ACCESSORY CLAMPING SYSTEM FOR COUCH TOP

Abstract: An accessory has a fixed member and a rotatably supported and eccentrically mounted disk which are each inserted into a corresponding one of a pair of crescent-shaped indentations formed on a panel. As the disk is rotated, its center moves towards the fixed member, causing the disk to press against the inner wall of the indentation and locking the accessory to the panel securely.

Description: ACCESSORY CLAMPING SYSTEM FOR COUCH TOP BACKGROUND OF THE INVENTION This invention relates to a system for clamping to a couch top an accessory such as a patient immobilization device for head and neck treatments or stereotactic radiotherapy. Current trends in general purpose radiotherapy are directed towards more clinically efficient setups and treatments. As a result, devices for locating patients require precise and repeatable repositioning of six (three translational and three rotational) degrees of freedom with quick and easy attachment. In addition, there exists a need for flexibility within the locating system to accommodate a broad range of body shapes and treatment sites. A precise and repeatable indexing system that is quick and easy to attach is currently not available. Attachment schemes tend to be incorporated either with minor modifications or non-repeatable clamping arrangements, and not directly integrated into the couch top design. Some more advanced prior art systems clamp to accessory rails which are found on most radiotherapy couches. Accessory rails are generally fixed lengthwise along the side of the couch top. The rail attachment itself will generally secure all six degrees of freedom, but not repeatably. Manual adjustment is required to re-establish at least one translational and one rotational degrees of freedom once the device is removed. Some devices possess an additional interface between such an accessory rail clamping system and the actual accessory. Pins protruding from either the rail clamping system or the accessory mate with clearance holes. This provides for one translational and two rotational degrees of freedom precisely secured and two translational and one rotational degrees of freedom loosely secured. Although quick and easy to attach, this is not a precise and repeatable locating system as a whole or even at the subsystem level. Locating systems that actually attach to the treatment surface are essentially custom jobs developed by individual hospital personnel. Pins protruding from either the couch top surface or the accessory mate with clearance holes. This also provides for one translational and two rotational degrees of freedom precisely secured and two translational and one rotational degrees of freedom loosely secured. Neither is this a precise and repeatable locating system since, by necessity, clearance exists between the hole and the pin. Capturing two treatment surface edges is another means of locating. Flanges attached to the accessory protrude below the surface of the couch securing one translational and two rotational degrees of freedom precisely and one translational and one rotational degrees of freedom loosely. This leaves one last degree of freedom left unsecured. Stereotactic head frames, although not considered for general purpose radiotherapy, do lock down six degrees of freedom, but they are not quick and easy to attach, being bolted in most cases. They do not secure to the treatment surface because a higher precision is required than in general purpose radiotherapy. Attachment is generally to the frame. These devices typically require a separate manual adjustment for precision fine tuning of position by using an external reference such as a laser. SUMMARY OF THE INVENTION It is therefore an object of this invention to provide an improved clamping system capable of quickly and easily clamping an accessory such as a patient immobilization device to a couch top for the patient with precision and repeatability. A clamping system embodying this invention, with which the above and other objects can be accomplished, may be characterized as comprising a panel having at least one pair of indentations and a target accessory to be clamped to it having a fixed disk-shaped member and an eccentrically mounted rotatable disk attached to it such that they each can be inserted into a corresponding one of the indentations. With the eccentricity of the mounting of the rotatable disk properly selected, the target accessory can be securely affixed to the panel by rotating the eccentrically mounted disk around its shaft, say, by means of a lever attached to it, such that these two disks move towards each other, each inside the corresponding indentation, so as to lock the accessory securely and repeatably to the panel. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and form a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the principles of the invention. In the drawings: Fig. 1 is an diagonal view of an accessory clamping system embodying this invention when a bar, which may be a part of an accessory to be clamped, is clamped to a couch top; Fig. 2 is an diagonal view of a portion of the accessory clamping system of Fig. 1 when the bar is about to be clamped to the couch top; and Fig. 3 is an enlarged plan view of the eccentrically mounted disk and the lever of the clamping system of Figs. 1 and 2. DETAILED DESCRIPTION OF THE INVENTION In Figs. 1 and 2, numeral 10 indicates a generally rectangular panel on a couch top, to which an accessory such as a patient immobilization device is adapted to be secured. The panel 10 is provided with pairs of indexing indentations 15 on mutually opposite side edges, each pair having one of the indentations on one of the side edges and the other on the other of the side edges such that each pair of the indexing indentations 15 is transversely across the panel surface opposite to each other. According to a preferred embodiment of the invention, these indentations 15 are crescent-shaped and convex towards the other of the pair. Numeral 20 indicates a bar which is to be secured onto the panel 10 by making use of these indexing indentations 15. It is approximately of the same length as the width of the rectangular panel 10, that is, its length is about the same as the separation between each pair of the indexing indentations 15 and may be regarded as a part of an accessory such as a patient immobilization device or a frame to which such an accessory is adapted to be securely attached. Attached to the lower surface of the bar 20 at one of its ends is a circular disk-shaped member 25, herein referred to as the fixed disk, adapted to fit inside any of these indexing indentations 15. A lever 30 is provided at the other end of the bar 20, attached to a vertical shaft 35 which is rotatably supported by the bar 20 and to which a circular disk 40 is eccentri¬ cally mounted, as shown in Fig. 3. Thus, this eccentrically mounted disk 40 is adapted to rotate with and around the shaft 35 such that, when the lever 30 extends perpendicularly to the direction of extension of the bar 20 as shown by solid line in Fig. 3, the center of the circular disk 40 is on the side of the shaft 35 towards the other end of the bar 20. Quick and easy attachment of the bar 20 to the panel 10 is accomplished by first rotating the lever 30 by 90 degrees to the direction away from the other end of the bar 20, as shown by dotted lines in Fig. 3, thereby also moving the eccentrically mounted disk 40 away from the other end of the bar 20, that is, increasing the distance between the two disks 25 and 40 on the bar 20 by a small distance determined by the eccentricity of the mounting of the rotatable disk 40. With the lever 30 thus oriented, the bar 20 is positioned as shown in Fig. 2 such that the fixed disk 25 and the eccentrically mounted disk 40 are each fit inside a corresponding one of a selected pair of the indexing indentations 15. Thereafter, the lever 30 is rotated such that the eccentrically mounted disk 40 will move towards the other end of the bar 12, thereby reducing the distance of separation between the fixed disk 25 and the eccentrically mounted rotatable disk 40. The separation between the pairs of indentations 15, the distance between the fixed disk 25 and the dimensions of the rotatable disk 40 including the eccentricity of its mounting to the shaft 35 are so determined that this rotation of the lever 30 causes the bar 20 to be clamped securely onto the panel 10 between the selected pair of indentations 15. In other words, the attachment is effected by a simple rotation by 90 degrees of the lever 30 from an unlocked position to a locked position. When locked, a clamp force is generated which effectively secures all three translational and three rotational degrees of freedom. Since the crescent-shaped indentations 15 are fixed, positioning is definitively precise and repeatable. The invention has been described above with reference to only one example but the illustrated example is not intended to limit the scope of this invention. Many modifications and variations are possible within the scope of the invention. For example, the fixed disk 35 may be replaced by a member having a different shape, and the indentations 15 need not necessarily be crescent-shaped. Indentations of any shape capable of properly accepting and engaging such a fixed member to lock the bar can serve the purpose of this invention. The lever 30 may be replaced by any means for causing the eccentrically mounted disk 40 to be rotated around the shaft 35, including a cap adapted to start slipping after a certain maximum torque has been reached. As shown in Fig. 3, an O-ring 50 may be used around the eccentrically mounted disk 40, as well as around the fixed disk 25 at the interface with the inner walls of the indentations 15 so as to distribute clamp force, to reduce wear, to accommodate variations in spacing with the arcuate inner walls of the indentations 15 and to keep the eccentrically mounted disk 40 from loosening by increasing sliding friction. The language in the specification, as well as in the claims, is intended to be interpreted broadly. The expression "indentations", for example, is intended to include configurations which may look more like a hole or a groove, as long as they have inner walls facing away from each other such that the fixed disk 25, or a member of any other shape which can reasonably substitute for it, and the eccentrically mounted disk 40 at opposite ends of the bar 20, as described above, can be received therein and cause the bar 20 to be locked to the panel 10. It is also to be reminded that the bar 20, as used above in the description, may be only a portion of the accessory to be clamped to the panel 10 or a mere representation of any target device which is intended to be clamped to the panel 10 and hence need not have all regular attributes of what one generally calls "a bar" such as being elongated or defining a direction of extension.

