WO2014125386A1

WO2014125386A1 - Hydraulic adjusting system for adjusting a collimator used in a ct apparatus

Info

Publication number: WO2014125386A1
Application number: PCT/IB2014/058509
Authority: WO
Inventors: Wei Chen
Original assignee: Koninklijke Philips N.V.
Priority date: 2013-02-18
Filing date: 2014-01-24
Publication date: 2014-08-21

Abstract

The present invention provides a hydraulic adjusting system for adjusting a collimator used in a CT apparatus. The hydraulic adjusting system comprises two first hydraulic cylinders disposed at the collimator cradle, a first piston rod extending out of each one of two first hydraulic cylinders, a driving block provided at a free end of the first piston rod, and a driven block disposed at each end of each one of two collimator blades, wherein the driving block is arranged to align with a gap formed between one driven block of one of two collimator blades and one driven block of the other one of two collimator blades. The hydraulic adjusting system according to the present invention is simpler in structure, lighter in weight and cheaper in costs than a conventional adjusting system.

Description

HYDRAULIC ADJUSTING SYSTEM FOR ADJUSTING A

COLLIMATOR USED IN A CT APPARATUS

FIELD OF THE INVENTION

The invention relates to a collimator used in a CT (computed tomography) apparatus, in particular to a hydraulic adjusting system for adjusting the collimator used in the CT apparatus.

BACKGROUND OF THE INVENTION

A collimator is usually used in a CT apparatus so that X-ray may be focused onto a desired region of a subject to be examined, pass through the patient and then land on the imaging detectors. The collimator generally comprises a base, a collimator cradle supported by the base and two collimator blades mounted movably onto the collimator cradle. It is usually necessary to adjust a collimator slit between two collimator blades and/or a position of the collimator cradle relative to the base for calibration of X-ray so that the detectors may receive the X-ray passing through the subject to be examined. To this end, an adjusting system for adjusting the collimator is provided.

A conventional adjusting system for adjusting the collimator usually comprises a motor, a gearbox and belt transmission, and a screw mechanism. The conventional adjusting system has a lot of components which make the adjusting system very complicated, heavy and expensive, especially when the adjusting system has two or more motors, two or more gearboxes, two or more precision screws, pulleys and belts. The latter usually appears when more different movements/adjustments are required, which further increases markedly the complication, the weight and the expenses of the collimators. Furthermore, in the conventional adjusting system for adjusting the collimator, special fixtures are usually needed to eliminate a backlash of the screw mechanism and compensate an accumulative tolerance of the screw mechanism. Otherwise, an adjustment precision of the collimator will be affected adversely.

Thus, there is a need to make improvements on the conventional adjusting system for adjusting the collimator.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a hydraulic adjusting system for adjusting a collimator used in a CT apparatus which is simpler in structure, lighter in weight and cheaper in expenses than the conventional adjusting system.

It is an other object of the present invention to provide a hydraulic adjusting system for adjusting a collimator used in a CT apparatus which reduces a deformation of the collimator because of a smaller centrifugal force caused by a lighter collimator mass during rotation of the gantry, thereby improving the precision of the collimator. Further, the collimator cradle can be redesigned with less material.

It is a further object of the present invention to provide a hydraulic adjusting system for adjusting a collimator used in a CT apparatus which would not result in any backlash or accumulative tolerance of the screw mechanism which affect adversely the precision of the adjustments.

According to one aspect of the present invention, it is to provide a hydraulic adjusting system for adjusting a collimator used in a CT apparatus. The collimator comprises a base mountable onto a gantry system of the CT apparatus so as to support the collimator, a collimator cradle supported by the base, and two collimator blades attached movably to the collimator cradle via a guide mechanism and defining a collimator slit between them. A pushing means is disposed to push two collimator blades toward each other to reduce the collimator slit. The hydraulic adjusting system comprises:

two first hydraulic cylinders disposed at the collimator cradle;

a first piston rod extending out of each one of two first hydraulic cylinders;

a driving block provided at a free end of the first piston rod; and

a driven block disposed at each end of each one of two collimator blades, wherein the driving block is arranged to align with a gap formed between one driven block of one of two collimator blades and one driven block of the other one of two collimator blades.

