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BACKGROUND OF THE INVENTION
The present invention relates to an extracorporeal lithotripter. Such
lithotripters are known in the art, and utilized an ellipsoidal reflector.
An ellipsoid will be recognized as a solid of revolution with two focal
points. The ellipsoidal reflector is truncated short of the second focal
point. A rubber or the like diaphragm closes the open end of the
ellipsoidal reflector. The reflector is filled with water with a saline
content, and a spark gap is provided at the first focus point in the
reflector. The reflector is positioned adjacent a body having a kidney
stone or other concretion to be disintegrated. The diaphragm presses
against the body, and the second focal point of the ellipsoidal reflector
is brought into coincidence with the kidney stone or other concretion.
High voltage pulses produce sparks across the spark gap. These, in turn,
flash some of the water into steam, and may also cause some dissociation
of the hydrogen and oxygen. The result is a series of shockwaves or
pulses. These shockwaves are focused by the walls of the reflector and
pass through the water in the reflector, through the diaphragm, which is
pressed against the skin of the body, and through the tissues of the body
to focus on the second focus point coincident with the kidney stone or
other concretion. A series of such shocks, generally less than an hour for
a treatment, result in reduction of the stone to small particles which
pass from the body with the urine.
Such treatment is effected from exteriorly of the body, and it may require
no hospitalization, or sometimes merely overnight hospitalization.
Advantages of a lithotripter with an isocentric system have previously
been recognized, for example see Puppo U.S. Pat. No. 5,230,329. In such an
isocentric system the reflector, often referred to as the shockhead, and
the aiming or localization device or devices, such as an X-ray system are
supported for rotation about a common center. The concretion to be
destroyed is positioned on this center, and the aiming system can be moved
to locate the stone from different angles, and the shockhead can be moved
to cause the shockwaves to attack the concretion from different angles,
thereby hastening destruction thereof. In the system disclosed by Puppo in
U.S. Pat. No. 5,230,329 the aiming or localization system, and the
shockhead are mounted on a common ring. This has advantages in rigidity
and balance. However, other advantages can be realized by separately
mounting the shockhead and the localization system for independent
rotation about a common center. Independent movement of the radiological
localization or aiming apparatus and of the shockhead, both aimed at the
isocenter of the system permits the doctor or clinician to choose the most
convenient angle of approach to the patient by simple positioning of the
shockhead. For example, the patient can be treated in supine, prone, or
lateral positions with a choice of dorsal, ventral or lateral approach.
The patient is not moved between localization and treatment, thus insuring
high accuracy of the stone localization process. Localization is effective
by means of fluoroscopic or X-ray techniques. This is done by making a
biplane sighting of the calculus at two different angles, and centering
the target in each. Initially, the radiological axis is placed in a
vertical position and the table supporting the patient is moved
horizontally in order the center the stone in the field of view. At this
point, the stone lies on the vertical axis of the system. Subsequently,
the fluoroscopy apparatus is moved to an arbitrary position, and a second
sighting is made. The table then is moved only vertically to center the
stone, bringing it into focus. It be emphasized that this is also the
treatment position. The patient is not moved thereafter. This method of
localization is rapid, and does not suffer from any loss of accuracy
caused by excessive patient movement. The angle between the two
radiological projections is not fixed, but can be suitably chosen by the
physician to reflect clinical needs.
OBJECTS AND SHORT SUMMARY OF THE PRESENT INVENTION
It is an object of the present invention to provide an extracorporeal
lithotripter having an isocentric system with independent rotation of the
shockhead and the X-ray aiming system.
An ancillary object of the invention is to provide means for axially
shifting the shockhead so that the radiological aiming system and the
shockhead can be rotated independently without interference with one
another.
In effecting the foregoing objects, we provide two supporting arms
rotatable about a common center. The radiological apparatus includes an
X-ray tube and a fluoroscopic target mounted diametrically opposite to one
another on the opposite ends of one of the arms and on a common diameter
through the isocenter. The shockhead is mounted on another arm, so that it
is axially movable to provide clearance between the aiming system and the
shockhead.
