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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a medical locating apparatus, particularly to a
medical locating apparatus which can suitably be used in brain surgery.
2. BACKGROUND OF THE RELATED ART
As CT scanners and MRI scanners are becoming very popular, neurosurgery has
encountered a turning point. Namely, the conventional diagnostic imaging
such as cranial plain roentgenography and cerebral angiography are now
predominantly being replaced by the three-dimensional diagnostic imaging
based on computerized analysis data in the field of brain surgery.
In order to reproduce such locational information specified on the image of
CT scanning and the like, a medical locating apparatus which locates the
site which needs surgical operation, as disclosed, for example, in
Japanese Provisional Patent Publication No. 327/1987, is employed. The
medical locating apparatus of the disclosure consists of a plurality of
arms provided on a bed, a plurality of potentiometers disposed to the
joints of the respective arms and an indicating unit disposed at the tip
of the arm, by which the site to be operated is detected based on the
signal from the potentiometers.
However, since the arms in such conventional medical locating unit are
designed to be moved via the respective joints, clutch means must be
provided on all of the joints so as to stop the entire locating apparatus.
To dispose a heavy clutch means at a high position near the indicating
unit is not preferred in view of operability and stability of the locating
apparatus.
Meanwhile, since the angles of the respective joints are detected by the
potentiometers, the apparatus are not only required to have an A/D
converter but also readily affected by the temperature change.
Further, since the weight of each arm is not well-balanced, operation of
the arms requires a great operating physical force, presenting poor
operability, disadvantageously.
SUMMARY OF THE INVENTION
This invention was accomplished noting such prior art technique and
provides a medical locating apparatus which has excellent operability and
requires neither clutch means to the joint which is brought close to the
patient nor A/D conversion, and which is not affected by the temperature
change.
In order to attain the intended object as described above, the medical
locating apparatus according to this invention comprises:
a first link pivotally supported intermediate its ends at a pivot by said
first support;
a second link pivotally supported at an upper end portion of said first
link;
a third link pivotally supported at a distal end portion of said second
link, and rotatable about a longitudinal axis;
a connection shaft connecting said first link with said second link;
a crank member pivotally supported at said connection shaft;
a first auxiliary link and a second auxiliary link, both pivotally
supported at respective first end portions at a lower end portion of said
first link;
a first sub-link, disposed to be parallel with said first link, connecting
a second end portion of said first auxiliary link with a second end
portion of said second auxiliary link;
a second sub-link, disposed to be parallel with said first link, connecting
the second end portion of said second auxiliary link and a first end
portion of said crank member;
a third sub-link, disposed to be parallel with said second link, connecting
a proximate end portion of said third link with a second end portion of
said crank member; an indicating unit mounted at a lower end of the third
link;
first and second magnetic clutches and first and second rotary encoders,
respectively provided at said pivot and at the connection shaft connecting
said first auxiliary link with said first sub-link for enabling rotational
engagements thereat;
a third magnetic clutch provided at the connection shaft connecting said
second auxiliary link with said second sub-link for enabling engagement
therebetween; and
rotary encoders provided at the connection shaft connecting said second
link with said third link, at the longitudinal axis of said third link,
and at a rotary shaft of said indicating unit for providing outputs
corresponding to their respective rotations, respectively.
The locating unit according to another aspect of the invention further
comprises a first counterweight provided on a second end of said first
auxiliary link to protrude horizontally therefrom and a second
counterweight provided on one end portion of said second auxiliary link to
protrude upwardly therefrom;
said firsts counterweight and said second counterweight interlocking with
said first auxiliary link and said second auxiliary link, respectively.
Incidentally, in the above and following descriptions, while the expression
"link" substantially means the numbered link arm, it indirectly also means
the linkage including the link arm; and the expression "to pivot" means
that the both end portions of the link are swung like a seesaw on the
fulcrum assumed at the middle thereof, whereas the expression "to rotate"
means that the link rotates on the longitudinal axis thereof like a drill.
