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Description  |
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FIELD OF THE INVENTION
The present invention pertains to a device for noninvasive stereotactic
immobilization in reproducible position.
BACKGROUND OF THE INVENTION
For the radiation therapy of patients, in whom, for example, a tumor was
diagnosed in the head by means of computerized tomography, it is necessary
to immobilize the head of the patient relative to a reference system that
is already secured in position during the tomography. For this purpose, a
stable head ring is, in general, already attached to the patient's head
before the computerized tomography. The location of the tumor with regard
to this head ring, which serves as a reference system, can then be
determined during the computerized tomography. This head ring, on which
various instruments may be arranged, must either remain on the head of the
patient or be arranged there again in reproducible position for further
therapy.
In current therapeutic practice, it is possible for head rings to remain on
the head due to the fact that the head ring is immovably fixed by means of
pins which penetrate into the head of the patient from the outside. As a
disadvantage, the patient must wear the head ring fixed in this manner for
the entire time in the case of longer periods of therapy, which can be
associated with pain, at any rate, however, with discomfort. Also, it is
not always possible, e.g., in the case of small children, to use this type
of attachment of the head ring, since damage to the bone structure may
occur.
To avoid the problems mentioned above, an attempt was made to create a
noninvasive, but reproducible fixation system for stereotactic radiation
therapy. In this system, a mask made of dressing material was applied
around the head of the patient, whereby the dressing material was then
fixed by means of a spray to the individual contours of the patient. In
this case, it was necessary to give the patient an opportunity to breathe
by means of special devices, e.g., tubes, while the mask was being applied
and fixed. After the mask hardened, it was sawed along the sides of the
head and over the top of the head into a front part and a rear front, and
both halves were provided with a joint on the one side and a closing
mechanism on the other side and were associated with a reference system,
e.g, a head ring. Also, after the mask hardened and it was removed from
the patient, openings for seeing and breathing could be inserted into the
mask.
As a result, a noninvasive system for stereotactic immobilization that can
be applied and removed had been created.
In the first place, a great disadvantage of this system concerns the only
moderately accurate reproducibility of the position of the head ring to be
set by means of the mask. Patients, who undergo a treatment with this mask
spread out over a period of, e.g., several days, do not require the same
spacing of the mask parts on each day of the treatment. This spatial
requirement or the pressure requirement on the mask may change depending
on the time of day, the state of health, the condition of the patient, or
similar circumstances. This change cannot result from the mask produced as
described above, since the spacings between its parts are determined in
the state, in which it was first applied and joined. Thus, if the face of
the patient swells up, such a mask may lead to unpleasant feelings of
difficult breathing in him. If the face of the patient should appear to
have an overall smaller spatial requirement on a later day of treatment,
then there is a risk that the above-described mask will be loose, and the
accuracy of the treatments to be carried out with it will no longer be
guaranteed.
Another great disadvantage of the mask designed according to the above
state of the art concerns the fact that its acceptance by the patient is
very poor. Already during the first application, the patient must breathe
by means of breathing aids, e.g., air tubes, especially because even the
lower jaw must be inserted into the mask in order to achieve a
satisfactory firmness. Even the eyes are covered during the preparation
procedure. All the above can lead to the patient feeling claustrophobic,
especially because this patient must remain in one position as much as
possible during the hardening time.
Other disadvantages concern especially the relatively poor stability of
this mask and the fact that, based on its brittle properties, it is
relatively susceptible to impacts of any kind.
SUMMARY OF THE INVENTION
The task of the present invention is to create a device for noninvasive,
stereotactic immobilization in reproducible position, which no longer has
the above-described disadvantages of the state of the art. Such a device,
which is readily accepted by the patient and can be utilized with high
accuracy, should especially be proposed.
This task is solved by an improved device which is designed as a mask
having parts conforming to the anatomical contour of a patient and having
connections for adjusting the relative positions of the mask parts.