Specifically, the shockhead is mounted by means of a pivot moveably mounted
relative to a rotatable arm with the pivot being axially moveably toward
and away from the isocenter in a common plane perpendicular to the
isocenter. The shockhead further is mounted by a pivoted arm connected to
the shockhead and to the moveable arm. Movement of the first mentioned
pivot toward and away from the isocenter causes the shockhead to move in a
pivoted or arcuate manner axially of the isocenter so that the shockhead
can be retracted from the plane of the radiological system, or placed
within such plane to permit movement of the radiological system and the
shockhead independently of one another, or to move the shockhead into
operating position substantially within such plane.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic side view showing the concept of the moveable
patient table, and movement of the locating device and positioning of the
shockhead for concretion destruction;
FIG. 2 is a view similar to FIG. 1, but absent the patient and table to
illustrate further aspects of the invention;
FIG. 2a is a front view illustrating the useful operating range of the
shockhead including the reflector;
FIG. 3 is another somewhat diagrammatic representation corresponding to
FIGS. 1 and 2, but taken at right angles thereto;
FIG. 4 is a perspective view of an actual machine constructed in accordance
with the principles of the invention and showing also a computer control
table and a monitor;
FIG. 5 is another perspective view taken from a different perspective, and
with the aiming system and shockhead in a different position; and
FIG. 6 is a view similar to FIG. 5, but showing the aiming system in a
different position, and the shockhead moved into operating position.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Attention first should be directed to FIGS. 1-3 for an understanding of the
concept of the present invention. Structural details are better shown in
FIGS. 4-6, and will be referred to later. A patient supporting table 10 is
shown in FIG. 1. The table is radiotransparent so that X-rays can readily
pass through it. The table is adjustable lengthwise as indicated by the
arrows 12, and is also adjustable vertically as indicated by the double
arrow 14. Such movement is effected by toothed rack and motor driven pinon
arrangements which are known. A patient indicated at 16 lies on the table
for destruction of a kidney stone or the like 18.
The patient and table are omitted from FIGS. 2 and 3 for clarity of
illustration. The structure, as shown somewhat schematically in FIGS. 1-3,
includes a main support 20 having a center line or axis of rotation 22. A
substantially U-shaped support 24 is rotatably supported by a suitable
shaft on the axis of rotation 22, which shaft is rotatable from within the
support 20 by means of conventional electric motor and gear drive. The
U-shaped arm or support 24 includes an upwardly extending portion 26
having a branch arm 28 extending parallel to the axis of rotation 22 in a
direction away from the main support 20. The arm 24 further has a
downwardly directed arm 30 formed integrally with the arm 26 and in a
straight line therewith. It will be understood that the reference to up
and down is with regard to the apparatus as illustrated in FIG. 3. A lower
horizontal arm 32 extends from the lower end of the arm 30. The arm 32 at
the end thereof suitably supports an X-ray tube or radiation emitting
device 34 that is aimed inwardly of the U-shaped arm or support 24 to
intersect the axis of rotation or center line 22. A support 36 is provided
at the end of the arm 28 and suitably supports an image intensifier 38
which is located directly opposite the X-ray tube 34, and receives X-ray
radiation as indicated generally by the lines 40 after it has passed
through the body of the patient 16. In FIG. 1 it will be seen that the
operating range of the X-ray tube and of the image intensifier is about
120.degree., i.e. 60.degree. to either side from the vertical. The X-ray
tube or apparatus is illustrated in one position at an extreme at 34, and
at the other extreme at 34'. Similarly, the image intensifier is moveable
from one extreme at 38 to the other extreme at 38'. Locating the stone 18
from two different positions determines precisely where the stone is in
the patient's body.
With specific reference to FIG. 3, there is seen a second rotary support 42
which also is rotatable about the center line or axis of rotation 22. As
will be understood, this is readily accomplished by having a hollow shaft
supporting the U-shaped rotatable support 24 with a second shaft extending
through it to the rotatable support 42. Different gearing is provided for
rotating the two shafts, by way of electric motors as prime movers. The
rotatable support 42 carries a shockhead 44 having a truncated ellipsoidal
reflector 46. The rotatable support member 42 as is indicated in FIG. 2 is
rotatable over an arc of about 250.degree., indicated by the arcuate line
47. This allows the shockhead to be used either from above the patient, or
below the patient. For kidney stone destruction the useful operating range
of the shockhead and reflector is about 20.degree., as indicated in FIG.
2a.
The reflector 46 is generally of known construction, having a first focal
point indicated at F-1 and a second focal point F-2 disposed beyond the
end of the reflector, and intended to be rendered coincident with the
kidney stone 18. As is conventional, the open truncated end of the
reflector is closed by a rubber or the like diaphragm 48 intended to
engage the body of the patient. As is known, the reflector includes a pair
of electrodes defining a spark gap located at the first focal point F-1. A
series of high voltage electrical discharges across the spark gap results
in a succession of shockwaves which are focused by the walls of the
ellipsoidal reflector on the second focus point F-2, the shockwave passing
through the water in the reflector and diaphragm, and through the
diaphragm to the patient's body and focused on the kidney stone.
As is seen in FIG. 3 the shockhead is mounted by means of a link 50
pivotably secured to the rotatable support 42 at one end, and pivotably
connected to the shockhead 54 relatively toward the upper end thereof,
with the parts positioned as seen in FIG. 3. The shockhead further is
connected by a pivot at the lower corner 56 to a pivot support 58 on a
rack 60 suitably mounted for linear movement up and down the support 42.