The medical locating unit includes first to third links, first to third
sub-links and a crank member constituting a main parallel link and
subsidiary parallel links. Since the respective links are interlocked
respectively with the corresponding parallel links, clutch means need not
be disposed to all of the shafts connecting the links, but only to the
pivot locating at a relatively low position, to the connection shaft
connecting a first auxiliary link with the first sub-link and to the
connection shaft connecting a second auxiliary link with the second
sub-link. Accordingly, the links need not be operated by the respective
heavy clutches, the present apparatus enjoys excellent operability, and
such constitution is also preferred from the standpoint of stability of
the entire apparatus.
Further, since the angles of the links are detected by rotary encoders
which require no A/D conversion and are not affected by temperature
changes, the present apparatus also enjoys excellent locating accuracy.
The locating apparatus also includes a first counter weight and a second
counter weight provided to project horizontally from the other end of the
first auxiliary link and upward from one end portion of the second
auxiliary link to pivot interlocking therewith, respectively, the links
can be operated with a very small operating physical force, providing
excellent operability.
The gist of the invention is not limited to the above description, and the
objects of the invention together with the advantages, features and
applications thereof will be apparent by reading the following description
taken in conjunction with the attached drawings. It should be understood
that suitable modifications or variations without departing from the
spirit of the invention are all included in the scope of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows perspectively a medical locating apparatus according to one
embodiment of the invention;
FIG. 2 shows schematically in side view the structure above and including
the first link;
FIG. 3 shows schematically in side view the structure shown in FIG. 2, in
which the third link is pivoted;
FIG. 4 shows schematically in side view the structure shown in FIG. 2, in
which the second link is pivoted; and
FIG. 5 shows schematically in side view the structure shown in FIG. 2, in
which the first link is pivoted.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the invention will be described below referring to the
attached drawings. A patient P lies on a bed 1. (In FIG. 1, the bed 1 is
depicted extremely schematically.) A horizontal shaft 2 is fixed to the
head end of the bed 1 to be parallel with the longitudinal direction of
the bed 1. The horizontal shaft 2 is secured between a pair of jaws 3a,
consisting of an upper jaw and a lower jaw, of an L-shaped metal fitting
3. Meanwhile, another horizontal shaft 4 is secured between the other pair
of jaws 3b, also consisting of an upper jaw and a lower jaw, of the
L-shaped metal fitting 3 to be parallel with the transversal direction of
the bed 1. The clamping force of these two pairs of jaws 3a,3b can be
adjusted by levers 5, respectively, so that the horizontal shafts 2,4 can
be rotated on the longitudinal axes .alpha..sub.1, .alpha..sub.2,
respectively.
A first bracket 6 is fixed to the horizontal shaft 4 extended parallel to
the transverse direction of the bed 1, and a perpendicular shaft 7, which
is rotatable on the axis .dbd..sub.3 thereof, is disposed on the first
bracket 6. On the perpendicular shaft 7 are disposed a magnetic clutch
C.sub.1 and a rotary encoder R.sub.1. The angles in the apparatus of the
invention are all detected by rotary encoders which require no A/D
conversion and are little affected by the temperature. A second bracket 8
is also secured on the upper end of the perpendicular shaft 7, and another
horizontal shaft 9, which is rotatable on the axis .alpha..sub.4, is
supported on the second bracket 8. The horizontal shaft 9 is also provided
with a magnetic clutch C.sub.2 and a rotary encoder R.sub.2. A third
bracket 10 having an L-shaped cross section is provided at the other end
of the horizontal shaft 9.
A vertical first link 11 is pivotally supported at a point intermediate its
ends at a pivot X mounted to on the third bracket 10. A magnetic clutch
C.sub.3 and a rotary encoder R.sub.3 are provided on the pivot X. A second
link 12 is pivotally supported at a point intermediate its ends to the
upper end portion of the first link 11 by a connection shaft
.alpha..sub.5. A tip metal fitting 13 is attached to the tip of the second
link 12, and a pivotal metal fitting 15 is pivotally supported on the
connection shaft a .alpha..sub.6 disposed to the tip metal fitting 13, the
pivotal metal fitting 15 being secured at the middle of a third link 14.
