U.S. patent application number 17/173427 was filed with the patent office on 2021-07-22 for combined radiotherapy and mri apparatus.
The applicant listed for this patent is ELEKTA LIMITED. Invention is credited to Kevin BROWN, Dan THOMPSON, Gregory TRAUSCH.
Application Number | 20210219841 17/173427 |
Document ID | / |
Family ID | 1000005495335 |
Filed Date | 2021-07-22 |
United States Patent
Application |
20210219841 |
Kind Code |
A1 |
TRAUSCH; Gregory ; et
al. |
July 22, 2021 |
COMBINED RADIOTHERAPY AND MRI APPARATUS
Abstract
The present invention provides a combined radiotherapy and MRI
system in which an imaging coil is mounted on a mechanical arm. The
position of the imaging coil is thus known and in embodiments can
be controlled to prevent collisions with the patient and
unfavourable interactions between the imaging coil and the
radiation beam.
Inventors: |
TRAUSCH; Gregory;
(Billinghurst, GB) ; BROWN; Kevin; (Horsham,
GB) ; THOMPSON; Dan; (East Grinstead, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELEKTA LIMITED |
Crawley |
|
GB |
|
|
Family ID: |
1000005495335 |
Appl. No.: |
17/173427 |
Filed: |
February 11, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14887534 |
Oct 20, 2015 |
10945605 |
|
|
17173427 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 5/1049 20130101;
A61B 5/055 20130101; A61N 5/10 20130101; A61B 5/0036 20180801; A61N
2005/1055 20130101; A61B 5/4836 20130101 |
International
Class: |
A61B 5/00 20060101
A61B005/00; A61N 5/10 20060101 A61N005/10; A61B 5/055 20060101
A61B005/055 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2014 |
GB |
1418885.8 |
Claims
1.-20. (canceled)
21. A radiotherapy system, comprising: a patient support; a
radiotherapy device configured to generate a therapeutic beam of
radiation incident upon a treatment volume; a magnetic resonance
imaging (MRI) apparatus configured to generate imaging data of an
imaging volume which encompasses the treatment volume, the MRI
apparatus defining a bore in which the patient support can be at
least partially positioned; an arm controlled by a control system;
and an imaging coil having a first side that is fixedly attached to
the MRI apparatus by the arm, wherein the imaging coil is arranged
within the bore; wherein: the imaging coil comprises a conducting
coil and electronic circuitry coupled to the conducting coil,
wherein the electronic circuitry is configured to control the
conducting coil and the electronic circuitry is located along the
first side, wherein the first side is a proximal side of the
imaging coil with respect to the arm; the arm has a length
extending within the bore toward the first side of the imaging
coil; the control system is configured to move the arm relative to
and within the bore to prevent the electronic circuitry from
intersecting the beam when the conducting coil intersects the beam
when generating the imaging data of the imaging volume; and the
imaging coil is configured to detect MRI signals emitted from the
imaging volume within the bore.
22. The system according to claim 21, wherein the control system is
configured to move the arm such that the movement of the arm
adjusts a position of the imaging coil relative to the patient
support.
23. The system according to claim 21, further comprising a
detection system configured to detect the position of the imaging
coil relative to a patient on the patient support.
24. The system according to claim 23, wherein the detection system
comprises a proximity sensor.
25. The system according to claim 23, wherein the detection system
comprises MRI-imagable markers mounted on the imaging coil.
26. The system according to claim 23, wherein the position of the
imaging coil within the bore is configured to be varied in
dependence on the position of the imaging coil relative to the
patient.
27. The system according to claim 21, further comprising one or
more image capture devices configured to capture images of: a
patient on the patient support; and the imaging coil relative to
the patient.
28. The system according to claim 27, wherein the control system is
configured to: receive the captured images from the one or more
image capture devices; and move the arm to prevent collisions
between the patient and the imaging coil based on the captured
images.
29. The system according to claim 21, wherein the control system is
configured to move the arm such that the movement of the arm
adjusts an orientation of the imaging coil.
