U.S. patent number 3,838,284 [Application Number 05/335,634] was granted by the patent office on 1974-09-24 for linear particle accelerator system having improved beam alignment and method of operation.
This patent grant is currently assigned to Varian Associates. Invention is credited to Raymond D. McIntyre, Craig S. Nunan.
United States Patent |
3,838,284 |
McIntyre , et al. |
September 24, 1974 |
LINEAR PARTICLE ACCELERATOR SYSTEM HAVING IMPROVED BEAM ALIGNMENT
AND METHOD OF OPERATION
Abstract
A linear particle accelerator having detection apparatus for
detecting the presence of and correcting for beam misalignment. The
linear accelerator includes a charged particle accelerator system
and deflection coils for changing both the positional and angular
displacement of a charged particle beam. A target is disposed in
the particle beam path for emitting X-rays upon being struck by the
charged particles. The photon field pattern developed by the target
takes the form of a forward-peaked lobe configuration extending
from the target. An arrangement of radiation responsive electrodes
is disposed in the radiation field for developing electrical
signals responsive to changes in the lobe pattern. The signals
developed by the radiation responsive electrodes are applied to
differential servo circuitry for applying signals to the deflection
coils to correct for both positional and axial misalignment of the
particle beam.
Inventors: |
McIntyre; Raymond D. (Los Altos
Hills, CA), Nunan; Craig S. (Los Altos Hills, CA) |
Assignee: |
Varian Associates (Palo Alto,
CA)
|
Family
ID: |
23312613 |
Appl.
No.: |
05/335,634 |
Filed: |
February 26, 1973 |
Current U.S.
Class: |
250/385.1;
250/399; 250/397; 378/137 |
Current CPC
Class: |
A61N
5/1048 (20130101); G01T 1/29 (20130101) |
Current International
Class: |
A61N
5/10 (20060101); G01T 1/00 (20060101); G01T
1/29 (20060101); G01t 001/18 () |
Field of
Search: |
;250/396,397,398,399,320,374,382,384,385,389 ;313/93,55
;324/71EB |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lawrence; James W.
Assistant Examiner: Willis; Davis L.
Attorney, Agent or Firm: Cole; Stanley Z. Morrissey; John
J.
Claims
Having thus described out invention, we claim:
1. A linear particle accelerator apparatus including means for
forming and projecting a beam of charged particles along a
substantially linear path, means for deflecting the particle beam,
target means disposed in the beam path for emitting radiation upon
being struck by charged particles; detector means having first
sensor means for developing first signals representative of the
position of the point at which the particle beam strikes the target
means, and second sensor means for developing second signals
representative of the angle of incidence of the particle beam on
the target means; and circuit means coupled to said first and
second sensor means for presenting output indications
representative of both the position of the particle beam and the
angle of incidence of the beam on the target means.
2. A linear particle accelerator apparatus as defined in claim 1
including control circuit means coupled between said first and
second sensing means and said deflection means for applying control
signals to said deflection means in dependence on the value of said
first and second signals to cause the particle beam to be deflected
in response to a displacement of the position at which the beam
strikes the target means and to a change in the angle of incidence
of said beam on the target means.
3. An apparatus as defined in claim 1 wherein said emitted
radiation has a field pattern which generally takes the form of a
lobe configuration extending from said target means, said first
sensor means disposed to monitor radiation levels in proximity to
the center of said radiation lobe and said second sensor means
disposed to monitor radiation levels in proximity with the outer
edges of said radiation lobe.
4. An apparatus as defined in claim 3 wherein said first sensor
means comprises a plurality of electrodes disposed on opposite
sides of an axis of symmetry of said radiation lobe and in
proximity with said axis, and said second sensor means comprises a
plurality of electrodes disposed on opposite sides of said axis of
symmetry and more remote from said axis than said plurality of
electrodes of said first sensor means.
5. An apparatus as defined in claim 3 wherein said first sensor
means comprises four electrodes disposed in a plane perpendicular
to an axis of symmetry of said radiation lobe and spaced from said
axis at substantially equal distances, and said second sensor means
comprises four electrodes disposed in a plane perpendicular to said
axis of symmetry and spaced from said axis at substantially equal
distances being greater than the distances of said electrodes of
said first sensor means.