The special advantage of the mask designed according to the present
invention lies in the fact that, since the mask is provided, on its
connection means, with means for adjusting the relative position of the
mask parts to one another, a possibility is created for following the
changing pressure requirement of the head of the patient. As a result, the
connection means for the mask parts is simultaneously a means for
adjusting the pressure for the mask. Therefore, by reducing the mask
pressure, e.g., it can be prevented that a patient cannot, therefore, be
treated with sufficient accuracy because the head ring fixed by the mask
is not fixed rigidly enough in its position. Unpleasant feelings of
difficult breathing can also be prevented in patients who temporarily have
a greater spatial requirement by the fact that the mask is, all in all,
enlarged via the adjustment means. Therefore, the mask will be accepted by
the patient at any time and thus will make an accurate treatment possible.
The mask parts should advantageously consist of a thermoplastic material.
The processing of this material is especially simple, since it can easily
be adapted to the contours of the head of the patient after it has been
heated, e.g., in warm water, and it hardens while cooling.
Such materials can be selected such that they do not adhere to the
patient's skin and hair, which improves the acceptance and the later
detachability of the mask after hardening. In addition, such thermoplastic
materials, in the hardened state, are hard enough to guarantee the
reproducibility of the position of the head ring; however, they still have
a sufficient elasticity to withstand even hard impacts of any kind and to
return to their original position after elastic deformation.
Due to the excellent stiffness of the thermoplastic materials in the mask
according to the present invention, there is no longer the need to
integrate the lower jaw part, so that the patient can breathe freely at
least through the mouth already when the mask is applied.
It is possible to form the mask parts at least partially from a
thermoplastic material that is designed as permeable to air. Such plastic
mats can be perforated and/or have a netlike design, and they can make it
possible for the patient to additionally breathe through his nose and to
see through the perforations or the gaps in the net, with the mask still
being sufficiently stable during the application. Thus, the acceptance and
the comfort during the application and wearing of the mask are
considerably increased, whereby the state of claustrophobia can be ruled
out to a large extent.
In a preferred embodiment of the present invention, the mask has a rear
part and a multilayered front part, whereby the back of the head of the
patient is supported by the rear part, while the patient is preset in
position by means of a first layer of the front part, e.g., by means of
strips of thermoplastic material, and is later completely immobilized by
another layer, which may consist, e.g., of a mat of the material.
In the embodiment discussed above, it is also possible for a front mask
part of one layer to have a support section made of a thermoplastic
material, which accommodates the root of the nose of the patient. This
section may consist of a heated, softened plastic and, for example, may be
connected with an upper strip, which presets the patient's forehead in
position. The other end of this Support for the root of the nose is
thereafter molded to the root of the nose of the patient and thus forms an
individually adapted, additional means of support and alignment for the
mask.
The mask parts, which would cover the area of the mouth of the patient, are
preferably left out at these points, so that this patient can breathe
easily through the mouth during the application and wearing of the mask.
In another aspect of the device according to the present invention, the
connection means for connecting the mask parts with one another as well as
with the reference system consists of two groups of strips, which are
arranged vertically to the side of the head of the patient, in which
groups of strips one strip is mechanically connected with the reference
system. The arrangement of the groups of strips to the side of the head
makes it possible to shape the mask for the first time without problems,
while the patient lies on the back of his head, and to reapply the mask in
the case of further treatment likewise without problems.
The device according to the present invention can preferably be designed
such that the mask parts have strips attached to their longitudinal edges,
which strips are joined and attached to the connecting strip with the
reference system during the putting together and during the first and
repeated application of the mask, whereby additional spacing strips of
various widths can be placed between them, and by their variation in
width, the relative position of the mask parts can be adjusted to one
another. An especially simple, applicable implementation of the principle
of the mask, which is changeable under pressure, now arises here. The
strips located on the mask parts are attached to the side edges adjacent
to the longitudinal sides of the head and can be simply applied flat to a
means of connecting with the reference system, which means are provided,
e.g., with guide rails. By the connection means having a suitable design,
it does not matter here how many parts the mask consists of, such that a
high possibility of variation with regard to the design of the mask is
achieved here. The pressure variation of the mask, i.e., the
adjustability, is achieved by means of spacing strips, which can be
inserted among the strips located on the mask parts. These spacing strips
can have different widths and thus provide the possibility of adjusting
the pressure for the mask, which is very accurate and easy to use.
