U.S. patent application number 16/516760 was filed with the patent office on 2020-01-23 for patient support bridge methods and apparatus.
The applicant listed for this patent is Hyperfine Research, Inc.. Invention is credited to Christopher Thomas McNulty, Todd Rearick.
Application Number | 20200022612 16/516760 |
Document ID | / |
Family ID | 67515186 |
Filed Date | 2020-01-23 |
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United States Patent
Application |
20200022612 |
Kind Code |
A1 |
McNulty; Christopher Thomas ;
et al. |
January 23, 2020 |
PATIENT SUPPORT BRIDGE METHODS AND APPARATUS
Abstract
According to some aspects, a bridge adapted for attachment to a
magnetic resonance imaging system and configured to facilitate
positioning a patient within the magnetic resonance imaging system
is provided. Embodiments of the bridge comprise a support having a
surface configured to support at least a portion of the patient,
the support being moveable between an up position and a down
position, wherein the surface is substantially vertical in the up
position and substantially horizontal in the down position, a hinge
configured to allow the support to be moved from the up position to
the down position and vice versa, and a base configured to attach
the bridge to the magnetic resonance imaging system. According to
some aspects, a magnetic resonance imaging system is provided
having a bridge configured to facilitate positioning a patient
within the magnetic resonance imaging system attached thereto.
Inventors: |
McNulty; Christopher Thomas;
(Guilford, CT) ; Rearick; Todd; (Cheshire,
CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hyperfine Research, Inc. |
Guilford |
CT |
US |
|
|
Family ID: |
67515186 |
Appl. No.: |
16/516760 |
Filed: |
July 19, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62811361 |
Feb 27, 2019 |
|
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62700711 |
Jul 19, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/0555 20130101;
A61B 90/14 20160201; G01R 33/34084 20130101; G01R 33/3802 20130101;
G01R 33/307 20130101; G01R 33/422 20130101; A61B 5/70 20130101;
G01R 33/34007 20130101; A61B 6/04 20130101; G01R 33/4833 20130101;
G01R 33/543 20130101; G01R 33/445 20130101; G01R 33/3806
20130101 |
International
Class: |
A61B 5/055 20060101
A61B005/055 |
Claims
1. A bridge adapted for attachment to a magnetic resonance imaging
system and configured to facilitate positioning a patient within
the magnetic resonance imaging system, the bridge comprising: a
support having a surface configured to support at least a portion
of the patient, the support being moveable between an up position
and a down position, wherein the surface is substantially vertical
in the up position and substantially horizontal in the down
position; a hinge configured to allow the support to be moved from
the up position to the down position and vice versa; and a base
configured to attach the bridge to the magnetic resonance imaging
system.
2. The bridge of claim 1, wherein the hinge comprises a pivot
portion coupled to the support to allow the support to pivot
between the up position and the down position.
3. The bridge of claim 2, wherein the support comprises a groove
and the pivot portion comprises a tongue inserted into the groove
to couple the pivot portion to the support.
4. The bridge of claim 3, wherein the tongue is comprised of a
plastic material.
5. The bridge of claim 3, wherein the support is comprised of a
plastic material.
6. The bridge of claim 2, wherein the pivot portion comprises a
first bore and the base comprises a second bore, and wherein the
hinge further comprises a shaft inserted through the first bore and
the second bore to couple the pivot portion to the base and to
allow the pivot portion to rotate about the shaft to cause the
support to pivot between the up position and the down position.
7. The bridge of claim 1, wherein the surface of the support has a
length of between 8 inches and 16 inches.
8. The bridge of claim 1, wherein the surface of the support has a
width of between 12 inches and 30 inches.
9. The bridge of claim 1, wherein the bridge is rated for a 500
pound patient.
10. The bridge of claim 9, wherein the bridge has a safety factor
of at least 2.5.
11. The bridge of claim 9, wherein the bridge has a safety factor
greater than or equal to 2.5 and less than or equal to 4.0.
12. The bridge of claim 9, wherein the bridge has a safety factor
greater than or equal to 2.5 and less than or equal to 4.3.
13. The bridge of claim 1, wherein the base includes a plurality of
bores configured to allow the bridge to be bolted to the magnetic
resonance imaging system.
14. The bridge of claim 13, wherein at least the portion of the
base that includes the plurality of bores is made of steel.
15. The bridge of claim 13, wherein the bridge is bolted to a
B.sub.0 magnet of the magnetic resonance imaging system.
16. The bridge of claim 2, wherein the bridge further comprises a
counter-balance mechanism that resists pivoting of the support from
the up position to the down position.
17. The bridge of claim 16, wherein the counter-balance mechanism
comprises at least one torsion spring that resists pivoting of the
support from the up position to the down position.
18. The bridge of claim 17, wherein the at least one torsion spring
is coupled to the pivot portion so that, when the pivot portion is
rotated, the at least one torsion spring slows the rate at which
the support pivots from the up position to the down position.
19. The bridge of claim 18, further comprising a lock-out switch
that, when activated, is configured to disable a motor drive of the
magnetic resonance imaging system.
20. The bridge of claim 19, wherein the lock-out switch is
configured to be activated when the support is moved to the down
position and an additional weight is applied to the support.
21. The bridge of claim 19, wherein the lock-out switch is
configured to be activated when the support is placed in the down
position.
22. The bridge of claim 19, wherein the lock-switch comprises at
least one sensor configured to detect when a patient is positioned
on the support.
23. A magnetic resonance imaging system comprising: a B.sub.0
magnet configured to generate a magnetic field suitable for
magnetic resonance imaging; a conveyance mechanism configured to
allow the magnetic resonance imaging system to be moved to
different locations; and a bridge configured to facilitate
positioning a patient within the magnetic resonance imaging system,
the bridge comprising: a support having a surface configured to
support at least a portion of the patient, the support being
moveable between an up position and a down position, wherein the
surface is substantially vertical in the up position and
substantially horizontal in the down position; a hinge configured
to allow the support to be moved from the up position to the down
position and vice versa; and a base attaching the bridge to the
magnetic resonance imaging system.
24. The magnetic resonance imaging system of claim 23, wherein the
hinge comprises a pivot portion coupled to the support to allow the
support to pivot between the up position and the down position.
25. The magnetic resonance imaging system of claim 23, wherein the
support comprises a groove and the pivot portion comprises a tongue
inserted into the groove to couple the pivot portion to the
support.
26. The magnetic resonance imaging system of claim 25, wherein the
tongue is comprised of a plastic material to reduce eddy currents
generated in the bridge when the magnetic resonance imaging system
is operated.
27. The magnetic resonance imaging system of claim 25, wherein the
support is comprised of a plastic material.
28. The magnetic resonance imaging system of claim 24, wherein the
pivot portion comprises a first bore and the base comprises a
second bore, the hinge further comprising a shaft inserted through
the first bore and the second bore to couple the pivot portion to
the base and to allow the pivot portion to rotate about the shaft
to cause the support to pivot between the up position and the down
position.
29. The magnetic resonance imaging system of claim 23, wherein the
surface of the support has a length of between 8 inches and 16
inches.
30. The magnetic resonance imaging system of claim 23, wherein the
surface of the support has a width of between 12 inches and 30
inches.
31. The magnetic resonance imaging system of claim 23, wherein the
bridge is rated for a 500 pound patient.
32. The magnetic resonance imaging system of claim 31, wherein the
bridge has a safety factor of at least 2.5.
33. The magnetic resonance imaging system of claim 31, wherein the
bridge has a safety factor greater than or equal to 2.5 and less
than or equal to 4.0.
34. The magnetic resonance imaging system of claim 31, wherein the
bridge has a safety factor greater than or equal to 2.5 and less
than or equal to 4.3.
35. The magnetic resonance imaging system of claim 1, wherein the
base includes a plurality of bores accommodating respective bolts
that attach the base to the magnetic resonance imaging system.
36. The magnetic resonance imaging system of claim 35, wherein at
least the portion of the base comprising the plurality of bores is
made of steel.
37. The magnetic resonance imaging system of claim 35, wherein the
base of the bridge is bolted to the B.sub.0 magnet of the magnetic
resonance imaging system.
38. The magnetic resonance imaging system of claim 24, wherein the
bridge further comprises a counter-balance mechanism that resists
pivoting of the support from the up position to the down
position.
39. The magnetic resonance imaging system of claim 38, wherein the
counter-balance mechanism comprises at least one torsion spring
that resists pivoting of the support from the up position to the
down position.
40. The magnetic resonance imaging system of claim 39, wherein the
at least one torsion spring is coupled to the pivot portion so
that, when the pivot portion is rotated, the at least one torsion
spring slows the rate at which the support pivots from the up
position to the down position.