The rack 60 is provided with teeth 62 which mesh with a spur gear 64
driven by a reversible electric motor 66. An upstop 68 is provided for the
rack 60.
With the rack and shockhead in limited upward position as shown in FIG. 3,
the diaphragm 48 impinges against the body of the patient, and the second
focus point F-2 is coincident with the kidney stone due to location of the
kidney stone on the center line 22 by movement of the table 10.
The pivotable mounting of the shockhead is important, since, as just noted,
in raised position it positions the second focus point F-2 on the kidney
stone. With the rack in lowered position the shockhead lies flat against
the rotatable support 42. The shockhead is then positioned away from the
patient so that shockhead may move as desired without possible engagement
(while moving) with the patient. Furthermore, it is completely out of the
way of the support arm 24. The support arm 24 has been referred to as
U-shaped, but with the parts positioned as in FIG. 3, it is better
referred to as a C-shaped support.
Independent rotation of the X-ray tube and image intensifier relative to
the shockhead is readily effected. The C-arm 24 is supported from within
the support by a hollow shaft driven by a reversible electric motor and
suitable gearing. A solid shaft extends from within the support through
the hollow shaft to the rotatable support 42, and is driven by independent
gearing and a reversible electric motor.
The isocentric lithotripter of the present invention has now been
conceptually disclosed. Certain details of construction are shown in FIGS.
4-6. The same numerals are utilized as heretofore, and complete
redescription therefore is unnecessary. However, certain further details
will be described. The lithotripter is readily placed in an existing room
without necessity of revising the architecture or construction of the
existing room. To this end, the lithotripter is provided with a flat base
or platform 74 which is simply placed on the existing room floor 76. The
support 20 heretofore disclosed is mounted on this platform. Also mounted
on the platform is a telescoping, two part table support 78 which includes
an outer fixed portion 80 containing a reversible electric motor and
suitable gearing, including an output spur gear (not shown) engagable with
the teeth 82 of a rack formed along the vertical edge of the inner
telescoping portion 84 of the support.
The telescoping portion 84 at its upper end supports a horizontal table
support structure 86 on which the patient supporting table 10 is moveable
lengthwise by suitable structure such as a rack on the underside of the
table engaging the teeth of a spur gear driven by a reversible electric
motor.
The table 10 as previously has been disclosed is constructed of
radiotransparent material to allow X-ray viewing of the kidney stone or
other concretion. The table is of generally elongated shape, and is
provided with a substantial edge cut out 88 over which the patient lies to
allow access of the diaphragm 48 of the reflector 46 to the patient's body
when approached from below, rather than above.
Positioning of the kidney stone by lengthwise and vertical adjustment,
positioning of the shockhead to clear the patient, or to effect engagement
with the patient, and movement of the X-ray emitter and image intensifier
could all be effected manually, but preferably are effected much more
quickly by use of a computer 88 shown in FIG. 4.
Although the C-arm 24 is rotatable, the X-rays emitted by the X-ray tube at
all times pass through the center line or axis of rotation of the C-arm,
whereby two X-ray views of the kidney stone permit manipulation of the
table to place the kidney stone precisely on the center line. The patient
may move himself laterally to insure that the stone will be on the center
plane of the X-ray apparatus to insure positioning of the stone properly.
The construction of the support 42 and the moveable, pivotable support of
the shockhead insures that the second focus point F-2 the reflector will
always lie on the center line or axis of rotation 22 to insure that the
second focus point F-2 will always lie in coincidence with the kidney
stone when the kidney stone has been positioned on the center line.
Due to the isocentric nature of the lithotripter this is true whether the
shockhead is above the patient as in FIGS. 1 and 4 or below the patient,
as in FIGS. 5 and 6.
Although reference has been made to X-ray or fluoroscopic location and
viewing of the kidney stone, it is sometime preferable to use ultrasound,
and this would be positioned similarly to the disclosed X-ray
apparatus,.for revolving or turning about the isocenter of the apparatus.
Pendulum movement, either below or above the patient, of the shockhead over
an arc of a few degrees leaves the reflector at all times focused on the
kidney stone, due to the isocentric geometry of the lithotripter. Such
movement allows slightly different engagement of the shockwaves with the
kidney stone, and this has been found to produce more rapid fragmentation
of the stone than a fixed approach.
The specific example of the invention as herein shown and described is for
illustrative purposes only. Various changes may occur to those skilled in
the art, and will be understood as forming a part of the present invention
insofar as they fall within the spirit and scope of the appended claims.
* * * * *
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