This implementation possibility presents an especially favorable form of
connecting the strips connected with the reference system with the strips
arranged on the mask parts, as well as with the spacing strips for a tight
fitting of the mask. The groups of strips can be held together securely
and can be rapidly detached by means of clamps, which, e.g., are seated in
grooves that are formed in all the connecting strips and which hold the
strips together from the outside. In this case, it is advantageous to
provide a clamp both above and below for each group of strips, in which
case the clamps can be provided in various designs and are each adapted to
the width of the spacing strips. The outer strips can also have auxiliary
aids, such as, e.g., recesses for holding the clamps. If the need should
arise to rapidly remove the mask for any reason, then this can occur
simply by the fact that the clamps are rapidly pulled off, by means of
which the front mask parts are pulled off towards the front in a simple
manner.
A detachable support for the back of the head, which is also at least
partially made of a plastic material, can be arranged on the reference
system for the support of the back of the head and for further
stabilization of the mask position.
In addition, the present invention pertains to a set of mask parts, which
can be especially used with an above-described device according to the
present invention for noninvasive, stereotactic immobilization in
reproducible position.
Using thermoplastic materials for the fixation of body parts of patients is
known. These fixation materials are, in general, softened in warm water
and then pulled from the front over the head of the patient to be attached
to the side parts, e.g., on a plate. The patient is thereby immobilized,
whereby this immobilization has an accuracy with a deviation of 3 to 5 mm
according to use. As a disadvantage, the immobilization system achieved in
this manner is not generally used for procedures of radiation therapy due
to the poor accuracy when it is used again, in which procedures accuracies
with deviations of less than 1.5 mm are required.
Therefore, another task of the present invention is to make available a set
of mask parts, in which it is guaranteed that a mask can be created, which
offers reproducible immobilization of a patient with sufficient accuracy
and which can be arranged on a reference system for radiation therapy,
especially when using the device according to the present invention.
This task is solved by the set of mask parts, which is designed to
accommodate relative adjustment of the positions of the mask parts. The
arrangement of a section for the root of the nose or the bridge of the
nose of the patient gives the resulting mask a very good stability and a
good reference point for the reproducibility of the position of the parts
attached to the mask. This is especially based on the fact that the bone
structure in the area of the root of the nose lies directly under the skin
and thus is available as a hard contour. The mask parts are, according to
the present invention, provided, on the side edges which come to lie in
the vertical position, with connecting parts for connecting with one
another as well as with a reference system.
In addition, adjusting means are provided, with which the relative
positions of the mask parts can be adjusted to one another. Thus, the
already previously known advantages with regard to the adjustability of
the pressure of the mask become noticeable. The set of mask parts may be
suitable for all patients based on its thermoplastic deformability as the
unit size and thus can be produced and marketed in a cost-favorable
manner. This has a positive effect on the use, e.g., of the device
according to the present invention for several patients, since, according
to the adjustment of the mask, one head ring can be used for several
masks.
The set of mask parts according to the present invention is preferably
designed such that the connecting parts consists of strips having the same
length for all mask parts, and the adjusting means are made from spacing
strips of various widths. A system for adjusting the pressure for the mask
is again made possible here, which is simple to produce and arrange, and
in which the strips permit a very simple assembly of the mask with, e.g.,
a head ring, by placing them one on top of another together with the
spacing strips and a connecting strip.
The strips can be connected mechanically, e.g., by means of riveting, on
the vertical side edges of the mask parts, by means of which an especially
secure hold is obtained. However, it is also possible to glue the side
parts together with the strips.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is now described in detail by means of an exemplary
embodiment with reference to the attached pages of figures, in which
FIG. 1A shows, on the top, a front or rear mask part made of thermoplastic
material in the initial state;
FIG. 1B shows a fixation strip for the forehead area of the patient made of
thermoplastic material in the initial state, and
FIG. 1C shows a fixation strip for the upper jaw area of the patient made
of thermoplastic material in the initial state, whereby holes for the
attachment of strips are provided on the side edges of the mask parts
shown;
FIG. 2A shows a top view of a strip to be arranged on the edges of the mask
parts;
FIG. 2B shows a side view of the strip shown in FIG. 2A;
FIG. 3A shows a top view of a connecting strip, on which the strips in FIG.
