy sampling
instrument.
[0035] FIG. 21B is a perspective view of an inner shaft disposed
inside the helical biopsy sampling instrument of FIG. 21A.
[0036] FIG. 22 is a perspective view of a helical needle for
extraction or insertion of fluid.
[0037] FIG. 23A is a perspective view of a helical surgical
instrument with a resection loop in its active position.
[0038] FIG. 23B is a perspective view of a helical surgical
instrument with a resection loop in its retracted position.
[0039] FIG. 24 is a perspective view of a helical temporary implant
placement instrument.
[0040] FIG. 25 is a perspective view of a helical permanent implant
placement instrument.
[0041] FIG. 26 is a perspective view of a helical instrument for
delivering cold.
[0042] FIG. 27 is a perspective view of a helical instrument having
a drilling tip.
[0043] FIG. 28 is a perspective view of a helical instrument used
solely for piercing.
[0044] FIG. 29 is a perspective view of a helical instrument having
a guide wire.
[0045] FIG. 30 is a perspective view of a helical instrument having
a guide wire in addition to a core serving another instrumental
function.
[0046] FIG. 31 is a perspective view of a helical surgical
instrument with a cutting tool, gripping, spreading or clipping
tip.
[0047] FIG. 31A is a perspective view of a nibbling tool for the
helical instrument illustrated in FIG. 31.
[0048] FIG. 31B is a perspective view of a gripping tool for the
helical instrument illustrated in FIG. 31.
[0049] FIG. 31C is a perspective view of a spreading tool for the
helical instrument illustrated in FIG. 31.
[0050] FIG. 32 is a perspective view of a helical surgical
instrument with a laser tip.
[0051] FIG. 33 is a perspective view of a helical endoscopic
instrument.
[0052] FIG. 34 is a perspective view of a helically mounted light
source.
[0053] FIG. 35 shows the combination of a light delivery channel
with a helical tube serving another function.
[0054] FIG. 36 is a perspective view of a helical instrument for
delivering pulverizing.
[0055] FIG. 37 is a perspective view of a helical instrument for
delivering low intensity ultrasound for imaging purposes.
DETAILED DESCRIPTION OF THE INVENTION
[0056] The present invention relates to a method of mapping a
curved path for stereotactic surgery so a rigid curved instrument,
having the same shape as the path, can be navigated to the intended
area. The utilization of a curved path for stereotaxis offers a
number of options and benefits unavailable for a straight
instrument. Generally, the field of access is greatly increased for
a curved path. FIG. 1 illustrates the field of coverage for a
straight instrument 5 (the region marked A) which is inserted into
the cranium 6 through a small opening 7. FIG. 2 illustrates the
field of coverage for a curved instrument 10 (the region marked B)
which is inserted into the same cranium 6 through the same opening
7. As demonstrated by these two figures, the curved instrument can
be made to cover a greater area than a straight instrument. Hence,
the availability of a curved path allows stereotactic procedure to
become a viable option in greater number of situations.
[0057] There are a number of situations where a curved path will be
the preferred option because any straight path to the area to be
accessed passes through a considerable amount of brain tissue. One
such situation is illustrated in FIG. 3, where a lesion is located
deep within the brain, in the pineal body 15. Here, along any
straight path such as L, an instrument penetrates sensitive
structures such as the cerebellum 16 or blood vessel 17, and risks
serious damage. The curved path H enters the cranium 18 to the left
of the mid-sagittal plane S and utilizes a less risky channel, via
cerebrospinal fluid 19, to the lesion area.
[0058] In other instances, a straight path may exist, but it would
be more invasive than a curved path. A common situation
exemplifying this principle is illustrated in FIG. 4. Here a tumor
20 lies fairly closely below the cerebral cortex 23 of the brain
25. A direct straight path would risk unacceptable damage to the
sensory cortex 21 or motor cortex 22, and the consequential loss of
sensation or control in the corresponding parts of the body. The
current solution is to approach the tumor 20 via the path L, that
is through the frontal lobe 26. This path passes through a great
deal of white matter 27, with risk to the long-range connectivity
of the brain that is hard to assess for the individual patient
since the connection geometry is variable. If a curved path can be
used, however, it can access the tumor via the path H, through the
frontal lobe 26. This path meets far less brain tissue, and the
frontal lobe 26 is currently the path of choice (for straight
instruments) when accessing other target points. Similarly, in FIG.