The connection shaft .alpha..sub.6 is also provided with a rotary encoder
R.sub.4. The third link 14 is attached to the pivotal metal fitting 15 to
be rotatable on the longitudinal axis .alpha..sub.7 thereof. A lever 16 is
formed integrally with the pivotal metal fitting 15 to project upward
therefrom, on which a rotary encoder R.sub.5 for detecting the rotational
amount of the third link 14 is mounted. (It should be noted, however, that
the rotary encoder R.sub.5 is depicted intentionally smaller than the
actual relative size for clearer understanding of the relationship with
other parts.) Incidentally, the tip metal fitting 13 has a notch 17 for
avoiding interference with the upper end portion of the third link 14.
An indicating unit 18 is pivotally supported by a connecting shaft
.alpha..sub.8 as a rotary shaft to the lower end portion of the third link
14. The indicating unit 18 is provided with an indicating needle 19 and a
counter weight 20 on each side of the connecting shaft .alpha..sub.8, so
that the weight of the indicating needle 19 and that of the counter weight
20 may be balanced at the connection. shaft .alpha..sub.8. The connection
shaft .alpha..sub.8 is provided with a rotary encoder R.sub.5. The main
link system is as described above, and sub-link systems are combined
therewith.
A first auxiliary link 21 and a second auxiliary link 22 are pivotally
supported at one end portions thereof on the connection shaft
.alpha..sub.9 provided on the lower end of the first link 11,
respectively, the former being longer than the latter. A crank member 23
is also pivotally supported on the connection shaft .alpha..sub.5
connecting the first link 11 and the second link 12. The connection shaft
.alpha..sub.10 provided at one end portion of the first auxiliary link 21
and the connection shaft .alpha..sub.11 provided at the other end portion
of the second link 12 are connected by a first sub-link 24 which is
parallel with the first link 11. The connection shaft .alpha..sub.10 is
provided with a magnetic clutch C.sub.4 and a rotary encoder R.sub.7. A
first counterweight W.sub.1 which can be pivoted interlocking with the
first auxiliary link 21 is provided on the magnetic clutch C.sub.4,
disposed on the other end of the first auxiliary link 21, to protrude in
the horizontal direction. A second counterweight W.sub.2 which can be
pivoted interlocking with the second auxiliary link 22 is connected to on
the connection shaft .alpha..sub.9 provided at one end portion of the
second auxiliary link 22. The counterweight W.sub.2 is provided on the
side of the first auxiliary link 21 and connected to the connection shaft
.alpha..sub.9 of the second auxiliary 22 with a shaft (not shown) which
penetrates the first auxiliary link 21. The connection shaft
.alpha..sub.13 provided at the other end portion of the second auxiliary
link 22 and the connecting shaft .alpha..sub.12 disposed at one end
portion of the crank member 23 are connected by a second sub-link 25 which
is parallel with the first link 11. The connection shaft .alpha..sub.9 is
provided with a magnetic clutch C.sub.5. Further, the connection shaft
.alpha..sub.14 provided at the other end portion of the crank member 23
and the connecting shaft .alpha..sub.15 of the lever 16 of the rotary
metal fitting 15 are connected by a third sub-link 26 which is parallel
with the second link 12.
As described above, in the apparatus according to this embodiment, the
connection shaft .alpha..sub.5 .fwdarw.connection shaft .alpha..sub.9
.fwdarw.connection shaft .alpha..sub.10 .fwdarw.connection shaft
.alpha..sub.11 constitute a main parallel link A; the connection shaft
.alpha..sub.5 .fwdarw.connection shaft .alpha..sub.9 .fwdarw.connection
shaft .alpha..sub.13 .fwdarw.connection shaft .alpha..sub.12 constitute a
first subsidiary parallel link B.sub.1 ; and the connection shaft
.alpha..sub.5 .fwdarw.connection shaft .alpha..sub.6 .fwdarw.connection
shaft .alpha..sub.15 .fwdarw.connection shaft .alpha..sub.14 constitute a
second subsidiary parallel link B.sub.2.
