WO2008031853A1

WO2008031853A1 - Diffusor tip for the homogenous light distribution of low energy x-rays in a medium

Info

Publication number: WO2008031853A1
Application number: PCT/EP2007/059595
Authority: WO
Inventors: Hansjörg ALBRECHT; Hans-Joachim Cappius; Tilmann HÄUPL; Michael Haschke; Frank Wacker; Jürgen BEUTHAN
Original assignee: Laser- Und Medizintechnologie Gmbh Berlin
Priority date: 2006-09-12
Filing date: 2007-09-12
Publication date: 2008-03-20
Also published as: DE102006043551A1; DE112007002080A5

Abstract

The invention relates to a device for irradiating a target volume in the inside of a body, wherein the device is designed such that the radiation conducted to the device is spread evenly around a longitudinal radiation direction in a rotationally symmetrical manner from the x-ray to the device or is emitted by X-ray fluorescence.

Description

Diffuser tip for homogeneous radiation distribution of low-energy X-radiation in a medium

The invention relates to a device for the most uniform possible irradiation of the environment of an applicator introduced into a body with X-radiation. In addition, the invention relates to a method for the most uniform possible irradiation of the environment of an applicator introduced into a body with X-radiation.

State of the art

In medicine, the irradiation of malignant changes in the body is an established method for the treatment of space-occupying processes. The radiation beyond the biocompatibility of the target volume is carried out by introducing encapsulated radionuclides into the target volume or by means of radiation sources from outside the body. An advantage of introducing encapsulated radionuclides is the homogenous radiation delivery around the capsule, whereby the healthy tissue lying outside the target volume can be spared with appropriate arrangement. Disadvantageous in the introduction of radionuclides is the required shielding of the radiation in advance of the introduction and during transport, since the radionuclides are continuously active in radiation. Also, depending on local legislation, special permits are required to take precautionary measures and to ensure special waste disposal. In addition, the decay of the radionuclide, which indeed generates the effective radiation, is time-dependent and thus makes the dosimetry of the applied radiation quantity in the volume more difficult. Dosimetry ensures that radiation is above the biologically tolerated level only within the predefined target volume and that the surrounding healthy tissue is not irreparably damaged.

Radiation sources outside the body, such as linear accelerators or X-ray sources have the advantage that radiation is emitted only when it is switched on, but the great disadvantage of damaging healthy tissue lying between the radiation source and target volume until the radiation reaches the target volume and damages it as intended. This limits the number of irradiations due to the tolerance of the irradiated, healthy tissue.

Approaches for directing the radiation via tubular devices, or for generating Bremsstrahlung with introduced within the body devices are described in US 5,153,900 and WO 2003/024527.

A procedure for the irradiation of target volume by means of partially introduced into the body devices is described in WO 2004/1 12890.

The generation of Bremsstrahlung ("X-radiation") is associated with heat generation, wherein the heat dissipation from the impact zone of the electron beam a major problem for the durability of the device and the stability of the radiation with respect to wavelength distribution, beam geometry and intensity represents. In this respect, the approaches from US Pat. No. 5,153,900 and protective rights applications derived therefrom are disadvantageous since the heat dissipation is not ensured in any embodiment and has a disadvantageous effect on the dosimetry. Also, the heat dissipation to the tissue around the distal end of the device, which need not necessarily be with their thermal volume of action in the target volume, not always tolerable - such as in sensitive structures (nerves, blood or lymph vessels, etc.).

Analogously to the diffuse optical distribution of light around a scattered-surface tap (cf., DE 41 37 983.7), the solution according to the invention is intended to distribute low-energy X-ray radiation as homogeneously as possible in a target volume.

In recent years, several attempts have been made to develop a low power, miniature, X-ray source (Dinsmore M et al., Med. Phys. 1996 Jan, 23 (1): 45-52). The currently used principle is based on the secondary generation of X-radiation. In this case, a conventional X-ray tube is used to generate the X-radiation. The high-energy photons collimated in a collimator strike a molybdenum target in a hollow needle, interact there and act as quasi-point-like material-characteristic X-ray sources (Gutman G et al., Phys. Med. Biol., 49 (2004): 4677-4688).