5 a lesion 30 lies closely under the cortex 31 but cannot be
reached by a straight path that passes quickly through the cortex
31; the curved path H can reach it more directly.
[0059] In still other situations, a straight path may simply be
more labor-intensive. In FIG. 6, several drug or radiation sources,
36, 37, 38 can be placed by a single procedure along a curved path
H, in a direction which would require a straight one to pass
through the visual cortex 35. In FIG. 7, the two target sites 41
and 42, where scan data suggest a need for biopsy samples, are
individually reachable but no acceptable straight path meets both.
They thus require two openings in the cranium 43, and two separate
brain penetrations, 44, 45, along straight paths L1 and L2. In
contrast, the curved path H allows collection of material from both
sites from a single opening, without meeting the motor cortex 46,
the sensory cortex 47, or the visual cortex 48. This avoids the
additional cost, risk, and effort of using two paths rather than
one.
[0060] In FIG. 2, multiple penetrations are necessary even with a
curved probe, but they can both use the same drill hole in the
skull and pass through essentially the same place in the cortex,
even though they go to widely divergent points. FIG. 2 shows the
increased volume of the brain reachable through a single skull
hole.
[0061] FIG. 8 shows that with curved probes H1 and H2, a single
opening 51 in the cranium 52 can suffice for biopsy of a suspect
region 53 in multiple directions, mapping its extent in each.
[0062] In view of the figures above, the benefits of the curved
path are multitudinous. But it should be understood that not every
set of curved paths will be a viable option. In order for any
curved path to be considered, the path must meet an important
criterion. It is imperative that a rigid curved instrument having a
shape identical to the shape of the path can be navigated through
the brain matter without significantly deviating from the
determined course. Specifically, the instrument must be able to
travel along the path without cutting across the surrounding
tissues. To make only a line of damage, the body of the rigid
surgical instrument must slide along the path pierced by the tip.
For most curved shapes, such rigid instrument sliding along a path
is impossible; if a golf club form, for instance, slides along the
line of its shaft, the head leaves a sheet of damaged points. If
the head slides in its own direction, the shaft creates sideways
damage. Hence, the curve must be such that the rigid instrument
slides only along the path traced by its tip.
[0063] To achieve this goal, the shape of the surgical instrument,
and hence, the shape of the path must be that of a helix. As
illustrated in FIG. 9, helix H is a well-known shape which is
defined as a curve wound evenly around an arbitrarily placed
cylinder of constant radius r, making a constant angle .alpha. with
the cylinder's axis. A helix has the characteristic in that as the
angle .alpha. approaches 0 degrees, the helix approaches the
limiting shape of a straight line. In the other extreme, as the
angle .alpha. approaches 90 degrees, the helix approaches the
limiting shape of a circular arc. Therefore, a straight line and a
circular arc are a special case of the general form of a helix.
[0064] These two features, of motion with damage only at the tip,
and of controllability by a fixed passive constraint, are
consequences of the same `slide along itself` property of the class
of helical curves (including the degenerate straight and circular
cases). They are both important where the precision of brain
surgery is required, but in less complex tissues (where hand
insertion guided by continuously updated images may be preferable
to a pre-planned path), only the first is needed. In FIG. 13 the
helical instrument 80 pushed by hand 85 is being guided through
muscle 81 and avoiding blood vessels 82 for a target 83, guided by
an ultrasound imaging system 84; it is not critical which part of
the muscle tissue it meets, and muscle is sufficiently flexible
that if the hand turns the instrument slightly, in a motion that is
not merely a slide along the helix, the tissue can follow this
sideways motion without tearing. The surgeon can then continue the
sliding penetration, arriving more accurately at the target as a
result of response to image feedback.