41. The magnetic resonance imaging system of claim 23, wherein the
bridge further comprises a lock-out switch coupled to the
conveyance mechanism that, when activated, disables a motor drive
of the conveyance mechanism.
42. The magnetic resonance imaging system of claim 41, wherein the
lock-out switch is activated when the support is moved to the down
position and an additional weight is applied to the support.
43. The magnetic resonance imaging system of claim 42, wherein the
lock-out switch comprises at least one sensor configured to detect
when a patient is positioned on the support.
44. A method of imaging a portion of anatomy of a patient while the
patient is at least partially supported by a standard medical bed,
the method comprising: positioning a magnetic resonance imaging
system and the bed proximate one another; moving a bridge attached
to the magnetic resonance imaging system from a vertical position
to a horizontal position so that the bridge overlaps a portion of
the bed; positioning the patient via the bridge so that the portion
of anatomy of the patient is within an imaging region of the
magnetic resonance imaging system; and acquiring at least one
magnetic resonance image of the portion of the anatomy of the
patient while the patient is at least partially supported by the
bed and at least partially supported by the bridge.
45. The method of claim 44, wherein moving the bridge from the
vertical position to a horizontal position disables a conveyance
mechanism of the magnetic resonance imaging system.
46. The method of claim 44, wherein positioning the patient via the
bridge disables a conveyance mechanism of the magnetic resonance
imaging system.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn. 119
to U.S. Provisional Application Ser. No. 62/700,711 filed Jul. 19,
2018 and titled "Methods and Apparatus for Patient Positioning in
Magnetic Resonance Imaging," and U.S. Provisional Application Ser.
No. 62/811,361 filed Feb. 27, 2019 and titled "Methods and
Apparatus for Patient Positioning in Magnetic Resonance Imaging,"
each application of which is herein incorporated by reference in
its entirety.
BACKGROUND
[0002] Magnetic resonance imaging (MRI) provides an important
imaging modality for numerous applications and is widely utilized
in clinical and research settings to produce images of the inside
of the human body. As a generality, MRI is based on detecting
magnetic resonance (MR) signals, which are electromagnetic waves
emitted by atoms in response to state changes resulting from
applied electromagnetic fields. For example, nuclear magnetic
resonance (NMR) techniques involve detecting MR signals emitted
from the nuclei of excited atoms upon the re-alignment or
relaxation of the nuclear spin of atoms in an object being imaged
(e.g., atoms in the tissue of the human body). Detected MR signals
may be processed to produce images, which in the context of medical
applications, allows for the investigation of internal structures
and/or biological processes within the body for diagnostic,
therapeutic and/or research purposes.
[0003] MRI provides an attractive imaging modality for biological
imaging due to the ability to produce non-invasive images having
relatively high resolution and contrast without the safety concerns
of other modalities (e.g., without needing to expose the subject to
ionizing radiation, e.g., x-rays, or introducing radioactive
material to the body). Additionally, MRI is particularly well
suited to provide soft tissue contrast, which can be exploited to
image subject matter that other imaging modalities are incapable of
satisfactorily imaging. Moreover, MR techniques are capable of
capturing information about structures and/or biological processes
that other modalities are incapable of acquiring. However, there
are a number of drawbacks to MRI that, for a given imaging
application, may involve the relatively high cost of the equipment,
limited availability and/or difficulty in gaining access to
clinical MRI scanners and/or the length of the image acquisition
process.
[0004] The trend in clinical MRI has been to increase the field
strength of MRI scanners to improve one or more of scan time, image
resolution, and image contrast, which, in turn, continues to drive
up costs. The vast majority of installed MRI scanners operate at
1.5 or 3 tesla (T), which refers to the field strength of the main
magnetic field B.sub.0. A rough cost estimate for a clinical MRI
scanner is approximately one million dollars per tesla, which does
not factor in the substantial operation, service, and maintenance
costs involved in operating such MRI scanners.
[0005] Additionally, conventional high-field MRI systems typically
require large superconducting magnets and associated electronics to
generate a strong uniform static magnetic field (B.sub.0) in which
an object (e.g., a patient) is imaged. The size of such systems is
considerable with a typical MRI installment including multiple
rooms for the magnet, electronics, thermal management system, and
control console areas. The size and expense of MRI systems
generally limits their usage to facilities, such as hospitals and
academic research centers, which have sufficient space and
resources to purchase and maintain them. The high cost and
substantial space requirements of high-field MRI systems results in
limited availability of MRI scanners. As such, there are frequently
clinical situations in which an MRI scan would be beneficial, but
due to one or more of the limitations discussed above, is not
practical or is impossible, as discussed in further detail
below.
SUMMARY
[0006] Some embodiments include a bridge adapted for attachment to
a magnetic resonance imaging system and configured to facilitate
positioning a patient within the magnetic resonance imaging system,
the bridge comprising a support having a surface configured to
support at least a portion of the patient, the support being
moveable between an up position and a down position, wherein the
surface is substantially vertical in the up position and
substantially horizontal in the down position, a hinge configured
to allow the support to be moved from the up position to the down
position and vice versa, and a base configured to attach the bridge
to the magnetic resonance imaging system.
[0007] Some embodiments include a magnetic resonance imaging system
comprising a B.sub.0 magnet configured to generate a magnetic field
suitable for magnetic resonance imaging, a conveyance mechanism
configured to allow the magnetic resonance imaging system to be
moved to different locations, and a bridge configured to facilitate
positioning a patient within the magnetic resonance imaging system,
the bridge comprising a support having a surface configured to
support at least a portion of the patient, the support being
moveable between an up position and a down position, wherein the
surface is substantially vertical in the up position and
substantially horizontal in the down position, a hinge configured
to allow the support to be moved from the up position to the down
position and vice versa, and a base attaching the bridge to the
magnetic resonance imaging system.
[0008] Some embodiments include a method of imaging a portion of
anatomy of a patient while the patient is at least partially
supported by a standard medical bed, the method comprising
positioning a magnetic resonance imaging system and the bed
proximate one another, moving a bridge attached to the magnetic
resonance imaging system from a vertical position to a horizontal
position so that the bridge overlaps a portion of the bed,
positioning the patient via the bridge so that the portion of
anatomy of the patient is within an imaging region of the magnetic
resonance imaging system, and acquiring at least one magnetic
resonance image of the portion of the anatomy of the patient while
the patient is at least partially supported by the bed and at least
partially supported by the bridge.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Various aspects and embodiments of the disclosed technology
will be described with reference to the following figures. It
should be appreciated that the figures are not necessarily drawn to
scale.
[0010] FIG. 1 illustrates a portable magnetic resonance imaging
system with a bridge to assist in positioning a patient;
[0011] FIG. 2A illustrates a fold-up bridge shown in a vertical or
up position, in accordance with some embodiment;
[0012] FIG. 2B illustrates the fold-up bridge illustrated in FIG.
2A in a horizontal or down position, in accordance with some
embodiments.
[0013] FIG. 3 illustrates components of a fold-up bridge, in
accordance with some embodiments;
[0014] FIG. 4A illustrates a model of a bridge, in accordance with
some embodiments;
[0015] FIG. 4B illustrates a stress plot of the model of the bridge
illustrated in FIG. 3A;
[0016] FIG. 4C illustrates a deflection plot of the model of the
bridge illustrated in FIG. 3A.
[0017] FIG. 4D is Figure A.19 from the IEC 60601-1 illustrating the
human body mass distribution for patient support surfaces;
[0018] FIGS. 5A and 5B illustrate components of a fold-up bridge
with a counter-balance mechanism, in accordance with some
embodiments;
[0019] FIG. 6A illustrates a portable MRI system with a bridge in
the vertical position;
[0020] FIG. 6B illustrates a portable MRI system with a bridge in
the horizontal position;
[0021] FIG. 6C illustrates a patient positioned within a portable
MRI system and supported by a fold-out bridge.
DETAILED DESCRIPTION
[0022] The MRI scanner market is overwhelmingly dominated by
high-field systems, and particularly for medical or clinical MRI
applications. As discussed above, the general trend in medical
imaging has been to produce MRI scanners with increasingly greater
field strengths, with the vast majority of clinical MRI scanners
operating at 1.5T or 3T, with higher field strengths of 7T and 9T
used in research settings. As used herein, "high-field" refers
generally to MRI systems presently in use in a clinical setting
and, more particularly, to MRI systems operating with a main
magnetic field (i.e., a B.sub.0 field) at or above 1.5T, though
clinical systems operating between 0.5T and 1.5T are often also
characterized as "high-field." Field strengths between
approximately 0.2T and 0.5T have been characterized as "mid-field"
and, as field strengths in the high-field regime have continued to
increase, field strengths in the range between 0.5T and 1T have
also been characterized as mid-field. By contrast, "low-field"
refers generally to MRI systems operating with a B.sub.0 field of
less than or equal to approximately 0.2T, though systems having a
B.sub.0 field of between 0.2T and approximately 0.3T have sometimes
been characterized as low-field as a consequence of increased field
strengths at the high end of the high-field regime. Within the
low-field regime, low-field MRI systems operating with a B.sub.0
field of less than 0.1T are referred to herein as "very low-field"
and low-field MRI systems operating with a B.sub.0 field of less
than 10 mT are referred to herein as "ultra-low field."
