U.S. patent application number 13/163025 was filed with the patent office on 2011-10-13 for movable integrated scanner for surgical imaging applications.
Invention is credited to David Graves, Gord Klimenko, Tony Lentz, Jonathan Li, John Saunders, James Schellenberg, Hong Yu.
Application Number | 20110251480 13/163025 |
Document ID | / |
Family ID | 38833014 |
Filed Date | 2011-10-13 |
United States Patent
Application |
20110251480 |
Kind Code |
A1 |
Graves; David ; et
al. |
October 13, 2011 |
Movable Integrated Scanner for Surgical Imaging Applications
Abstract
A patient imaging system includes a patient support table, an
MRI system including a cylindrical magnet and a PET system
including positron detectors mounted in a ring. The magnet defines
a cylindrical bore for receiving the patient on the table where the
magnet is mounted for rotation about a vertical axis on a slew ring
carried on rails allowing longitudinal movement. The PET ring is
mounted in the bore for longitudinal movement. The quench tube for
the magnet passes through the slew ring with a rotary union at the
axis. The shielding covers include a fixed upper part and a lower
part which rotates about the axis with the magnet. The magnet is
arranged in a two or three room diagnostic configuration in which a
holding bay houses the magnet and the diagnostic patients are
organized in the three rooms each cooperating with the magnet bay
as the magnet is rotated.
Inventors: |
Graves; David; (Winnipeg,
CA) ; Saunders; John; (Winnipeg, CA) ;
Klimenko; Gord; (Winnipeg, CA) ; Lentz; Tony;
(Winnipeg, CA) ; Yu; Hong; (Winnipeg, CA) ;
Li; Jonathan; (Winnipeg, CA) ; Schellenberg;
James; (Winnipeg, CA) |
Family ID: |
38833014 |
Appl. No.: |
13/163025 |
Filed: |
June 17, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11765845 |
Jun 20, 2007 |
|
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13163025 |
|
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60805241 |
Jun 20, 2006 |
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Current U.S.
Class: |
600/411 |
Current CPC
Class: |
G01R 33/481 20130101;
A61B 5/0035 20130101; G01R 33/38 20130101; A61B 5/055 20130101;
G01R 33/28 20130101 |
Class at
Publication: |
600/411 |
International
Class: |
A61B 5/055 20060101
A61B005/055 |
Claims
1. Apparatus for obtaining a scanned image of a part of a patient
comprising: a patient support table; and a magnetic resonance
imaging system for obtaining images of a part of the patient, the
magnetic resonance imaging system comprising: a magnet for use with
a control system for controlling and varying the magnetic fields, a
radio frequency transmission and detection system for eliciting and
detecting from the part of the patient nuclear magnetic resonance
signals, in response to the magnetic fields, including an RF probe
arranged to be located adjacent to the part of the patient and a
computer and display monitor for decoding and displaying the
detected signals; the magnet defining a cylindrical bore arranged
such that the part of the patient is positioned in the bore so as
to lie in the magnetic field of the magnet while the patient is
located in place on the table; and a positron emission tomography
scanning system (PET) for use in conjunction with the magnetic
resonance imaging system.
2. The apparatus according to claim 1 wherein there is provided
relative movement between the magnet and the table.
3. The apparatus according to claim 1 wherein the PET system is
movable relative to the magnet.
4. The apparatus according to claim 1 wherein the PET system and
the magnet are mounted such that the field of view of the magnet
coincides with the field of view of the PET of the patient on the
table.
5. The apparatus according to claim 1 wherein the PET includes
optical fibers extending along the bore to carry optical signals
from scintillation detectors thereof to an exterior control
system.
6. The apparatus according to claim 1 wherein the PET includes a
wireless communication system to carry optical signals from
scintillation detectors thereof to an exterior control system.
7. A hybrid imaging system comprising: a magnetic resonance
scanner; and a second modality imaging system disposed in the same
radio frequency isolation space as the magnetic resonance scanner,
the second modality imaging system including radiation detectors
configured to detect at least one of high energy particles and high
energy photons.
8. The hybrid imaging system as set forth in claim 7, further
including magnetic shielding arranged to reduce magnetic fields
from the magnetic resonance scanner.
9. The hybrid imaging system as set forth in claim 8, wherein the
second modality imaging system is a positron emission tomography
(PET) scanner.
10. The hybrid imaging system as set forth in claim 9, wherein the
radiation detectors include photomultiplier tubes and
scintillators.
11. The hybrid imaging system as set forth in claim 8, wherein the
magnetic shielding includes active shielding coils configured to
generate a compensatory magnetic field that at least partially
cancels the magnetic fields from the magnetic resonance
scanner.
12. The hybrid imaging system as set forth in claim 7, further
including rails for providing movement of one or both of the
magnetic resonance scanner and the a second modality imaging
system.
13. The hybrid imaging system as set forth in claim 7, wherein the
magnetic resonance scanner and the second modality imaging system
are physically separate units that are spaced apart by a gap, and
the hybrid imaging system further includes a patient bed disposed
in the gap between the magnetic resonance scanner and the second
modality imaging system and configured to load a patient disposed
on the patient bed into either the magnetic resonance scanner or
the second modality imaging system.
14. The hybrid imaging system as set forth in claim 7, wherein the
second modality imaging system includes a positron emission
tomography (PET) scanner.