[0065] Although it is preferred that the shape of the path and the
instrument be that of a near-perfect helix, some deviation is
possible without substantial degradation of the useful properties
of the helical shape. Some examples will be described for the
purpose of illustrating this principle.
[0066] As described above, a perfect helix is a curve wound evenly
around an arbitrarily placed cylinder of constant radius r, making
a constant angle .alpha. with the cylinder's axis. However, the
shape may have slightly deviating r and/or angle .alpha. without
substantially affecting the outcome, so long as the deviation is
not excessive. The exact range of deviation which can exist without
unduly affecting the effectiveness of the curved instrument,
however, will vary depending on several factors such as the
rigidity of the surgical instrument, the type of procedure being
conducted, and the flexibility of the tissues being penetrated.
[0067] Further, it may be possible to deviate from a perfect helix
to a greater extent where the deviation is periodic. An example
would be a near-helical shape where the radius r and the angle
.alpha. deviate by a fixed amount at an evenly-spaced interval,
where at every other interval, the radius r and the angle .alpha.
deviate oppositely to the one before.
[0068] In addition, it may be possible, and perhaps useful, to have
a curved instrument only a portion of which has a helical shape.
Other slight modifications, not specifically mentioned herein, may
also be possible, so long as the general helical shape is
intact.
[0069] In mapping the proper curved path having the helical shape,
the first step is to generate an accurate medical image of the
portion of the affected area of a human body. The image should
cover all of the pertinent regions, and particularly the region to
be accessed by the surgical instrument, the surrounding region, and
potential entry sites.
[0070] A multitude of methods currently exists for obtaining
medical images. Some common examples are scans using MRI, PET, CAT,
plain radiographs, etc. Other means may include commercially
prepared body maps or detailed 3-D models. Whichever the method, it
must provide detailed information as to the respective location,
shape, and size of the varying tissues, organs, blood vessels, and
other important matters, such that a surgeon can determine the path
which avoids the undesired regions.
[0071] Although the images obtained may be viewed in their original
format, it is preferred that they be viewed in digitized form, and
interfaced with other devices such as a computer or digital signal
processor. In this way, they may be easily manipulated and
superimposed with other images or otherwise manipulated for easy
viewing.
[0072] After an accurate image is obtained, the region to be
accessed, or target area, and some potential opening sites must be
identified. The surrounding region is then observed and analyzed
for sensitive tissues, organs, blood vessels, and other matters
which need to be avoided by the surgical instrument. A helical
curve is then superimposed onto the image such that the curve is
able to access the desired region via one of the chosen opening
sites without intersecting any of the sensitive areas. In choosing
the path, it is useful to try a number of helices having different
combinations of radius r and the angle .alpha. until a helix
meeting all of the criteria is determined.
[0073] When selecting the path, it may be possible to have several
helical curves which meet the criteria. In such a case, several
factors may be considered in choosing the particular helical path
which will be used for the surgical procedure. One important factor
is the overall distance of the path through the tissue. Generally,
the shorter the better. Another factor which may be considered is
the pitch, or the acuteness of the angle .alpha.. It is generally
preferred that the helix with the least acute angle .alpha. be
chosen. A number of other factors may also be considered, such as
the risks associated for a particular path taking into
consideration the type and nature of the tissue in the regions the
path will intersect.
[0074] To choose the optimal path, quantitative values may be
assigned to these and other relevant factors. For each path using a
particular helix, a total utility value may be assigned to each of
the combinations. After a number of combinations is considered, the
utility values may be compared, and the path-helix combination
having the highest utility value may be chosen.
[0075] While the general method of mapping described above is
useful, the medical potential of helical surgical instruments would
be significantly diminished without a practical way to choose an
access path appropriate to a patient's particular needs and his or
her structural geometry, both of which vary. Successful choice
requires a way to specify a particular path, a way to assess what
tissues it meets, a way to see what change may improve an
unsatisfactory choice, and a way to make such a change; all of
which must be easy to use, to minimize errors and the time spent by
the surgeon. The choice must then be translated easily and clearly
into specific procedure in the operating room.