Preferably, the driving block is in a tapered shape.

Preferably, the driven block has a slanting surface and/or a roller for contacting the driving block.

Preferably, the hydraulic adjusting system further comprises a limit rod for limiting a maximum range of movement of the two collimator blades.

Preferably, the two first hydraulic cylinders are operated in a controlled way simultaneously through a first directional valve disposed in the fluid lines.

Preferably, the hydraulic adjusting system further comprises a first hydro-control check valve and a second hydro-control check valve disposed in the fluid lines for keeping the first piston rods of the two first hydraulic cylinders stopped and locked in place.

Preferably, the hydraulic adjusting system further comprises a control unit for controlling the first directional valve.

Preferably, the collimator cradle is supported movably by the base via two guide rods, the hydraulic adjusting system further comprises:

a second hydraulic cylinder disposed at the base; and

a second piston rod extending out of the second hydraulic cylinder and fixed to the collimator cradle. Preferably, the second hydraulic cylinder is operated in a controlled way through a second directional valve disposed in the fluid lines.

Preferably, the hydraulic adjusting system further comprises a third hydro-control check valve and a fourth hydro-control check valve disposed in the fluid lines for keeping the second piston rod of the second hydraulic cylinder stopped and locked in place.

Preferably, the hydraulic adjusting system further comprises a control unit for controlling the first directional valve and/or the second directional valve.

Preferably, a pump is provided to pump the hydraulic fluid to the two first hydraulic cylinders and the second hydraulic cylinder. Instead of a respective pump for each of hydraulic cylinder, it is possible to further simplify the hydraulic adjusting system and thus reduce the costs by using a single pump.

Preferably, the pushing means comprises one or more springs, blocks formed from elastomeric material or hydraulic cylinders.

According to other aspect of the present invention, it is to provide a collimator used in a CT apparatus comprising a hydraulic adjusting system as above-mentioned.

These and other objects, features and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the

combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a collimator comprising a hydraulic adjusting system according to the present invention.

FIG. 2 is a perspective view of the collimator of FIG. 1 as viewed from an opposite side.

FIG. 3 is an exploded perspective view of the collimator of FIG. 1.

FIG. 4 is a schematic view showing a hydraulic circuit of a hydraulic adjusting system according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODFMENTS

As shown in FIGS.1-3, a collimator 1 used in a CT apparatus comprises a base 3 which is mountable onto a gantry system (not shown in the drawings) of the CT apparatus so as to support the collimator, a collimator cradle 5 supported by the base 3, and two collimator blades 7 defining a collimator slit 8 between them. The collimator cradle 5 comprises a frame 9 defining a central opening 11 and a projection 13 extending from each one of two opposite sides 12 of the frame 9. The collimator cradle 5 is attached movably by the base 3 via two guide rods 15. Each guide rod 15 passes through a through hole 17 defined in each projection 13 and is fixed to the base 3 at one end. The diameter of the guide rod 15 is slightly less than an inner diameter of the through hole 17 so that the collimator cradle 5 is slidable along the guide rod 15 if necessary. However, the free end of the guide rod 15 has a diameter-increasing portion to prevent the collimator cradle 5 from falling from the guide rod 15.

A guide rail 21 is fixed to each one of two other opposite sides 23 of the frame 9. A sliding block 25 defining a guide groove 27 is fixed respectively to a first side 29 of each one of two collimator blades 7. The guide groove together with the guide rail forms a guide mechanism. Of course, it is possible to use a guide mechanism in other form. A driven block 31 is fixed respectively to a second side 32 of each one of two collimator blades 7 through the screws 33. The second side 32 is opposite to the first side 29 of each one of two collimator blades 7. Two collimator blades 7 are placed within the central opening 11 of the frame 9 and the guide groove 27 defined in each one of the sliding blocks 25 engages with the guide rail 21. Two collimator blades 7 are hold in place through the screws 35. The screw 35 passes through the through hole 38 defined in the projection 13 of the collimator cradle 5 and is connected to the collimator blade 7. A spring 37 is disposed between the screw 35 and the collimator blade 7 and the screw 35 also passes through the spring 37. The springs 37 tend to push two collimator blades 7 toward each other to reduce the collimator slit 8 defined between two collimator blades 7. It should be appreciated that a plurality of blocks formed from elastomeric material or hydraulic cylinders, instead of the springs 37, may be used to push two collimator blades toward each other.