30. The system according to claim 21, further comprising a
plurality of imaging coils.
31. The system according to claim 30, wherein at least one of the
plurality of imaging coils is fixedly positioned beneath the
patient support.
32. The system according to claim 31, further comprising a
plurality of arms associated with the plurality of imaging coils,
wherein at least one of the plurality of imaging coils is fixedly
attached to the MRI apparatus by an associated one of the plurality
of arms and is arranged within the bore.
33. The system according to claim 21, wherein the patient support
comprises a patient support translatable along a longitudinal axis
relative to the bore.
34. The system according to claim 21, wherein the electronic
circuitry is configured to process at least one of: signals
received by the conducting coil; and signals for transmission by
the conducting coil.
35. A radiotherapy system, comprising: a patient support; a
radiotherapy device configured to generate a therapeutic beam of
radiation incident upon a treatment volume; a magnetic resonance
imaging (MRI) apparatus configured to generate imaging data of an
imaging volume which encompasses the treatment volume, the MRI
apparatus defining a bore in which the patient support can be at
least partially positioned; an arm; an imaging coil having a first
side that is fixedly attached to the MRI apparatus by the arm,
wherein the imaging coil is arranged within the bore; wherein: the
imaging coil comprises a conducting coil and electronic circuitry
coupled to the conducting coil, wherein the electronic circuitry is
configured to control the conducting coil and the electronic
circuitry is located along the first side, wherein the first side
is a proximal side of the imaging coil with respect to the arm; and
the arm has a length extending within the bore toward the first
side of the imaging coil; and a control system comprising a
processor configured to execute instructions to: control the
imaging coil to detect MRI signals emitted from the imaging volume
within the bore; generate imaging data of the imaging volume; and
move the arm relative to and within the bore to prevent the
electronic circuitry from intersecting the beam when the conducting
coil intersects the beam when generating the imaging data of the
imaging volume.
36. The system according to claim 35, further comprising a
detection system configured to detect the position of the imaging
coil relative to a patient on the patient support.
37. The system according to claim 36, wherein the detection system
comprises a proximity sensor.
38. The system according to claim 36, wherein the detection system
comprises MRI-imagable markers mounted on the imaging coil.
39. The system according to claim 36, wherein the position of the
imaging coil within the bore is configured to be varied in
dependence on the position of the imaging coil relative to the
patient.
40. The system according to claim 35, wherein the patient support
comprises a patient support translatable along a longitudinal axis
relative to the bore.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 14/887,534, filed on Oct. 20, 2015 (now allowed), which claims
priority from United Kingdom Patent Application No. 1418885.8,
filed on Oct. 23, 2014. The contents of the above-referenced
applications are expressly incorporated herein by reference in
their entireties.
TECHNICAL FIELD
[0002] The present invention relates to a combined radiotherapy and
magnetic resonance imaging (Mill) apparatus.
BACKGROUND
[0003] Recent developments in the field of radiotherapy have
focussed on integrating an imaging system with the therapeutic
system. The goal is to provide real-time feedback on the location
of an anatomical feature within the patient (e.g. a tumour) such
that a therapeutic radiation beam can be more accurately controlled
to target that feature.
[0004] One suggested approach is to combine a linear
accelerator-based therapeutic system with a magnetic resonance
imaging (MM) system within a single apparatus, known as an
MRI-Linac. Such apparatus is described in a number of earlier
applications by the present Applicant, including U.S. patent
application Ser. No. 12/704,944 (publication no 2011/0201918) and
PCT publication no 2011/127947. In the systems described in these
earlier applications, the patient can be imaged and treated
substantially simultaneously while lying in the same position.
[0005] One feature of the MM system is an "imaging coil"--a
transmitter/receiver typically comprising a coil and processing
electronics--which picks up the low-amplitude electromagnetic
signals generated within the patient as part of the MRI process. In
a conventional MRI system, the imaging coil is placed directly on
the patient so as to maximise the efficiency with which those
signals are detected. For example, it is known to manufacture
imaging coils using a certain geometry so as to fit closely to
certain parts of the human anatomy.