15. The hybrid imaging system as set forth in claim 7, wherein the
magnetic resonance scanner and the second modality imaging system
are spaced apart, the hybrid imaging system further including a
retractable radio frequency screen selectively extendible between
the magnetic resonance scanner and the second modality imaging
system.
Description
[0001] This application is a divisional application of application
Ser. No. 11/765,845 filed Jun. 20, 2007 which is presently
pending.
[0002] This application claims the benefit under 35 USC 119 of the
filing date of Provisional Application 60/805241 filed Jun. 20,
2006.
[0003] This invention relates to a movable apparatus for obtaining
medical scanned images of a patient. The apparatus may provide the
possibility for combining and sequencing both PET and MRI detection
capability for surgical imaging applications. The apparatus may
provide movement in both translational and rotational directions to
optimize the utility and effectiveness of the system.
BACKGROUND OF THE INVENTION
[0004] Both PET (Positron Emission Tomography) and MRI (Magnetic
Resonance Imaging) are known techniques which can be used to image
the body. In the case of PET, a solution is injected or taken into
the body, the solution which contains molecules with positron
emitting atoms. Therefore, once positron detector geometry is
properly positioned around the patient, and once software is used
to identify the location of the positron emission, the location and
concentration of positron emitting molecules can be detected. One
of the major molecules used is a derivative of glucose which can
enter the cells as glucose but is not metabolised as glucose and so
the regions of major activity in the body can be detected. If the
molecules are specific for cancer then this imaging technique can
be utilised to detect the location of the tumour. PET however does
not provide any anatomical information, only information on the
location of the positron emitting molecules. The
[0005] PET images need to registered to the anatomy of the patient
and this is where MRI can be very useful.
[0006] With MRI, a high field magnet, typically superconducting, is
arranged in a torus configuration (like a donut) and with the
patient lying down inside the magnet the magnetic field allows a
pulsed and sequenced magnetic and EM field to probe the body to
produce soft tissue images, which allow the trained radiologist to
determine with high probability the anatomy of the patient. MRI is
sometimes performed using contrast agents to provide even better
contrast between different soft tissue types. MRI techniques are
very good at detecting the anatomical location of many but not all
tumours.
[0007] These two imaging techniques, MRI and PET, are orthogonal
techniques, in that the PET detection technology can be constructed
in such a way that it is unaffected by magnetic fields and the MRI
system can be constructed to be unaffected by the PET techniques.
For this reason, if an integrated PET and MRI detector system can
be constructed, then the two systems can be operated in parallel or
almost parallel manners in both space and time to allow for
improved and more complete detection of tumour locations within the
body.
[0008] PET and MRI can be used to obtain a functional image
combined with anatomical image to provide the clinician with far
more information than either technique alone. For example, positron
emitting molecules can be developed which interact only with
certain receptors in the brain and so these receptors can be
observed by PET and then their actual location in the brain
determined by the MRI.
[0009] PET imaging is also an established technique, with general
knowledge being available as well as many patents on specific
configurations of PET detectors.
[0010] U.S. Pat. No. 5,998,792 discusses a variable detector
geometry in 1999, and describes PET imaging as follows:
[0011] In nuclear imaging, a radiopharmaceutical such as .sup.99m
Tc or .sup.201 T1 is introduced into the body of a patient. As the
radiopharmaceutical decays, gamma rays are generated. These gamma
rays are detected and used to construct a clinically useful
image.
[0012] Positron emission tomography (PET) is a branch of nuclear
medicine in which a positron-emitting radiopharmaceutical such as
.sup.18 F-Fluorodeoxyglucose (FDG) is introduced into the body of a
patient. Each emitted positron reacts with an electron in what is
known as an annihilation event, thereby generating a pair of 511
keV gamma rays. The gamma rays are emitted in directions
approximately 180 degrees apart, i.e. in opposite directions.
[0013] A pair of detectors registers the position and energy of the
respective gamma rays, thereby providing information as to the
position of the annihilation event and hence the positron source.
Because the gamma rays travel in opposite directions, the positron
annihilation is said to have occurred along a line of coincidence
connecting the detected gamma rays. A number of such events are
collected and used to reconstruct a clinically useful image.
[0014] Various detector systems have been used in PET imaging. One
class of PET systems can be termed non-rotating systems. The most
common non-rotating systems have one or more rings of detector
elements disposed in a circle about the patient. Other non-rotating
systems include cylindrical shell detector systems and hexagonal
multi-plate systems. In each of these systems, the detector
surrounds or nearly completely surrounds the object to be scanned.
Since coincidence events at substantially all transverse angles
within a slice can be detected, system sensitivity is does not vary
much between locations in a transverse slice.
[0015] Another class of PET systems can be termed rotating systems.
Partial ring systems and dual or triple head gamma camera systems
with coincidence detection capabilities fall into this category.
One type of partial ring system includes two arcs of radiation
sensitive detectors disposed on a generally circular rotating
gantry. The arcs of radiation detectors are fixed with respect to
each other so that their centers are generally diametrically
opposed, with a slight angular offset. Rotating systems have
partial transverse angle coverage such that it is necessary to
rotate the detectors about the patient (or vice versa) in order to
sample the transverse angles needed to reconstruct fully
tomographic images. The sensitivity of these systems thus varies
across the detector field of view. This variation in sensitivity is
taken into account during processing of the coincidence data.