Alternatively, the guide rail may be formed integrally with the collimator cradle. The sliding block and/or the driven block may be formed integrally with the collimator blade. Further, the guide rail may be formed to associate with the collimator blade while the guide groove may be formed to associate with the collimator cradle. It should be appreciated that two collimator blades may be guided on the collimator cradle in any other known way without departing from the scope of the present invention.

The hydraulic adjusting system according to the present invention comprises two first hydraulic cylinders 39 disposed at the collimator cradle 5, preferably on one of the projections 13 of the collimator cradle 5. A driving block 43 is provided at a free end of a first piston rod 41 extending out of each one of two first hydraulic cylinders 39. The driving block 43 is arranged such that it generally aligns with a gap 45 formed between one driven block 31 of one of two collimator blades and one driven block 31 of the other one of two collimator blades. The driving block 43 may be in a tapered shape, preferably in a cone shape. The tip of the driving block 43 points to the gap 45 formed between two driven blocks. Preferably, the driven blocks 31 each have a slanting surface 47 at its end to match with the driving block 43 in a tapered shape. Of course, it is also feasible that the tip of the driving block 43 points to the hydraulic cylinder 39. In this case, the driven blocks 31 each have a slanting surface 49 at the outside of its end to match with the driving block 43 in a tapered shape. To form a smooth and reliable contact between the driving block 43 and each one of the driven blocks 31, a roller 50 may be disposed at each one of the driven blocks 31 so that the driving block 43 may contact the roller 50 during adjusting the collimator slit 8.

Since two first hydraulic cylinders 39 are disposed on one of the projections 13 of the collimator cradle 5, the driving blocks 43 are generally offset from the collimator slit 8 defined between two collimator blades 7. The driven blocks 31 on the collimator blade 7 being close to the two first hydraulic cylinders 39 may have a short length while the driven blocks 31 on the collimator blade 7 being away from the two first hydraulic cylinders 39 may have a long length to extend beyond the corresponding collimator blade 7. Thus, the gaps 45 formed between the driven blocks of one collimator blade and the driven blocks of the other collimator blades generally align with the driving blocks 43 respectively. It is also feasible that one of two first hydraulic cylinders 39 is disposed on one of the projections 13 of the collimator cradle 5 while the other one of two first hydraulic cylinders 39 is disposed on the other one of the projections 13 of the collimator cradle 5.

The hydraulic adjusting system according to the present invention may further comprise a second hydraulic cylinder 51 disposed at the base 3. A second piston rod 53 extending out of the second hydraulic cylinder 51 is fixed to the collimator cradle 5. When the fluid within the second hydraulic cylinder 51 drives the second piston rod 53 to move, the collimator cradle 5 may slide along the guide rods 15 relative to the base 3.

FIG. 4 is a schematic view showing a hydraulic circuit of a hydraulic adjusting system according to the present invention. In FIG. 4, a dotted line box B_L in the left side represents schematically an adjustment for the collimator slit 8 defined between two collimator blades 7 and a dotted line box B_R in the right side represents schematically an adjustment for the position of the collimator cradle 5 relative to the base 3.

The hydraulic circuit comprises a first line LI leading to a fluid source S and a pump P which is disposed in the first line LI and pumps the hydraulic fluid from the fluid source S. The first line LI braches into a second line L2 and a third line L3. The second line L2 connects to a first directional valve VI . A fourth line L4 and a fifth line L5 also connect to the first directional valve VI . The fourth line L4 further braches into a sixth line L6 and a seventh line L7. The sixth line L6 and the seventh line L7 lead to a first chamber 39a of the first hydraulic cylinders 39 respectively. The fifth line L5 further braches into a eighth line L8 and a ninth line L9. The eighth line L8 and the ninth line L9 lead to a second chamber 39b of the second hydraulic cylinders 39 respectively in which the first piston rod 41 is disposed. The first directional valve VI also connects to the fluid source S. The first line LI also connects to the fluid source S via an overflow valve V3.