When using the novel system of needle-like anode X-ray tube as photon-based radiosurgical system could be generated at a voltage of 40 kV, an anode current of 200 uA and an exposure time of 300 sec, a dose of 5 Gy. The effects of ionizing X-rays on tumor tissue are the result of direct interaction with matter. For a therapeutic effect of ionizing radiation in liver tissue is required according to the current state of the art, a dose of> 10 Gy in the target volume.

WO 2005/120201 describes a possibility of deflecting the radiation at the distal end of a tubular device which essentially produces a beam lobe which is out of alignment with the tubular device - A -

must be aligned, but always limited to a small solid angle. Thus, the uncertainty in the irradiation is that close to the device in discrete directions perpendicular to the beam directed onto the device, a high intensity, but distant from the device and at the edges of the beam beam, an expiring damage zone, which is highly dependent on the externally applied radiation amount and energy has. The secure detection of a target volume can therefore only be done by multiple applications from different sides of the target volume.

Inventive solution

In order to solve the problem of complete penetration of a target volume with a predetermined radiation dose, a device is preferably provided in the form of a scattering body or diffuser which transmits or defines an X-ray scattering substance or a substance mixture in the form of small X-ray deflecting particles (scattering particles) in a X-ray transmissive X-ray weakening matrix comprises or contains, wherein the substance or the substance mixture is preferably evenly distributed, so that a rotationally symmetric radiation distribution about the axis of this scattering body (diffuser) directed X-radiation takes place.

Through the use of suitable scattering bodies or scattering bodies in combination with suitable fluorescence targets, which causes a conversion of the primary X-ray radiation directed onto the fluorescent target into a low-energy X-ray fluorescence spectrum, a largely isotropic distribution of the dose in the target volume can be achieved.

A continuation of the inventive idea is the use of X-ray-fluorescent particles instead of or mixed with the above-mentioned scattering particles. Elements of higher atomic numbers which are suitable for X-ray fluorescence, eg zinc, europium, etc., completely constitute these particles or constitute an outer layer or part of an outer layer of these X-ray-fluorescent particles. The use of X-ray radiation which is strongly absorbed in the scattering body is also made possible by the introduction of the body into the body through, for example, a tubular device and the subsequent scattering in the scattering body far from the surface, without taking into account other boundary conditions such as heat generation or radiation outside Target volume of lying body elements have to take. By varying the parameters of the x-ray source, in an x-ray tube, for example, acceleration voltage, tube current, anode material, filters and collimators, it is possible to adapt the radiation to the size of the target volume. Since the scattering body thus itself forms a radiation source which can be brought directly to the target volume and is not removed from the target volume, there is no damage to surrounding tissue. An accurate dose distribution is precisely predictable and, when using low-energy X-ray radiation on the human and animal body, has a steep dose edge drop compared to other established types of radiation. Thus, the method can be used without any effect restriction in the vicinity of radiation-sensitive structures. The application is thereby simplified compared to other radiosurgical methods and the dose planning and the therapy control can be carried out with the conventional imaging methods according to the prior art (ultrasound, magnetic resonance tomography, computed tomography, etc.).

The application is not explicitly limited to the radiosurgical application, but open z. Also for illumination purposes (for example X-ray film exposure, X-ray radiation via fluorescence into optical radiation) or other desired interaction mechanisms of ionizing radiation, even outside the application to the human or animal body.

For a conceivable application on the human or animal body, the X-ray radiation from external sources can be conducted into the body virtually loss-free by means of a percutaneously placed X-ray waveguide. X-ray light guides are capillary structures in which the X-ray radiation is passed on by multiple total reflection. This process is common to normal optical fibers. parable. However, the air is passed on to reduce absorption. Furthermore, the critical angles for the total reflection of X-rays are extremely small, so that only small curvatures of the X-ray fibers are possible. X-ray fibers are made of glass, the inner diameters of the capillaries are in the μm range. They can be summarized in bundles. By shaping the bundles in the entrance area, it is possible to detect a large solid angle of the radiation emitted by the tube and to form a parallel x-ray beam therefrom.

The X-ray light guides can be embedded in metal cannulas and thus have sufficient stability for percutaneous application to human and animal bodies. When using stainless steel cannulas sterilization of the cannulas is possible by known methods, which would allow multiple use of the X-ray fibers. The capillaries can be closed off by radiolucent windows, which prevent bodily fluids from entering the capillaries. Diffusers of the invention placed on the cannulas (diffuser tips I scatterers) can be used for the isotropic distribution of the radiation.

