WO2007060242A1

WO2007060242A1 - Medical radiation therapy device

Info

Publication number: WO2007060242A1
Application number: PCT/EP2006/068956
Authority: WO
Inventors: Tim Use; Sven Oliver GRÖZINGER; Klaus Herrmann
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG; Siemens Corp
Priority date: 2005-11-28
Filing date: 2006-11-27
Publication date: 2007-05-31
Anticipated expiration: 2008-05-28
Also published as: DE102005056698B4; DE102005056698A1

Abstract

In the radiation therapy device, in particular for particle beam therapy, an exit window (8) of a radiation channel (2) is displaceable in a longitudinal direction (12) . As a result, the exit window (8) can be moved during the irradiation as close as possible to the target volume (30) to be irradiated so as to achieve the most optimum irradiation. At the same time, an imaging system can be set optimally with the exit window (8) retracted for the purpose of a preceding positional verification.

Description

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Description

Medical radiation therapy device

The invention relates to a medical radiation therapy device, in particular for particle beam therapy.

In radiation therapy with the aid of particles such as, for example heavy ions or protons, a particle beam that is guided in a radiation channel and enters the radiation therapy room via an exit window of the radiation channel is produced in a suitable accelerator. The target volume to be irradiated in the patient to be treated (for example a tumor) must in this case be aligned as accurately as possible to the isocenter of the irradiation device. The patient is usually immobilized on a patient couch while the radiation therapy is being carried out, and so a movement of the patient is excluded as far as possible and the target volume is stationary with reference to the particle beam.

Radiation therapy units are, for example, disclosed in US 4,726,046 and in DE 100 10 523 Al.

Before beginning the radiation therapy, it is customary to use an imaging system to undertake a positional verification in order to balance the current actual position of the target volume with a position of the target volume forming the basis of the therapy planning. That is to say, the imaging diagno^¬ sis is used to check whether the target volume is actually located at the supposed location. The imaging system in this case typically comprises a radiation source, in particular a X-ray radiation source, and a suitable detector. The posi^¬ tional verification is undertaken directly before carrying out the radiation therapy, while the patient is already lo- cated in the immobilized position for the radiation therapy. In this case, the imaging system requires a certain free space about the target volume. The X-ray radiation source is here arranged, for example, in front of the end of the radia- tion channel or in the immediate vicinity or around the end of the radiation channel. Consequently this requisite free space necessitates that the end of the radiation channel be spaced from the target volume by a certain air gap that is of the order of magnitude of approximately 1.0 m.

When the irradiation with the particle beam is being carried out, it is customary to arrange at least one beam detector and passive radiation elements in the beam path at the end of the radiation channel directly in front of the exit window. Their total length in the direction of radiation is approximately 0.5 m. The exit window therefore is at a not inconsid^¬ erable distance from the target volume to be irradiated. How^¬ ever, treating the target volume as precisely as possible re- quires aiming at positioning the exit window as close as pos^¬ sible to the target volume, since the particle beam that is guided inside the radiation channel in a vacuum loses focus appreciably at the air. The accuracy of the irradiation is consequently reduced, and so there is a risk of irradiating healthy tissue as well. In order to keep this expansion of the focus as slight as possible, the radiation exit window is brought up as close as possible to the target volume. Because of the cramped space, the imaging can in this case be carried out only from certain directions.

It is the object of the invention to enable the exit window to be positioned close to the target volume during radiation therapy without impairing the positional verification by means of the imaging system.

