System for manufacturing radioisotopes by bremsstrahlung comprising bent converter

Abstract

FIELD: nuclear physics.SUBSTANCE: invention relates to a system and method for producing radioisotopes through photonuclear reactions. The system comprises elements sequentially arranged along the irradiation axis (Z): an accelerator (1) of electrons accelerated along the irradiation axis (Z), a scanning unit (2), a focusing unit (3) for forming a beam (10f) converging to a first focusing point (Fx) located on the irradiation axis (Z), a converting unit (4) located between the focusing unit (3) and the first focusing point (Fx) and comprising one or more converters (4.1-4.n) of bremsstrahlung designed to convert the focused beam (10f) into a beam (11x) of photons, as well as a target holder (5h). Moreover, one or more converters (4.1-4.n) are bent in such a way that the focused beam (10f) intersects each of the converters (4.1-4.n) of bremsstrahlung at an angle (α ) intersections ranging from 65 to 115° at all points, preferably from 75 to 105° at all points.EFFECT: prevention of premature thermal destruction of the converter while maintaining a focused high-intensity electron beam and providing highly focused X-ray radiation.13 cl, 5 dwg, 1 tbl

Description

AREA OF TECHNOLOGY

[0001] The present invention relates to a device for producing radioisotopes by irradiating a target with X-rays generated by bremsstrahlung during bombardment of a converter with a high-energy electron beam. In particular, the present invention relates to a specific converter geometry that reduces the heat generated by the electron beam and allows the use of conventional cooling systems to maintain the converter temperature within acceptable limits. BACKGROUND OF THE INVENTION

[0002] Radioisotopes can be produced through various reactions using charged particles or using photonuclear reactions (such as X-rays). For example, 225 Ace can be created by decay 225 Ra, formed as a result of photonuclear reactions caused by X-ray irradiation of a target 226Ra. The energy of the X-rays, which is directly related to the energy of the electron beam, must be precisely controlled to produce the desired isotope. For example, irradiating the target 226 Ra can produce 223 Ra, 224 Ra and 225 Ra depending on the photoirradiation energy. Other examples of radioisotopes commonly used in medical applications include 99mTc.

[0003] X-rays can be produced by irradiating a transducer with a high-energy electron beam. The transducer is positioned between a high-energy electron beam source, which includes an electron accelerator such as a rhodotron or linear accelerator, and a target (in the example 226The transducer is formed by a foil of a metal with a high Z number, such as Ti or Ta. When the transducer is struck by an electron beam, it slows down, and the released energy is converted into X-rays, which reach the target, forming the desired radioisotope. This mechanism is called "bremsstrahlung."

[0004] Since only part of the electron beam's energy is converted into bremsstrahlung, the remainder is converted into heat. Thermal degradation of the converter is a serious problem. For this reason, the converter must be cooled. Conventional coolers use a gas such as helium or a liquid such as water.

[0005] To improve converter cooling and / or ensure a wider geometric distribution of the resulting photon beam by the converter, WO 1999052587 proposes scanning an electron beam over the scanned region of the converter using magnetic scanning coils. US 20120025105 combines scanning of the electron beam with target movement synchronized with the scanning of the electron beam, such that the target is constantly exposed to the full intensity of the bremsstrahlung produced by the converter.

[0006] WO 2017076961 describes a focusing lens used to collimate or focus an electron beam. Collimating an electron beam is beneficial because a diverging electron beam increases the divergence of the generated photons. This, in turn, requires larger targets to collect the photons. The focusing lens can be formed from magnets and can be a multipole lens, such as a quadrupole, hexapole, or octupole lens.

[0007] Despite previous improvements, the problem of sufficiently cooling the converter using conventional cooling systems to prevent premature thermal degradation of the converter remains. The present invention solves the dual problem of preventing premature thermal degradation of the converter using conventional cooling means while maintaining a focused, high-intensity electron beam and, consequently, highly focused X-ray radiation. The solution offered by the present invention to achieve this dual goal is explained below. SUMMARY OF THE INVENTION

[0008] The present invention is defined in the attached independent claims. Preferred embodiments are defined in the dependent claims.In particular, the present invention relates to a system for producing radioisotopes, comprising: • an electron accelerator configured to generate an electron beam, which is accelerated electrons, along an irradiation axis (Z), • a scanning unit configured to deflect the electron beam according to a given scanning pattern to form a scanned beam, • a focusing unit containing one or more magnets, configured to focus the scanned beam over a first irradiation plane (X, Z) towards a first focusing point (Fx) located on the irradiation axis (Z) to form a focused beam, wherein the first irradiation plane (X, Z) is defined by the irradiation axis (Z) and a first transverse axis (X), wherein X⊥Z, • a converting unit located between the focusing unit (3) and the first focusing point (Fx) and containing one or more converters (4.1-4.n) bremsstrahlung, designed to convert the focused beam into a photon beam, • a converter cooling system designed to cool one or more bremsstrahlung converters, • a target holder designed to hold the target.