[0006] In a combined radiotherapy and MRI system, however, this
solution is not possible as the interaction of the radiation beam
with the imaging coil generates secondary electrons which would
increase the dose in the skin of the patient. An alternative
solution is required.
SUMMARY OF INVENTION
[0007] According to a first aspect of the present invention, there
is provided a system, comprising: a patient support, a radiotherapy
device for generating a therapeutic beam of radiation incident upon
a treatment volume; and a magnetic resonance imaging (MRI)
apparatus for generating imaging data of an imaging volume which
encompasses the treatment volume. The MRI apparatus defines a bore
in which the patient support can be at least partially positioned,
and comprises an imaging coil, fixedly attached to the MRI
apparatus by an arm and arranged within the bore, for detecting MM
signals emitted from the imaging volume.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] For a better understanding of the present invention, and to
show more clearly how it may be carried into effect, reference will
now be made, by way of example, to the following drawings, in
which:
[0009] FIG. 1 shows a side view of a combined radiotherapy and MRI
system in cross-section according to embodiments of the present
invention;
[0010] FIG. 2 shows an end view of a combined radiotherapy and MRI
system in cross-section according to embodiments of the present
invention; and
[0011] FIG. 3 shows an imaging coil according to embodiments of the
present invention.
[0012] FIG. 4 shows a schematic functional structure for a control
apparatus according to embodiments of the present invention.
DETAILED DESCRIPTION
[0013] FIGS. 1 and 2 show a combined radiotherapy and MRI system 10
according to embodiments of the present invention. FIG. 1 shows a
side view of the system in cross-section, while FIG. 2 shows an end
view of the system. Those skilled in the art will appreciate that
certain features of the system have been omitted from one or other
of the Figures for clarity purposes.
[0014] The system comprises a bed 12, for supporting a patient in
the apparatus. The bed 12 is movable in a direction parallel to a
horizontal axis (labelled "I"), such that a patient resting on the
bed can be moved into and out of the apparatus. The bed 12 may form
a cantilever section that projects away from a support structure
(not illustrated). In one embodiment, the bed 12 is moved along the
translation axis relative to the support structure in order to form
the cantilever section, i.e. the cantilever section increases in
length as the bed is moved and the support structure remains
stationary. In other embodiments, the bed 12 may be supported along
its length as it moves along the translation axis, such that there
is no cantilever section.
[0015] The system 10 further comprises a radiotherapy apparatus
which delivers doses of radiation to a patient supported by the bed
10. The radiotherapy apparatus comprises a source of radiation 14
and a collimating device 16 (collectively known as a radiation
head), which together generate a beam of therapeutic radiation 18.
The source of radiation may take any suitable form (e.g. a
radioactive source, a linear accelerator, etc), and the beam may be
formed using any suitable ionizing radiation, such as x-rays,
electrons or protons (for example). The radiation will typically
have an energy which is capable of having a therapeutic effect in a
patient positioned on the bed 10. For example, a therapeutic x-ray
beam may have an energy in excess of 1 MeV.
[0016] The collimating device 16 may be any device suitable for
collimating the radiation beam to take a desired shape (for
example, to conform to the shape of a target within the patient).
In one embodiment, the collimating device 16 comprises a multi-leaf
collimator, known to those skilled in the art. Such a device
comprises one or more banks of elongate leaves (and typically
comprises two such banks on opposite sides of the beam), with each
leaf being individually moveable into and out of the radiation beam
in order to block that part of the beam from reaching the patient.
In combination, the leaves collectively act to shape the beam
according to a desired cross-section.
[0017] The radiation head is mounted on a chassis 20, and
configured such that the radiation beam 18 is directed towards and
intersects with the axis I. The chassis 20 is continuously
rotatable around the axis I, with the point of intersection of the
radiation beam with the axis I being known as the "isocentre" of
the apparatus. In this way, radiation can be directed towards a
patient on the bed 12 from multiple directions, reducing the dose
which is delivered to healthy tissue surrounding the target for
treatment (e.g. a tumour).