[0016] This description of the PET rotating and non-rotating
geometries refers to the PET detector itself, and not to an
integrated scanner using PET/MRI. US Pat. No. 6,674,083 (Tanaka)
issued Jan. 6, 2004 discusses a positron emission tomography
apparatus.
[0017] The article "The New Challenges of Brain PET Imaging
Technology", written in Current Medical Imaging Reviews, 2006, 2,
3-13, authored by Habib Zaidi and Marie-Louise Montandon,
demonstrates through a prototype construction that combined PET I
MRI scanners are possible. "Whole-Body Imaging with PET/MRI",
European Journal of Medical Research, Jun. 30, 2004, page 309-312,
states, regarding the combination of PET and MRI into a single
scanner,
[0018] "The combination of these two excellent diagnostic imaging
modalities into a single scanner offers several advantages in
comparison to PET and MRI alone".
[0019] "Simultaneous PET and NMR", The British Journal of
Radiology, 75(2002),S53-S59 describes a small prototype PET scanner
that is MR compatible is described. In this case, four meter
sections of optical fiber are used to transport the scintillation
signals to photomultiplier tubes that are removed from the high
magnetic field area of the bore. They discuss the potential
advantages for both temporal and spatial correlation. As they
indicate in this paper,
[0020] "incorporation of PET and MR scanners into a single gantry
would keep subject motion and tissue deformation between PET and MR
acquisitions to an absolute minimum, as is the approach adopted for
the combined PET and CT systems described elsewhere in this special
issue (their references 2, 3) "
[0021] Additional papers that include Simon Cherry as author are:
"Simultaneous PET and MR imaging", Y. Shao et al, Phys. Med. Biol.
1997 October 42(10), 1965-70; "Contemporaneous positron emission
tomography and MR imaging at 1.5T", K. Farahani et al, J. Magn.
Res. Imaging 1999 March, 9(3):497-500; "A study of artefacts in
simultaneous PET and MR imaging using a prototype MR compatible PET
scanner", R B Slates et al, Phys. Med. Biol. 1999 August;
44(8):2015-27.
[0022] An additional publication is "MR-PET: Combining Function,
Anatomy and More", M. Schwaiger et al, September 2005 Medical
Solutions, pp.25-30. This publication provides a simple diagram
which shows a Magnetom Espree with a modified bore liner assembly.
In this bore liner assembly is shown an RF body coil, above which
is the PET camera elements. The diagram indicates that PET is
acquired with a ring inserted into the magnet--simultaneous
acquisitions are possible.
[0023] In U.S. Pat. No. 4,939,464 (Hammer) issued Jul. 3, 1990 is
disclosed a combination NMR/PET scanner which uses light pipes to
communicate the scintillation events to the exterior of the magnet.
The PET scanner ring is mounted in the magnet bore and is moveable
relative thereto.
[0024] In U.S. Pat. No. 6,946,841 (Rubashov) issued Sep. 20, 2005
is disclosed a combination NMR/PET scanner for breast tissue which
where the PET scanner ring is mounted outside the magnet bore and
the patient is moved between the two scanning positions.
[0025] In U.S. Pat. No. 5,719,400 (Cherry) issued Feb. 17, 1998 is
disclosed a high resolution detector for use in PET scanning which
is suitable for use in combined PET/MRI systems.
[0026] Further, previous publications and patents have shown it is
possible to move a high-field superconducting MRI system in
translation.
[0027] In U.S. Pat. No. 5,735,278 (Hoult et al) issued Apr. 7, 1998
is disclosed a medical procedure where a magnet is movable relative
to a patient and relative to other components of the system. The
moving magnet system allows intra-operative MRI imaging to occur
more easily in neurosurgery patients, and has additional
applications for liver, breast, spine and cardiac surgery patients.
The system is used as follows:
[0028] The magnet is at first some distance from the operating
table, either in the side or back of the surgical room or perhaps
within a holding bay area; When imaging is required, the MRI magnet
is advanced from its holding area and positioned in the imaging
position over the table;
[0029] Images are taken and magnet is retracted to its holding
area.
Thus the MRI system consists of:
[0030] Magnet;
[0031] Rails, installed on the site;
[0032] Magnet mover system, which consists of a magnet carriage,
cable carrier, and mover control system.
SUMMARY OF THE INVENTION
[0033] According to a first aspect of the invention there is
provided an for obtaining a scanned image of a part of a patient
comprising:
[0034] a patient support table;
[0035] and a magnetic resonance imaging system for obtaining images
of a part of the patient, the magnetic resonance imaging system
comprising:
[0036] a magnet for use with a control system for controlling and
varying the magnetic fields, a radio frequency transmission and
detection system for eliciting and detecting from the part of the
patient nuclear magnetic resonance signals, in response to the
magnetic fields, including an RF probe arranged to be located
adjacent to the part of the patient and a computer and display
monitor for decoding and displaying the detected signals;
[0037] the magnet defining a cylindrical bore arranged such that
the part of the patient is positioned in the bore so as to lie in
the magnetic field of the magnet while the patient is located in
place on the table;
[0038] the magnet being mounted for movement relative to the table
horizontally in a direction longitudinal of the table, the mounting
providing a first position of the magnet in which the part of the
patient is positioned in the magnetic field of the magnet while the
patient remains in place on the table; and a positron emission
tomography scanning system (PET) mounted on the magnet for use in
conjunction with the magnetic resonance imaging system.