The object is achieved according to the invention by means of a medical radiation therapy device having a radiation channel, also denoted as radiation tube, that extends in the di^¬ rection of radiation and has at the end an exit window for a particle beam. The position of the exit window is displace- able in this case in the direction of radiation. Owing to the displaceability of the exit window, the latter can be displaced in a direction of radiation relative to the target volume of the patient which is stationary during the positional verification and the irradiation, and the spacing between the target volume and the exit window can thereby be varied. When carrying out the radiation therapy, the exit window is firstly moved into a retracted position such that as large a free space as possible is achieved between the exit window and the target volume to be irradiated. Subse- quently, the imaging system is used to undertake a positional verification. Since the exit window is in the retracted posi^¬ tion, adequate free space is made available for the imaging system, and so a positional verification can be carried out from any position. Subsequent to the positional verification, the exit window is moved into a front position as close as possible to the target volume, and so the air space between the exit window and target volume is as slight as possible. Consequently, owing to the displaceability of the exit window a very good variability in the direction of orientation of the imaging is attained for the positional verification on the one hand. On the other hand, the lengthening of the ra^¬ diation channel means that the particle beam in the vacuum is up very close to the target volume to be irradiated, and so the particle beam outside the radiation channel loses focus as little as possible owing to the reaction with the air.

It is preferred in this case that the exit window can be moved in the direction of radiation approximately up to the length of the requisite free space for the imaging system. This longitudinal mobility is therefore, in particular, ap^¬ proximately 0.5 - 1 m.

In accordance with a preferred embodiment, a detector block is fastened in front of the exit window, that is to say ar- ranged in a stationary fashion with reference to the exit window, particularly directly at the radiation channel or radiation tube. This detector block in this case comprises, in particular, at least one detector for the particle beam, and passive radiation elements. Owing to the stationary positioning, the detector block is therefore displaced in a longitu^¬ dinal direction together with the exit window. Owing to the direct arrangement at the exit window, the detector and the passive radiation elements can be adjusted optimally with reference to the particle beam.

In order to enable the adjustability of the exit window with the aid of the simplest possible structural means, the radia- tion channel has at least one longitudinally variable seg^¬ ment. This section is expediently designed here telescopi- cally. As an alternative to this, in a preferred embodiment it is of elastic design such that its length is variable ow^¬ ing to the elasticity. In particular, the elastic segment is here designed in the manner of a corrugated hose or corru^¬ gated tube. A high degree of longitudinal variability of the radiation channel is attained with comparatively simple structural means owing to these measures.

In accordance with an expedient development, it is provided, furthermore, that the segment whose length can be varied has a reduced diameter by comparison with a front region of the radiation channel. The front region of the radiation channel is orientated towards the exit window in this case. The req- uisite energy for the longitudinal adjustment is kept as slight as possible owing to this measure, since, specifi^¬ cally, an ultra high vacuum of approximately 10^~8 mbar pre^¬ vails in the interior of the radiation channel. In the event of a lengthening of the radiation channel, the inner volume of the radiation channel is increased, and this leads to an additional pressure reduction. Since work is done against at^¬ mospheric pressure in the event of lengthening, the use of a segment of lesser diameter keeps the further pressure drop, and thus the requisite energy for the longitudinal adjust- ment, slight.

The diameter of the segment is here expediently only 0.2 to 0.7 times the diameter of the radiation channel in the front region. In particular, the diameter of the segment is less than half as large as that of the front region.

In order to ensure as stable as possible an arrangement of the segment, the latter is fastened between two sections of the radiation channel via flanges.

Furthermore, it is provided for as stable as possible a de^¬ sign that the front region is movably mounted on a support frame. In this case, the bearing is preferably such that the respective longitudinal position of the exit window can be fixed. This ensues, for example, via mechanical locking or blocking elements or else by the blocking of a drive unit, which are provided for the mobility.

It is expedient here for the front region to be movable by motor, pneumatically or hydraulically . For example, a motor is provided here that has a transmission, a linear motor, a pneumatically or hydraulically extendable cylinder, etc. This drive is expediently designed here in such a way that it can lock or hold the front region in the respective longitudinal position with the aid of a sufficiently high level of retain^¬ ing force .

Exemplary embodiments of the invention are explained in more detail below with the aid of the drawings in which, in re^¬ spect of schematically and greatly simplified illustrations:

figure 1 shows a partially illustrated radiation therapy de- vice in accordance with a first alternative, and figure 2 shows a partially illustrated radiation therapy de^¬ vice in accordance with a second alternative.

Identically acting parts are provided with the same reference numerals in the figures .