2 can be arranged and which is connected with a reference system;
FIG. 3B shows a side view of the connecting strip shown in FIG. 3A;
FIG. 4A shows a top view of a head ring serving as a reference system with
schematically shown attachment means for the connecting strip shown in
FIG. 3 and treatment apparatus to be placed thereon;
FIG. 4B is a local sectional view taken on the line IV--IV of FIG. 4A;
FIG. 5A shows a rear view of a holder for a support for the back of the
head for attachment to a head ring according to FIG. 4.
FIG. 5B shows a side view of the holder;
FIG. 6 shows a perspective view of the entire device according to the
present invention;
FIG. 7 is a sectional view taken on the line VII--VII of FIG. 6; and
FIG. 8 is a sectional view taken on the lines VIII--VIII of FIG. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1A shows a front or rear mask part 10 which is made of a thermoplastic
material and is perforated in a netlike manner in the present exemplary
embodiment. On the lower edge of this mask part is provided a recess 12,
which provides an opening for the mouth area of the patient, when used as
the front part of the mask, and an opening for the neck area of the
patient when used as the rear part. On the left and right longitudinal
sides of the mask part 10, attachment extensions 11 are provided over
essentially the entire length for arranging the strips 20 (FIG. 2). In
this embodiment, the attachment extensions 11 are provided with holes,
which permit their later rigid connection, e.g., by means of riveting,
with the strips 20 (shown in FIGS. 2A and 2B).
FIG. 1B shows a fixation strip 13 made of thermoplastic material, which is
used to temporarily immobilize the forehead area of the patient using the
mask according to the present invention. The fixation strip 13 is not
perforated since it is not placed over the eyes or the mouth of the
patient, and again, it has, on its side edges to the left and to the
right, holes for connection with a strip 20 of the means of connection
with a reference system.
FIG. 1C shows a fixation strip 14 for the upper jaw area of a patient. On
its side edges, this fixation strip also has holes for the attachment of a
strip 20 and, in its middle area, which comes to lie above the upper lip
of the patient, is tapered so as not to protrude into the mouth area of
the patient.
The strip 20 shown in FIGS. 2A and 2B is applied to the respective mask
parts even before the mask is placed on the patient. The strip 20 shown
here is designed for arranging on a front part or rear part 10. For this
purpose, it has connecting holes 21, which pass through their wider side,
as well as connecting pins rivets 22, which stick out from it. The
position of the holes 21 and the pins 22 corresponds to the position of
the holes of the attachment extension 11 of the mask part 10. Two strips
20 are applied by means of the connecting pins 22 and the left and right
attachment extension 11 of a mask part 10, and they are riveted, i.e.,
rigidly connected, with these through the connecting holes 22. In FIG. 2B
recesses 23 are arranged at the points, where the connecting pins 22 and
connecting holes 21 are arranged. When the pins are inserted through the
holes in the marginal edges 11 of the part 10 and are riveted or
shortened, attention must be paid that no attachment part protrudes beyond
the surface 24 of the strip 20, so that it is later guaranteed that the
strips lie flat on top of one another. When the parts 10, 13 and 14 are
captured between two strips 20, as shown in FIG. 6, one of the strips 20
may be inverted top-to-bottom to enable the parts 10, 13 and 14 to be
captured between the two strips. As shown in FIGS. 2A and 2B, the spacings
between the pairs and holes are the same above and below the longitudinal
mid-point of each strip, but with the sequence of pins or rivets 22 and
holes 21 reversed. In the lower half of the strip, the holes are
designated 21' and the rivets are designated 22'. Above the mid-point of
the strip 20 each recess 23 has one pin or rivet 22 and two holes 21.
Below the mid-point of each strip 20, each recess 23' has two pins or
rivets 22' and one hole 21'. When inverted, the rivets 22' register with
the holes 21, and the rivets 22 register with the holes 21'. For this
purpose, rivets are used, which are provided with countersunk heads and
are inserted into countersunk sections 25 of the connecting holes 21.