6. An apparatus as defined in claim 5 wherein said four electrodes
in said first sensor means are each disposed in one of the
quadrants of a circular cross section of said radiation lobe taken
at right angles to said axis of symmetry.
7. An apparatus as defined in claim 5 wherein said four electrodes
in said sensor means are each disposed in one of the quadrants of a
circular cross section of said radiation lobe taken at right angles
to said axis of symmetry.
8. An apparatus as defined in claim 6 including a beam flattening
filter means having a cross section of variable slope disposed
between said target means and said detector means, and said four
electrodes in said first sensor means disposed to receive
substantially one radiation passing through the filter means at
points of maximum slope.
9. An apparatus as defined in claim 7 including a beam flattening
filter means having a cross section of variable slope disposed
between said target means and said detector means, and said four
electrodes in said first sensor means disposed to receive
substantially one radiation passing through the filter means at
points of maximum slope.
10. A system comprising a charged particle accelerator for forming
and projecting a beam of charged particles along a path, means for
varying the alignment of said beam path, target means disposed in
said path, said target means being capable of generating a
radiation field upon being struck by said beam, and inner sensor
means disposed in said radiation field for monitoring changes in
radiation intensity in an inner portion of said field, said changes
in said radiation intensity in said inner portion of said field
being representative of changes in the position on said target
means at which said beam strikes said target means.
11. The system of claim 10 further comprising outer sensor means
disposed in said radiation field for monitoring changes in
radiation intensity in an outer portion of said field, said changes
in said radiation intensity in said outer portion of said field
being representative of changes in the angle of incidence of said
beam on said target means.
12. The system of claim 11 wherein said inner sensor means and said
outer sensor means comprise planar electrodes, said electrodes all
being coplanar with each other.
13. The system of claim 11 wherein said inner sensor means
comprises an inner set of radiation responsive elements disposed
symmetrically about and spaced apart from an axis and lying in a
plane perpendicular to said axis, and said outer sensor means
comprises an outer set of radiation responsive elements disposed
symmetrically about and spaced apart from said axis and lying in
said plane, the radiation responsive elements of said outer set
being spaced further apart from said axis than the radiation
responsive elements of said inner set.
14. The system of claim 13 wherein said inner set of radiation
responsive elements comprises four planar electrodes disposed in a
quadrature relationship with respect to each other about said axis,
and said outer set of radiation responsive elements comprises four
planar electrodes disposed in a quadrature relationship with
respect to each other about said axis, each of said planar
electrodes comprising a sheet of electrically conductive material
secured to a planar surface on an electrically insulating electrode
support structure.
15. The system of claim 14 wherein each of said planar electrodes
is secured to said planar surface of said insulating electrode
support structure by a vacuum deposition bond.
16. The system of claim 11 wherein said inner sensor means and said
outer sensor means are disposed in an ionization chamber, said
ionization chamber beig disposed in said radiation field.
17. The system of claim 16 wherein said ionization chamber further
comprises a hermetically sealed housing member containing an
ionizable gas, said inner sensor means and said outer sensor means
each comprising a plurality of planar electrodes, each of said
electrodes of said inner sensor means and said outer sensor means
comprisng a sheet of electrically conductive material secured to a
planar surface of an electrically insulating electrode support
structure disposed within said housing member.
18. The system of claim 17 wherein said inner sensor means
comprises four electrodes arranged in a quadrature relationship
with respect to each other in a disposition symmetrical about and
spaced apart from an axis perpendicular to the planar surface of
said electrode support structure, and said outer sensor means
comprises four electrodes arranged in a quadrature relationship
with respect to each other in a disposition symmetrical about and
spaced apart from said axis, the electrodes of said outer sensor
means being spaced further apart from said axis than the electrodes
of said inner sensor means.
19. The system of claim 10 further comprising a flattening filter
disposed in said radiation field intermediate said target means and
said inner sensor means.
20. The system of claim 19 wherein said inner sensor means
comprises radiation responsive elements disposed in said radiation
field in alignment with the steepest slope of said flattening
filter.
21. A system comprising a charged particle accelerator for forming
and projecting a beam of charged particles along a path, means for
varying the alignment of said beam path, target means disposed in
said path, said target means being capable of generating a
radiation field upon being struck by said beam, and outer sensor
means disposed in said radiation field for monitoring changes in
radiation intensity in an outer portion of said field, said changes
in said radiation intensity in said outer portion of said field
being representative of changes in the angle of incidence of said
beam on said target means.