The third line L3 connects to a second directional valve V2. A tenth line L10 and a eleventh line Ll l also connect to the second directional valve V2. The tenth line L10 leads to a first chamber 51a of the second hydraulic cylinder 51. The eleventh line Ll l leads to a second chamber 51b of the second hydraulic cylinder 51 in which the second piston rod 53 is disposed. The second directional valve V2 also connects to the fluid source S.

The hydraulic adjusting system according to the present invention further comprises a control unit (not shown in the drawings) which connects electrically with the pump P, the first directional valve VI and the second directional valve V2. When it is necessary to adjust the collimator slit 8 defined between two collimator blades 7, an adjustment request is sent from the gantry system of the CT apparatus to the control unit. The control unit commands the first directional valve VI to move to the left or the right so that the fourth line L4 and the fifth line L5 are respectively in fluid communication with for example the second line L2 and the fluid source S. The hydraulic fluid thus is pumped to the first chambers 39a of the first hydraulic cylinders 39. As a result, the first piston rods 41 push the driving blocks 43 to move toward the gap 45 formed between two driven blocks 31 respectively. With movement of the driving blocks 43 in a tapered shape, the driven blocks 31 on one collimator blade 7 and the driven blocks 31 on the other collimator blade 7 are pushed against the action of the springs 37 to move away from each other so that two collimator blades 7 move away from each other, thereby increasing gradually the collimator slit 8 defined between two collimator blades 7. When the collimator slit 8 defined between two collimator blades 7 increases to a desired width, the control unit commands the first directional valve VI to move to a middle position so that the first piston rods 41 stop moving. The collimator slit 8 defined between two collimator blades 7 is fixed and remains unchanged. To prevent the collimator slit 8 from becoming too wide, a limiting rod 55 passes through a through hole 57 formed in a respective end of two collimator blades 7. The limit rod 55 limits a maximum range of movement of two collimator blades 7 by a stop such as a nut on each end of the limiting rod 55.

If the fourth line L4 and the fifth line L5 are respectively in fluid communication with the fluid source S and the second line L2, the first piston rods 41 pull the driving blocks 43 to move away from the gap 45 formed between two driven blocks 31 respectively, two collimator blades 7 moves toward each other under the action of the springs 37, thereby reducing gradually the collimator slit 8 defined between two collimator blades 7. When the collimator slit 8 defined between two collimator blades 7 reduces to a desired width, the control unit commands the first directional valve VI to move to a middle position so that the first piston rods 41 stop moving. The collimator slit 8 defined between two collimator blades 7 is fixed and remains unchanged.

When it is necessary to adjust the position of the collimator cradle 5 relative to the base 3, an adjustment request is sent from the gantry system to the control unit. The control unit commands the second directional valve V2 to move to the left or the right so that the tenth line L10 and the eleventh line Ll l are respectively in fluid communication with for example the third line L3 and the fluid source S. The hydraulic fluid thus is pumped to the first chamber 51a of the second hydraulic cylinder 51. As a result, the second piston rod 53 pushes the collimator cradle 5 to move away from the base 3. When the collimator cradle 5 moves to a desired position, the control unit commands the second directional valve V2 to move to a middle position so that the second piston rod 53 stops moving. The position of the collimator cradle 5 relative to the base 3 is fixed and remains unchanged.

If the tenth line L10 and the eleventh line Ll l are respectively in fluid communication with the fluid source S and the third line L3. The second piston rod 53 pulls the collimator cradle 5 to move toward the base 3. When the collimator cradle 5 moves to a desired position, the control unit commands the second directional valve V2 to move to the middle position so that the second piston rod 53 stops moving. The position of the collimator cradle 5 relative to the base 3 is fixed and remains unchanged.