The radiation therapy device in accordance with figures 1 and 2 comprises a radiation channel 2 that is designed as a tube and has a segment 4A, 4B of variable length. The segment 4A, 4B is fastened in each case between two sections of the ra^¬ diation channel 2 via flanges 6. The front end of the radia^¬ tion channel 2 is sealed with an exit window 8. The subregion orientated toward the exit window 8 forms a front region 10 of the radiation channel 2. This front region 10 is movably arranged in the longitudinal direction or direction of radia^¬ tion 12 and supported on a support frame 16. A drive is pro^¬ vided for the mobility of the front region 10 in the longitu- dinal direction 12. In the exemplary embodiment in accordance with figure 1, a drive motor 18 is provided here that acts on the geared rack 20 that is permanently connected to a support ring 21 of the front region 10. Consequently, the geared rack 20, and thus the front region 10 can be displaced to and fro via the drive motor 18 in the longitudinal direction 12. Con^¬ sequently, the geared rack 20, and thus the front region 10, can be displaced to and fro in the longitudinal direction 12 via the drive motor 18. In the exemplary embodiment, the di^¬ rection of radiation, and thus the longitudinal direction 12, runs in a horizontal direction. In a departure therefrom, it is also possible to provide directions of radiation deviating from the horizontal.

A detector block 22 is fastened in a stationary fashion at the exit window 8 in front of the exit window 8. A particle detector and passive radiation elements are arranged, in a way not illustrated in more detail here, in the detector block 22.

The radiation therapy device further comprises an imaging system that has a radiation source, in particular an X-ray radiation source 24, and an X-ray detector (not illustrated in more detail here) arranged opposite said X-ray radiation source. While the therapy is being carried out, a patient 26 is arranged on a patient couch 28 in an immobilized fashion in the longitudinal direction 12 in front of the exit window 8. A target volume 30 to be irradiated is thereby aligned ex^¬ actly in relation to a particle beam direction 12. This tar- get volume 30 is spaced from the exit window 8 in the direc^¬ tion of radiation 14 by the spacing A.

In the radiation therapy, the patient 26 is firstly brought into the envisaged immobilized position such that the target volume 30 is fixed in a stationary fashion in the therapy space. The next step is to use the imaging system to carry out a positional verification. In this case, the exit window 8 is held in a retracted position such that the spacing A is as large as possible and, together with the detector block 22 arranged in front of the exit window 8 is of the order of magnitude of approximately 1 m or more in the exemplary em^¬ bodiment. The spacing A is selected in this case in such a way as to enable the most optimum imaging possible, in order to attain high quality images. After positional verification has been performed, the exit window 8 is moved forward in the direction of the target volume 30 by an adjustment path S such that the exit window 8 is oriented as close as possible with the target volume 30. In the exemplary embodiment with the upstream detector block 22, the front end of the detector block 22 is positioned virtually directly at the patient 26. The free path length between the exit window 8 and the target volume 30 is therefore minimized.

For the purpose of the actual irradiation, the target volume 30 is then treated with a particle beam, for example a heavy ion beam. The particle beam is produced in this case in an accelerator (not illustrated in more detail here) and led through the radiation channel 2. An ultra high vacuum of typically approximately 10^~8 mbar is set in the radiation channel 2 in order to prevent a beam expansion.

In the exemplary embodiment according to figure 1, the seg^¬ ment 4A of variable length is designed as a corrugated hose or corrugated tube made from a sufficiently elastic material. The segment 4A is bounded at the ends by the flanges 6 with which it is sealed in a vacuum tight fashion at corresponding flanges of the radiation channel 2. The material of the seg- ment 4A in this way is of sufficient elasticity to enable the desired longitudinal displaceability and, simultaneously, to ensure the required sealing from the external surroundings.

In the exemplary embodiment of figure 1, the radiation chan^¬ nel 2 is firstly connected to the geared rack 20 via a front support ring 21 designed as a flange, and is also connected permanently to the support frame 16 via a rear support ring 21, likewise designed as a flange, so as to ensure a good me- chanical support for the entire radiation channel 2 in con^¬ junction with mobility of the front region 10.