[0039] Preferably the PET system is movable. Preferably the PET
system is mounted on the magnet for common movement therewith.
[0040] Preferably the magnet is movable longitudinally along its
axis.
[0041] Preferably the magnet is movable vertically. Preferably the
magnet is rotatable about a vertical axis through 180 degrees.
[0042] Preferably the PET system is mounted in the bore of the
magnet for common movement therewith.
[0043] Preferably the PET system is mounted such that the field of
view of the magnet coincides with the field of view of the PET.
[0044] Preferably the PET system is movable within the bore.
[0045] Preferably the PET system is mounted on the magnet at one
end such that movement of the magnet carries the PET to a position
aligned with the part of the patient.
[0046] Preferably the magnet is rotatable about a vertical axis to
move the PET to a position adjacent the patient.
[0047] Preferably the PET includes optical fibers extending along
the bore to carry optical signals from the scintillation detectors
to an exterior control system.
[0048] Preferably the PET includes a wireless communication system
to carry optical signals from the scintillation detectors to an
exterior control system.
[0049] Preferably the magnet is mounted on a rail system and the
PET system is mounted on same rail system for separate movement of
the PET system relative to the magnet.
[0050] According to a second aspect of the invention there is
provided an apparatus for obtaining a scanned image of a part of a
patient comprising:
[0051] a patient support table;
[0052] and a magnetic resonance imaging system for obtaining images
of a part of the patient, the magnetic resonance imaging system
comprising:
[0053] a magnet for use with a control system for controlling and
varying the magnetic fields, a radio frequency transmission and
detection system for eliciting and detecting from the part of the
patient nuclear magnetic resonance signals, in response to the
magnetic fields, including an RE probe arranged to be located
adjacent to the part of the patient and a computer and display
monitor for decoding and displaying the detected signals;
[0054] the magnet defining a cylindrical bore arranged such
.sub.that the part of the patient is positioned in the bore so as
to lie in the magnetic field of the magnet while the patient is
located in place on the table;
[0055] the magnet being mounted for rotation about a vertical
axis.
[0056] Preferably the magnet is movable longitudinally along its
axis.
[0057] Preferably the magnet is movable vertically. Preferably the
magnet is rotatable about a vertical axis through 180 degrees.
[0058] Preferably the magnet is rotatable about a vertical axis to
move a front end of the magnet to a position adjacent the
patient.
[0059] Preferably the magnet is movable on a support carried on
rails in a longitudinal direction and wherein there is provided a
turntable connecting the magnet to the support to allow the front
face of the magnet to be turned to face in one or other direction
along the rails.
[0060] The table may be a diagnostic table carried by the magnet
which can be extended into a room where the patient lies on the
diagnostic table and imaging is performed.
[0061] The table may be a surgical table which remains in place in
the room for relative movement of the magnet which can be extended
into a room where the patient lies on the surgical table and
imaging is performed. The magnet may be arranged to carry a
diagnostic table at one end and to co-operate with a surgical table
at the other end.
[0062] The system is installed in renovated hospital buildings or
in new buildings. The system can be installed in one-room or
two-room configurations. In the two-room configuration, the magnet
and MRI system is shared between the two rooms as needed by the
hospital staff, leading to increased cost effectiveness within the
business case.
[0063] Many room configurations can be discussed with this concept.
Many applications can also be discussed, with the applications
being limited by the size and extension of the operating room table
and the limitations of the MRI scanner.
[0064] In some regions and countries there is a premium placed on
patient safety which disallows the movement of the patient after
surgery has started.
[0065] Therefore, any design of the integrated PET/MRI scanner
should move the scanner instead of moving the patient. This
movement of the scanner could be in whole or in part, as long as
the patient does not move. This same restriction on usage may
eventually be true of interventional approaches, in that some
interventional techniques require a significant number of
penetrations of the body or aligned equipment items, which infer
that patient movement should not be done.
[0066] Further, the MRI system has a magnetic field which is not
equivalent in all directions with the magnetic field strength along
the axis being different than in the two orthogonal directions.
This means that the PET imaging portion of the system may be
optimally sited on an off-axis orientation, which implies that
rotation of the integrated scanner may be important.
[0067] The present arrangement moves the MRI in rotational and
vertical directions as well to ensure that the integrated scanner
is optimized.
[0068] The present arrangement assumes the presence of a scanner
system that integrates both MRI and PET capability, and patents the
movement of the integrated scanner in each of the six degrees of
freedom of movement for the surgical, interventional and diagnostic
imaging environments.
[0069] Additional unique multi-room layouts, configurations and
applications are possible when a rotating MR1 system is designed.
In this case, the following multi-room configurations are used as
examples to illustrate the variety of applications which are
possible, with all of these applications being financially
beneficial to the healthcare industry.
[0070] With these superconducting magnet systems, there are quench
tubes, gradient cables, cooling cables of water and helium, and
various control cables that need to be rotated as well. In
addition, the rotation must be managed so that the rotation is 180
degrees in one direction and potentially 180 degrees in the other,
if all 360 degrees of rotation is required.