For further shaping of the X-ray radiation scattered on the particles, the geometry of the scattering body described above can be adapted so that a uniform radiation emission occurs over the length. Likewise, for beam shaping, the concentration of the particles in the scattering body can vary along the axis of the x-radiation irradiated onto the scattering body. A variation of the particle type along the axis of the X-ray radiation irradiated onto the scattering body can also be provided for beam shaping.

Furthermore, the total length of the diffuser, the choice of materials or mixtures of materials for particles, for matrix and for a limiting body conceivable around the diffuser, the particle concentration and the matrix properties can be used to determine how much X-radiation the diffuser faces laterally and in the direction of the diffuser X-ray radiation leaves and thus the radiation distribution around the diffuser are predetermined. In a further embodiment, the scattering body has a tapered bore tapering distally with respect to the X-ray beam directed towards the diffuser during operation, whereby X-rays impinging on the cone are deflected laterally out of the beam axis by total reflection.

In continuation of the inventive idea, this deflected radiation can also be scattered by a diffuser located outside the conical bore.

In continuation of the inventive concept, the cone may be lined with a sheet of high refractive index radiation material to reduce the steepness of the cone bore.

In continuation of the inventive idea, a structure or a material can also be applied to the surface of the conical bore by deposition processes (crystal lattice, single or multiple coating, or the like) for diffracting X-ray radiation.

In a further embodiment, the target volume is supplied in a suitable manner to substances or substance mixtures which scatter a low-energy radiation introduced into the body via a tubular device or convert it into low-energy radiation by X-ray fluorescence. Low-energy radiation-scattering substances or particles achieve an increase in intensity at the radiation source-oriented interface between non-enriched and enriched with such substances areas by remission, which can be exploited for the achievement of a predetermined radiation dose in the target volume. The fact that X-ray fluorescence always produces a lower energy spectrum than the excitation radiation, coupled with the fact that low-energy radiation from human and animal tissue is absorbed better than high-energy radiation, thus makes it possible to influence the dose distribution in the target volume by the coupling of radiation with the presence of substances which scatter low-energy radiation introduced into the body or convert it into low-energy radiation by X-ray fluorescence. Description of the drawings

Some selected embodiments of the invention are noted in the drawings. These show in part further optional and depending on the application advantageous features. From the figures show:

Fig. 1: a first exemplary embodiment of the invention;

2 shows a second exemplary embodiment of the invention;

3 shows a third, exemplary embodiment of the invention;

4 shows a fourth exemplary embodiment of the invention; and

Fig. 5: a fifth exemplary embodiment of the invention;

FIG. 1 shows an x-ray beam (1) originating from an external source, which is low-energy and is guided into the body via suitable devices and is scattered in different directions via a diffuser body (2). The scattered X-rays (3) - here only some are shown by way of example - are distributed isotropically in the target volume by multiple scattering or conversion by fluorescence or both mechanisms.

Fig. 2 shows a similar configuration as Fig. 1, wherein the scattering body (4) is geometrically shaped differently - here as an example as a truncated cone - and thereby the X-rays (1) for a material-dependent mean free path between two scattering events more scattering body offers. This influences the radiation distribution of the scattered or fluorescence-converted x-rays (3) and provides possibilities for adapting the isodose lines to the target volume.

Similar to FIG. 2, FIG. 3 shows a geometric change of the scattering body

(5), but the X-radiation (1) is directed to a conical bore and as a result total reflection occurs at the surface, causing beam deflection. In addition, the radiation is passed through a scattering body (5), which the radiation scatters or converts by fluorescence into lower energy radiation, which then emerges as scattered radiation (3) in the target volume.

FIG. 4 shows a diffuser constructed of different compositions, which for the drawing is composed of blocks of different composition (6, 7, 8). A gradual transition between the materials compositions is also in accordance with the invention. In the exemplary embodiment in FIG. 4, a scattering body (6) with a substance mixture with a high proportion of X-ray fluorescence generating material is followed by a scattering body (7) with a low scattering concentration and closed by a scattering body (8) with a high scattering body concentration shown. The radiation is differently influenced and delivered to the surrounding target volume as scattered radiation (3). Again, the shape of the isodose lines is predictable through the design and choice of material composition.