[0018] The system 10 further comprises an Mill apparatus, for
producing images of a patient positioned on the bed 12. The Mill
apparatus includes one or more magnetic coils 22 which act to
generate a magnetic field for magnetic resonance imaging. That is,
the magnetic field lines generated by operation of the magnetic
coil 22 run substantially parallel to the central axis I. The
magnetic coils 22 may consist of one or more coils with an axis
that runs parallel to, or is coincident with the axis I. The
magnetic coils may be split into first and second magnetic coils
22a, 22b, each having a common central axis, but separated by a
window which is free of coils. In other embodiments, the magnetic
coils 22 may simply be thin enough that they are substantially
transparent to radiation of the wavelength generated by the source
of radiation 14. In yet further embodiments, the magnetic coils 22
may have a varying pitch, such that the pitch is relatively wide
where the coils 22 intersect the radiation beam 18, and relatively
narrow in one or more regions outside the radiation beam 18. The
magnetic coils may comprise one or more coils for generating a
primary magnetic field; one or more coils for generating a gradient
magnetic field that is superposed on the primary magnetic field and
allows spatial encoding of the protons so that their position can
be determined from the frequency at which resonance occurs (the
Larmor frequency); and/or one or more active shielding coils, which
generate a magnetic field outside the apparatus of approximately
equal magnitude and opposite polarity to the magnetic field
generated by the primary magnetic coil. The more sensitive parts of
the system 10, such as the source of radiation 14, may be
positioned in this region outside the coils where the magnetic
field is cancelled, at least to a first order.
[0019] The coils 22 may be arranged within a housing 24, which can
additionally contain a system for keeping the coils cool (e.g. a
cryogenic system based on liquid helium or similar). The housing
may also allow the system 10 to be kept clean, and reduces patient
anxiety whilst undergoing treatment. The internal space of the
housing (i.e. inside the coils 22) is often referred to as the
"bore".
[0020] The radiation source 14 is positioned to emit radiation
through the window defined by the two coils 22a, 22b. The radiation
beam may take any shape, but in embodiments of the invention can be
a fan beam, arranged with the fan's narrow dimension parallel to
the axis I. A fan-shaped beam may provide substantial radiation to
the patient through the narrow window, meaning that the coils 22a,
22b can be placed closer together than with conventional integrated
radiotherapy/imaging systems. This allows the coils 22a, 22b to
generate a more homogenous gradient field than would otherwise be
the case, increasing the quality of the images obtained by the MM
apparatus.
[0021] In use, the MRI system can provide real-time imaging of a
patient undergoing therapy, allowing accurate targeting of the
treatment volume by the radiation beam 18 (for example through
altered collimation by the collimating device 16), or automated
shutdown if the patient moves significantly.
[0022] One component of the MM system which has not been discussed
above is the RF system. This transmits radio signals towards the
patient, and detects the absorption at those frequencies so that
the presence and location of protons in the patient can be
determined. The RF system may include a single coil that both
transmits the radio signals and receives the reflected signals,
dedicated transmitting and receiving coils, or multi-element phased
array coils, for example. As described above, it is important that
the imaging coil be arranged as close to the patient as possible,
so as to detect the low-amplitude signals which are emitted by the
protons within the patient.
[0023] According to embodiments of the invention, the system 10
comprises an imaging coil 26 which is fixedly attached to the MRI
apparatus by an arm 28.
[0024] FIG. 3 shows a plan view of the imaging coil 26. The imaging
coil 26 comprises one or more electromagnetic coils 30 and
electronic circuitry 32 coupled to the electromagnetic coils,
arranged to process the signals received by the electromagnetic
coils 30 and/or process signals for transmission by the
electromagnetic coils 30. The circuitry 32 therefore comprises a Tx
chain and/or an Rx chain comprising one or more amplifiers, and
processing circuitry.