After the strip 20 is attached to the mask part 10, it forms a very wide
and flat seal on the side parts. Guide grooves 26, which are used to the
extent that the strips can later be inserted flat between the guide rails
31 of the connecting strip 30 shown in FIGS. 3A and 3B, are placed on the
upper and lower edges of the strips 20. Retaining grooves 27 are inserted
into the edges of the strips 20, which lie on the outside and serve for
the later use of a clamp for the holding together of the groups of strips.
As shown in FIG. 6, the strips 20 are connected to the strip 30 with
spacing strips 28 which are selected from a group of spacing strips of
various widths so as to provide adjustment of the relative positions of
the marks parts.
FIG. 3 shows the top view (left) and side view (right) of a connecting
strip 30, which makes it possible to connect the individual mask parts
with one another by means of the strips. The connecting strip consists of
a material with excellent bending strength and tensile strength,
especially of a metal or light metal material or of a GFK (glass-plastic
reinforced plastic) or CFK (carbon-fiber reinforced plastic) material. The
essential components of this connecting strip 30 are the guide rails 31,
the generally rectangular rail body 32, and the coupling shoulder 33
arranged on this body, with which the connecting strip 30 is coupled to a
reference system, in this case a head ring 40 (FIG. 4A). If the connecting
strip 30 is attached to the head ring 40, e.g., by means of a screw
connection, the strips 20 attached to the mask parts 11, 13, 14 can be
applied flat onto the surfaces 34 and 35 of the connecting strip 30, in
that the strips are inserted by inserting the groove 26 into the
corresponding guide formed by the rails 31 and are pushed until they stop.
The shape of the guide rails 31 and the shape of the groove 26
corresponding to these thus prevent the strips 20 from jamming. On its
outside, the connecting strip 30 also has two retaining grooves 36
corresponding to the retaining grooves 27 in position and size, since it
must also likewise be clamped to fix the mask.
The connecting strip 30 is designed for coupling onto the head ring 40
shown in FIG. 4. The connecting strip is applied, from the inside, in the
arrow direction I (see FIG. 3B and FIG. 4A) with the coupling shoulder 33
to a throughhole in one of the longitudinal legs 41 and it is coupled to
this leg, e.g., by means of a knurled screw. In this case, each of the
longitudinal legs has several throughholes 42 in order to be able to
guarantee the adaptation to various anatomical conditions. Upon
application of the connecting strip 30 in the arrow direction I, this
would project horizontally from the plane of projection in the view shown
in FIG. 4, while the guide rails 31 extend inwards along the direction
defined by the longitudinal legs 41. To arrange various surgical or
radiation-therapy auxiliary aids, blind holes 43 with seals 44 are
provided on the ends of the longitudinal legs 41 and on the crown of the
head ring 40. In addition, an attachment recess 45 with tapholes 46
inserted therein is located in the periphery of the crown of the head ring
40.
FIGS. 5A and 5B show a head support holder 50, which supports a head
support 51 made of plastic (shown in dashed line) for the back of the head
of a patient. The head support holder 50 is attached to the head ring 40
by means of the attachment shoulder 52 adapted to the attachment recess
45, while a head support 51 arranged on its surface, whose contour is
adapted to the back of the head of the patient, supports this and the rear
part of the mask from behind in the head ring.
It can be seen from the perspective view in FIG. 6 how the device according
to the present invention, in which a mask has been adapted to the contours
of a patient, appears as a completely assembled part. The entire device is
held together mainly by the head ring 40; the support for the back of the
head 50, 51 is attached to the head ring in the area of the back of the
head. On the two side legs of the head ring 40, the two connecting strips
30 are coupled to two opposite throughholes 42. Both the mask parts 10, 13
and the spacing strip 28 are inserted into the guide rails 31 of the
connecting strips 30. The groups of strips, consisting of the strips 20,
the spacing strip 28 and the connecting strip 30, are held together by
means of clamps 29. These clamps 29 are each adapted to the width of the
spacing strip 28. When removing these clamps, the two front mask parts 10,
13 are pulled off forwards out of the guides 31 without problems.
