U.S. patent application number 11/466792 was filed with the patent office on 2008-03-13 for dual-stage positioning system.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Asghar Ali Farooqui.
Application Number | 20080060133 11/466792 |
Document ID | / |
Family ID | 39168073 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080060133 |
Kind Code |
A1 |
Farooqui; Asghar Ali |
March 13, 2008 |
DUAL-STAGE POSITIONING SYSTEM
Abstract
A positioning system for positioning a patient support in an
imaging device is disclosed herein. The positioning system includes
a fine positioning subsystem coupled to the patient support and
adapted to position the patient support with fine precision along
the X-axis; and a coarse positioning subsystem coupled to the fine
positioning subsystem and adapted to position the patient support
with coarse precision along the X-axis. In an embodiment, the fine
positioning subsystem and the coarse positioning subsystem are a
dual-stage drive positioning system, with the first drive including
a screw mechanism and the second drive including a prime mover. In
an embodiment, a programmer is provided for configuring the fine
positioning subsystem to align the patient support based on a
velocity profile.
Inventors: |
Farooqui; Asghar Ali;
(Karnataka, IN) |
Correspondence
Address: |
PETER VOGEL;GE HEALTHCARE
3000 N. GRANDVIEW BLVD., SN-477
WAUKESHA
WI
53188
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
39168073 |
Appl. No.: |
11/466792 |
Filed: |
August 24, 2006 |
Current U.S.
Class: |
5/601 |
Current CPC
Class: |
A61B 6/0487
20200801 |
Class at
Publication: |
5/601 |
International
Class: |
A47B 13/00 20060101
A47B013/00 |
Claims
1. A positioning system for positioning a patient support in an
imaging device comprising: a fine positioning subsystem coupled to
the patient support, adapted for positioning the patient support
with fine precision; and a coarse positioning subsystem coupled to
the fine positioning subsystem, adapted for positioning the patient
support with coarse precision, wherein the fine positioning
subsystem and the coarse positioning subsystem are configured to
position the patient support along an X-axis.
2. The positioning system as in claim 1, wherein the fine
positioning subsystem is configured to position the patient support
with micrometer precision, and the coarse positioning subsystem is
configured to position the patient support with millimeter
precision.
3. The positioning system as in claim 1, wherein the fine
positioning subsystem is configured to position the patient support
with a precision of one micrometer for a range of 0-300 micrometers
along the X-axis.
4. The positioning system as in claim 1, wherein the coarse
positioning subsystem is configured to position the patient support
with a precision of one millimeter for a range of 0-2000
millimeters along the X-axis.
5. The positioning system as in claim 1, wherein the fine
positioning subsystem comprises a screw drive mechanism operating
in a closed loop.
6. The positioning system as in claim 5, wherein the screw drive
mechanism includes a screw arrangement and an electric motor
coupled to the screw arrangement and configured to drive the screw
arrangement.
7. The positioning system as in claim 6, wherein the screw drive
mechanism is coupled to the patient support through a fine
feed.
8. The positioning system as in claim 1, wherein the coarse
positioning subsystem is configured to be a prime mover operating
in a closed loop.
9. The positioning system as in claim 8, wherein the coarse
positioning subsystem includes a screw drive mechanism, hydraulic
drive mechanism or belt drive mechanism.
10. The positioning system as in claim 1, wherein the fine
positioning subsystem is coupled to the coarse positioning
subsystem through a coarse feed.
11. The positioning system as in claim 1, wherein the imaging
device is one of a computed tomography device, a positron emission
tomography device, a magnetic resonance imaging device, an
ultrasound imaging device and an X-ray device.
12. A positioning system with a dual-stage drive assembly for an
imaging device, comprising: (a) a patient support capable of moving
along an X-axis; (b) a first drive coupled to the patient support,
adapted for fine positioning of the patient support with fine
precision along the X-axis; and (c) a second drive coupled to the
first drive, adapted for coarse positioning of the patient support
with coarse precision along the X-axis.
13. The positioning system as in claim 12, wherein the first drive
is configured to position the patient support with micrometer
precision, and the second drive is configured to position the
patient support with millimeter precision.