[0025] As shown in FIG. 3, the circuitry 32 is arranged to one side
of the imaging coil 26, with the majority of the planar view taken
up by the coil 30. In particular, according to embodiments of the
invention, electronic circuitry is not included within the coil 30,
above the coil, or below the coil. Instead, the circuitry 32 is
placed to the side of the coil 30, and arranged around one or more
sides of the imaging coil 26.
[0026] The arm 28 is fixedly attached at its near end to the
housing 24, or to the frame of the system 10 itself (not
illustrated). This fixation point may be at one end of the housing
24, as in the illustrated embodiment, or within the bore itself. At
its far end, the arm 28 is coupled to the imaging coil 26. The arm
may comprise one or more joints, articulations and/or
extending/contracting parts (such as pneumatic pistons, for
example), which allow the imaging coil 26 to be moved within and
around the bore of the system 10. In addition to manipulating the
position of the imaging coil 26, the arm 28 may comprise a
mechanism for altering the orientation of the imaging coil 26. The
imaging coil 26 can thus be positioned and/or oriented within the
bore with a high degree of positional accuracy. In some
embodiments, the imaging coil 26 may be attached to the MRI
apparatus by more than one arm.
[0027] The system 10 further comprises a control apparatus 11,
which is coupled to the various components of the system 10 and
controls their operation. The control apparatus will typically
comprise a suitably programmed computer, but may also comprise
dedicated electronic circuits. As shown in FIG. 4, the control
apparatus 11 may also control the MRI parts of the system so as to
provide imaging information of the treatment volume of the patient.
For example, the control apparatus 11 may control the magnetic coil
22 to generate a magnetic field of a certain strength, and a
certain gradient; the control apparatus 11 may control the imaging
coil 26 to generate RF signals; and the control apparatus 11 may
control the arm 28 to position and/or orient the imaging coil 26 in
a certain way. The control apparatus 11 may control the
radiotherapy parts of the system according to a predetermined
treatment plan and/or in dependence on the imaging data generated
by the MRI apparatus. For example, the control apparatus 11 may
control the radiation source 14 to generate radiation with a
controlled energy, and at a controlled time; the control apparatus
11 may control the collimating apparatus 16 to apply a given
collimation to the radiation; the control apparatus 11 may control
the gantry 20 to rotate to a certain angle, or to rotate a certain
angular distance at a certain rate. The control apparatus 11 may
further control the bed 12, so as to position the patient
appropriately within the bore.
[0028] As discussed above, and as shown in FIGS. 1 and 2, higher
imaging quality is achieved when the imaging coil 26 is placed as
close to the patient and the source of electromagnetic signals as
possible. As the intention of the combined MM and radiotherapy
system is to provide imaging of the volume undergoing treatment,
this entails placing the imaging coil 26 close to or in the path of
the radiation beam 18. The interaction of the imaging coil with the
radiation beam has potential problems, however. For example,
secondary electrons generated by interactions between the ionizing
radiation and the imaging coil may increase skin dose to the
patient if the imaging coil is placed too close to or in contact
with the patient. Further, the radiation beam 18 can damage the
electronic circuitry 32 which processes the signals received by and
transmitted by the coil 30.
[0029] According to embodiments of the invention, therefore, the
system 10 may be controlled within a set of constraints which serve
to reduce or minimize the risks associated with these
interactions.
[0030] For example, in one embodiment, the arm 28 may be controlled
so as to position the imaging coil 26 as close to the patient as
possible, but without touching the patient's skin. The imaging coil
26 may be positioned at least a predetermined minimum distance away
from the patient, e.g. 5 mm, 10 mm, or 20 mm, to ensure that the
patient does not come into contact with the imaging coil by making
an expected movement.