[0076] The 3-dimensional relation of path and data preferably
requires a 3-D graphic display, which for ease of depth-perceptual
judgment should be stereographic. Given a particular target point
P, there are five degrees of freedom in selecting a helix ending at
P, or six if a start is also chosen. This suggests control by the
six degrees of freedom--three translational, three rotational--of
an object held in space. Many control interfaces could be suggested
by one skilled in the art; the essential is that the user should be
able to move freely in the set of helices.
[0077] Within the display, since many important brain structures
are not directly visible in a patient's scan data, there must be a
labeled set of constructs aligned with the data as a guide to the
patient's anatomy. No one such electronic brain atlas is an
essential, but some electronic brain atlas should be included,
together with software features evident to one skilled in the art,
such as the highlighting and labeling of structures met by the
current helix, and facilities to modify which ones are displayed
and their transparency.
[0078] While there exists a number of ways to implement the
above-described system, it is preferred that a virtual reality
apparatus, such as the one described in the following publication
be adopted: T. Poston and L. Serra, The Virtual Workbench: Dextrous
VR, proceedings Association for Computing Machinery, Virtual
Reality Software and Technology (ACM VRST) 1994, G. Singh, S. K.
Feiner, D. Thalmann eds., World Scientific, 1994, pp. 111-122. This
is an apparatus by which the user grasps a 6-degree-of-freedom
sensor behind a mirror which reflects a stereographic display. A
handle appears in the display precisely where the user's
neuromuscular spatial sense reports that the sensor is currently
held, and in the same orientation, so that the handle can be
manipulated with hand-eye coordination, which is important for
dextrous, intuitive control. In the display, the handle is equipped
with a virtual tip whose shape depends on the tool function to
which it is currently assigned. Either one or two sensors can be
supported; in this case, it is useful to have such a handle in each
hand. General functions like file management, selection and
rotation of objects, etc., are provided by the software.
[0079] A number of approaches to selection of a path are possible,
in which the use of six-degree-of-freedom user input is required to
varying degrees. For the `hand-held` method described below, it is
essential; for the others it is helpful, but could be replaced by a
more cumbersome 2-D mouse input. Since the range of physically
available instrument geometries will always be finite, in most
cases it will be necessary to find the available helix geometry
nearest to that of the `ideal` helix H, and adjust its position
near H to satisfy the avoidance criteria.
[0080] FIG. 14 illustrates one process for selecting a helical path
using this apparatus. In the display, the user sees a virtual
selection tool 65 whose displacement and movement correspond
precisely with that of a sensor handle (not shown) which the user
manipulates. The virtual selection tool has a tip which is used
mark points of reference. The user first brings the virtual
selection tool tip T to a target point P of interest within the
display volume, and clicks a button on the sensor handle to mark
the point. After the point P has been marked, the user can move the
virtual selection tool to create a helical path having any
combination of radius rand the angle .alpha..
[0081] As shown in FIG. 14, the helix H is created around an
imaginary cylinder having a unique set of parameters depending on
the position of the tool tip T, and the direction in which the tool
points. At any given position of tip T, a line L is formed (and
preferably displayed) in the pointing direction, and L becomes the
axis of the cylinder around which the helix H is to be wrapped. The
radius R of the cylinder joins P to the nearest point N on L, and
is continually redefined as the user moves the handle and thus
redefines L. A tip radius line S (equal in length to R), is
orthogonal to L; we define Q as the point where it meets the
cylinder. Line S is initially parallel to R, but since it is
rigidly attached to the virtual selection tool at the tip T, the
point Q moves around the cylinder as the selection tool is twisted
about its axis L. For each successive position of the tool (until
the selection button is released, fixing the choice), a helix H is
created and displayed which joins Q to P around the cylinder, with
an amount of turn equal to the total angle that Q has traveled
around L in the moving coordinate frame of the selection tool.