The action of the mechanism will now be described. The structure above and
including the first link 11 is designed to be rotatable in the vertical
and horizontal directions with the aid of the shafts .alpha..sub.1 to
.alpha..sub.4. Referring now only to the action of the sub-link system,
when the third link 14 is pivoted on the connection shaft .alpha..sub.6,
as shown in FIG. 3, the shape of the second subsidiary parallel link
B.sub.2, and that of the first subsidiary parallel link B.sub.1 are
modified, and the amount of modification (i.e. the pivoted angle of the
third link 14) can be detected by the rotary encoder R.sub.4. Further,
this motion can be locked by the magnetic clutch C.sub.5. The third link
14 can be operated with a small operating physical force with the aid of
the second counter weight W.sub.2.
Next, when the second link 12 is pivoted upward on the connecting shaft
.alpha..sub.5, as shown in FIG. 4, the shape of the main parallel link A
and the second subsidiary parallel link B.sub.2 are modified, and the
amount of modification (i.e. the pivoted angle of the second link 12) can
be detected by the rotary encoder R.sub.7 disposed to the connection shaft
.alpha..sub.10. Since the crank member 23 is not pivoted in this process,
the vertical posture of the third link 14 can be maintained as such.
Incidentally, this motion can be locked by the magnetic clutch C.sub.4.
Further, the second link 12 can be operated with a small operating
physical force with the aid of the first counter weight W.sub.1.
Subsequently, when the first link 11 is pivoted on the pivot X to modify
the shape of the main parallel link A so as to bring the third link 14
farther, the pivoted angle of the first link 11 (the shift of the
indicating unit 18) can be detected by the rotary encoder R.sub.7. This
motion can be locked by the magnetic clutch C.sub.4. Further, the first
link 11 can also be operated with a small operating physical force with
the aid of the first counter weight W.sub.1. Besides, since the crank
member 23 is not pivoted either in this process, the vertical posture of
the third link 14 can be maintained as such.
Meanwhile, the rotational amount of the third link 14 on the longitudinal
axis .alpha..sub.7 thereof can be detected by the rotary encoder R.sub.5,
while the pivoted angle of the indicating unit 18 can be detected by the
rotary encoder Accordingly, the location of the tip of the indicating unit
18 can be detected based on the signals from the respective rotary
encoders R.sub.1 to R.sub.7, so that the tip of the indicating unit 18 can
be guided to the desired point based on the positional information from
the CT scanner and the like. Besides, in the apparatus according to this
embodiment, while the respective links can be operated freely on the pivot
X and on the other connection shafts .alpha..sub.5 . . . , the motions
thereof can be locked by the magnetic clutches C.sub.3 to C.sub.5 disposed
therebelow respectively. Accordingly, no heavy clutch means is needed to
be disposed to the connection shaft .alpha..sub.6 which is brought close
to the head of the patient P, providing excellent operability and
stability.
The constitution of the medical locating apparatus according to this
invention is as described above, and the main parallel link and the
subsidiary parallel links are formed by the first to third links, the
first to third sub-links and the crank member, in which the respective
links are interlocked with the corresponding parallel links, respectively.
Accordingly, clutch means need not be disposed to all of the connection
shafts of the links, but they may be disposed only to the pivot locating
relatively at a low position, to the connection shaft connecting the first
auxiliary link with the first sub-link and to the connection shaft
connecting the second auxiliary link with the second sub-link. Thus, the
links need not be operated by the respective heavy clutches, the present
apparatus enjoys excellent operability, and such constitution is also
preferred from the standpoint of stability of the entire apparatus.
Further, the angles of the links are detected by rotary encoders which
require no A/D conversion and are not affected by the temperature changes,
the present apparatus also enjoys excellent locating accuracy.
Moreover, since the first counterweight, which is disposed to protrude
horizontally from the other end portion of the first auxiliary link to
protrude and can be pivoted interlocking therewith, and the second
counterweight, which is disposed to protrude upward from one end portion
of the second auxiliary link and can be interlocked therewith are
provided, respectively, the links can be operated with a very small
physical force, providing excellent operability.
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