X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
1999-07-01
2001-08-14
Porta, David P. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Absorption
C378S065000
Reexamination Certificate
active
06275564
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to positioning systems for stereotactic radiation treatment, and particularly to a positioner for use with a radiation source housing and patient support table, the positioner ensuring that a radiation beam passes through an isocenter regardless of the relative movement or sagging of the table and the source housing.
BACKGROUND OF THE INVENTION
It is imperative in stereotactic radiation treatment to ensure that radiation beam, such as a linear accelerator (LINAC) central beam of radiation, passes as close as possible to the ideal isocenter, i.e., the theoretical intersection of a rotational axis (azimuth axis) of a table which carries the target (patient) and a rotational axis (elevation or roll axis) of the LINAC gantry. In general, the target lies in the patient's head and a stereotactic frame is provided for holding the head fixed with respect to the floor or the treatment table. The purpose of fixing the stereotactic frame is to ensure that the radiation beam always passes substantially through the isocenter during radiation treatment. One way of fixing the stereotactic frame is by mounting it on the table. Another way is to fix the stereotactic frame with respect to the floor. In each case, means are provided for attempting to position the frame such that the target is substantially in the isocenter.
In practice, however, while the heavy gantry moves to various gantry angles, the LINAC head sags. Moreover, the rotary bearing of the LINAC and/or the table are not ideal and this affects concentricity, inter alia. Consequently, the central radiation beam does not intersect the ideal isocenter. Thus, in general, unpredictable deformations of the structures supporting the radiation source or the target, as well as errors in determining the positions of the source or the target lead to inaccuracies in delivering the radiation beam to the isocenter.
SUMMARY OF THE INVENTION
The present invention seeks to provide an improved positioner for use with a radiation source housing and patient support table. The positioner is attachable to a radiation system having two axes of rotation for stereotactic treatment. The two axes may be the turning axes of the LINAC and table, for example. The positioner has its own axes of rotation independent of the rotational axes of the radiation system. When the positioner is attached to the radiation system, the rotational axes of the positioner are placed close to, but not necessarily collinear with, the rotational axes of the system. The target is rigidly referenced to the positioner. Thus, the target is irradiated with a precision determined by the positioner and not the radiation system.
The positioner comprises two rigid arms, one for attachment to the source housing and the other attachable to a stereotactic frame. The two arms pivot about a common axis and define an isocenter that always remains aligned with a radiation beam emanating from the radiation source regardless of the relative movement or sagging of the table and the radiation source housing. The two arms thus move in precise relation with the azimuthal, elevational and/or roll movements of the gantry and/or table.
There is thus provided in accordance with a preferred embodiment of the present invention a positioner useful in stereotactic radiation treatment of a patient by radiation from a radiation source from which a radiation beam is emitted along a beam axis, the positioner including a source adapter arm arranged to be attached to the radiation source such that the position of the source adapter arm is determined by the position of the radiation source, and a frame adapter arm pivotably attached to the source adapter arm about a pivot axis, the frame adapter arm defining a frame axis intersecting the pivot axis, the pivot axis and the frame axis being selected such that when the source adapter arm is attached to the radiation source, the pivot axis and the frame axis both intersect the beam axis.
In accordance with a preferred embodiment of the present invention the pivot axis and the frame axis are selected such that when the source adapter arm is attached to the radiation source, the pivot axis and the frame axis both intersect the beam axis generally at the same location, and most preferably, substantially at the same location. Preferably the pivot axis and the frame axis are generally orthogonal.
Further in accordance with a preferred embodiment of the present invention the positioner also includes a source adapter arm positioning assembly which adjusts attachment of the source adapter arm to the radiation source.
Still further in accordance with a preferred embodiment of the present invention the positioner also includes a patient support frame pivotably mounted to the frame adapter arm.
Additionally in accordance with a preferred embodiment of the present invention the positioner also includes a frame adapter arm positioning assembly which adjusts mounting of the patient support frame to the frame adapter arm.
In accordance with a preferred embodiment of the present invention the positioner also includes a beam collimator mounted onto the source adapter arm for collimating the radiation beam.
There is also provided in accordance with a preferred embodiment of the present invention a stereotactic radiation treatment system for treatment of a patient by radiation, including a radiation source from which a radiation beam is emitted along a beam axis, and a positioner including a source adapter arm arranged to be attached to the radiation source such that the position of the source adapter arm is determined by the position of the radiation source, and a frame adapter arni pivotably attached to the source adapter arm about a pivot axis, the frame adapter arm defining a frame axis intersecting the pivot axis, the pivot axis and the frame axis being selected such that when the source adapter arm is attached to the radiation source, the pivot axis and the frame axis both intersect the beam axis.
Preferably the stereotactic radiation treatment system also includes a patient support frame with respect to which a patient can be rigidly mounted such that a target area of the patient is located at an intersection of the pivot axis, the frame axis and the beam axis.
In accordance with a preferred embodiment of the present invention the source adapter arm is suspended from the radiation source. Alternatively in accordance with another preferred embodiment of the present invention the source adapter arm is at least partially suspended from the radiation source.
Further in accordance with a preferred embodiment of the present invention the stereotactic radiation treatment system includes a support element for supporting at least one of the source adapter arm and the frame adapter arm.
There is also provided in accordance with a preferred embodiment of the present invention a positioner useful in stereotactic radiation treatment of a patient by radiation from a radiation source from which a radiation beam is emitted along a beam axis, the positioner including a source adapter arm arranged to be attached to the radiation source such that the position of the source adapter arm is determined by the position of the radiation source, and the position of the source adapter arm relative to the radiation source is independent of the position of the gantry arm relative to the radiation source, and a measurement assembly mounted on the source adapter arm for making measurements with respect to a measurement axis, the measurement axis initially substantially intersecting the beam axis, the measurement assembly measuring a misalignment of the measurement axis with the beam axis.
In accordance with a preferred embodiment of the present invention the positioner also includes a patient support frame which includes a frame axis about which a patient is rotatable, wherein the patient is rigidly mountable to the support frame such that a target of the patient is located at an intersection of the beam axis, the measurement axis and the frame
Porta David P.
Townsend and Townsend / and Crew LLP
LandOfFree
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