[0082] If v is the vector from T to Q, and w the vector from T to
N, let u be the vector 1 v .times. w w
[0083] orthogonal to both, and l be the length of L. H may be
parametrised as the curve,
H(t)=N+cos(t)v+sin(t)u+(t/l)w
[0084] or coordinates as, 2 = ( N 1 + cos ( t ) v 1 + sin ( t ) u 1
+ ( t / l ) w 1 , ( N 2 + cos ( t ) v 2 + sin ( t ) u 2 + ( t / l )
w 2 , ( N 3 + cos ( t ) v 3 + sin ( t ) u 3 ( t / l ) w 3 ) ,
[0085] from t=0 (giving the point P) to t=l (giving the point 0),
which may be displayed in the normal way for three-dimensional
curves; compute H(t) for a closely-spaced sequence of t values from
0 to l, and call standard 3-D drawing routines (for instance, from
the library OpenGL installed on many graphics machines) to project
these points on the screen for a left or right view (both, when
viewing is stereo), masked by `Z-buffer` routines when the curve
passes behind another graphical object.
[0086] Some other selection procedures, useful in particular
circumstances, are listed below. It may sometimes be convenient for
the surgeon to make an initial specification by one procedure, such
as the one just described, and then make fine adjustments using
another, such as one of the following.
[0087] When it is important to choose a particular entry point E on
the skull or outer boundary of the brain, selecting E and the
target P, FIG. 15, leaves three degrees of freedom in the choice of
a helix. Fixing an intermediate point M determines two of these
degrees of freedom; since there is a unique flat circular arc A
through E, M and the target P, the remaining parameter essentially
measures the out-of-plane twisting a of the helix chosen. The helix
H can thus be selected by using the selection tool to choose M, and
then adjusting a either by twisting the tool handle about its own
axis, or by adjusting a slider. As well as being `entry and
intermediate` points, E and M could be chosen as co-targets with P
for the action of the instrument.
[0088] Alternatively, one may wish to fix the entry point E, the
target point P, and the tangential direction by which H approaches
it, FIG. 16. This direction, easily controlled by moving the tip D
of a line drawn from P, leaves one degree of freedom uncontrolled;
by stipulating that the cylinder radius equal the length of the
line PD, the system gives a correspondence between user movements
of D and the set of helices joining P to E.
[0089] Another such correspondence, FIG. 17, is created by using an
intermediate point M, as in FIG. 15, but letting the total twist
equal the logarithm of the ratio between the distances, A & B
of M from E and P. This avoids the need for a separate twist
control.
[0090] Given a choice of target P and values for radius and pitch,
and a position for the ring frame on which the arc A sketched in
FIG. 18 is mounted, each possible position of the point G at which
the guide block, discussed below, is rigidly attached to the frame
corresponds to a unique choice of position for the helix H, for
some angle of the arc with the axis L and angle on the arc at which
the guide block is placed. Thus a frame model with widgets at G
that can control radius and pitch, and G itself draggable from one
point in space to another, provides a control scheme closely
corresponding to actual mechanical settings, and thus particularly
intuitive for frame users. It has the advantage that the widgets at
G can be set to provide only radius and pitch values that are
available in probe hardware at the site where the intervention is
to be performed, avoiding the need for separate selection of the
`ideal helix` and then the best physically available approximation
to it.
[0091] Techniques well known to those skilled in the art can detect
which geometrical structures imported from a brain atlas as
polyhedra are intersected by H, and highlight them to bring the
fact to the user's notice. Inspecting the patient's scan data along
the curve can be accomplished by a texture-based `slicing tool` for
the virtual reality apparatus environment.
[0092] In some instances, a number of the helices found by the
chosen scheme for interaction may meet the minimum criteria. After
a particular helix H has been selected, a detailed study should be
conducted to determine the desirability of the particular helical
path chosen, taking into consideration the various factors
described above. Particularly, the helical path preferably should
at least avoid most, if not all, of the sensitive surrounding
areas, and intersect one of the intended opening sites.
[0093] The methods of mapping a curved path as described above may
be applied in a wide range of stereotactic procedures, and
generally the same or similar methods can be adopted regardless to
the type of procedure being performed. However, each of the
procedures may involve a different rigid surgical instrument. But
regardless to the type and nature of the instrument, it must have
the helical shape having the same pitch and radius as the helical
path to utilize the useful properties of the helix.