14. The positioning system as in claim 12, wherein the patient
support includes a carrier and at least two pairs of elongated
rails.
15. The positioning system as in claim 12, wherein the first drive
is configured to position the patient support with a precision of
one micrometer for a range of 0-300 micrometer.
16. The positioning system as in claim 12, wherein the first drive
includes a screw drive mechanism operating in a closed loop.
17. The positioning system as in claim 16, wherein the screw drive
mechanism includes a screw arrangement coupled to the patient
support and an electric motor coupled to the screw arrangement.
18. The positioning system as in claim 17, further comprising a
programmer for configuring the electric motor to position the
patient support based on a velocity profile.
19. The positioning system as in claim 18, wherein the velocity
profile includes mapping of velocity of the patient support in the
imaging device over volume of a scanned object.
20. The positioning system as in claim 12, wherein the second drive
is configured to be a prime mover operating in a closed loop.
21. A method of positioning a patient in an imaging device
comprising the steps of: (a) aligning a patient table along an
X-axis using a coarse positioning subsystem; (b) fine tuning the
alignment of the patient table with fine precision along the X-axis
using a fine positioning subsystem; (c) actuating the fine
positioning subsystem to align the patient table using a velocity
profile; and (d) adjusting the position of the patient table using
the velocity profile.
22. The method as in claim 21, wherein the velocity profile
includes mapping of velocity of the patient table passing through a
scanning beam in the imaging device over volume of a scanned
object.
Description
FIELD OF THE INVENTION
[0001] This invention generally relates to positioning systems.
More particularly, it relates to a positioning system with a
dual-stage drive assembly.
BACKGROUND OF THE INVENTION
[0002] In imaging devices, the position of the object to be imaged
and its control are often critical. The proper positioning or
aligning of the object is required to obtain images of high
quality. In diagnostic imaging devices, the positioning of the
patient is achieved by aligning the patient table or patient
support surface with reference to the radiation source and the
radiation detector.
[0003] Typically, positioning systems for a patient support in a
diagnostic medical imaging equipment include mechanisms for
effecting longitudinal and lateral movement to the patient support
for enabling convenient positioning of a patient lying on or
otherwise supported by the patient support for medical
examination.
[0004] Known configurations of a positioning system for a patient
support include a longitudinal drive mechanism and a lateral drive
mechanism having one of a manually operable configuration or a
drive motor.
[0005] However, these known configurations do not provide an
optimum positioning and arrangement of the drive mechanisms. For
example, in computer tomography (CT) imaging systems, the patient
support surface often needs to be placed with micrometer precision.
Some known CT tables use a screw drive or friction drive to convert
the rotary motion of a screw rod to linear motion of the patient
support. A servomotor is coupled to drive the screw rod in a closed
loop to achieve better control and precision. However, such CT
tables will not yield the required precision for positioning
patients, especially if accuracies in the range of one micrometer
are needed.
[0006] Thus it would be desirable to provide a positioning system
capable of positioning an object with enhanced precision in
comparison to known positioning systems. It would also be desirable
to provide a positioning system for use in medical imaging
applications where the patient needs to be accurately
positioned.
SUMMARY OF THE INVENTION
[0007] The above-mentioned shortcomings, disadvantages and problems
are addressed herein which will be understood by reading and
understanding the following specification.
[0008] The present invention provides a positioning system for
positioning a patient support in an imaging device. The positioning
system comprises: a fine positioning subsystem coupled to the
patient support, adapted for positioning the patient support with
fine precision; and a coarse positioning subsystem coupled to the
fine positioning subsystem, adapted for positioning the patient
support with coarse precision, wherein the fine positioning
subsystem and coarse positioning subsystem are configured to
position the patient support along an X-axis. In an embodiment, the
fine positioning subsystem is configured to position the patient
support with micrometer precision, and the coarse positioning
subsystem is configured to position the patient support with
millimeter precision. In an embodiment the fine positioning
subsystem is configured to position the patient support with a
precision of one micrometer for a specified range of 0-300
millimeters along the X-axis. In an embodiment the coarse
positioning subsystem is configured to position the patient support
with a precision of one millimeter for a range of 0-2000
millimeters along the X-axis.