22. The system of claim 21 further comprising inner sensor means
disposed in said radiation field for monitoring changes in
radiation intensity in an inner portion of said field, said changes
in said radiation intensity in said inner portion of said field
being representative of changes in the position on said target
means at which said beam strikes said target means.
23. The system of claim 21 wherein said outer sensor means
comprises four electrodes of arcuate configuration arranged in a
quadrature relationship with respect to each other in a coplanar
disposition symmetrical about and spaced apart from an axis
perpendicular to said plane.
24. The system of claim 22 further comprising circuit means for
coupling said inner and outer sensor means to said means for
varying the alignment of said beam path, whereby said inner and
outer sensor means can generate control signals and apply said
control signals to said means for varying the alignment of said
beam path in response to said monitored changes in radiation
intensity in said inner and outer portions of said radiation field,
thereby causing said beam to maintain a constant angle of incidence
upon said target means at a constant position on said target
means.
25. The method of continuously monitoring the orientation of a
radiation field produced by the bombardment of a beam of charged
particles upon a target means, said method comprising the steps of
locating first sensor means in said field, said first sensor means
being responsive to changes in the position on said target means at
which said beam strikes said target means, and locating second
sensor means in said field, said second sensor means being
responsive to changes in the angle of incidence of said beam on
said target means.
Description
CROSS REFERENCES TO RELATED PATENTS AND PATENT APPLICATION
U.S. Pat. No. 3,322,950 to J. S. Bailey et al, entitled "Linear
Accelerator Radiotherapy Device and Associated Beam Defining
Structure," issued May 30, 1967 and assigned to the same assignee
as the present invention.
U.S. Pat. No. 3,360,647 to R. T. Avery, entitled "Electron
Accelerator With Specific Deflecting Magnet Structure and X-ray
Target," issued Dec. 26, 1967 and assigned to the same assignee as
the present invention.
U.S. Pat. application Ser. No. 335,633 by R. D. McIntyre, entitled
"Transmission Ionization Chamber," filed concurrently herewith and
assigned to the assignee of the present application.
BACKGROUND OF THE INVENTION
This invention pertains to the art of particle accelerators, and
more particularly, to linear particle accelerators for use with
high-energy X-ray systems, such as those used in X-ray therapy.
Modern methods of treating cancer and other related diseases demand
high intensity levels of radiation for deep X-ray therapy
applications. Therefore, high energy radiotherapy devices operate
typically in a range of 4 to 25 million electron volts in order to
obtain the desired radiation intensity distribution. In X-ray
therapy it is necessary that the radiation be very precisely
directed in order to obtain maximum clinical benefit from the high
energy radiation.
Present day high energy X-ray systems generally comprise a charged
particle accelerator which forms and projects a beam of charged
particles onto a target for generating X-rays. The accelerated
particles are focused and in some cases bent at 90.degree. prior to
being directed toward a target.
A heavy metal primary collimator is generally located at the
downstream side of the target and is used to obtain the desired
X-ray beam configuration. A flattening filter and an ionization
chamber are normally positioned in the X-ray beam to measure dose
rate and to integrate the total dose in order to obtain uniform
intensity of the beam across a plane normal to the beam path. An
example of such a high-energy X-ray system is disclosed in the
aforementioned United States patent to J. S. Bailey et al.
If the beam of charged particles strikes the target at a point
displaced from the center of the target, the resulting pattern of
emitted X-rays is correspondingly displaced. Also, if the angle of
incidence at which the particle beam strikes the target is changed,
there is an angular change in the radiation pattern of X-rays
leaving the target. With positional and angular displacement of the
X-ray pattern resulting from positional and angular misalignment of
the charged particle beam striking the target, it is difficult, if
not impossible, to accurately direct the emitted X-rays.
Half-plate or quadrant radiation responsive electrodes placed in an
ionization chamber have been used to measure the distribution of
radiation intensity across a charged particle radiation field.
Generally, the quadrant electrodes have been symmetrically placed
about a centerline of the ion chamber. The ion chamber is then
positioned so that its centerline is coincident with the central
axis of a radiation field. Such an array of four electrodes will
provide signals proportional to the integral of radiation flux
passing through each quadrant and may be used to monitor symmetry
of the radiation field pattern about the central axis.