[0094] Furthermore, to drive a helical instrument along the path
chosen, it must be rigidly held or constrained by a controller. A
human or robot effector may move with it (as in FIGS. 12 and 13),
holding it and moving with it; or its motion may be constrained by
passing through a single or a plurality of guide blocks as
illustrated in FIG. 10 and FIG. 11, respectively. FIG. 10A shows a
block exploded into the two parts 70 and 71 in which it is most
easily manufactured, with a helical instrument 72 between them. Two
pieces of rigid metal, non-ferromagnetic if they are to be used in
the presence of MR imaging devices, may be milled by a flat bed
milling machine to the shapes shown; taking their common center as
origin, suppose the helix has the parametrized form
(x(s), y(s), z(s))=(r cos(s+p), r sin(s+p), as)
[0095] where p define's the phase angle by which the helix is
related to the x-axis where it passes through the (x,y) plane, and
that the instrument has thickness 2h. Then from the material for
part 70 one removes the material within h of any point (x(s), y(s),
z(s)), creating a channel 73 through which the instrument will pass
as shown by the curved arrow, and also the material with 3 x > r
cos ( z a + p )
[0096] to create the surface 74 along which part 70 will meet 71.
Similarly, in creating 71 one must remove the material within h of
any point on the helix, creating part 75 of the hole through which
the instrument will pass, and also the material with 4 x < r cos
( z a + p )
[0097] to create the surface 76 along which 71 will meet 70. The
surfaces must be smoothly polished, for a close fit of the two
parts and for smooth passage with minimal play for the helical
instrument passing between them. Although the outer portions of the
two parts are shown as rectangular, forming a combined rectangular
guide block 77 in FIG. 10B, any other outer shape which may
conveniently be clamped into a rigidly specified position may
equally be used.
[0098] FIG. 11 shows a pair of such blocks with their phases p
adjusted so that a helical instrument of the same radius, pitch and
thickness will pass through both of them when they are clamped in
line at an appropriate distance d; if the clamps can rotate about
the helix axis by an angle A, this distance changes by the amount 5
A ( a 2 ) .
[0099] Such rotation would make it convenient for each block to be
symmetrical about the axis of the helix it contains, but this is
not otherwise necessary; where the radius r is large, and the helix
not far from straightness, the block can be more practically sized
if it the axis does not pass through it.
[0100] As the instrument is inserted first into a guide block, FIG.
10, or set of blocks FIG. 11, rigidly held by a robot or
stereotactic frame, and then passes into a specimen, the guide
block or set of blocks restricts the portion passing through it to
a segment of a helical path (as a straight guide hole controls the
direction of a straight needle), pushing the instrument compels its
tip to move along the continuation of the same helical curve.
Hence, as with a straight instrument, a surgeon can maneuver the
instrument along a pre-determined path, with damage only along that
path. Pushing the instrument produces pressure at its tip, rather
than along its sides. A high degree of agreement between planned
and actual motion is thus possible. The same motion may be achieved
by active constraint (FIG. 12), where a carefully planned `wrist
motion` of a robot effector 60 drives the instrument along its
planned helical path 62 to reach a target 63 blocked for straight
instruments by the spine 64. However, with present technology the
passive constraint is the preferred precision in such a constraint
than in a robot with a six-degree-of-freedom effector, and (b) the
surgeon pushing the instrument through the passive constraint can
feel the tissue's degree of resistance to penetration, which can be
a valuable sensory cue to what tissue the instrument is meeting,
and hence whether insertion should continue.
[0101] The following is a sample of some of the stereotactic
procedures which may utilize the mapping method described, and
their corresponding instruments.
[0102] FIG. 19 shows a monopolar electrode 150, which may be used
for measurement or to deliver small currents for stimulation or
larger currents that flow through the tissue to a remote ground,
applying heat on the way until the current is too spread to be
significant: this is useful for such purposes as killing a tumor by
heat, but the volume heated is too large and imprecisely defined
for brain surgery. (It remains useful for work in, for example,
muscle.) As illustrated in FIG. 19 and FIG. 19A, the instrument has
an insulating rigid body 151 surrounding a conducting core 152, and
a conducting tip 154.