The exemplary embodiment according to figure 2 differs from the exemplary embodiment according to figure 1 essentially by the fact that instead of the segment 4A designed in the man^¬ ner of a corrugated tube, a section 4B of telescopic design is provided to the effect that the segment 4B has a reduced diameter, and that the segment 4B is arranged behind the rear support ring 21. Consequently, in this exemplary embodiment the front region is supported on the support frame 16 at two points via the support rings 21.

In the telescopic design of the segment 4B, two sufficiently stiff tubes are displaced into one another telescopically, the latter likewise being sealed here from the surroundings in a way not shown in more detail here, in order to maintain the ultra high vacuum in the radiation channel 2.

The diameter Dl of the segment 4B in the region of the tele- scopic tube is approximately only 1/3 of the diameter D2 of the radiation channel 2 in the front region 10 near the exit window 8. The diameter D2 of the front region 10 is typically approximately 350 mm, the radiation channel 2 typically hav^¬ ing in the region remote from the exit window 8 a diameter D2 in the range of approximately only 100 mm. The section 4B is arranged in this region of the radiation channel 2 remote from the exit window 8. Because of the reduced diameter, the increase in volume in the interior of the radiation channel 2 is kept slight in the event of a lengthening of the radiation channel 2. On the basis of the only slight increase in vol^¬ ume, the pressure reduction, and thus also the force to be applied for the displacement of the target volume 30, is also kept slight.

The variability in length described here for the radiation channel 2 enables all the components participating in the ra^¬ diation to be used optimally such that, firstly, it is possi- ble to conduct imaging for localizing the target volume 30 as effectively and accurately as possible, and that, at the same time, it is ensured that the particle beam treats the target volume 30 in as precise and focused a manner as possible dur^¬ ing the irradiation. The latter point is ensured by the re- duction in the spacing between the radiation channel 20 designed as a vacuum tube, and the target volume 30, that is to say the isocenter.

Claims

Patent claims

1. A medical radiation therapy device having a radiation channel (2) that extends in a longitudinal direction

(12) and has at the end an exit window (8) for a parti^¬ cle beam, the position of the exit window (8) being dis- placeable in the longitudinal direction (12) .

2. The radiation therapy device as claimed in claim 1, in which the exit window (8) can be moved in the longitudi^¬ nal direction (12) up to approximately the length of a free space that is required for an imaging system for positional verification before carrying out the radia- tion therapy.

3. The radiation therapy device as claimed in claim 1 or 2, in which a detector block (22) is fastened in the longitudinal direction (12) subsequent to the exit window (8) .

4. The radiation therapy device as claimed in one of the preceding claims, in which the radiation channel (2) has at least one length-variable segment (4A, 4B) .

5. The radiation therapy device as claimed in claim 4, in which the segment (4B) is of telescopic design.

6. The radiation therapy device as claimed in claim 4, in which the segment (4A) is of elastic design so that its length is variable owing to the elasticity.

7. The radiation therapy device as claimed in claim 6, in which the elastic segment (4A) is designed in the manner of a corrugated hose.

8. The radiation therapy device as claimed in one of claims 4 to 7, in which the segment (4B) has a reduced diameter (Dl) .

9. The radiation therapy device as claimed in claim 8, in which the diameter (Dl) of the segment (4B) corresponds approximately to only 0.2 to 0.7 times the diameter (D2) of the radiation channel in a front region (10) facing the exit window (8) .

10. The radiation therapy device as claimed in one of claims 4 to 9, in which the segment (4A, 4B) is fastened be^¬ tween two sections of the radiation channel (2) via flanges (6) .

11. The radiation therapy device as claimed in one of the preceding claims, in which a front region (10) of the radiation channel (2) is mounted movably on a support frame (16) in such a way that the respective longitudi- nal position of the exit window (8) can be fixed.

12. The radiation therapy device as claimed in claim 11, in which the front region (10) can be moved by motor, pneu^¬ matically or hydraulically .