Claims: WHAT IS CLAIMED IS; 1. An accessory clamping system comprising: a panel having at least one pair of indentations; a target member to be clamped to said panel; a fixed member which is insertable into said indentations and affixed to said target member; a disk which is eccentrically mounted to a shaft and insertable into said indentations, said shaft being rotatably supported by said target member, said fixed member and said eccentrically mounted disk being separated by a distance which is approximately the same as the separation between said pair of indentations; rotating means for rotating said disk around said shaft, eccentricity of said shaft with respect to said disk being such that rotation of said disk around said shaft, while said disk and said fixed member are respectively in a corresponding one of said pair of indentations, can cause said target member to be clamped to said panel. 2. The accessory clamping system of claim 1 wherein said panel has a plurality of pairs of indentations on side edges thereof. » 3. The accessory clamping system of claim 1 wherein said rotating means comprises a lever which extends perpendicularly from said shaft. 4. The accessory clamping system of claim 1 wherein said target member is an elongated bar, said fixed member is attached to one end of said bar and said shaft is mounted to said bar at the other end thereof. 5. The accessory clamping system of claim 1 wherein said indentations are each crescent- shaped, said pair of indentations being convex towards each other.

Inventors: HAUGER TODD M, OLIVER EDWARD A, HAUGER, TODD, M., OLIVER, EDWARD, A.
Applicants: VARIAN ASSOCIATES, VARIAN ASSOCIATES, INC.
Application year: 1997
Main classification: A61B6
IPC codes: A61B6, A61N5