[0071] The magnet system moves into a room within 1 minute, and the
doors open within seconds, so the limiting factor on effectiveness
of usage of the magnet system is providing the patients into and
out of the room, prepping the patients if required, and discussing
the imaging with the patients. It is known that a reasonable amount
of time per imaging event is 60 minutes, and therefore the movement
of the MRI scanner into and out of a room is not the limiting time
value. As well, the efficiency of a multi-room system becomes more
difficult to schedule as the need for both diagnostic and
interventional procedures occurs. The following configurations are
now possible:
[0072] A three room diagnostic configuration in which a central
magnet holding bay houses the magnet and the diagnostic patients
are organized in the three rooms. The doors to room one open, the
magnet holding bay becomes part of room one, the magnet does not
move but may extend its diagnostic table, the patient lies on the
diagnostic table, imaging is performed, no need to do intervention
is found, the patient exits the diagnostic table and the magnet
moves back into the holding bay, ready for use by one of the other
rooms. The magnet then may draw in its table, rotates to the doors
for that room, and the process for the other room begins. In this
case, the magnet does not move in a translational direction, such
as on rails, but simply rotates.
[0073] A two room system which is in the corner of the hospital. In
this case, the magnet both rotates and translates. There is a
central magnet holding room, with doors in each of the two 90
degree directions, and the magnet can rotate its diagnostic table
in whichever direction is required, or can rotate to allow the
opposite end of the magnet to enter the room first. This approach
allows existing diagnostic functionality and applications to be
used in either room, or allows both rooms to serve as
intra-operative rooms without any significant change to magnet
controls and monitoring. This two room corner system cannot be done
without a rotating magnet. Similarly, any room configuration which
is not of the in-line variety needs to have a rotating magnet.
[0074] In addition, in-line configurations can have increased
flexibility as well if rotation is allowed. For example, one can
join two diagnostic rooms with a magnet holding room in the middle.
In this case, the MRI system rotates so that the diagnostic table
is always the first entry into the room. This allows the diagnostic
rooms to be as small as possible, allowing maximum density of the
MRI system and the smallest cost in terms of square footage for the
diagnostic room.
[0075] Many other room configurations can obviously be imagined for
those skilled in the art of medical architecture and imaging
systems.
[0076] If the MRI and PET methods are integrated together into a
single device, one has an integrated scanner which uses orthogonal
imaging technologies. Whereas previous work has assumed that the
MR/PET scanner is stationary, a scanner which is capable of
translational and rotational movement has unique attributes which
are incorporated into this patent claim.
[0077] The following improvements arise:
[0078] PET Imaging can be done in one room, followed by MRI imaging
in an adjacent room, based on the needs of the patient and surgical
team, thus increasing the financial payback of the medical
installation. In this case, there may be two different patients in
these two rooms, and one patient needs PET imaging and one needs
MRI.
[0079] More flexible PET and MR integration can be considered, in
that when imaging a floppy gland during surgery no patient movement
is required in order to perform imaging on multiple body sites.
[0080] If the PET imaging equipment is offset from the MRI field of
view, simultaneous or near simultaneous imaging can provide
information on more than one location within the body without
moving the magnet.
[0081] If the PET imaging equipment is offset from the MRI field of
view, the surgical team can image the same body part by first
imaging using MRI capability and than move the magnet to achieve
PET imaging capability of the same body part, thus allowing a
flexibility of design for positioning the PET scintillators
relative to the center of the field of view of the magnet.
[0082] If both PET and MRI detectors are designed as separate
subsystems, but placed on the same rail system, it is possible to
allow a given operating room to have independent PET and MRI
detection applications at different times during the day.
[0083] If both PET and MRI detectors are available, and if the
ceiling hung systems have the capability of being rotated, then the
MRI and PET detectors can be used separately with a non-moving
patient through the rotational and translational movement of the
scanner system. In this case, the patient might be having an MR!
scan, something is observed, after which the magnet is removed from
the patient, the magnet is then rotated so that the PET system is
pointed towards the patient, after which the PET system is moved
over the patient, and the PET imaging is performed. There are some
differences in the magnetic field of the MRI system for axial and
non-axially oriented equipment elements which causes the rotational
ability of the scanner system to be important.
[0084] If both PET and MRI detectors are available, and if the
ceiling hung systems have the capability of being translated in
both x and y coordinates, rotated and vertically lifted, then
additional and different designs may be possible for the PET and
MRI configurations.
[0085] With additional movement possibilities, the shimming effort
required to provide the magnetic system with a homogenous
environment is greatly reduced. Currently, the rebar in the floor
makes a difference to the magnetic imaging system, unless it is
stainless steel. If the MRI system can be moved in a multitude of
manners, it is possible to find the optimum location within the
room to provide imaging.
[0086] In addition, another complication of installing the ceiling
hung system is that the table system moves with the floor but the
ceiling system moves with the ceiling. If there is any sag in the
ceiling that is not present in the floor, the systems move relative
to each other, which changes the exact height distances. By
allowing the magnet to move vertically, the same distance can be
maintained between table and magnet. This approach is used instead
of simply moving the table in those operations and circumstances
where moving the patient even a little bit changes the imaging or
affects the patient safety. For example, certain organs and glands,
such as the prostate, may be so floppy or so degenerated that table
motion is not allowed. In addition, when interventional work is
being done, certain positions of the intervening tubes, needles or
other apparatus is so sensitive that table motion is not
recommended.
