Pulse or digital communications – Repeaters – Testing
Reexamination Certificate
2000-06-20
2001-10-23
Church, Craig E. (Department: 2882)
Pulse or digital communications
Repeaters
Testing
Reexamination Certificate
active
06307876
ABSTRACT:
The present invention relates to a linear accelerator for therapeutic use.
The overall geometry of a linear accelerator is ideally constructed so as to enable the output beam of the radiation source to be directed at any chosen site within the patient. In order to avoid excessive doses being applied to healthy tissue, the incident direction is normally varied throughout the treatment period, the various directions each converging on a single point. This single point thereby receives a full dose whilst the surrounding areas receive only a minimal dose.
For this reason, the radiation source is normally rotatable about the longitudinal axis of the table. In our application WO 97/13552, we described a system in which the table was rotatable about its vertical axis. This provided a system in which access to a designated area within the patient could also be obtained via a plurality of directions lying along lines of longitude. This permitted a combination of rotations of the source and of the table, further reducing the dose applied to surrounding areas. However, in this arrangement, the range of directions is limited by the maximum relative rotation of the table. This rotation must be limited in order to prevent the table obstructing the rotational path of the radiation source.
Another system available from the applicant involves a plurality of small Cobalt sources arranged in the sphere and directed toward the centre of that sphere. Each source can be concealed or revealed via a suitable shutter, allowing control over dosage aspect. However, it is impractical to provide further collimation of individual beam sources due to the sheer number of individual sources present. Also, the system is in practice limited to use for treating the head as the Cobalt sources need to be near the patient in order to be effective. It is also impractical to add an imaging structure.
The present invention therefore provides an apparatus for treatment by radiotherapy, comprising:
a patient table
a directional radiation source directed generally toward the patient table,
the table and source being movable relative to each other at least axially with respect to the table and rotationally around that axis,
the source being directionally adjustable within at least a plane including the longitudinal axis of the table;
and including means to correlate axial relative motion of the table and directional adjustment of the source.
Thus, the source of such an apparatus can be rotated about the table to access the predetermined position along a series of cones centred on the predetermined position and of the variable angle. Thus, the apparatus effectively accesses the predetermined position via lines of latitude rather than longitude. This largely eliminates the inaccessible zone provided by the system of WO 97/13552, and avoids a single convergence point directly above and below the predetermined point. it also provides a single radiation source which can therefore be collimated to provide accurate beam shaping and intensity control.
Thus, whilst existing arrangements maintain an isocentre fixed relative to the source just above the patient table, the present invention does not, instead compensating by movement of the patient table.
It is preferred if the source is directionally adjustable across an included angle of at least 20°, preferably more than 30°.
The source is suitably held within a ring member centred substantially on the patient table.
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patent: 5386453 (1995-01-01), Harrawood et al.
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patent: WO 94 13205 (1994-06-01), None
patent: WO 97 13552 (1997-04-01), None
patent: WO 97 35641 (1997-10-01), None
Church Craig E.
Elekta AB
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