With certain conditions of beam misalignment, this quadrant
arrangement has been found to be unsatisfactory in detecting
assymetry of the field at a plane remote from the ion chamber
itself. For example, it is possible to have both a positional
displacement of the charged particle beam on the target in
combination with a change in the angle at which the beam strikes
the target. In previous high-energy X-ray systems of the type which
includes a charged particle beam impinging on a target, a heavy
metal collimator located downstream of the target, and a field
flattening filter and ion chamber, the charged particle beam may be
controlled in such a manner as to cause the quadrant electrodes to
indicate a balanced condition: however, the balanced field would
only exist in the plane of the ion chamber and not at other planes
remote from the ion chamber.
SUMMARY OF THE INVENTION
The present invention is directed toward a radiation responsive
detection system for controlling the alignment of a charged
particle beam in order to maintain a desired radiation pattern,
thereby overcoming the noted disadvantages, and others, of previous
systems.
Based upon the principle that the radiation or photon field
generated by a target being struck by charged particles will take
the form of a forward-peak lobe pattern, it has been found that a
slight change in the angle of incidence of the particle beam on the
target results in a substantial tilt of this radiation lobe
pattern. It has also been determined that a change in the position
on the target at which the beam of particles strikes a target
results in a corresponding displacement of the lobe pattern.
Accordingly, it has been found that by placing an outer set of
radiation responsive electrodes at positions to monitor the extreme
edges, or shoulders, of the photon field, the tilt of the lobe may
be measured with a high degree of accuracy. A separate set of inner
electrodes are then placed to measure radiation passing through the
steepest slope of the flatness filter in order to detect changes in
position of the lobe. Changes in the photon field due to tilt of
the lobe at the inner portions of the lobe are compensated for by
increased absorption in the flatness filter; therefore, the inner
set of electrodes are unresponsive to changes in the tilt of the
lobe. Thus, the inner electrodes provide only an indication of
positional changes of the lobe.
In one aspect of the present invention, there is the provision of a
particle accelerator which includes apparatus for forming and
projecting a beam of particles into a substantially linear path.
The linear accelerator also includes means for deflecting the
particle beam, such as angular error symmetry servomechanism coils
and positional error symmetry servomechanism coils. A target is
disposed in the path of the particle beam for emitting X-rays upon
being struck by particles. A radiation detector arrangement is
placed in the radiation field for measuring certain parameters of
the pattern of radiation, and a control circuit is coupled between
the radiation detector and the beam deflector for correcting for
angular and positional displacement of the particle beam.
In another aspect of the present invention, the detector
arrangement includes radiation responsive electrodes for monitoring
radiation intensity at the outer edges of the radiation field and
electrodes positioned to monitor radiation intensity at positions
close to an axis of symmetry of the radiation field in order to
develop signals representative of changes in two parameters of the
radiation pattern.
In another aspect of the present invention, there is the provision
of an inner set of four electrodes which are each disposed in one
of the quadrants about an axis of symmetry of the radiation field,
and an outer set of four electrodes which are disposed more distant
from the axis than the inner electrodes and each positioned in one
of the quadrants.
In another aspect of the present invention, there is the provision
of a method of aligning a charged particle beam, both with respect
to angular changes of the longitudinal axis and displacement
changes of the beam, by monitoring the tilt and changes in the
position of a lobe radiation pattern which is formed when the
particles strike a target.
The objects and advantages of the invention will become apparent
from the following description of a preferred embodiment of the
invention as read in conjunction with the accompanying drawings and
in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram, schematic view illustrating in basic
form a high energy X-ray sysem incorporating beam alignment
apparatus of the present invention;
FIG. 2 is a schematic view illustrating forward-peaked lobe
patterns resulting from changes in the alignment of the charged
particle beam;
FIG. 3 is a plan view illustrating an arrangement of electrodes for
monitoring the radiation pattern;
FIG. 4 is a sectional view of the electrode assembly of FIG. 3
taken along lines 4--4, and associated electrical servomechanism
circuitry; and
FIG. 5 is a sectional view of the electrode assembly illustrated in
FIG. 3 taken along lines 5--5, and associated electrical
servomechanism circuitry.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 generally illustrates a high energy X-ray system comprising
a particle accelerator system 10 for accelerating and projecting
charged particles onto a target 12. Upon being struck by the
charged particles, the target 12 emits high energy X-rays.