[0009] All of the electron accelerator, scanning unit, focusing unit, converting unit, and target holder are aligned along the irradiation axis (Z) and are located downstream of each other in this sequence, wherein "downstream" is defined relative to the direction of the electron beam. The present system differs from the prior art systems in that one or more bremsstrahlung converters are curved such that the focused beam intersects each of the one or more bremsstrahlung converters at an intersection angle (a) of from 65° to 115° at all points, preferably from 75° to 105° at all points.

[0010] In the first embodiment, the scanning unit is configured to deflect the electron beam along a predetermined scanning pattern extending along the first transverse axis (X) and the second transverse axis (Y), wherein X⊥Y⊥Z. The focusing unit is configured to focus the scanned beam also over the second irradiation plane (Y, Z) toward the second focusing point (Fy) located on the irradiation axis (Z). The second focusing point (Fy) may be the same as the first focusing point (Fx) or different from it. One or more bremsstrahlung converters have the shape of an ovoid cap, preferably a spherical cap, defined by a first curved cross-section in the first irradiation plane (X, Z) and a second curved cross-section in the second irradiation plane (Y, Z).

[0011] Each of the one or more bremsstrahlung converters has a first curved cross-section in the first irradiation plane (X, Z), which is preferably defined substantially by an arc of a circle of radius (d1-dn) centered at the first focal point (Fx). "Substantially an arc of a circle" is defined herein as a curved segment having a radius of curvature that varies by no more than 10% along the length of the curved cross-section. Alternatively or simultaneously, each of the one or more bremsstrahlung converters has a second curved cross-section in the second irradiation plane (Y, Z), which is preferably defined substantially by an arc of a circle of radius (d1-dn) centered at the second focal point (Fy). It is preferable that the second focal point (Fy) is the same as the first focal point (Fx) (i.e. Fx=Fy).

[0012] In the second embodiment, the scanning unit is configured to deflect the electron beam along a predetermined scanning pattern extending only along the first transverse axis (X). One or more bremsstrahlung converters have the shape of a cylindrical cross-section defined by a curved cross-section in the first transverse plane (X, Z) and surface generators extending along the second transverse axis (Y), wherein X⊥Y⊥Z. Each of the one or more bremsstrahlung converters has a first curved cross-section in the first irradiation plane (X, Z), which is preferably defined substantially by an arc of a circle of radius (d1-dn) centered at the first focal point (Fx).

[0013] The focusing unit can be configured to form a focused beam, wherein the focusing half-angle (β) is formed at the first focusing point (Fx) with the irradiation axis (Z) in the first irradiation plane (X, Z) and is from 20 to 55°, preferably from 30 to 45°.

[0014] One or more bremsstrahlung converters can be made of tantalum (Ta) or tungsten (W), or titanium (Ti). Each of the one or more bremsstrahlung converters has a thickness (L90) measured along the radius of curvature, which is preferably no more than 3 mm, preferably the thickness (L90) is from 0.2 to 2.5 mm, more preferably from 0.5 to 1.5 mm. In addition, it is preferable that the n-th bremsstrahlung converter, located closest to the target holder, has a greater thickness (L90) than the first bremsstrahlung converter, located closest to the focusing unit.

[0015] The converter unit may contain from 1 to n bremsstrahlung converters separated from each other by cooling channels, where n is from 2 to 8, preferably from 3 to 5. The converter cooling system may provide for gas or liquid forced cooling flowing through the channels.

[0016] The present invention also relates to a process for producing a radioisotope by irradiating a target with X-rays, comprising: • providing a system as defined above, • loading a target onto a target holder, • scanning and focusing a beam of accelerated electrons into a converting unit to produce X-rays, • irradiating the target with the X-rays thus produced.