[0103] An important risk in stereotactic brain surgery is that of
damage to a blood vessel. In open surgery the surgeon can detect
such damage visually, and repair it by various methods; when an
instrument is being driven through tissue, both detection and
repair are more difficult. Two features will thus sometimes be
desirable in a helical instrument intended for penetration of the
brain: (a) detection of bleeding (by taking fluid samples, and
examining them in situ or extracted via a tube), (b) cauterization
using heat from bipolar electrical current. FIG. 20 shows a helical
instrument 160 for facilitating a bipolar scheme, with a power
cable 161 surrounding a fluid channel 162 supplying electrodes 164
of alternating polarity (marked + and -). The current then flows
only very near the electrodes, which is useful for sharply
localized work, and in particular for cauterizing a wound made by
the instrument itself. The instrument has an opening for fluid
samples 163, and electrodes 164 of alternating polarity around a
non-conducting ring 165.
[0104] FIG. 21A illustrates a helical biopsy sampling instrument
170. It has a rigid curved tube 171 of a helical shape and a
rotatable window head 172. As illustrated in FIG. 21B, the
instrument 170 has a flexible, turnable, and withdrawable inner
shaft 173 with a collection chamber for storing the sample.
Rotating 173 within 172 opens and closes the chamber 174 relative
to the position selected for the helix before insertion.
[0105] FIG. 22 illustrates a helical needle which can be used to
extract material for analysis (biopsy) or because it requires
removal, or to deliver medicine or other fluids, to areas of the
body where a straight needle would have difficulty in reaching. It
has a hollow core 183 inside a rigid body 181, and a sharp point
and an opening at the tip 182.
[0106] FIG. 23A and FIG. 23B illustrate a resection instrument 185
having a rigid curved tube 186 with a flexible, turnable inner
shaft 189. In the active position, FIG. 23A, the resection wire
forms a loop 187 at the tip 188 of the instrument 185; in its
retracted position, FIG. 23B, the loop 187 is closed and displaced
inside the rigid tube 186.
[0107] FIG. 24 illustrates a temporary implant placement instrument
190 which can release radiation or drugs through the tip 191 of the
instrument, from the material chamber 192.
[0108] FIG. 25 illustrates a permanent implant placement having a
rigid outer tube 196, a rigid or flexible inner core 197 and a
detachable drug source or device 198 at the tip, which can be
pushed off by advancing the core 197.
[0109] FIG. 26 illustrates an instrument 200 for cooling or heating
an isolated area of a body. The instrument includes a cable or heat
pipe core surrounded by an insulating sheath 201. At the tip is a
thermocouple or pipe tip 202 for chilling.
[0110] FIG. 27 illustrates a drilling instrument 205 with a
rotating flexible shaft 206 inside the rigid body 207 and a cutting
burr 208 attached at its end.
[0111] Another use for a rigid helical penetrating instrument is in
conjunctions with non-rigid ones; a class that includes catheters
and endoscopes. A non-rigid instrument is guided by its
surroundings, moving within fluid (most often blood or
cerebrospinal fluid (CSF)) between the walls of the fluid space
(most often a blood vessel or a ventricle). It can rarely be guided
to push through parenchymal tissue in a planned way, even if it has
a sharp tip, because flexibility allows it to turn aside at a wall
or a variation in tissue resistance. This limits the points it can
reach, and the routes by which it may arrive there. A rigid device,
however, can be pushed through tissue, and even drill through bone
(for instance, using an instrument illustrated in FIG. 27). This
opens a channel which can then be exploited by a flexible device.
This is currently a standard procedure with straight rigid
instruments: a straight channel is pierced by a probe, reaching a
cavity such as a ventricle and entering it in a convenient
direction; it is then withdrawn, and a flexible instrument pushed
in through the channel that has been opened. This flexible
instrument can then follow the cavity by the usual mechanics of
such instruments, reaching a target without further tissue
damage.