[0023] As discussed above, conventional MRI systems require
specialized facilities. An electromagnetically shielded room is
required for the MRI system to operate and the floor of the room
must be structurally reinforced. Additional rooms must be provided
for the high-power electronics and the scan technician's control
area. Secure access to the site must also be provided. In addition,
a dedicated three-phase electrical connection must be installed to
provide the power for the electronics that, in turn, are cooled by
a chilled water supply. Additional HVAC capacity typically must
also be provided. These site requirements are not only costly, but
significantly limit the locations where MRI systems can be
deployed. Conventional clinical MRI scanners also require
substantial expertise to both operate and maintain. These highly
trained technicians and service engineers add large on-going
operational costs to operating an MRI system. Conventional MRI, as
a result, is frequently cost prohibitive and is severely limited in
accessibility, preventing MRI from being a widely available
diagnostic tool capable of delivering a wide range of clinical
imaging solutions wherever and whenever needed. Typically, patient
must visit one of a limited number of facilities at a time and
place scheduled in advance, preventing MRI from being used in
numerous medical applications for which it is uniquely efficacious
in assisting with diagnosis, surgery, patient monitoring and the
like.
[0024] As discussed above, high-field MRI systems require specially
adapted facilities to accommodate the size, weight, power
consumption and shielding requirements of these systems. For
example, a 1.5T MRI system typically weighs between 4-10 tons and a
3T MRI system typically weighs between 8-20 tons. In addition,
high-field MRI systems generally require significant amounts of
heavy and expensive shielding. Many mid-field scanners are even
heavier, weighing between 10-20 tons due, in part, to the use of
very large permanent magnets and/or yokes. Commercially available
low-field MRI systems (e.g., operating with a B.sub.0 magnetic
field of 0.2T) are also typically in the range of 10 tons or more
due to the large amounts of ferromagnetic material used to generate
the B.sub.0 field, with additional tonnage in shielding. To
accommodate this heavy equipment, rooms (which typically have a
minimum size of 30-50 square meters) have to be built with
reinforced flooring (e.g., concrete flooring), and must be
specially shielded to prevent electromagnetic radiation from
interfering with operation of the MRI system. Thus, available
clinical MRI systems are immobile and require the significant
expense of a large, dedicated space within a hospital or facility,
and in addition to the considerable costs of preparing the space
for operation, require further additional on-going costs in
expertise in operating and maintaining the system.
[0025] In addition, currently available MRI systems typically
consume large amounts of power. For example, common 1.5T and 3T MRI
systems typically consume between 20-40 kW of power during
operation, while available 0.5T and 0.2T MRI systems commonly
consume between 5-20 kW, each using dedicated and specialized power
sources. Unless otherwise specified, power consumption is
referenced as average power consumed over an interval of interest.
For example, the 20-40 kW referred to above indicates the average
power consumed by conventional MRI systems during the course of
image acquisition, which may include relatively short periods of
peak power consumption that significantly exceeds the average power
consumption (e.g., when the gradient coils and/or RF coils are
pulsed over relatively short periods of the pulse sequence).
Intervals of peak (or large) power consumption are typically
addressed via power storage elements (e.g., capacitors) of the MRI
system itself. Thus, the average power consumption is the more
relevant number as it generally determines the type of power
connection needed to operate the device. As discussed above,
available clinical MRI systems must have dedicated power sources,
typically requiring a dedicated three-phase connection to the grid
to power the components of the MRI system. Additional electronics
are then needed to convert the three-phase power into single-phase
power utilized by the MRI system. The many physical requirements of
deploying conventional clinical MRI systems creates a significant
problem of availability and severely restricts the clinical
applications for which MRI can be utilized.
[0026] Accordingly, the many requirements of high-field MRI render
installations prohibitive in many situations, limiting their
deployment to large institutional hospitals or specialized
facilities and generally restricting their use to tightly scheduled
appointments, requiring the patient to visit dedicated facilities
at times scheduled in advance. Thus, the many restrictions on high
field MRI prevent MRI from being fully utilized as an imaging
modality. Despite the drawbacks of high-field MRI mentioned above,
the appeal of the significant increase in SNR at higher fields
continues to drive the industry to higher and higher field
strengths for use in clinical and medical MRI applications, further
increasing the cost and complexity of MRI scanners, and further
limiting their availability and preventing their use as a
general-purpose and/or generally-available imaging solution.
[0027] The low SNR of MR signals produced in the low-field regime
(particularly in the very low-field regime) has prevented the
development of a relatively low cost, low power and/or portable MRI
system. Conventional "low-field" MRI systems operate at the high
end of what is typically characterized as the low-field range
(e.g., clinically available low-field systems have a floor of
approximately 0.2T) to achieve useful images. Though somewhat less
expensive than high-field MRI systems, conventional low-field MRI
systems share many of the same drawbacks. In particular,
conventional low-field MRI systems are large, fixed and immobile
installments, consume substantial power (requiring dedicated
three-phase power hook-ups) and require specially shielded rooms
and large dedicated spaces. The challenges of low-field MRI have
prevented the development of relatively low cost, low power and/or
portable MRI systems that can produce useful images.
[0028] The inventors have developed techniques enabling portable,
low-field, low power and/or lower-cost MRI systems that can improve
the wide-scale deployability of MRI technology in a variety of
environments beyond the current MRI installments at hospitals and
research facilities. As a result, MRI can be deployed in emergency
rooms, small clinics, doctor's offices, in mobile units, in the
field, etc. and may be brought to the patient (e.g., bedside) to
perform a wide variety of imaging procedures and protocols. Some
embodiments include very low-field MRI systems (e.g., 0.1T, 50 mT,
20 mT, etc.) that facilitate portable, low-cost, low-power MRI,
significantly increasing the availability of MRI in a clinical
setting.
[0029] There are numerous challenges to developing a clinical MRI
system in the low-field regime. As used herein, the term clinical
MRI system refers to an MRI system that produces clinically useful
images, which refers to an images having sufficient resolution and
adequate acquisition times to be useful to a physician or clinician
for its intended purpose given a particular imaging application. As
such, the resolutions/acquisition times of clinically useful images
will depend on the purpose for which the images are being obtained.
Among the numerous challenges in obtaining clinically useful images
in the low-field regime is the relatively low SNR. Specifically,
the relationship between SNR and B.sub.0 field strength is
approximately B.sub.0.sup.5/4 at field strength above 0.2T and
approximately B.sub.0.sup.3/2 at field strengths below 0.1T. As
such, the SNR drops substantially with decreases in field strength
with even more significant drops in SNR experienced at very low
field strength. This substantial drop in SNR resulting from
reducing the field strength is a significant factor that has
prevented development of clinical MRI systems in the very low-field
regime. In particular, the challenge of the low SNR at very low
field strengths has prevented the development of a clinical MRI
system operating in the very low-field regime. As a result,
clinical MRI systems that seek to operate at lower field strengths
have conventionally achieved field strengths of approximately the
0.2T range and above. These MRI systems are still large, heavy and
costly, generally requiring fixed dedicated spaces (or shielded
tents) and dedicated power sources.
[0030] Low-field and very low-field MRI systems have been developed
that are capable of producing clinically useful images, allowing
for the development of portable, low cost and easy to use MRI
systems not achievable using state of the art technology. According
to some embodiments, an MRI system can be transported to the
patient to provide a wide variety of diagnostic, surgical,
monitoring and/or therapeutic procedures, generally, whenever and
wherever needed. There are challenges to providing an MRI system
that can be transported to the patient and/or operated outside
specialized facilities (e.g., outside secure and shielded rooms), a
number of which are addressed using the techniques described in
U.S. patent Ser. No. 10/222,434 (hereinafter, "the '434 patent"),
titled "Portable Magnetic Resonance Imaging Methods and Apparatus,"
issued Mar. 5, 2019, which patent is herein incorporated by
reference in its entirety.
[0031] Another challenge involves positioning the patient within
the MRI system for imaging. As discussed above, conventional MRI is
confined to specialized facilities, including a room for the device
itself that is outfitted with extensive shielding and must meet
stringent safety regulations, including requiring the room to be
secure and free from ferrous material due to the high field
strengths involved in conventional clinical MRI. Standard hospital
beds are constructed using ferrous material, often steel,
prohibiting there use with conventional clinical MRI systems. As a
result, a patient must be brought to the specialized facility
dedicated to the MRI system and transferred to a custom bed
designed for use with the MRI system.