Downstream from the target 12 is a heavy metal primary collimator
14 which is used to obtain the desired X-ray beam configuration.
Positioned downstream of the primary collimator 14, and aligned
with the opening in the collimator, is a flattening filter 16 and
an ionization chamber 18. The ionization chamber 18 is disposed in
the radiation field to measure dose rate and for integrating the
total radiation in order to generate electrical signals which are,
in turn, used to maintain alignment of the particle beam. A
jaw-shaped movable collimator 20 is positioned downstream from the
flattening filter and ionization chamber for varying the radiation
field size.
More particularly, the particle accelerator system 10 includes a
charged particle accelerator 22 for forming charged particles,
accelerating the particles, and focusing the particles into a beam.
Angular error symmetry servomechanism coils 24, which are
associated with the particle accelerator 22, primarily serve the
function of changing the angle of incidence at which the beam of
charged particles strike the target 12.
The beam of particles generated by the accelerator 22 passes
through a beam transport system 26 and through position error
symmetry servomechanism coils 28. The beam transport system 26
includes deflecting and focusing coils and various slits for
shaping the particle beam. The position error servomechanism coils
28 primarily serve the function of changing the location on the
target 12 at which the particle beam strikes the target.
Disposed between the position servomechanism coils 28 and the
target 12 is a beam bending magnet 30 which serves to bend the beam
of charged particles through a 90.degree. angle. Reference is made
to the aforementioned United States Patent to R. T. Avery for an
example of an electron accelerator which utilizes 90.degree. beam
bending techniques. It should be noted, however, that the practice
of the present invention does not require such bending of the
beam.
FIG. 2 illustrates the general configuration of a photon field
generated at the target 12 when the target is struck by charged
particles. For purposes of illustration, the photon field, which
takes the form of a forward-peaked lobe pattern 36, is illustrated
in a separate figure; however, it is to be understood that such a
lobe pattern would actually exist in the X-ray system of FIG.
1.
As illustrated in FIG. 2, if the beam of charged particles strikes
the target 12 at a point corresponding to the center of the target,
as illustrated by the solid line 32, then the axis of symmetry 34
of the lobe 36, both of which are illustrated by solid lines, will
extend perpendicular to the plane of the target 12. If, however,
the beam of charged particles strikes the target 12 at an angle of
incidence different from 90.degree. and at a point displaced from
the center of the target, as illustrated by the broken line 38, the
resulting lobe pattern 40 will be tilted by an amount corresponding
to the change in the angle of incidence of the particle beam. This
change is illustrated by the change in intensity, designated 0 at
the shoulders of the lobe. The broken line 42 indicates the
symmetrical axis of the tilted lobe pattern 40.
FIG. 3 illustrates in more detail the ionization chamber 18. More
particularly, the ionization chamber includes an arrangement of
electrodes for measuring parameters of the radiation lobe pattern
in order to detect both changes in the angle of incidence of the
particle bem and changes in the point at which the particle beam
strikes the target.
The electrodes take the form of four planar electrodes 44, 46, 48,
50, each of which is situated in one of the quadrants of the
circular disc-shaped ionization chamber. The electrodes 44, 46, 48,
50, which comprise the inner set of electrodes, are each slightly
spaced from a central axis of the disc-shaped chamber 18 and each
extends outwardly for a distance of approximately 1/4 of the radial
distance of the ionization chamber. As illustrated in FIG. 1, the
inner quadrant electrodes are positioned under the flattening
filter 16 at locations directly beneath the steepest slope of the
flattening filter. By so positioning these inner quadrant
electrodes, the tilt of the lobe pattern in the region of the
flattening filter is compensated for by increased absorption in the
flattening filter. Thus, these inner quadrant electrodes are only
responsive to changes in the position of the radiation lobe. Each
of the inner electrodes 44, 46, 48, 50 is connected to a
corresponding one of four output terminals 52, 54, 56, 58.
