Title:
DUAL-STAGE POSITIONING SYSTEM
Kind Code:
A1


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)
Application Number:
11/466792
Publication Date:
03/13/2008
Filing Date:
08/24/2006
Assignee:
GENERAL ELECTRIC COMPANY (Schenectady, NY, US)
Primary Class:
International Classes:
A47B13/00
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Primary Examiner:
POLITO, NICHOLAS F
Attorney, Agent or Firm:
GE Healthcare, IP Department (Wauwatosa, WI, US)
Claims:
I claim:

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

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

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.

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.

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.

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.

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

The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification.

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.

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.

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.

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

FIG. 1 is a schematic diagram of an imaging device capable of using a positioning system described in an embodiment of the invention;

FIG. 2 is a schematic diagram of a positioning system as in an embodiment of the invention;

FIG. 3 is a schematic diagram of a fine positioning subsystem as described in an embodiment of the invention;

FIG. 4 is a schematic diagram of a coarse positioning subsystem as described in an embodiment of the invention; and

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.