[0031] In order to achieve this, the imaging coil can be provided
with a detection system 34 (shown in FIG. 3), which allows the
position of the imaging coil 26 to be determined relative to a
patient on the bed 12. The detection system 34 may comprise one or
more MRI-imageable markers, such that the MM system can directly
image the detection system and thus determine the position of the
imaging coil 26 relative to the patient. In addition, or
alternatively, the detection system 34 may comprise a proximity
sensor arranged to detect nearby objects. In either case, the
detection system may provide feedback to the control apparatus 11
such that the arm 28 is controlled to ensure that the patient and
the imaging coil 26 do not come into contact with each other, and
remain an appropriate distance apart at all times.
[0032] Alternatively, the system 10 may comprise one or more
cameras (not illustrated) arranged to view the imaging coil 26 and
the patient within the bore, and to provide feedback to the control
apparatus 11 such that the arm 28 can be controlled to prevent
collisions between the patient and the imaging coil 26. In this
embodiment, the imaging coil 26 may not require a detection system
34.
[0033] In this way, the position of the imaging coil 26 can be
controlled to prevent it from coming into contact with a patient
undergoing radiotherapy treatment, while ensuring that the coil 26
is nonetheless as close to the patient as possible to pick up the
low-amplitude electromagnetic signals emitted as part of the MRI
process.
[0034] It can be seen in FIG. 1 that the imaging coil 26 is placed
within the path of the radiation beam 18. In fact, according to
embodiments of the invention only the electromagnetic coil 30
itself may be placed within the path of the beam; the electronic
circuitry 32 is outside the path of the beam 18. According to
embodiments of the invention, the arm 28 may be constrained, or the
control apparatus 11 may be constrained, such that the electronic
circuitry 32 may never enter the path of the beam 18. For example,
the arm 28 may be unable to move the imaging coil in a direction
along the axis I, and may be constrained to move the imaging coil
26 only vertically (i.e. directly towards and away from the bed
12). In this way, provided the arm 28 has the correct length in a
direction parallel to the axis I, the electronic circuitry 32 will
never enter the radiation beam 18.
[0035] In other embodiments, the arm 28 may be able to move the
imaging coil 26 in a direction parallel to the axis I and/or rotate
the imaging coil around the axis I, but can be controlled--based on
the knowledge of the radiation beam 18 dimensions and the imaging
coil 26 position within the control apparatus 11--such that the
electronic circuitry 32 does not enter the beam 18.
[0036] In this way, according to embodiments of the invention, the
position of the imaging coil 26 is always known precisely, and the
system can be controlled to avoid harmful interactions between the
radiation beam 18 and the electronic circuitry 32.
[0037] It will be appreciated by those skilled in the art that the
imaging coil 26 need not be placed within the path of the radiation
beam 18. When the gantry is rotated to certain angles, for example,
the radiation beam 18 may not pass through the imaging coil at
all.
[0038] The system 10 may comprise one or more further imaging
coils, to enhance further the ability to pick up low-amplitude
electromagnetic signals emitted from the patient. For example, a
second imaging coil 40 may be provided within the housing 24,
beneath the bed 12 and in line with the radiation beam 18 (and thus
the treatment volume). The second imaging coil 40 may also comprise
an electromagnetic coil and processing circuitry, but in the
illustrated embodiment is in a fixed position. The fixed position
is such that the electronic circuitry cannot fall within the path
of the radiation beam.
[0039] Those skilled in the art will appreciate that yet further
imaging coils (not illustrated) may be provided on respective arms,
in a similar manner to the first imaging coil 26. For example, the
further imaging coils may be attached to arms fixed to an opposite
end of the housing 24 to the arm 28. In this way, the further
imaging coils can be controlled to approach the treatment volume
from an opposite direction and so cover a wider area.
[0040] The present invention thus provides a combined radiotherapy
and MRI system in which an imaging coil is mounted on a mechanical
arm. The position of the imaging coil is thus known and in
embodiments can be precisely controlled to prevent collisions with
the patient and unfavourable interactions between the imaging coil
and the radiation beam.
[0041] Those skilled in the art will appreciate that various
amendments and alterations can be made to the embodiments described
above without departing from the scope of the invention as defined
in the claims appended hereto.
* * * * *