[0032] For patients that are ambulatory, this may mean requiring
the patient to enter the secure room housing the MRI device and
positioning themselves on a MRI-safe bed integrated with the MRI
device. For patients that are not ambulatory or are otherwise
immobilized, the patient may need to be first transferred to a
customized MRI-safe bed to be transported to the secure room and
then transferred to the integrated bed of the MRI system. Such
requirements limit the circumstances in which a patient can undergo
MRI and in some cases prohibits the use of MRI entirely. For
example, transfer of non-ambulatory and/or immobile patients to an
MRI safe bed or wheel chair to transport the patient into the
secure room and, potentially, another transfer to the integrated
bed or patient support of the MRI system is difficult and, in some
circumstances, not feasible for medical safety reasons.
Additionally, MRI safe beds are costly and not widely
available.
[0033] The inventors have developed techniques that allow MRI to be
performed in conjunction with a standard patient support, such as a
standard hospital bed or standard wheelchair, thereby eliminating
the requirement of transferring patients one or more times, as well
eliminating costs and availability issues associated with
specialized MRI safe transports (e.g., beds, wheelchairs, etc.).
Additionally, techniques that allow MRI to be performed, for
example, from a standard hospital bed, facilitate point-of-care
MRI. According to some embodiments, MRI is performed at field
strengths that are low enough to allow for imaging to be performed
on a patient positioned on or in a standard patient support, for
example, a patient lying on a standard hospital bed or seated in a
standard wheelchair. As used herein, a standard hospital bed or
standard wheelchair refers to a patient support that has not been
outfitted for use with conventional high-field MRI. Standard
hospital beds or wheelchairs will often be constructed of
ferromagnetic material, such as steel, that prevents there use with
high-field MRI.
[0034] Imaging a patient from, for example, a standard hospital bed
may require positioning target anatomy of the patient within an MRI
system located proximate the hospital bed on which the patient is
lying. The inventors have developed techniques for facilitating the
positioning of a patient within the MRI system for imaging of
desired anatomy of the patient from the patient's bed. For example,
FIG. 1 illustrates a portable low-field MRI system 100 that has
been moved into position proximate a standard hospital bed 190 to
perform MRI on a patient 199 who may be confined to the bed for
convenience, comfort or stabilization and/or because the patient is
unconscious, immobilized or otherwise is not ambulatory or cannot
be safely moved. Portable MRI system 100 may be a local
installation deployed in an emergency room, operating room,
intensive care unit, doctor's office, etc. that can be moved to bed
190, or in some cases, bed 190 can be wheeled to the MRI system.
Because of the low-field strengths of MRI system 100, bed 190 can
be safely positioned in close proximity to MRI system 100.
[0035] To bridge the gap between bed 190 and MRI system 100, the
MRI system may be equipped with a bridge 173 mounted to MRI system
100 to facilitate positioning patient 199 within the imaging region
of MRI system 100. Specifically, bridge 173 provides a surface 110
over which patient 199 can be moved so that the patient's anatomy
being imaged (e.g., the patient's head) can be positioned within
the imaging region of the MRI system. However, the inventors have
recognized a number of drawbacks of exemplary bridge 173
illustrated in FIG. 1. For example, as illustrated in FIG. 1, fixed
bridge 173 protrudes out from the MRI system, thereby increasing
the footprint of the system. As a result, navigating the MRI system
down hallways and through doorways is more difficult. Additionally,
the useable surface of bridge 173 is limited and the construction
of the bridge may not be suitable for heavier patients. As a
result, bridge 173 may be difficult to use with larger and/or
heavier patients and may not be rated to support the heaviest
patients.
[0036] The inventors have recognized the benefits of patient
support bridge capable of supporting larger and heavier patients
and have appreciated the benefits of such a bridge that can
accommodate a range of gaps between the MRI system and a patient
bed and/or that provide more overlap between the bridge and the
bed. Specifically, for patient comfort, safety and/or to facilitate
more convenient positioning of a patient, particularly larger
and/or heavier patients, it is desirable to equip a portable MRI
system with relatively large dimensioned bridges capable of safely
supporting a wide range of patients. However, there are a number of
issues associated with the design and development of relatively
large dimensioned bridges capable of supporting the weight of
larger patients.
[0037] For example, larger bridges increase the footprint of the
MRI system even further, making it more difficult (or impossible)
to transport the MRI system down hallways and to fit the MRI system
through the doorways of the health care facilities in which they
are deployed. To address the problem of increased footprint for the
MRI system, the inventors have developed a fold-out bridge that can
be folded-down to facilitate positioning the patient within the
imaging region of the MRI system and to support the patient during
an imaging procedure and that can be folded-up during transport of
the MRI system so that the MRI system can be more easily moved down
hallways and through doorways to the patient.
[0038] Additionally, providing a bridge capable of safely
supporting larger, heavier patients requires robust construction.
Typically, such patient supports would be constructed using large
amounts of metal material capable of withstanding the significant
stresses resulting from supporting the weight of heavier patients.
However, significant quantities of metal may negatively impact the
operation of the magnetic resonance imaging system to which the
bridge is attached by distorting the main magnetic field and/or
producing substantial eddy currents during operation of the
magnetic resonance imaging system that negatively impact image
quality. To mitigate this problem, some embodiments include a
fold-up bridge in which the metal composition of the bridge is
minimized to the extent possible to provide a bridge capable of
supporting heavier patient while minimizing the impact on the
operation of the magnetic resonance imaging system. Thus, the
exemplary fold-up bridges described herein may be capable of
supporting large and/or heavy patients safely and securely, thus
taking advantage of the benefits of larger dimensioned bridges
without significantly impacting the ability to move the MRI system
down hallways and through doorways.
[0039] Following below are more detailed descriptions of various
concepts related to, and embodiments of, a fold-out bridge that can
be moved from a vertical position for stowing during transport of a
portable low-field MRI system or when the MRI system is not in use
to a horizontal position to facilitate positioning of the patient
for point-of-care MRI. It should be appreciated that the
embodiments described herein may be implemented in any of numerous
ways. Examples of specific implementations are provided below for
illustrative purposes only. It should be appreciated that the
embodiments and the features/capabilities provided may be used
individually, all together, or in any combination of two or more,
as aspects of the technology described herein are not limited in
this respect or to the specific combinations described.
[0040] FIGS. 2A and 2B illustrate an exemplary fold-out bridge for
supporting a patient during positioning and imaging, in accordance
with some embodiments. Bridge 200 is configured to be placed in a
stowed or "folded-up" position (also referred to simply as the "up"
or "vertical" position) or placed in an operational or
"folded-down" position (also referred to simply as the "down" or
"horizontal" position), respectively. Bridge 200 includes a support
210 configured to bridge a gap between the MRI system to which the
bridge is attached and a patient support (e.g., a hospital bed) to
which the MRI system is proximately located. Support 210 comprises
a surface 210a designed to support the patient during positioning
and imaging when the bridge is placed in the down position shown in
FIG. 2B.
[0041] When bridge 200 is in the down position, surface 210a of
support 210 is substantially horizontal to provide support for the
patient. Support 210, and particularly surface 210a, may be made of
material that reduces friction between a patient and the bridge,
such as a smooth plastic, to facilitate positioning of the patient
within the imaging region of the MRI system without producing eddy
currents during operation of the system. As shown in FIG. 2A, when
bridge 200 is in the up position, surface 210a (which is visible in
FIG. 2B) of support 210 is substantially vertical so that the
support does not add substantially, if at all, to the dimensions of
the magnetic resonance imaging system (e.g., when the bridge is in
the up position, the bridge does not increase the outer perimeter
or footprint of the system).
[0042] Bridge 200 comprises a hinge 250 that allows support 210 to
pivot from the up position to the down position and vice versa
(e.g., hinge 250 allows bridge 200 to be moved between the
positions illustrated in FIGS. 2A and 2B). According to some
embodiments, hinge 250 comprises a shaft 255 that allows support
210 to pivot or rotate from the vertical position shown in FIG. 2A
to the horizontal position shown in FIG. 2B and vice versa.
Specifically, exemplary bridge 200 comprises a base 252 and a pivot
portion 258 through which shaft 255 passes to allow the pivot
portion 258 to rotate about the shaft when folding up and folding
down the bridge.