By means of an operating sequence for applying and shaping the device
according to the present invention, its function should become even
clearer below with reference to FIG. 4A through FIG. 8.
First, the head support holder 50 is attached to the crown of the head ring
40 and secured by means of screws to be inserted into the tapholes 46. A
head support 51, consisting of plastic, is located on the head support
holder. A mask rear part 10, which is provided with two strips 20, is
applied to two connecting strips 30 and attached with clips. This takes
place on the side of the connecting strip, which has the shorter extension
of the guide rails 31, that is, using glued-on attachment extensions with
the glue side in the direction of the connecting strip. The guide rails 31
are now coupled via their coupling shoulders 33 to opposite suitable
throughholes 42 of the longitudinal legs 41 of the head ring 40 and firmly
screwed there by means of a knurled screw 47 at a position indicated by
the arrow I in FIG. 4A.
At this time, the thermoplastic material parts must be in the heated, i.e.,
soft state.
The patient now lies the back of his head into the rear part of the mask
and thus also onto the head support and thereby first shapes the rear
contours of his mask. While the mask is hardening, the clips remain as a
support on the connecting strips 30 and the strips 20.
After the rear mask part has been shaped and hardened, a spacing strip,
which is of the same length and depth as the strips 20 and is provided
with the same guide grooves on the upper edges, can now first be pushed
into the longer section, extending forwards, of the guide which is formed
from the rails 31. The width of this spacing strip can later be varied by
replacement with another in order to guarantee the function of the
dimensional adaptation of the mask according to the present invention. The
fixation strips 13 and 14, arranged with their side parts on a strip 20,
are now each heated in hot water, i.e., softened, and shaped over the
forehead and the upper lip of the patient, whereby the two strips 20,
arranged on the side edges, are again pushed into the guides, which are
each formed from the two rails 31 of the two connecting strips 30. Thus,
the two strips 20 for both fixation strips 13 and 14 come to lie above the
spacing strip between the guide rails. It must be guaranteed here that
they lie flat. During the hardening, attachment clips are again applied
around the now present group of strips.
In connection hereto, a section for the bridge of the nose can be prepared
from a thermoplastic material, whose upper end is connected with the
not-yet-hardened fixation strip for the forehead and whose lower end is
adapted, in the soft state, to the root of the nose of the patient to thus
provide a broader point of support and fixation for the head after the
hardening of the strip.
Finally, a mask front part 10, which is provided with strips 20 on its
sides, is heated and thus softened. This mask front part is applied over
the face of the patient so that the recess 12 causes the mouth area of the
patient to remain open. The front mask part 10 is made of thermoplastic
material, which is perforated in a netlike manner, and thus, it guarantees
that the patient can breathe through the nose and see through the gaps in
the net during the application of this mask part 10. During the shaping
procedure, the strips 20 on the side of the front mask part 10 are again
inserted into the guide, formed from the rails 31, and come to lie on the
strips 20 for the fixation strips 13 and 14.
The retaining grooves 27 of all strips 20 inserted into the guide rails and
into the retaining groove 36 of the connecting strip 30 come to lie
aligned with one another between the guide rails 31 during the insertion
procedure and thus represent a constant groove, into which a clamp 29 can
be inserted in a locking manner for the attachment of all strips 20 and
thus of the mask parts to one another as well as with the connecting strip
30. Recesses on the outside of each of the outer strips 20 of the mask
front part and rear part are used here to attach the clamp clasps. In the
first place, the clamps 29 are designed in their size in such a way that
they are appropriate for the spacing strip 28 used first. Sets of clamps
of various sizes can be provided for spacing strips of various widths, so
that a sufficient attachment of the groups of strips and thus of the mask
parts is always guaranteed, and according to the present invention, it is
possible to adjust the pressure or the spacing at any time with a firm but
rapidly detachable fit.
Especially suitable thermoplastic materials for the mask parts are
polyester, especially oxepanone or polycaprolactone; a suitable material
is marketed under the name OPTI-MOLD & EZ-MOLD supplied by WFR/Aquaplast
Corporation, Wyckoff, N.J.
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