[0009] In another embodiment, a positioning system with a
dual-stage drive assembly for an imaging device is described. The
positioning system comprises: a patient support capable of moving
along an X-axis; a first drive coupled to the patient support,
adapted for fine positioning of the patient support with fine
precision along the X-axis; and a second drive coupled to the first
drive, adapted for coarse positioning of the patient support with
coarse precision along the X-axis. In an embodiment a programmer is
provided for configuring the fine positioning subsystem to move and
position the patient support based on a velocity profile. The
velocity profile may include mapping velocity of the patient
support while scanning along the X-axis over volume of a scanned
object. The velocity of the patient support may be directly
proportional to the cross section of the object being scanned.
[0010] In yet another embodiment a method of positioning a patient
in an imaging device is provided. The method comprises the steps
of: (a) aligning a patient table along an X-axis using a coarse
positioning subsystem; (b) fine tuning the alignment of the patient
table with fine precision along the X-axis using a fine positioning
subsystem; (c) activating the fine positioning subsystem to
position the patient table using a velocity profile; and (d)
adjusting the position of the patient table using the velocity
profile. In an embodiment, the velocity profile includes mapping of
velocity of the patient support, in an imaging device over volume
or cross section of a scanned object.
[0011] Various other features, objects, and advantages of the
invention will be made apparent to those skilled in the art from
the accompanying drawings and detailed description thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic diagram of an imaging device capable
of using a positioning system described in an embodiment of the
invention;
[0013] FIG. 2 is a schematic diagram of a positioning system as in
an embodiment of the invention;
[0014] FIG. 3 is a schematic diagram of a fine positioning
subsystem as described in an embodiment of the invention;
[0015] FIG. 4 is a schematic diagram of a coarse positioning
subsystem as described in an embodiment of the invention; and
[0016] FIG. 5 is a flow chart indicating a method of positioning a
patient in an imaging device as described in an embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] In the following detailed description, reference is made to
the accompanying drawings that form a part hereof, and in which is
shown by way of illustration specific embodiments that may be
practiced. These embodiments are described in sufficient detail to
enable those skilled in the art to practice the embodiments, and it
is to be understood that other embodiments may be utilized and that
logical, mechanical, electrical and other changes may be made
without departing from the scope of the embodiments. The following
detailed description is, therefore, not to be taken as limiting the
scope of the invention.
[0018] In an embodiment, a dual-stage positioning system is
disclosed. The positioning system is provided with a coarse
positioning subsystem for providing a reference and a fine
positioning subsystem for providing high precision alignment.
[0019] In various embodiments a positioning system using a
dual-stage drive assembly for an imaging device is disclosed. The
embodiments, however, are not so limited, and may be implemented in
connection with other systems such as industrial imaging system,
tracking systems, various positioning systems etc. In an
embodiment, the positioning system imparts very high precision for
the required range and coarse precision for the remaining
displacement range. In another embodiment, the movement of the
object being scanned is programmed as per the cross sectional
volume of the part. A velocity profile, a mapping between the
velocity of the patient support over a cross section of area or
volume of the object being scanned is calculated. The velocity of
the patient support is directly proportional to the volume of the
object. In an embodiment, the movement of the patient support is
programmed based on the velocity profile. Various parts require
different types of velocity profiles, which can be preprogrammed
and easily executed whenever required.
[0020] FIG. 1 is a schematic diagram of an imaging device capable
of using a positioning system described in an embodiment of the
invention. The imaging device 100 can be one of a computed
tomography device, a positron emission tomography device, a
magnetic resonance imaging device, an ultrasound-imaging device and
an X-ray device. One skilled in the art will however appreciate
that, the imaging device is not limited to the examples mentioned
above and the invention shall have full scope of the claims.
