Patient Positioning Device for Radiation Therapy

Patient positioning systems are used for accurate and reproducible positioning of a patient for radiation therapy, diagnostic imaging, surgery, and other medical procedures. During these procedures, it is important to immobilize a part or parts of the patient's body. Accurate positioning of the body part is also important in repeat treatments so that the precise same location of the bodies are exposed to the radiation each time. Therefore, different types of devices have been made to immobilize body parts and to index the body to the treatment table to assure proper and repeatable alignment for radiation therapy.

One example of such a patient positioning system is the Exact Indexed Immobilization system sold by applicant, and described in U.S. Pat. No. 5,806,116. The Exact system utilizes a tabletop with indentations along opposite sides, and a lock bar extending across the tabletop with a disk at each end adapted to be received in opposing indentations. The Exact lock bar is secured to the tabletop with an eccentric cam which tightens the ends of the bar into engagement with the indentations of the tabletop.

While the Exact system is generally an acceptable product, there are features causing potential concern. For example, the rotation of the cam lever causes the bar to move slightly relative to the tabletop, such that the patient positioning is not precise and consistent. Also, the Exact lock bar utilizes an O-ring on each end of the bar, which is not resistant to radiation. Therefore, over time, the O-ring may degrade to a degree wherein the bar does not mount as securely to the tabletop. The O-ring may also ultimately fail due to repeated and extensive exposure to the radiation. Furthermore, the thermoplastic patient fixation or restraint devices normally used in patient positioning systems tend to shrink over time, as a result of the initial heating and molding of the thermoplastic. Such shrinkage ultimately may lead to bending of the Exact bar when the restraint is forced downwardly over the patient. Such bending of the bar may lead to migration of the bar out of the tabletop notches. Also, patient swelling may impart stresses on the Exact bar which may preclude secure attachment of the bar to the tabletop or Exact repeatable positioning of the bar.

Therefore, a primary objective of the present invention is the provision of an improved patient positioning system for radiation therapy treatment.

Another objective of the present invention is the provision of a patient positioning system which is repeatably precise and accurate.

Another objective of the present invention is the provision of a patient positioning system which provides secure interlocking connection between the lock bar and the tabletop.

A further objective of the present invention is the provision of a patient positioning system which is easy and simple to use.

Another objective of the present invention is the provision of a patient positioning system which is durable in use and economical to manufacture.

These and other objectives have become apparent from the following description of the invention.

The patient-positioning device of the present invention includes a table having opposite sides with indexing notches along each side. A patient restraint member is registered on an elongated lock bar and is adapted to extend over a portion of the patient's body to position the patient on the table. The lock bar has a downwardly extending ball on each end is adapted to snap-fit into opposing pairs of the notches on each side of the table. The notches each have a radius to matingly engage the ball, which is self centering in the notch. A shoulder in each notch retentively engages the ball to prevent relative movement between the lock bar and the table.

FIG. 1 is an exploded perspective view of the radiation therapy interlock system of the present invention, with a lock bar positioned above the tabletop and a patient fixation device before molding.

FIG. 2 is a view similar to FIG. 1 showing the lock bar snap-fit into position on the tabletop, with the patient restraint device removed for clarity.

FIG. 3 is a sectional view of the lock bar taken along lines 3--3 of FIG. 2.

FIG. 4 is an enlarged side elevation view showing the lock bar snap-fit into position on the tabletop.

FIG. 5 is a side elevation view showing the lock bar with a molded patient fixation device.

The interlock system of the present invention is particularly useful for accurate and repeatable patient positioning for radiation therapy treatment, as well as for other diagnostic and treatment procedures. As seen in FIG. 1, a table base or carriage 10 is provided with a tabletop 12. The tabletop 12 is mounted for longitudinal movement upon side rails 14 attached to the opposite sides of carriage 10.

The tabletop 12 has a plurality of notches 16 along the opposite sides. The notches 16 are adapted to receive the opposite ends of a lock bar 18 to which a patient restraint member 20 is secured. The notches 16 serve as indexes for repeated treatments of individual patients.

More particularly, as best seen in FIG. 4, each notch 22 extends through the tabletop 12, with an upper reduced diameter portion 22 and an enlarged diameter portion 24. The portions 22, 24 define a shoulder 26 in the notch 16.

The lock bar 18 includes a male extension 28, preferably in the shape of a ball, a seen in FIG. 3. The ball 28 is connected to the lock bar 18 with a threaded bolt 30. It is understood that the male extension 28 of the lock bar 18 may take shapes other than spherical, as shown in the drawings, with the alternative shapes providing a snap-fit connection between the lock bar 18 and the notches 16 of the tabletop 12. The lock bar 18 also includes a pair of upwardly extending studs 32 which are secured to the bar 18 by bolts 34. The studs 32 are adapted to matingly register with holes 20B of the patient restraint device 20 so that the device 20 is positioned on the lock bar 18. The device 20 also has a bottom groove 20A sized to receive the bar 18.

In use, the lock bar 18 with the mounted patient restraint 20 is positioned over the patient. The balls 28 of the lock bar 18 are snap-fit into the desired opposing pairs of notches 16 in the tabletop 12 so as to secure the lock bar 18 to the table top 12. As seen in FIG. 4, the ball 28 is retentively engaged by the shoulder 26 of the notch 16, which is positioned above the mid point or equator of the ball 28. The ball 28 is also self-centering within the notch 16.

As seen in FIG. 4, the tabletop 12 also includes a pair of slots 36 on each side of each notch 16. If the eccentric cam action lock bar of U.S. Pat. No. 5,806,116 is used, the slots 36 accommodate the tab on the end of the lever arm thereof.

The preferred embodiment of the present invention has been set forth in the drawings, specification, and although specific terms are employed, these are used in a generic or descriptive sense only and are not used for purposes of limitation. Changes in the form and proportion of parts as well as in the substitution of equivalents are contemplated as circumstances may suggest or render expedient without departing from the spirit and scope of the invention as further defined in the following claims.