[0087] In addition, it is discussed to provide interventional
capability within the system. Currently, there is technology called
the Miyabi table from Siemens that provides docking onto the
diagnostic table of Siemens. When the magnet can be rotated, this
provides a new freedom of workflow for a room layout.
[0088] The advantages of the rotational system are not only for
ceiling mounted systems. For floor-mounted systems, providing a
rotating capability for the MRI allows the same advantages.
[0089] As well, it is possible to have relative movement between
the PET and MRI systems. The PET system may be part of the bore
system of the MRI, and can be moved relative to the field of view
of the MRI. This movement relative to the MRI field of view may
allow better or improved imaging performance.
[0090] Further, once one can rotate, translate or vertically move
the integrated scanner, additional scanner designs become possible.
In those cases where simultaneous scanning is desired, the PET
focus area and the MRI field of view can be co-located through the
design and configuration of the systems.
[0091] The integrated PET/MRI system can be suspended from the
ceiling or mounted on a floor mounted bearing, with either system
providing rotation of the magnet. The MRI system may also be
suspended from the ceiling on rails, such that it can also be
translated in space using the rail system. The rotational mechanism
can either be located between the magnet and the rails, or above
the rails. The below track and above track rotators have different
properties for different configurations. The below track rotator
allows for easiest upgrade of existing sites, whereas the above
track rotator works like a roundhouse in a railway yard, in that
the rail, MRI system and all associated systems are rotated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0092] FIG. 1 is a side elevational view of an MRI magnet which
includes the ability to allow rotation about a vertical axis and
provides the addition of a PET detection system.
[0093] FIG. 2 is a side elevational view of the magnet of FIG. 1
showing further details of the covers and the diagnostic table
which are omitted from FIG. 1 for convenience of illustration.
[0094] FIG. 3 is a cross-sectional view of the bore of the magnet
of FIG. 1 showing the PET detector ring inside the bore.
[0095] FIG. 4 is a schematic plan view of the magnet system of FIG.
1 mounted in a two room configuration.
[0096] FIG. 5 is a schematic plan view of the magnet system of FIG.
1 mounted in a three room configuration.
DETAILED DESCRIPTION
[0097] FIG. 1 shows the integrated PET/MRI scanner with rotating
capacity. Ceiling rails 1 are bolted onto the structural steel of
the building using Rail Clamps 17. Two ceiling rails are used, at a
width apart approximately the same as the width of the magnet,
although other widths are possible.
[0098] The magnet 3 is mounted onto the rails using a magnet Mover
System 2. The upper part of the magnet Mover System traverses the
rails, and does not rotate. The lower part of the magnet Mover
System is connected to Slew Ring 11 so that it can rotate relative
to the upper part. The Slew Ring 11 is motor driven, and carefully
rotates the magnet system over a given angle, such as 90 degrees,
180 degrees or 270 degrees depending on the type of room layout
being implemented. For both translational and rotational movements,
the motor drive system can include gentle acceleration and
deceleration in keeping with the requirements of the magnet system.
The lower part of the magnet Mover System is bolted to the magnet
using the Rotator to Magnet System 12.
[0099] For the rotational magnet system using the slew ring 11, it
is necessary to allow rotation of the quench tube system so there
is provided a fixed quench tube 14 mounted on the rails 1 and a
rotational quench tube part 13 attached to the magnet. These quench
tubes are joined together with a rotary union mounted at the
iso-center of the magnet system, directly above the magnet and
central of the slew ring, so that the rotation does not put undue
stresses on the quench system. As it is difficult to ensure that
the exact iso-center is achieved, it is practical to use a flex
connection that absorbs some portion of the stresses that occur
during rotation.
[0100] For a rotational MRI system it is also necessary to ensure
that the cabling can be properly guided through the rotational arc.
One method to do this uses a Cable Management System 19 that
contains multiple tube guides, with different guides being used for
communication cabling, power cabling, low voltage cabling,
monitoring cabling and helium lines. The separation of these cables
and the guidance of these cables through the rotational movement
ensures that no binding and eventual breakage occurs. Again these
components pass through the slew ring and connect to components
carried on the rails with the movement of the magnet by a cable
carrier system 9.
[0101] The magnet Mover System is moved via the belt drive
translational system 18. This system uses wheels on top of the rail
to carry the weight, and Drive Wheels 20 below the rail and
contacted with the rail to allow movement to occur.
[0102] Drive wheels and weight bearing wheels are placed on both of
the rails, to ensure an even distribution of weight and a straight
tracking performance for the system. A driveshaft may be used
between the left and right belt drive translational systems to
ensure that they move in harmony. In this case, a single motor may
be used to drive both drive wheel sets. For safety, in the event of
power outage, it is useful to have a
[0103] Hand Crank 15 that allows the operators to remove the magnet
from the patient if this movement is required. Operation of the
hand crank requires the clutch to be disengaged in this particular
design.
[0104] In addition to the translational movement provided by the
rails and the rotational movement provided by the slew ring,
vertical adjustment movement of the bore of the magnet is possible
by adjustment of the height of the slew ring on the support 12.