[0021] In an embodiment, the imaging device 100 comprises an
imaging gantry 105. The imaging gantry 105 includes a tunnel 125
for receiving a patient 110 and a radiation source 130 for
providing radiations. A patient support 115 having a patient
support surface is provided for engaging and supporting the patient
110. A positioning system 120 is provided for moving and aligning
the patient support 115, which is received in the tunnel 125 of the
imaging device 100. For better quality images and desired results
the patient support needs to be positioned with fine precision. In
an embodiment, the fine precision is in the range of micrometer
precision. In an embodiment, the positioning system is designed to
align or position the patient support along an X-axis with a
precision of one micrometer for a range of 0-300 millimeters. The
positioning system will be explained in detail with reference to
FIG. 2. While the patient support 115 in FIG. 1 includes a patient
support surface upon which a patient may lie down, the patient
support may also include a patient support surface that supports a
patient or a portion of the patient in another orientation, such as
a patient who is standing or arranged vertically while pressed
against a surface of the patient support, or whose body is strapped
to, or otherwise attached or coupled to, the support surface. The
imaging device is one of a computed tomography device, a positron
emission tomography device, a magnetic resonance imaging device, an
ultrasound imaging device and an X-ray device.
[0022] FIG. 2 illustrates a schematic diagram of a positioning
system as in an embodiment of the invention. The positioning system
comprises a patient support 215 having a patient support surface
and a positioning system 220. The patient support 215 may comprise
a carrier and two or more elongated rails (not shown). The carrier
can be used for engaging and supporting a patient. The elongated
rails can be provided at the bottom side of the carrier and can
extend between the opposing sides of the patient support 215. The
elongated rails are provided for co-operation during longitudinal
movement of the carrier. The patient support 215 is configured to
move along the X-axis of an imaging device or laterally using the
positioning system 220.
[0023] The positioning system 220 comprises a fine positioning
subsystem 221 and a coarse positioning subsystem 226. The patient
support 215 is a patient table. The patient support 215 is coupled
to the fine positioning subsystem 221 through a fine feed 222. The
fine feed 222 may be any mechanism, which can connect the fine
positioning subsystem 221 to the patient support 215. This may
include a clamp, or a bracket or any other holding means. The fine
positioning subsystem 221 is capable of aligning or positioning the
patient support 215 with a precision of a micrometer. In an
embodiment, the fine positioning subsystem 221 aligns the patient
support 215 with a precision of one micrometer for a range of 0-300
millimeters along the X-axis of the imaging device. However, it
will be understood that the fine positioning system 221 may
position the patient support 215 with other fine precisions. The
fine positioning subsystem 221 is further coupled with the coarse
positioning subsystem 226. In an embodiment the fine positioning
subsystem 221 is a precision screw mechanism. The precision screw
mechanism includes a screw arrangement 223 and an electric motor
225 coupled to the screw arrangement. The electric motor 225 is
connected to the screw arrangement 223 by means of a timer belt
224. The fine positioning subsystem will be explained in detail in
FIG. 3.
[0024] The coarse positioning system 226 is configured to be prime
mover. In an embodiment the coarse positioning subsystem 226
includes one or more double-end shaft motors (not shown) comprising
shafts that extend outwardly in opposite directions. One or more
timer pulleys 227 can be mounted on each end of the double-end
shaft motor. One or more belts 228 can extend over the timer
pulleys 227. The belts can be coupled to the double-end shaft motor
through a coupling device (not shown). The belt 228 can also be
coupled to fine positioning subsystem 221 through a coarse feed
229. As the fine positioning subsystem 221 is coupled with the
patient supporting 215, the coarse positioning subsystem 226 will
be able to move the patient support 215 laterally. The coarse
positioning subsystem 226 is configured to align the patient
support with a precision of one millimeter for a range of 0-2000
millimeters. However the various ranges of precisions may be
achieved using the same concept but with different design as per
the requirements of the particular application. By using the coarse
positioning subsystem 226 a reference position is achieved, and
using the fine positioning subsystem 221 the patient support 215 is
aligned or positioned with micrometer precision. The coarse
positioning subsystem using double-end shaft motors will be
explained in detail in FIG. 4.
[0025] In an embodiment the coarse positioning subsystem is
configured to be a prime mover operating in a closed loop. However
the coarse positioning system may be configured to be a coarse
screw drives mechanism, a hydraulic drive mechanism and friction
drive mechanism.