[0112] The use of a helical instrument increases the options in
such channel creation. This may be done by simply piercing the
tissue with a helical instrument as illustrated in FIG. 28, that is
a simple penetrating device; but in some cases the flexible
instrument may not follow the resulting channel accurately, since
it must flex to do so. In this case it is appropriate to pierce
with a hollow helical instrument shown in FIG. 29 down which a
flexible guide wire 210 can be inserted. When the channel has been
created, the surgeon can remove the helical instrument while
leaving the guide wire 210 in place, and then slide a flexible
instrument along it. (A channel to contain a guide wire is a common
feature of the design of such flexible instruments, but the
`Seldinger technique` of using a guide wire to change the
instrument that follows a given path has not been extended to paths
created by rigid instruments, which have been only straight.). A
guide wire channel 217 may also be included in a rigid helical
instrument 215, illustrated in FIG. 30, containing a channel 219
serving the passage of energy, electrical current, or
biological/therapeutic material, in either direction.
[0113] A helically opened channel may be useful in endoscopic work,
even where there is already an access to some cavity for flexible
instruments, since it is often necessary to have several
instruments simultaneously in place: light, camera, and active
tools guided by what is seen in the camera view. Both to avoid
overcrowding the access path, and to gain a more felicitous set of
relative positions of these devices, there is use for delivering
some of them by helical paths created by rigid insertion, rather
than by insertion of a flexible catheter. The extra degrees of
freedom provided by a helix over a straight path will allow the
surgeon more freedom in the setting up of positions, with less
damage in arriving there. The helical implements useful in such
work will include: scissors, by which tissue can be cut; nibblers,
by which bone or tissue can be cut away; forceps, by which tissue
can be grasped; and spreaders, by which tissue can be forced
apart.
[0114] FIG. 31 illustrates an instrument 220 having a rigid,
helical tube 221, a fixed hand grip 222, a turning hand grip 223,
and a cutting tool 224. A wire 225 is attached to the hand grip 223
and to the cutting tool 224. The cutting tool 224 can be made to
open and close by rotating the hand grip 223 around its pivot 226
as demonstrated by the two exploded views. Various other tools may
be attached to the instrument 220 in place of the cutting tool 224,
such as the nibbling tool 227 in FIG. 31A; a gripping tool 228 in
FIG. 31B; and the spreading tool 229 in FIG. 31C.
[0115] FIG. 32 illustrates a helical instrument with a steerable
laser tip 230 which is fed by a cable 234 in a rigid helical body
235. The laser delivers highly localized radiation 231 with which
to burn away unwanted material, separate tissues, or cauterize
wounds.
[0116] FIG. 33 illustrates an endoscope with a camera 240 at its
tip and an electrical or optical fiber connection 241 disposed
inside a rigid body 242. An endoscope requires light to see by,
preferably lighting the view from the side. FIG. 34 shows a light
casting tip 245.
[0117] FIG. 35 illustrates the incorporation of an optic fiber or
power channel 250 for a light source 251 shedding light on the
action of an implement such as the gripper shown in FIG. 31B
(placed on both sides of the gripper jaw), reducing the number of
separate instruments that must enter the brain. Such a lighting
feature may be added to any of the instruments here described.
[0118] FIG. 36 illustrates an ultrasonic aspirator, with a
vibrating source 255 of directed ultrasound 256 to pulverize
tissue, a liquid insertion tube 257 to make a slurry of it, an
extraction tube 258 by which to suck out the result, and fluid
channels 259 with the power channel 260 inside the rigid helical
tube 261.
[0119] FIG. 37 illustrates a source 271 of lower intensity
ultrasound 272, so that ultrasound receivers elsewhere can collect
data from which a detailed image of the region around the source
can be reconstructed.
[0120] It should be understood by those skilled in the art that the
above list of applications is presented here only as a way of
illustrating the wide range of ways that the present invention can
be used, and therefore, should not be construed as being a complete
list of the possible application. Hence, various modifications,
additions and substitutions are possible for the invention
described herein, without departing from the scope and spirit of
the invention as disclosed in the accompanying claims.
* * * * *