[0043] Base 252 is configured to attach to the MRI system and
includes stop 253 (see FIG. 2A) and stop 254 (see FIG. 2B) that
provide end stops to prevent further pivoting of the bridge when
the horizontal position and vertical position are reached,
respectively. Base 252 further comprises counter-bores 245 (e.g.,
bores 245a, 245b and 245c) to accommodate bolts that allow bridge
200 to be securely attached to the MRI system. For example,
according to some embodiments, base 252 is constructed with three
counter-bores to accommodate respective M8 bolts that securely
attach the base of the bridge directly to the B.sub.0 magnet of the
MRI system (e.g., as shown in FIGS. 6A-6C discussed below). Bolting
the bridge to the MRI system in this manner contributes to the
bridge being able to withstand the torque produced by the weight of
a patient.
[0044] As discussed above, the inventors have recognized the
benefits of providing a bridge that can accommodate larger (e.g.,
wider) and heavier patients and that can bridge larger gaps between
a patient bed and the MRI system and/or that provide additional
overlap with the patient bed when placed in the down position.
According to some embodiments, a fold-out bridge is constructed
having a width of between 12 and 36 inches and a length of between
8 and 24 inches. For example, exemplary bridge 200 has a width W of
at least 24 inches and a length L of at least 12 inches to provide
a relatively large surface to accommodate a variety of patients and
to bridge a variety of gaps. The length of the bridge refers to the
dimension generally in a direction outward from the MRI system.
[0045] By increasing the length of the bridge, larger gaps can be
bridged and/or larger overlaps with a patient bed can be achieved.
The width of the bridge refers to the dimension generally in a
direction tangent to the MRI system. By increasing the width of the
bridge, wider patients may be more comfortably accommodated and
supported. Hospital equipment for acute care is often rated to
accommodate patients weighing 500 lbs. (e.g., hospital beds are
often rated to support 500 lb. patients). According to some
embodiments, bridge 200 is also rated for 500 lb. patients and may
be constructed to have a safety factor of at least 2.5 (i.e., that
have a yield strength of at least 2.5 times the rating). According
to some embodiments, bridge 200 is rated for 500 lb. patients and
is constructed to have a safety factor of 4.0 or more, examples of
which are described in further detail below.
[0046] FIG. 3 illustrates components of a fold-out bridge 300 to
illustrate exemplary construction details, in accordance with some
embodiments. Similar to bridge 200 described above, bridge 300
includes a support 210 having a surface 210a configured to support
a patient during positioning and imaging. Bridge 300 further
includes a hinge 250 comprising base 252 and pivot portion 258
that, when coupled together via shaft 255, allows support 210 to
pivot from a vertical position to a horizontal position and vice
versa. For exemplary bridge 300, support 210 may be coupled to
pivot portion 258 using a tongue-and-groove interface.
Specifically, support 210 includes a groove 217 configured to
receive tongue 257, which extends out from pivot portion 258. To
couple the support to the pivot portion, tongue 257 may be inserted
into groove 217 and screwed or bolted into place to secure support
210 to pivot portion 258.
[0047] To construct hinge 250, pivot portion 258 comprises
shoulders 259a and 259b between which is provided gap 263 sized to
accommodate base 252. Shoulders 259a, 259b and stop 254 of base 252
include cooperating bores 265 through which shaft 255 is inserted
to allow support 210 to pivot between the up and down positions.
When constructed, shaft 255 is secured within bores 265 of the base
and pivot portions with nuts 266a and bolts 266b at both ends of
the shaft. Thus, pivot portion 258 is allowed to rotate about the
shaft so that support 210 can be moved from the vertical position
(i.e., in which planar surface 210a is substantially vertical) when
not in use to the horizontal position (i.e., in which the planar
surface 210a is substantially horizontal) to facilitate positioning
a patient within the imaging region of the MRI system and to
support the patient during imaging. As discussed above, bridge 300
can be bolted to the MRI system via bolt holes 245a-c (e.g., bolted
to the lower B.sub.0 magnet of the MRI system so that it is level
with the patient surface within the imaging region of the MRI
system as shown in FIGS. 6A-C discussed below).
[0048] Bridge 300 may further include ball plungers 280a and 280b
that facilitate holding the bridge in the vertical position when
the bridge is not being used. For example, ball or spring plungers
280a and 280b may be positioned on either side of base 252 to
interact with shoulders 259a and 259b of pivot portion 258.
Specifically, to move bridge 300 from the vertical to the
horizontal position, the shoulders of the pivot portion must first
overcome the resistance provided by the spring loaded ball plungers
(i.e., to pivot bridge 300 out of the vertical position, shoulders
259a and 259b must first move over the ball plungers, which provide
a counter-resistance to the initial rotation of the pivot portion).
Accordingly, because an initial force exceeding the resistance of
the ball plungers is needed to move the bridge out of the vertical
position, a measure of safety is provided by reducing the chances
that bridge 300 will unintentionally fall from the vertical
position to the horizontal position. Bridge 300 may also include
rubber stoppers 293 configured to fit within corresponding holes
provided in stop 253 of base 252 to reduce noise produced when
shoulders 259a, 259b contact stop 253 when the bridge is moved to
the down position and/or to absorb some of the impact of the bridge
should the bridge fall or if the bridge is roughly handled during
transition to the horizontal position.
[0049] FIG. 4A illustrates a model of a fold-out bridge 400
constructed to support larger and/or heavier patients, in
accordance with some embodiments. The model illustrated in FIG. 4A
was used to perform a number of performance tests on exemplary
bridge 400 designed to provide a relatively large surface to
facilitate patient positioning and constructed to support heavier
patients (e.g., to achieve a 500 lb. rating). The following
dimensions, materials and construction details are provided merely
as description of the exemplary bridge 400 on which stress tests
were performed and do not limit the aspects of a fold-out bridge in
this respect. In particular, different dimensions, materials and
designs may be used to construct a fold-out bridge and different
aspects of a fold-out bridge discussed herein may be used in
different combinations. Bridge 400 illustrates one example of a
suitable fold-out bridge capable of supporting larger and/or
heaving patients and that provides a relatively large surface to
facilitate patient positioning and support.
[0050] Bridge 400 is provided with a support 210 having a
relatively large surface area, for example, a width of 24 inches
and a length of 14.4 inches measured from the far side of support
210 to the center of the curved interface of base 252 where bridge
400 is bolted to the MRI system (i.e., at counter-bore 245b).
Support 210 is formed, at least in part, by a 1 inch thick plastic
platform that provides a surface 210a over which a patient can be
moved to position the patient within the MRI system. Similar to the
construction of exemplary bridge 300, pivot portion 258 is coupled
to support 210 via a tongue-and-groove interface and coupled to the
base via a 16 mm diameter shaft 255 inserted through shoulder
portions 259a and 259b. For exemplary bridge 400, shoulders 259a
and 259b are constructed of metal (e.g., aluminum) and tongue
portion 257 is constructed of plastic (or other non-metallic
material). Base 252 may be constructed from steel and may comprise
three counter-bores 245a-c for bolting bridge 400 to the B.sub.0
magnet of the MRI system (e.g., using three corresponding M8
bolts). In this way, components of bridge 400 that undergo the
greatest amount of stress may be constructed of metal and
components that undergo less stress may be made of plastic (or
other non-metallic material) to minimize eddy current production
when the MRI system is operated while providing a bridge with
robust construction.
[0051] To evaluate the performance of exemplary bridge 400, stress
tests were simulated on the model of bridge 400 to ensure that the
design achieves a 500 lb. rating with a safety factor suitable for
patient support equipment. In particular, using the above described
construction details, a mesh was applied to the model of bridge 400
as shown in FIG. 4A and the stresses resulting from the weight of a
patient were simulated via finite element analysis. The weight that
bridge 400 is required to support for a 500 lb. patient was
obtained from the International Electrotechnical Commission (IEC)
60601-1 International Standard. Specifically, IEC 60601-1
establishes a number of safety requirements and performance
standards for medical equipment.
[0052] Figure A.19 of IEC 60601-1, which is reproduced herein as
FIG. 4D, shows an example of human body mass distribution that was
used to determine how the weight of a 500 lb. patient is
distributed over the patient support surface of the exemplary
bridges described herein. As shown in FIG. 4D, Figure A.19 of IEC
60601-1 specifies the length dimension (in millimeters) and the
percent of a patient's body mass that is contributed by significant
segments of the human body lying in a supine position.
Specifically, the head accounts for 7.4% of the mass of the
patient, the torso accounts for 40.7%, the upper arms together
account for 7.4% and the lower arms another 7.4%, the upper legs
account for 22.2% and the lower legs account for 14.8%. When a
patient is positioned within a portable MRI system, the head lies
within the imaging region and is supported by the MRI system (e.g.,
by the helmet on which the transmit/receive coils are located) so
that the bridge need support at least some portion of the torso,
shoulder and arm portions of the body. The full contribution of the
torso and the upper arms is approximately 50% (48.1%) of the body
mass of the patient. Accordingly, in approximate numbers, for a
bridge having a 500 lb. rating and a safety factor of 1, the bridge
would be required to support 250 lbs. (i.e., 50% of the patient's
total weight). For a safety factor of 2.5, the bridge would need to
support 625 lbs (i.e., 50% of the patient's weight times 2.5) and,
for a safety factor of 4, the bridge would need to support 1000
lbs. (i.e., 50% of the patients weight times 4).