[0026] FIG. 3 illustrates schematic diagram of a fine positioning
subsystem as described in an embodiment of the invention. In an
embodiment, the fine positioning subsystem is configured to be a
first drive 321. An imaging device is provided with a patient
support 315 having a patient support surface for supporting and
engaging a patient. The first drive is connected to the patient
support 315 through a fine feed 323. The fine feed 323 may be any
mechanism, which can connect the fine positioning subsystem 321 to
the patient support 315. This may include a clamp, a bracket or any
other holding means. The first drive 321 includes a very high
precision screw drive mechanism operating in a closed loop. The
precision screw drive mechanism includes a screw arrangement 322
and an electric motor 325 connected with the screw arrangement 322
for driving the screw arrangement. The screw arrangement 322 is
coupled with the electric motor 325, for driving the screw
arrangement, through a timer belt coupled drive 324. In an
embodiment the screw used in the screw arrangement is a ground ball
screw with preloading for backlash free execution. In an embodiment
the electric motor is a stepper or a servomotor.
[0027] In an embodiment the fine positioning subsystem 321 is
programmed to move the patient support 315, based on a velocity
profile. The fine positioning subsystem 321 is provided with a
programmer 326 for configuring the fine positioning subsystem 321
for moving or positioning the patient support 315 based on a
velocity profile. The programmer 326 is coupled with the electric
motor 325. The displacement of scanning part of the object being
scanned can be programmed as per the cross sectional area or volume
of the part. The velocity of patient moving along the X-axis
through the scanning beam in an imaging device is directly
proportional to the volume of the object being scanned. Thus in a
particular area of cross section, if the volume is more, then
scanning time will be more compared to parts with lesser area of
cross section or volume. By programming the movement of the patient
support surface the scanning time may be reduced. In effect, if a
part with less volume of cross section is being scanned, it
requires less time and hence the patient support may be moved
quickly. This will reduce the time of scan. Various parts of the
object will have different types of velocity profiles, which can be
preprogrammed and easily executed whenever required.
[0028] For programming the displacement of the patient support the
velocity profile of the object is obtained. The velocity profile
includes mapping of velocity of the patient support in an imaging
device over the cross sectional area/volume of the object being
scanned.
[0029] FIG. 4 illustrates a schematic diagram of a coarse
positioning subsystem as described in an embodiment of the
invention. In an embodiment the coarse positioning subsystem is
configured to be a second drive 400. The coarse positioning
subsystem is provided to operate in a closed loop. An imaging
device is provided with a patient support 415 having a patient
support surface for supporting and engaging a patient. The patient
support 415 can comprise a carrier 450 that engages and supports a
patient. The patient support 415 is a patient table capable of
moving along the X-axis of the imaging device. The patient support
415 can also comprise structural members such as elongated rails
445 for enabling the movement of the carrier 450 along a horizontal
or X-axis. The carrier 450 is slidably mounted on the elongated
rails 445 of the patient support 415. The second drive 400 for
moving the patient support 415 is a rotary-to-linear motion
converter. The second drive 400 can comprise one or more double-end
shaft motors 425. The double-end shaft motor 425 can be a stepper
or a servomotor. Operation of the double-end shaft motor 425 causes
a linear motion of the patient support 415. The second drive 400 is
connected with the first drive through a coarse feed 229. The
coarse feed 229 includes any holding or attaching means capable of
attaching the second drive to the first drive. This may includes
brackets, clamps or any other holding means. One or more belts 440
for example; tooth belt can be coupled to the double end shaft
motor 425 via a coupling device 410. The coupling device 410
provides smoother engagement and eliminates chatter. The coupling
device 410 can be configured to be an electro-mechanical
clutch.
[0030] The second drive 400 may further comprise multiple timer
pulleys 427 rotatably placed beneath the patient support 415.
Operation of the double-end shaft motor 425 causes rotation of the
timer pulley 405. The timer pulleys 405 drive the belt 440
extending between the timer pulleys 405. The belt 440 in turn
secures the first drive 212 through the coarse feed. The first
drive 212 is coupled to the patient support through the fine feed.
Therefore, the rotation of the timer pulleys 405 causes a linear
movement of patient support 415.