[0105] The magnet has a round magnet bore 8 into which the table
and patient can be positioned to allow imaging to occur. For a
magnet such as the Siemens Espree (trade mark) magnet, the MRI Bore
is 70 cm in diameter and approximately 125 cm in length. The magnet
has a field of view 4 of 30 cm.times.45 cm.times.45 cm. The field
of view is the volume within the system that allows high quality
imaging to occur, and coincides with the volume over which the
magnet field can be maintained within appropriate linearity. The
patient's anatomy of interest is positioned within the field of
view to allow imaging to occur.
[0106] A PET Detector Ring 5 is co-located with the magnet field of
view, with each individual detector on the ring being connected via
optical fiber in a bundle of fibers 6 to the multipliers 7 that are
located above or around the magnet. The multipliers are shown on
the top of the magnet, however they could be placed in alternative
positions within the magnet. The optical fiber is wound in the
cable carrier 9 which typically carries magnet and associated
cables 10 that include quench tube, helium lines, water coolant
lines, gradient cables, RF cables, control lines, and a variety of
additional monitoring and sensing lines as required for various
applications that are attached to the bore, cover-set, and other
MRI elements. The cable carrier and associated cabling uses the
cable carrier guides 16 to maintain the correct shape of the cables
as they are moved with the system.
[0107] FIG. 1 shows an integrated PET/MRI scanner suitable for
simultaneous scanning, because the PET imaging volume, which is
inside the PET detector ring, overlaps the MRI field of view.
Alternate designs are also possible. For example, if the PET
detector ring is moved to the end of the MRI bore, then the imaging
volumes of the two imaging systems are not coincident, which would
allow simultaneous imaging of two different body parts.
Non-simultaneous scanning of the same body part in this scanner
configuration must involve relative movement between the patient
and the scanner. In general, this can be accomplished via one or a
combination of three methods:
[0108] Move the integrated PET/MRI scanner and not the patient
[0109] Move the PET scanner inside the bore of the MRI without
moving the patient.
[0110] Move the patient in some way. However it is preferable that
the patient is never moved during scanning, and therefore methods 1
and 2 are preferred.
[0111] While FIG. 1 has shown a rotational PET/MRI scanner, it is
possible to build a rotational MRI scanner for purely MRI scanning
needs so that the same construction can be used with the PET
scanner omitted.
[0112] FIG. 3 shows further details of the movable PET scanner
suitable for simultaneous scanning, and is equivalent to the
PET/MRI configuration of FIGS. 1 and 2. Thus the PET detector ring
is mounted to move inside the bore. The magnet Bore 8 has five
spacing and drive rails 32, onto which is fitted the pet detector
ring 5. This pet detector ring is driven back and forth through the
bore using the drive rails 32, but the diagnostic or operating
table 34 is sized such that no collision occurs as these elements
are being moved inside the bore. The PET detector ring 5 has on its
inside circumference a multitude of individual PET detectors 55
which generate their output, typically through scintillation, with
this output being passed into optical fibers 6 which allow
transmission from the scintillator detectors to the multipliers 7.
Two variations on the placement method of the optical fiber are
possible where either the optical fiber goes through the sidewall
of the bore, and so this method is only appropriate for the case
where the PET detector ring does not move inside the bore, or the
optical fiber does not go directly through the bore but instead is
led to the end of the bore, where an optical fiber management
system can accommodate the slack. In this design, the patient
enters only from the opposite end of the bore 8, because the other
end is used for optical fiber management. Alternatively, more
sophisticated optical fiber management can be provided to allow
both ends of the PET/MRI integrated scanner to be used.
[0113] An alternative design to those above can use wireless
transmission of optical signals, with the bore having clear areas
within its design which allows for light to pass through. In this
arrangement, the PET detector ring generates EM wavelength suitable
for optical fiber to transmit directly into the optical fiber and
on to the multiplier.
[0114] Alternatively a system can be provided in which the PET
scanner and magnet field of view are fixed in position relative to
each other, with the entire integrated scanner moving instead. In
this case, the integrated scanner moves on the ceiling rails, and
rotates or moves vertically, in the manner that has already been
discussed.
[0115] FIG. 2 shows a rotational MRI shielding cover-set.
Conventional designs for such covers for magnets used in MRI are
well known by persons skilled in the art. This cover-set is
designed with an upper portion 21 which does not rotate and a lower
portion 22 which does rotate, with the two portions being separated
at a rotational seam 23.
[0116] FIG. 2 also shows a configuration which uses a diagnostic
table 24 extending from the left side of the magnet. For the
specific case of the Siemens Espree (trademark) magnet, the
diagnostic table is attached to the magnet and can move in and out
of the magnet for diagnostic imaging. The figure also shows the
control panel 25 for the system. In this case, there is a set of
controls installed on the magnet which includes a pendant control
26 connected to the magnet by a cable.
[0117] FIG. 4 shows a floor layout in which the translating,
rotating and vertically moving scanner is used in a two room
configuration to service both an adult and a child. FIG. 7a shows a
two room layout in which first room 41 is separated from second
room 42 via sliding doors 23, with patients and medical team
accessing the rooms via patient entry doors 44. The integrated
scanner can move between these two rooms. FIG. 4 shows two
positions for this integrated scanner. The rails 1
[0118] allow the scanner to move between the rooms. The scanner
position in room 41 is shown as it moves towards the surgical
imaging position, in which the scanner 3 moves over the table 50
and in which the Siemens diagnostic table 24 is attached to the
rear of the scanner as is the custom with the Siemens Espree
(trademark), for example, This same scanner, when required, can be
moved to a second position in room 42 in which the scanner 3 is
rotated to allow the diagnostic table 24 to be positioned far
interventional work. This rotation increases the utility of the
system by minimizing the amount of space and access required in the
second room 42.