[0053] To evaluate bridge 400 for a 500 lb. rating, the stresses on
bridge 400 resulting from a 500 lb. patient were simulated by
distributing 250 lbs. of weight over the surface of the bridge
(i.e., 50% of the patient's weight that the bridge needs to
support), as shown by the downward arrows in FIGS. 4A-4C. Using the
materials and dimensions discussed above, this distributed weight
produced the stress plot shown in FIG. 4B. A maximum stress of
6,981 psi resulted at the corners of the base indicated by arrows
353a and 353b. The yield strength of exemplary bridge 400 was also
assessed to evaluate the maximum stress that bridge 400 can
withstand. The yield strength of bridge 400 was determined to be
30,000 psi. Thus, exemplary bridge 400 achieves a 500 lb. rating
with a safety factor of 4.3. Specifically, the yield strength of
the bridge is 4.3 times greater than the maximum stress resulting
from simulating the forces applied on bridge 400 by a 500 lb.
patient.
[0054] FIG. 4C illustrates a deflection plot showing the
deformation of the bridge under the 250 lb. simulated weight. The
maximum deflection of the bridge resulting from the simulation was
1.5 mm at the far end of support 210. In particular, the arrows
show the location of the bridge without the simulated force
applied. In FIGS. 4B and 4C, the displacement resulting from the
applied 250 lbs. is shown at 36.4 scale to exaggerate the
displacement so that it can be visualized (i.e., the actual
displacement is 36.4 times smaller than it appears in the plots
shown in FIGS. 4B and 4C). Thus, a 250 lb. weight distributed
across bridge 400 to simulate the stresses resulting from a 500 lb.
patient resulted in a maximum displacement of 1.5 mm at end 210b of
support 210.
[0055] The inventors have recognized that some embodiments of a
fold-out bridge may be relatively large and heavy, particularly
when dimensioned and constructed to facilitate positioning and
support of larger, heavier patients. For example, an exemplary
bridge may be dimensioned to have a length of between 1 and 2 feet
or more and a width of between 1.5 and 2.5 feet or more, resulting
in bridges that can weigh between 8 and 15 lbs. or more. Larger,
heavier bridges have the potential to injure if the bridge
accidentally falls from the vertical position. To prevent a bridge
from being able to free fall, the inventors have developed a
counter-balance mechanism configured to slow the rate at which the
bridge can transition from the up position to the down position.
The counter-balance mechanism provides an additional safety
precaution that protects patients and medical personnel from
possible injury, as discussed in further detail below.
[0056] FIGS. 5A and 5B illustrate components for a bridge 500, in
accordance with some embodiments. Exemplary fold-out bridge 500 may
comprise many of the same components described in connection with
bridge 300 illustrated in FIG. 3 and/or bridge 400 illustrated in
FIGS. 4A-C. However, bridge 500 includes a counter-balance
mechanism configured to slow the rate at which fold-out bridge 500
can pivot to the horizontal position. According to some
embodiments, the counter-balance mechanism comprises torsion
springs 275a and 275b. Torsion springs 275a and 275b are configured
to fit over respective ends of shaft 555. Each torsion spring 275a,
275b is configured with end portions 276a and 276b that protrude
out from the spring in the direction of the shaft, as can be seen
best in the magnified portion of one end of the counter-balance
component illustrated in FIG. 5B.
[0057] In particular, end portions 276a are arranged in the
direction of the axis of shaft 555 and positioned on the perimeter
of the respective torsion spring and are configured to fit into a
corresponding indexing hole 278 provided in indexing components
277a, 277b. End portions 276b are similarly arranged and configured
to fit into respective indexing holes 278 provided in shoulders
559a and 559b of pivot portion 558. Specifically, indexing
components 277a, 277b comprise a plurality of indexing holes 278
around the perimeter (see e.g., exemplary indexing holes 278a and
278b illustrated in FIG. 5B) to accommodate end portions 276a.
Shoulders 559a and 559b comprise notches 556a and 556b to
accommodate respective torsion springs. Notches 556a and 556b
comprise bores 265 through which shaft 555 passes and further
comprise indexing holes 278 into which end portions 276b are
inserted (as best seen by indexing hole 278d provide next to bore
265 within notch 556b). For example, end portion 276b of each
torsion spring 275a, 275b fits into the respective indexing holes
278c and 278d so that the torsion spring is coupled to indexing
component 277 at one end and pivot component 558 at the other
end.
[0058] Shaft 555 includes flats 555a and 555b configured to fit
into respective indexing components 277a and 277b. Specifically,
flats 555a and 555b are configured to be inserted into slots 279
provided in respective indexing components 277a, 277b (as seen best
in the magnified view shown in FIG. 5B) and secured by screws 566a
and 566b at opposite ends of shaft 555. To facilitate operation of
the counter-balance mechanism, corresponding screw holes 236a and
236b are provided through stop 254 of base 252 and into shaft 555,
respectively, to accommodate screw 235 to hold shaft 255 in place.
Specifically, screw 235 is inserted through screw hole 236a in the
base and into screw hole 236b in shaft 555 to prevent the shaft
from rotating when pivot portion 558 rotates during transitions
between the up and down positions. Preventing shaft 255 from
rotating ensures that rotation of pivot portion 558 causes the
torsion springs 275a, 275b to wind or tighten to slow the rate at
which pivot portion 558 can rotate, as discussed in further detail
below. Sleeves 260a and 260b cover respective torsion springs 275a
and 275b when the bridge is assembled.
[0059] When constructed as described above, shaft 555 is fixed in
place and prevented from rotating by inserting the shaft through
bores 265 and into slots 279 of the respective indexing portions
277a, 277b and screwing the shaft in place via screws 566a, 566b
and 235. By inserting end portions 276a and 276b of the torsion
springs 275a, 275b into the indexing portions 277a, 277b and pivot
portion 558, respectively, rotation of pivot portion 558 from the
vertical position to the horizontal position causes the torsion
springs to tighten due to the fixed connection between end portions
276a to the indexing components 277a, 277b (which does not rotate)
and the fixed connection between end portions 276b and the indexing
holes 278c, 278d in notches 556a, 556b, respectively, by which end
portions 276b are rotated along with the pivot portion 558. That
is, because indexing holes 278c and 278d and end portions 276b are
aligned in the direction of the shaft axis but are positioned
off-axis, the rotation of the pivot portion causes the torsion
spring to tighten as indexing holes 278c and 278d rotate about the
axis of the shaft. Thus, when the bridge pivots from a vertical to
a horizontal position, the twisting of the torsion springs slows
the rotation of support 210 to prevent the bridge from rotating in
free fall. The spring constant of the torsion springs can be
selected to achieve the desired level of control of the rate at
which the bridge is allowed to transition between the up and down
positions. In this manner, bridge 500 includes a counter-balance
mechanism providing an additional safety mechanism to reduce the
chances of injury when using a fold-out bridge.
[0060] As discussed above, the exemplary fold-out bridges described
herein are configured to attach to a portable magnetic resonance
imaging system to facilitate positioning and supporting a patient
during point-of-care MRI. FIGS. 6A, 6B and 6C illustrate a portable
low-field MRI system to which the exemplary fold-out bridges
described herein can be attached. Specifically, portable low-field
MRI system 1000 can be deployed in virtually any environment to
image patients, for example, from a standard hospital bed located
in emergency rooms, intensive care units, operating rooms, neonatal
units, clinics, primary care offices, recovery units, etc. where
conventional MRI is typically not available. Exemplary fold-out
bridge may be configured to facilitate positioning and support of
large, heavy patients without substantially increasing the
footprint of the MRI system by virtue of being capable of being
stowed in the vertical position during transport or when not in use
and folded-down when needed to perform, for example, point-of-care
MRI.
[0061] In particular, to facilitate transporting portable MRI
system 1000 to locations at which MRI is needed, portable MRI
system 1000 is equipped with a fold-out bridge 600, which may
include any one or more of the features of a fold-out bridge
described herein. FIG. 6A illustrates bridge 600 configured in its
up position so that support 610 is substantially vertical and does
not add significantly (or at all) to the footprint of the MRI
system. As a result, bridge 600 does not impede moving the portable
MRI system down hallways and through doorways. FIG. 6A also
illustrates a deployable guard 1040 in its deployed position to
indicate the 5-Gauss line for the MRI system as its being
transported or when it is stored away or otherwise not in use. As
discussed in U.S. application Ser. No. 16/389,004, titled
"Deployable Guard for Portable Magnetic Resonance Imaging Device,"
filed on Apr. 19, 2019, which is herein incorporated by reference
in its entirety, the guard can be deployed to demarcate the
physical boundary within which the magnetic field is above a
specified field strength to provide a visual signal when the MRI
system is being moved to a different location. In addition, as
illustrated in FIG. 6B, when bridge 600 is up, the bridge provides
a barrier to the imaging region of the MRI system where the
magnetic field is strongest.