Fig. 5 shows another embodiment of the scattering or X-ray fluorescent substances. Here is a low-loss introduction of X-radiation into the body by an X-ray guide (9), which is positioned in front of the target volume (12), which is located directly on a blood vessel (1 1). The radiation, which is either low energy and then passes through an exit window (10) without significant interference, or optionally higher energy and is converted via a fluorescent target in low-energy X-radiation (1) is directed to the target volume. By means of a substance in the blood vessel, which acts as X-ray scattering, the radiation components (3) not absorbed in the target volume are scattered and redirected to the target volume, or X-ray-fluorescing and the radiation is converted into still therapeutically-biologically effective X-radiation. This enhancement effect increases the dose in the target area and reduces the risk of damage to the blood vessel. In a similar arrangement, according to the invention, it is also possible, via a minimally invasive approach, for example a long cannula, to create a depot of such a substance from the perspective of the X-ray guide behind a target volume. Also according to the invention, the Aufsätti- tion of the target volume with said substance in order to achieve the enhancement effect via an increase in intensity by this saturation with scattering material.

List of reference numbers

1 X-ray from external source

2 diffuser / diffuser

3 scattered X-rays or X-ray fluorescence

4 geometrically adapted scattering body (embodiment)

5 conical bore provided with scattering body (embodiment)

6 litter with composition X

7 scattering bodies with composition Y

8 scattering bodies with composition Z

9 X-ray conductor

10 exit window (optionally also fluorescence target)

1 1 blood vessel with "Radiosensitizer"

12 target volume (tumor)

Claims

claims

1. A device for irradiating a target volume in the interior of a body, characterized in that the device is designed to uniformly rotationally symmetrical radiation to the device scattered about a radiation longitudinal direction of the device directed to the device X-ray or radiate by X-ray fluorescence.

2. Apparatus according to claim 1, characterized Porsche Style nzeichnet that the

Device for scattering radiation-deflecting particles has.

3. Device according to claim 1, characterized Porsche Style nzeichnet that the device has radiation-deflecting particles that scatter X-ray radiation, mixed with fluorescent particles that produce X-ray fluorescence.

4. Apparatus according to claim 2 or 3, characterized in that the particles are composed entirely of X-ray diffusing respectively X-ray fluorescent materials or of a mixture of both materials.

5. Apparatus according to claim 2 or 3, dadu rch in that the particles have an outer layer, or a part of an outer layer of X-ray scattering respectively X-ray fluorescent material, or of a mixture of both materials.

6. Apparatus according to claim 2, 3, 4 or 5, characterized in that the particles used for scattering are embedded in a partially or completely radiation-permeable matrix.

7. The device according to claim 1, characterized Porsche Style nzeichnet that the device for scattering has a conical bore, which is formed and arranged that during operation of the device scattering occurs as a result of total reflection at the conical bore.

8. The device according to claim 7, characterized Porsche Style nzeichnet that with a material used for a during operation of the device

Radiation high index of refraction is lined.

9. Apparatus according to claim 8, characterized Porsche Style nzeichnet that the lining is given by a film-like material.

10. The device according to claim 8, characterized Porsche Style nzeichnet that the lining is formed by addition of the material of high refractive index as a crystalline layer.

1 1. A device according to claim 8, characterized Porsche Style nzeichnet that the lining is made by deposition of the material from the gas phase.

12. The device according to claim 1 1, characterized Porsche Style nzeichnet that the lining is formed by a sequence of several materials with different refractive index for the radiation, which is designed so that it causes a lattice diffraction of the radiation during operation.

13. Apparatus for irradiating a target volume in the interior of a body characterized in that the device is a tubular

A device for low-loss conduction of low-energy radiation into the body, and arranged on or in the vicinity of the distal end of the tubular device scattering body with a substance or mixture of substances that has the property of scattering low-energy radiation or in X-ray fluorescence.

14. A method for irradiating a target volume in the interior of a body characterized in that low-energy radiation is passed through a tubular device with low loss in the body and this scattered in a target volume by a substance deposited in the target volume or a mixture of substances or converted into X-ray fluorescence.