Radiant energy – Irradiation of objects or material – Ion or electron beam irradiation
Reexamination Certificate
2003-01-08
2004-03-23
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Ion or electron beam irradiation
Reexamination Certificate
active
06710362
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an apparatus and a method for irradiating tumour tissue of a patient by means of an ion beam, in accordance with the independent claims.
The most recently developed ion beam scanning apparatuses and methods, such as those on which, for example, the European Patent Application 98 117 256.2 is based, allow increased precision in the irradiation of deep-lying tumours.
Using those apparatuses and methods, the target volume, such as a tumour of a patient, is broken down into layers of identical range, which layers are then scanned area-wise in a grid pattern using an ion beam. The ion beam is brought into a treatment space in relation to a fixed coordinate system, the spatial angle of an ion beam axis in the treatment space being fixed or emission from different spatial angles being possible by means of a gantry.
In order for the tumour of a patient to be positioned in that fixed coordinate system of the irradiation space, the patient must first be brought into the correct desired position relative to that coordinate system so that the actually irradiated or scanned volume of the ion beam conforms to the planned target volume of the tumour in the patient. It is, moreover, necessary in the case of such known systems for the patient to be maintained in the desired position during irradiation. In order to maintain the desired position, complicated devices such as individually fabricated thermoplastic mask systems are used for fixing the patient in position, in order to adjust the patient with millimetre accuracy before irradiation and to stabilise the patient by means of the mask during irradiation. Using the known apparatuses and methods, it is accordingly possible only to irradiate spatially fixed target volumes such as, for example, tumours in the head and neck region and tumours close to the spinal column, wherein either the head alone is fixed in position by means of a suitable mask or a full body mask stabilises the spinal column.
Irradiation of moving target volumes, for example in the thoracic region, has not hitherto been possible using such methods. For example, breathing movement causes the target volume to be displaced by a few centimetres in the thoracic region and, as a result, the desired millimetre precision is made impossible. It is accordingly impossible to achieve fixing in position with millimetre accuracy when, at the same time, internal movements cause displacement of the target volume in the centimetre range. In addition, movement of the target volume whilst beam scanning is being carried out causes substantial dose non-uniformities.
Whereas it would be possible, in the case where the ions in the ion beam have constant energy, for the relatively fast, area-wise, grid-patterned scanning to follow, in terms of time, the lateral movements of the target volume in the centimetre range, the accelerator is not able to vary the energy sufficiently fast to follow the organ movements in terms of depth, for example as a result of breathing or heartbeat in the thoracic region of a tumour patient.
BRIEF SUMMARY OF THE INVENTION
The problem of the invention is to provide an apparatus and a method for irradiating tumour tissue of a patient by means of an ion beam, wherein the ion beam can be adapted to spatial and temporal change, especially spatial and temporal periodic changes in the target volume, both perpendicular to the beam direction and in terms of depth.
The problem is solved by the subject-matter of the independent claims. Features of preferred embodiments are defined in the dependent claims.
In accordance with the invention, the apparatus for irradiating tumour tissue of a patient by means of an ion beam has a device for deflecting the ion beam for slice-wise and area-wise scanning of the tumour tissue and has an accelerator having an ion beam energy control device for step-wise and depth-wise scanning of the ion beam. In addition, the apparatus has an ion-braking device, which is used as a depth-wise scanning adaptation apparatus for adapting the range of the ion beam and which has faster depth-wise adaptation than the energy control device of the accelerator. Furthermore, the apparatus has a movement detection device for detecting a temporal and positional change in the location of the tumour tissue in a treatment space and has a control device which controls the deflecting device and the depth-wise scanning adaptation apparatus for adjustment of the ion beam direction and ion beam range, respectively, when scanning the tumour tissue in the event of temporal and positional change in the location of the tumour tissue in the treatment space.
The apparatus according to the invention has the advantage that moving target volumes of a patient who is moving can be irradiated with the same precision as non-moving target volumes in a patient who is fixed in position. For that purpose, the movement detection device detects the movements of the patient during irradiation, and the irradiation points are correspondingly corrected with the aid of a control device. In principle, it is no longer necessary, in the case of this apparatus, for the patient to be initially adjusted with millimetre accuracy in the fixed spatial coordinates because, with the aid of the movement detection device, the actual initial location of a patient can also be adapted to the treatment program and/or the treatment program corrected accordingly.
In a preferred embodiment of the invention, the apparatus has two electromagnets, by means of which the deflecting apparatus makes possible area-wise scanning. The electromagnets deflect the ion beam orthogonally to the ion beam axis in an X direction and a Y direction, which are, in turn, perpendicular to one another, in order to provide area-wise scanning of the tumour tissue which, relative to depth-wise scanning by means of the ion beam energy control device, is fast. For that purpose, the electromagnets are controlled by fast-reacting power units and measurement devices. Those devices can accordingly also be used to carry out correction and adaptation when scanning tumour tissue in the case of temporal and positional change in the location of the tumour tissue in the treatment space orthogonally to the ion beam axis.
In a preferred embodiment of the invention, the apparatus has at least one accelerator, by means of which the energy of the ion beam is adjustable so that the tumour tissue can be irradiated slice-wise, staggered in terms of depth. That is associated with the advantage that the entire tumour tissue can be successively scanned slice-wise, the range of the ion beam being adjustable from slice to slice by modifying the energy of the ion beam. For that purpose, the accelerator consists essentially of a synchrotron or a synchrocyclotron, in which ions of equal mass and equal energy can be accelerated step-wise to higher energies. Because of the complexity of the control functions for the accelerator, the energy of the ion beam cannot be adapted to specified ranges within the irradiation space or within the tumour volume sufficiently quickly or with the requisite precision for it to be possible to follow the movements of the tumour tissue, or patient, automatically.
In a preferred embodiment of the invention, the depth-wise scanning adaptation apparatus therefore has two ion-braking plates of wedge-shaped cross-section, which cover the entire irradiation field of the ion beam and allow fast depth-wise scanning adaptation in the case of moving tumour tissue.
For that purpose, in a preferred embodiment of the invention, the ion-braking plates are arranged on electromagnetically actuatable carriages. With the aid of those electromagnetically actuatable carriages, the position of the wedge-shaped ion-braking plates can be changed within milliseconds and, accordingly, the length of the braking path of the ions provided in an overlap region of the wedge-shaped braking plates can be varied by the ion-braking plates. For that purpose, the ion-braking plates overlap in the entire irradiation field of the
Kraft Gerhard
Weber Ulrich
Frommer & Lawrence & Haug LLP
Gesellschaft fuer Schwerionenforschung mbH
Kalivoda Christopher M.
Lee John R.
Santucci Ronald R.
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