[0062] FIG. 6B illustrates portable MRI system 1000 with bridge 600
configured in the down position and FIG. 6C illustrates bridge 600
deployed in the down position to bridge the gap between patient bed
190 and MRI system 1000 to allow patient 199 to be positioned
within the imaging region of the MRI system and to support patient
199 during imaging. As discussed above, bridge 600 may be bolted to
the B.sub.0 magnet to secure the bridge to the MRI system. For
example, as shown in FIG. 6B, portable MRI system 1000 comprises a
B.sub.0 magnet 1005 that includes at least one first permanent
B.sub.0 magnet 1010a and at least one second permanent B.sub.0
magnet 1010b magnetically coupled to one another by a ferromagnetic
yoke 1020 configured to capture and channel magnetic flux to
increase the magnetic flux density within the imaging region 1065
(field of view) of the MRI system. For exemplary MRI system 1000,
bridge 600 is bolted to the lower magnet 1010b so that when it is
deployed (i.e., positioned in the down position as shown in FIGS.
6B and 6C), support 610 provides a continuation of the planar
surface 1015 of the magnet housing to facilitate positioning the
patient within imaging region 1065 and providing relatively level
support to the patient during imaging. FIG. 6B also illustrates a
conveyance mechanism 1080 of MRI system 1000 that facilitates
moving the MRI system from one location to another, as discussed in
further detail below.
[0063] FIG. 6C illustrates patient 199 positioned within the
imaging region of MRI system 1000 for imaging of the patient's head
from hospital bed 190. As shown, once the patient is positioned
with the imaging region and during the imaging process, the
patient's head is supported by helmet 1030 (which comprises radio
frequency transmit and receive coils), at least a portion of the
patient's torso and arms are supported by fold-out bridge 600 and
the remainder of the patient's weight is supported by patient bed
190. As discussed above, some embodiments of a fold-out bridge are
dimensioned and constructed to support large and heavy patients.
For example, bridge 600 may be rated for a 500 lb. patient with a
safety factor of 2.5 or more. According to some embodiments, bridge
600 may be rated for a 500 lb. patient with a safety factor of 4.0
or more (e.g., a safety factor of 4.3), for example, using the
various exemplary bridge constructions described above in
connection with any of exemplary bridges 300, 400 or 500.
[0064] The inventors have recognized that a fold-out bridge may
also be used as an additional safety feature that ensures that the
portable MRI system cannot be accidentally moved when the bridge is
supporting a patient and/or otherwise in use. As discussed above,
portable MRI system 1000 includes a conveyance mechanism configured
to allow the portable MRI system to be transported to desired
locations. Referring to FIG. 6B, portable MRI system 1000 comprises
a conveyance mechanism 1080 having a drive motor 1086 coupled to
drive wheels 1084. Conveyance mechanism 1080 may also include a
plurality of castors 1082 to assist with support and stability as
well as to facilitate transport of the MRI system. In this manner,
conveyance mechanism 1080 provides motorized assistance in
transporting MRI system 1000 to desired locations.
[0065] According to some embodiments, conveyance mechanism 1080
includes motorized assistance controlled using a controller (e.g.,
a joystick or other controller that can be manipulated by a person)
to guide the portable MRI system during transportation to desired
locations. According to some embodiments, the conveyance mechanism
comprises power assist means configured to detect when force is
applied to the MRI system and to engage the conveyance mechanism to
provide motorized assistance in the direction of the detected
force. For example, rail 1050 illustrated in FIG. 6B may be
configured to detect when force is applied to the rail (e.g., by
personnel pushing on the rail) and engage the drive motor to
provide motorized assistance to drive the wheels in the direction
of the applied force. As a result, a user can guide the portable
MRI system with the assistance of the conveyance mechanism that
responds to the direction of force applied by the user. The drive
motor may be operated in other ways, such as via buttons, roller
ball or other suitable mechanism located on the MRI system, or
using touch screen controls on a mobile computing device 1025
communicatively coupled to the MRI system, as the aspects of
motorized control is not limited in this respect.
[0066] Motorized transport has the potential for being accidentally
engaged, resulting in unintentional movement of the MRI system that
could injure a patient or medical personnel. For example, medical
personnel may forget to turn off the motorized transport or
motorized assist after the MRI system has been positioned for
imaging (e.g., transported to a location adjacent a patient's
hospital bed). Accidental contact with the rail or unintentional
interaction with a joystick or other on-system or mobile control of
the motor drive could cause the MRI system to move while a patient
is positioned within the imaging region of the system or during
positioning of the patient prior to imaging. Such accidental
movement of the MRI system has the potential to injure the patient
or medical personnel. To prevent unintentional movement of the MRI
system, the inventors have developed a lock-out mechanism that
disables any motorized conveyance components when the bridge is
transitioned to the down position and is supporting sufficient
patient weight. For example, the lock-out mechanism may include a
switch that disables the motor drive when actuated by the bridge.
According to some embodiments, a sensor that detects weight on the
support of the bridge is provided and, in response to detecting the
presence of a patient, disables the drive motor and/or other
components involved in motorized transport or motorized assist to
ensure that the MRI system is immobilized when the system is
supporting a patient.
[0067] An exemplary lock-out switch configured to disable the motor
drive of the MRI system is described in connection with FIG. 5A. As
discussed above, rubber plugs 293 can be used to absorb noise and
reduce wear when the bridge is placed in the horizontal position.
Alternatively, or in addition to the plugs, the bores formed in
stop 253 of the base into which the plugs are positioned may also
include an electromechanical lock-out switch that, when activated,
disables the motor drive of the MRI system. For example, one or
more springs may be placed in the bores (or otherwise coupled to
the bridge) such that the weight of the patient causes compression
of the springs to actuate a switch that locks-out the motor drive.
The spring(s) may be selected such that the weight of the bridge
when placed in the down position does not compress (or
insufficiently compresses) the spring so that the bridge itself
does not lock out the motor drive. However, the additional weight
of a patient causes the springs to compress sufficiently to
activate a switch that disables the motor drive so that the
portable MRI system cannot be accidentally moved when a patient is
present.
[0068] According to some embodiments, the weight of the bridge
itself when placed in the horizontal position is sufficient to
engage the lock-out switch and disable the motor drive. In this
way, moving the bridge from the vertical to the horizontal position
will immobilize the MRI system and prevent unintentional movement
of the MRI system. It should be appreciated that other types of
switches may be used to detect the present of a patient on the
bridge and/or detect when the bridge has been moved from the
vertical to the horizontal position to disable the motor drive of
the system, as the aspects are not limited in this respect. The
sensor that detects patient presence and/or detects when the bridge
has been placed in the horizontal position to engage the lock-out
switch may be mechanical, electrical, electromechanical, pneumatic,
hydraulic or any combination thereof.
[0069] Thus, low-field MRI system 1000 equipped with fold-out
bridge 600 can be used to perform point-of-care MRI on a patient,
including large and heavy patients. For example, to perform
point-of-care MRI on a patient from a standard medical bed, the MRI
system and the bed can be positioned proximate one another. In some
embodiments, the MRI system is portable and can be moved into
position near the hospital bed by medical personnel pushing the MRI
system into place and/or using a motor drive conveyance system to
move the MRI system into position. In some instances, the MRI
system may need to be transported from another room or unit within
the hospital. In other instances, the MRI system may already be
located in the same room as the patient and need only be moved next
to the bed of the patient. In other circumstances, a hospital bed
is transported to the MRI system and moved into place proximate the
MRI system for imaging. During the positioning of the MRI system
and the patient bed near one another, a fold-out bridge attached to
the MRI system may be positioned in the vertical or up position
(e.g., in the vertical position illustrated in FIG. 6A) to
facilitate transport of the system down hallways and/or through
doorways and/or to facilitate positioning the MRI system and the
bed in close proximity (e.g., positioning the MRI system and the
foot or head of the bed adjacent one another).