The ionization chamber 18 also includes an outer set of four planar
electrodes 60, 62, 64, 66, each of which is positioned in the same
quadrant as one of the inner electrodes 44, 46, 48, 50. The
electrodes of the outer set are of an arcuate configuration with
the center of curvature of the curved portions thereof being the
central axis of the disc-shaped chamber 18. The electrodes of the
outer set are radially spaced from the central axis of the
ionization chamber at positions more remote than the inner
electrodes. The electrodes of the outer set are disposed at
locations to detect the intensity of the radiation lobe pattern at
the outer edges, or shoulders, of the lobe to thereby measure the
tilt of the lobe. Each of the outer electrodes 60, 62, 64, 66 is
electrically connected to a corresponding one of four output
terminals 68, 70, 72, 74.
The planer electrodes 44, 46, 48, 50, 60, 62, 64, 66 are all placed
in a single plane in the ionization chamber 18 and are supported by
an insulative plate 67 which is positioned in a disc-shaped housing
member. A planar high voltage electrode (not shown) is placed in
spaced parallel relationship with the other electrodes, and the
chamber 18 is filled with an ionizable gas. Thus, each of the
detector electrodes collects ion current proportional to the
radiation field intensity averaged over the electrode area. The
aforementioned United States Patent Application by R. D. McIntyre
provides further details of the construction of the ionization
chamber 18.
As illustrated in FIG. 4 the inner electrodes 46, 48 are connected
to the input terminals of a differential servoamplifier 76 having
its output terminal connected to one of the terminals of a
positional error symmetry servomechanism coil 78. The other
terminal of this coil 78 is connected directly to ground. Also, a
meter 80 is connected between the output terminal of the
differential servoamplifier 76 and ground to provide an indication
of the value of the compensating signal being applied to the
positional servomechanism coil 78.
Similarly, as illustrated in FIG. 5 the other inner electrodes 44,
50 are connected to the input terminals of a differential
servoamplifier 82 having its output terminal connected to one of
the terminals of another positional error symmetry servomechanism
coil 84. The other terminal of this coil 84 is connected directly
to ground. Also, the output terminal of the differential
servoamplifier 82 is connected through a meter 86 to ground.
Thus, the electrodes 46, 48 serve to monitor along one coordinate
axis the displacement of the radiation lobe which is representative
of the location at which the particle beam strikes the target 12.
The electrodes 44, 50 serve to detect changes in the beam position
along a second coordinate axis perpendicular to the first axis.
Thus, the signals developed by the electrodes 44, 46, 48, 50, when
applied to the positional servomechanism coils 78, 84, primarily
correct for changes in the position at which the particle beam
strikes the target.
The outer electrodes 62, 64 are connected to the input terminals of
another differential servoamplifier 88 having its output terminal
connected to one of the terminals of an angular error symmetry
servomechanism coil 90. The other terminal of this coil 90 is
connected directly to ground. Also, a meter 92 is connected between
the output terminal of the servoamplifier 88 and ground. Similarly,
the other outer electrodes 60, 66 are connected to the input
terminals of still another differential servoamplifier 94 having
its output terminal connected to one of the terminals of another
angular error symmetry servomechanism coil 96. The other terminal
of this coil 96 is connected directly to ground, and a meter 98 is
connected between the output terminal of the differential
servoamplifier 94 and ground.
Thus, the outer electrodes 62, 64 are responsive to the large
changes in intensity at the shoulders of the lobe pattern. Changes
in the intensity of the lobe pattern correspond to changes in the
angle of incidence of the particle beam on the target. Thus, the
electrical signals developed by the outer electrodes 62, 64, when
applied through the differential servoamplifier 88, are used to
control the energization of the angular error symmetry
servomechanism coil 90. An indication of the angular compensation
is provided by the meter 92. The other outer electrodes 60, 66
provide similar compensation of the angular error along an axis
perpendicular to the axis of the electrodes 62, 64.
Accordingly, the present invention provides for both angular and
positional beam alignment at the point where the particle beam
strikes the target. Therefore, with the present invention it is
possible to maintain a constant axis of symmetry for the radiation
pattern emitted by the target.
Although the invention has been shown in connection with the
preferred embodiment, it will be readily apparent to those skilled
in the art that various changes in form and arrangement of parts
may be made to fit requirements without departing from the spirit
and scope of the invention as defined by the appended claims.
* * * * *