[0031] Each timer pulley 405 can be directly coupled to a feedback
device 435 at a first end. The feedback device 435 is a sensor
assembly providing an indication of an absolute position of the
patient support 415. The sensor assembly comprises a magnet secured
to the carrier 450 and a magnetic absolute linear position sensor
secured to one of the elongated rails 445 of the patient support
415. The relative position of the carrier 450 with respect to the
magnetic absolute linear position sensor of the elongated rails 445
can be determined from the output signal provided by the magnetic
absolute linear position sensor. The feedback device 435 can be
configured to be an encoder. More particularly, the feedback device
435 can be configured to be an absolute encoder for greater
positioning accuracy.
[0032] In an embodiment the output of the feedback device 435 may
be provided to the programmer 326. This will allow the programmer
326 to select the desired velocity profile based on the position of
the patient support.
[0033] The timer pulley 405 can also be coupled to a brake device
430 at a second end. The brake device can be a positive clamping
device. The brake device ensures that the carrier position is not
disturbed after the carrier is positioned at a predetermined
position. This provides a reference position for the first drive.
Further, the brake device 430 can configured to be an
electro-mechanical brake for better safety.
[0034] In an embodiment the second drive is configured to be a
coarse screw mechanism. This includes a screw arrangement capable
of positioning the patient support coarsely. The coarse screw
mechanism further includes an electric motor coupled to the screw
arrangement through a belt.
[0035] In an embodiment the second drive is configured to be a set
of hydraulic cylinders used to move the patient support along the
X-axis. Few cylinders placed in a particular configuration would
help to attain the required coarse position.
[0036] The fine positioning subsystem is actuated once an initial
reference position is reached and the electro mechanical brakes
actuated. These pair of brakes will rigidly hold the patient
support in its initial reference position and this will act as a
reference position to the fine positioning subsystem. This fine
positioning subsystem has a very precise screw mechanism coupled
with a stepper motor or servo motor in a close loop. The
displacement least count can be of one micrometer as the stroke is
limited to 300 mm only. The rigidity, accuracy, repeatability and
control will be absolute. The errors will be reduced drastically
because of the range control and least count.
[0037] FIG. 5 illustrates a flow chart indicating a method of
positioning a patient in an imaging device as described in an
embodiment of the invention. The method of positioning is
illustrated in 500. At block 510; a patient table is aligned along
the X-axis using a coarse positioning subsystem. At block 520, the
alignment of the patient table is fine tuned using a fine
positioning subsystem. The patient table may be aligned with a
precision of up to 1 millimeter for a range of 0-300 micrometers.
At block 530, the fine positioning subsystem is actuated to
position the patient table using a velocity profile. In an
embodiment the velocity profile includes mapping of velocity the
patient support in an imaging device over volume of a scanned
object. At block 540, adjusting the position of the patient table
using the velocity profile.
[0038] The manufacturing and production of the positioning system
is simplified when compared to the conventional positioning system
using super drive systems like magnetic motors or linear motors to
achieve similar accuracies and least count. The manufacturing cost
is saved around 40%. The positioning system requires less assembly
time and can be accommodated easily due to the flexibility of the
tooth belt used. Therefore the manufacturing, assembling, transport
and handling of the positioning system are simple, cheap and
reliable.
[0039] Since the positioning of the patient support is programmed
based on the velocity profile, the scanning time can be reduced. As
dual stage positioning system is used, the patient support and the
patient supported thereby may be placed with very high
precision.
[0040] Thus various embodiments of positioning system are
disclosed. However, it should be noted that the invention is not
limited to this or any particular application or environment.
Rather, the technique may be employed in a range of applications,
including medical imaging systems, industrial imaging systems,
tracking system or any other positioning technology, to mention a
few. The invention also discloses a method of aligning a patient
for exposing to radiations.
[0041] While the invention has been described with reference to
preferred embodiments, those skilled in the art will appreciate
that certain substitutions, alterations and omissions may be made
to the embodiments without departing from the spirit of the
invention. Accordingly, the foregoing description is meant to be
exemplary only, and should not limit the scope of the invention as
set forth in the following claims.
* * * * *