[0070] Once the MRI system and the bed are positioned proximate one
another, the fold-out bridge may be moved from the vertical
position to a horizontal position so that the bridge at least
partially overlaps the bed (e.g., the fold-out bridge 600 may be
moved from the vertical position illustrated in FIG. 6A to the
horizontal position illustrated in FIGS. 6B and 6C). The fold-out
bridge then provides a surface that bridges the gap between the MRI
system and the bed over which the patient can be moved. For
example, the portion of anatomy of the patient to be imaged may be
positioned within an imaging region of the MRI system via the
bridge and the bridge may provide support for the patient during
and after positioning the patient within the imaging region.
According to some embodiments, the fold-out bridge comprises a
lock-out switch that is engaged when sufficient patient weight is
placed on the bridge, thus disabling the motor drive and/or any
motorized components of the conveyance system to ensure that the
MRI system is immobilized. After positioning the patient within the
MRI system, at least one magnetic resonance image of the portion of
the anatomy of the patient may be acquired while the patient is at
least partially supported by the bed and at least partially support
by the bridge (e.g., as shown in FIG. 6C). In this way,
point-of-care MRI may be performed.
[0071] Having thus described several aspects and embodiments of the
technology set forth in the disclosure, it is to be appreciated
that various alterations, modifications, and improvements will
readily occur to those skilled in the art. Such alterations,
modifications, and improvements are intended to be within the
spirit and scope of the technology described herein. For example,
those of ordinary skill in the art will readily envision a variety
of other means and/or structures for performing the function and/or
obtaining the results and/or one or more of the advantages
described herein, and each of such variations and/or modifications
is deemed to be within the scope of the embodiments described
herein. Those skilled in the art will recognize, or be able to
ascertain using no more than routine experimentation, many
equivalents to the specific embodiments described herein. It is,
therefore, to be understood that the foregoing embodiments are
presented by way of example only and that, within the scope of the
appended claims and equivalents thereto, inventive embodiments may
be practiced otherwise than as specifically described. In addition,
any combination of two or more features, systems, articles,
materials, kits, and/or methods described herein, if such features,
systems, articles, materials, kits, and/or methods are not mutually
inconsistent, is included within the scope of the present
disclosure.
[0072] The above-described embodiments can be implemented in any of
numerous ways. One or more aspects and embodiments of the present
disclosure involving the performance of processes or methods may
utilize program instructions executable by a device (e.g., a
computer, a processor, or other device) to perform, or control
performance of, the processes or methods. In this respect, various
inventive concepts may be embodied as a computer readable storage
medium (or multiple computer readable storage media) (e.g., a
computer memory, one or more floppy discs, compact discs, optical
discs, magnetic tapes, flash memories, circuit configurations in
Field Programmable Gate Arrays or other semiconductor devices, or
other tangible computer storage medium) encoded with one or more
programs that, when executed on one or more computers or other
processors, perform methods that implement one or more of the
various embodiments described above. The computer readable medium
or media can be transportable, such that the program or programs
stored thereon can be loaded onto one or more different computers
or other processors to implement various ones of the aspects
described above. In some embodiments, computer readable media may
be non-transitory media.
[0073] The terms "program" or "software" are used herein in a
generic sense to refer to any type of computer code or set of
computer-executable instructions that can be employed to program a
computer or other processor to implement various aspects as
described above. Additionally, it should be appreciated that
according to one aspect, one or more computer programs that when
executed perform methods of the present disclosure need not reside
on a single computer or processor, but may be distributed in a
modular fashion among a number of different computers or processors
to implement various aspects of the present disclosure.
[0074] Computer-executable instructions may be in many forms, such
as program modules, executed by one or more computers or other
devices. Generally, program modules include routines, programs,
objects, components, data structures, etc. that perform particular
tasks or implement particular abstract data types. Typically the
functionality of the program modules may be combined or distributed
as desired in various embodiments.
[0075] Also, data structures may be stored in computer-readable
media in any suitable form. For simplicity of illustration, data
structures may be shown to have fields that are related through
location in the data structure. Such relationships may likewise be
achieved by assigning storage for the fields with locations in a
computer-readable medium that convey relationship between the
fields. However, any suitable mechanism may be used to establish a
relationship between information in fields of a data structure,
including through the use of pointers, tags or other mechanisms
that establish relationship between data elements.
[0076] The above-described embodiments of the present invention can
be implemented in any of numerous ways. For example, the
embodiments may be implemented using hardware, software or a
combination thereof. When implemented in software, the software
code can be executed on any suitable processor or collection of
processors, whether provided in a single computer or distributed
among multiple computers. It should be appreciated that any
component or collection of components that perform the functions
described above can be generically considered as a controller that
controls the above-discussed function. A controller can be
implemented in numerous ways, such as with dedicated hardware, or
with general purpose hardware (e.g., one or more processor) that is
programmed using microcode or software to perform the functions
recited above, and may be implemented in a combination of ways when
the controller corresponds to multiple components of a system.
[0077] Further, it should be appreciated that a computer may be
embodied in any of a number of forms, such as a rack-mounted
computer, a desktop computer, a laptop computer, or a tablet
computer, as non-limiting examples. Additionally, a computer may be
embedded in a device not generally regarded as a computer but with
suitable processing capabilities, including a Personal Digital
Assistant (PDA), a smartphone or any other suitable portable or
fixed electronic device.
[0078] Also, a computer may have one or more input and output
devices. These devices can be used, among other things, to present
a user interface. Examples of output devices that can be used to
provide a user interface include printers or display screens for
visual presentation of output and speakers or other sound
generating devices for audible presentation of output. Examples of
input devices that can be used for a user interface include
keyboards, and pointing devices, such as mice, touch pads, and
digitizing tablets. As another example, a computer may receive
input information through speech recognition or in other audible
formats.
[0079] Such computers may be interconnected by one or more networks
in any suitable form, including a local area network or a wide area
network, such as an enterprise network, and intelligent network
(IN) or the Internet. Such networks may be based on any suitable
technology and may operate according to any suitable protocol and
may include wireless networks, wired networks or fiber optic
networks.
[0080] Also, as described, some aspects may be embodied as one or
more methods. The acts performed as part of the method may be
ordered in any suitable way. Accordingly, embodiments may be
constructed in which acts are performed in an order different than
illustrated, which may include performing some acts simultaneously,
even though shown as sequential acts in illustrative
embodiments.
[0081] All definitions, as defined and used herein, should be
understood to control over dictionary definitions, definitions in
documents incorporated by reference, and/or ordinary meanings of
the defined terms.
[0082] The indefinite articles "a" and "an," as used herein in the
specification and in the claims, unless clearly indicated to the
contrary, should be understood to mean "at least one."
[0083] The phrase "and/or," as used herein in the specification and
in the claims, should be understood to mean "either or both" of the
elements so conjoined, i.e., elements that are conjunctively
present in some cases and disjunctively present in other cases.
Multiple elements listed with "and/or" should be construed in the
same fashion, i.e., "one or more" of the elements so conjoined.
Other elements may optionally be present other than the elements
specifically identified by the "and/or" clause, whether related or
unrelated to those elements specifically identified. Thus, as a
non-limiting example, a reference to "A and/or B", when used in
conjunction with open-ended language such as "comprising" can
refer, in one embodiment, to A only (optionally including elements
other than B); in another embodiment, to B only (optionally
including elements other than A); in yet another embodiment, to
both A and B (optionally including other elements); etc.
[0084] As used herein in the specification and in the claims, the
phrase "at least one," in reference to a list of one or more
elements, should be understood to mean at least one element
selected from any one or more of the elements in the list of
elements, but not necessarily including at least one of each and
every element specifically listed within the list of elements and
not excluding any combinations of elements in the list of elements.
This definition also allows that elements may optionally be present
other than the elements specifically identified within the list of
elements to which the phrase "at least one" refers, whether related
or unrelated to those elements specifically identified. Thus, as a
non-limiting example, "at least one of A and B" (or, equivalently,
"at least one of A or B," or, equivalently "at least one of A
and/or B") can refer, in one embodiment, to at least one,
optionally including more than one, A, with no B present (and
optionally including elements other than B); in another embodiment,
to at least one, optionally including more than one, B, with no A
present (and optionally including elements other than A); in yet
another embodiment, to at least one, optionally including more than
one, A, and at least one, optionally including more than one, B
(and optionally including other elements); etc.
[0085] Also, the phraseology and terminology used herein is for the
purpose of description and should not be regarded as limiting. The
use of "including," "comprising," or "having," "containing,"
"involving," and variations thereof herein, is meant to encompass
the items listed thereafter and equivalents thereof as well as
additional items.
[0086] In the claims, as well as in the specification above, all
transitional phrases such as "comprising," "including," "carrying,"
"having," "containing," "involving," "holding," "composed of," and
the like are to be understood to be open-ended, i.e., to mean
including but not limited to. Only the transitional phrases
"consisting of" and "consisting essentially of" shall be closed or
semi-closed transitional phrases, respectively.
* * * * *