It should be appreciated that adjusting the collimator slit 8 defined between two collimator blades 7 may be performed independently from or synchronously with adjusting the position of the collimator cradle 5 relative to the base 3.

According to the present invention, the hydraulic adjusting system may further comprise a first hydro-control check valve Kl in the fourth line L4 and a second hydro-control check valve K2 in the fifth line L5 and/or a third hydro-control check valve K3 in the tenth line L10 and a fourth hydro-control check valve K4 in the eleventh line Ll l . These hydro-control check valves are used to keep the first piston rods 41 of the first hydraulic cylinders 39 and the second piston rod 53 of the second hydraulic cylinder 51 stopped and locked at any position respectively as required by the gantry system, thereby improving the adjustment precision of the collimator.

Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims.

Claims

1. A hydraulic adjusting system for adjusting a collimator (1) used in a CT apparatus, the collimator (1) comprising a base (3) mountable onto a gantry system of the CT apparatus so as to support the collimator (1), a collimator cradle (5) supported by the base (3), and two collimator blades (7) attached movably to the collimator cradle (5) via a guide mechanism and defining a collimator slit (8) between them, wherein a pushing means is disposed to push two collimator blades (7) toward each other to reduce the collimator slit (8), the hydraulic adjusting system comprising:

two first hydraulic cylinders (39) disposed at the collimator cradle (5);

a first piston rod (41) extending out of each one of two first hydraulic cylinders (39); a driving block (43) provided at a free end of the first piston rod (41); and

a driven block (31) disposed at each end of each one of two collimator blades (7), wherein the driving block (43) is arranged to align with a gap (45) formed between one driven block (31) of one of two collimator blades (7) and one driven block (31) of the other one of two collimator blades (7).

2. The hydraulic adjusting system according to claim 1, wherein the driving block (43) is of a tapered shape.

3. The hydraulic adjusting system according to claim 1, wherein the driven block (31) has a slanting surface (47, 49) and/or a roller (50) for contacting the driving block (43).

4. The hydraulic adjusting system according to claim 1, further comprising a limit rod (55) for limiting a maximum range of movement of the two collimator blades (7).

5. The hydraulic adjusting system according to claim 1, wherein the two first hydraulic cylinders (39) are operated in a controlled way simultaneously through a first directional valve (VI) disposed in the fluid lines.

6. The hydraulic adjusting system according to claim 5, further comprising a first hydro-control check valve (Kl) and a second hydro-control check valve (K2) disposed in the fluid lines for keeping the first piston rods (41) of the two first hydraulic cylinders (39) stopped and locked in place.

7. The hydraulic adjusting system according to claim 5, further comprising a control unit for controlling the first directional valve (VI).

8. The hydraulic adjusting system according to any one of claims 1-6, wherein the collimator cradle (5) is supported movably by the base (3) via two guide rods (15), the hydraulic adjusting system further comprises:

a second hydraulic cylinder (51) disposed at the base (3); and

a second piston rod (53) extending out of the second hydraulic cylinder (51) and fixed to the collimator cradle (5).

9. The hydraulic adjusting system according to claim 8, wherein the second hydraulic cylinder (51) is operated in a controlled way through a second directional valve (V2) disposed in the fluid lines.

10. The hydraulic adjusting system according to claim 9, further comprising a third hydro-control check valve (K3) and a fourth hydro-control check valve (K4) disposed in the fluid lines for keeping the second piston rod (53) of the second hydraulic cylinder (51) stopped and locked in place.

11. The hydraulic adjusting system according to claim 8, further comprising a control unit for controlling the first directional valve (VI) and/or the second directional valve (V2).

12. The hydraulic adjusting system according to claim 8, wherein a pump (S) is provided to pump the hydraulic fluid to the two first hydraulic cylinders (39) and the second hydraulic cylinder (51).

13. The hydraulic adjusting system according to claim 1, wherein the pushing means comprises one or more springs, blocks formed from elastomeric material or hydraulic cylinders.

14. A collimator (1) used in a CT apparatus comprising a hydraulic adjusting system according to any one of claims 1-13.