[0119] The movement of the imaging system between the two rooms
will increase the complexity of the shimming requirements of the
MRI system, that is the difficulty of providing shielding for the
signals and magnetic field required for the MRI experiments. Also,
even if the particular locations within the various rooms are
difficult to shim for MRI usage, those locations can be still be
used for PET imaging, leading to an increased utility of the system
in various room configurations.
[0120] FIG. 5 shows a three room diagnostic configuration in which
a central magnet holding bay 60 houses the magnet 61 and the
diagnostic patients are organized in the three rooms 62, 63 and 64.
The doors 65 to one of the rooms 62, as selected from the three
rooms, can be opened for example by retraction to one side so that
the magnet holding bay becomes part of that room 62, the magnet
does not move but may extend its diagnostic table 66, the patient
lies on the diagnostic table, imaging is performed, no need to do
intervention is found, the patient exits the diagnostic table and
the magnet moves back into the holding bay, ready for use by one of
the other rooms. The magnet then may draw in its table 66, rotates
to the doors for that room, and the process for the other room
begins. In this case, the magnet does not move in a translational
direction, such as on rails, but simply rotates.
[0121] The front face can carry a PET scanning system so that the
PET can be moved into position if required. If there is no PET
system used, the front face may be arranged so that the magnet is
not symmetrical and requires that the front face be moved into the
position of the patient.
[0122] In an alternative arrangement, the magnet is mounted on a
rail system along which can roll a support and on which is carried
the slew ring allowing the magnet to rotate about its vertical
axis. In this way the front face of the magnet can be moved to face
the room. In this embodiment the patient table is located in the
respective room so that the magnet moves to and relative to the
table.
[0123] In addition, in-line configurations can have increased
flexibility as well if rotation is allowed. For example, one can
join two diagnostic rooms with a magnet holding room in the middle.
In this case, the MRI system rotates so that the diagnostic table
is always the first entry into the room. This allows the diagnostic
rooms to be as small as possible, allowing maximum density of the
MRI system and the smallest cost in terms of square footage for the
diagnostic room.
[0124] There are advantages to simply hanging the MRI magnet from
the ceiling. It is possible that vibration effects are reduced when
the magnet is suspended, instead of floor mounted, leading to
reduced vibrations and improved signal to noise performance.
[0125] It will be appreciated that the magnet may be arranged to
carry a diagnostic table at one end such that on entry into a
diagnostic room or on rotation of the magnet to co-operate with
that diagnostic room, the table is made available for patients in
that room. The magnet in a surgical situation is arranged to
co-operate with a table present in the room which remains in the
room when the magnet is moved so as to allow surgery to continue.
In a hybrid situation, the magnet may carry the table at one end
and be arranged to co-operate with a surgical table at the other
end, thus requiring rotation of the table about its vertical
axis.
[0126] Need for wall shielding, because when the magnet is rotated
the field can go through the other side of the wall, impinging on
hallways or other areas. The methods that can be used to limit this
effect include: standard techniques that use additional metal in
the walls to provide shielding, use of active coils embedded in the
walls that turn on only when the rotational action occurs, power
cycling of the MRI active coils, in which the active coils on the
magnet either are increased or decreased in current so that the
field does not extend so far.
[0127] Quench tube design, in which the quench tube must be
designed to go through the iso-center of the rotating mass
[0128] Cable routing design, in which the cabling is designed to be
rotated 180 degrees. One method of doing the cable routing is to
pre-route the cabling 90 degrees, and then the maximum cable
bending is +1-90 degrees to achieve the full 180 degrees rotation.
In this case, the cables are usually at the 90 degrees bend radius
during their lifetime. Alternatively, one can design a rotation
plate that allows 180 degree rotational couplings to couple the
cable on the magnet to the cable extending back to the fixed wall
mount location.
[0129] The arrangement described herein provides the following
features and advantages:
[0130] The use of the circular slew ring so that the magnet effects
of the ring are homogenous during rotation, which allows for the
minimum effect on the shimming software of the magnet.
[0131] For the Espree magnet, it is useful to pull in the
diagnostic table prior to rotation, to allow for a minimum radius
of rotation, a minimum strain on the rotating motor, and a maximum
for operator safety. If the diagnostic table would extend further
out of the magnet, it would increase the probability of collision
between the operator and the rotating system, or the collision
between the rotating system and equipment items inside the
room.
[0132] To allow rotation, the cover-set of the magnet, along with
the brackets that holds the cover-set onto the magnet provide an
upper part of the cover-set which does not rotate and a lower part
of the cover-set that does rotate with the magnet.
[0133] To optimize the rotational performance, there is provided a
motor system that gently accelerates and decelerates in a
programmed and programmable way. if the start and stop forces that
are exerted on the magnet are excessive, vibration can be caused
and potentially shorter life can occur.
[0134] To optimize the safety of the rotating system, the control
system includes "lock-outs" that will not allow the rotation to
occur unless the proper orientation, location, door condition or
other specific conditions are met by the environment. This lock-out
capability ensures that the magnet cannot be rotated if the
environment is not ready to receive the rotation.
* * * * *