[0017] The target can be selected from one of 226 Ra for production 225 Ace or 100 Mo to form 99mTc, or 186 W for production 187 Re, or 134 He for education 131 I, or68 Zn for production 67 Cu. BRIEF DESCRIPTION OF GRAPHIC MATERIALS

[0018] For a more complete understanding of the essence of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1(a) is a side view of the system according to the present invention. Fig. 1(b) is a perspective view of a first embodiment of the system according to the present invention. Fig. 1(c) is a perspective view of a second embodiment of the system according to the present invention. Fig. 2 is a view of a scanning and focusing unit according to the present invention. Fig. 3 is an example of a converting unit according to the present invention. Fig. 4(a) is a view of the maximum distance (Lα) traveled by an electron beam through a straight sheet of a bremsstrahlung converter according to the prior art, where α=β+90°. Fig.4(b) shows the maximum distance (Lα) traveled by the electron beam through the curved sheet of the bremsstrahlung converter according to the present invention, wherein 65°≤α≤115°. Fig. 4(c) shows the maximum distance (L90) traveled by the electron beam through the curved sheet of the bremsstrahlung converter according to a preferred embodiment of the present invention, wherein α=90°. Fig. 4(d) is a graphic representation of the standard maximum distance (Lα / L90) traveled by the electron beam through the curved sheet of the bremsstrahlung converter according to the present invention as a function of the angle α; the smallest value of Lα is L90 at α=90°. Fig. 5(a) shows the height (hi) characteristic of the scanned region of the straight bremsstrahlung converters according to the prior art, through which the scanned beam passes. Fig.5(b) shows the height (ci) characteristic of the scanned region of the curved bremsstrahlung converters according to the present invention, through which the scanned beam passes. Fig. 5(c) compares the heights (hi, ci) of the bremsstrahlung converters, through which the scanned beam passes, according to the prior art and according to the present invention. Fig. 5(d) graphically depicts the ratio of the heights (c1 / h1) of the bremsstrahlung converters, through which the scanned beam passes, depending on the half-angle (β) of focusing. DETAILED DESCRIPTION OF THE INVENTION.

[0019] The present invention relates to a system for producing radioisotopes by converting an electron beam into a photon beam and irradiating a target (5) with it. The system comprises an electron accelerator (1) configured to generate an electron beam (10), which is accelerated electrons, along the irradiation axis (Z). A scanning unit (2) is located downstream of the electron accelerator along the irradiation axis (Z). The scanning unit (2) is configured to deflect the electron beam (10) according to a given scanning pattern to form a scanned beam (10s). A focusing unit (3) is located downstream of the scanning unit along the irradiation axis (Z).The focusing unit contains one or more magnets (3m) designed to focus the scanned beam (10s) over the first irradiation plane (X, Z) in the direction of the first focusing point (Fx) located on the irradiation axis (Z) to form a focused beam (10f), wherein the first irradiation plane (X, Z) is defined by the irradiation axis (Z) and the first transverse axis (X), wherein X⊥Z.

[0020] The conversion unit (4) is located between the focusing unit (3) and the first focal point (Fx). The conversion unit contains one or more bremsstrahlung converters (4.1-4.n) designed to convert the focused beam (10f) into a photon beam (11x). The conversion unit is equipped with a converter cooling system (4c) designed to cool one or more bremsstrahlung converters (4.1-4.n).

[0021] The target holder (5h) is designed to hold the target (5) open at the first focusing point (Fx). The target holder is equipped with a target cooling unit (5c) designed to cool the target (5) when it is held in the target holder (5h).

[0022] All of the electron accelerator (1), scanning unit (2), focusing unit (3), converting unit (4), and target holder (5h) are aligned along the irradiation axis (Z) and located downstream of each other in this sequence, wherein “downstream” is defined relative to the direction of the electron beam.

[0023] The essence of the present invention is that one or more converters (4.1-4.n) of bremsstrahlung are bent in such a way that the focused beam (10f) intersects each of one or more converters (4.1-4.n) of bremsstrahlung at an intersection angle (α) of from 65° to 115° at all points, preferably from 75° to 105° at all points, more preferably the intersection angle (α) is 90°±5°. ELECTRON ACCELERATOR (1)

[0024] Electron accelerators are well known in the art. The present invention is not limited to any particular type of electron accelerator, provided that it is capable of producing a beam (10) of electrons with an energy of 10 to 40 MeV, preferably 15 to 30 MeV, preferably 20 to 25 MeV. The diameter of the electron beam (10) may be less than 10 mm. The electron accelerator may be, for example, a linear particle accelerator (e.g., a linear particle accelerator) or a leaf-type accelerator (e.g., a rhodotron). SCANNING UNIT (2)

[0025] The scanning unit is well known in the art. The present invention is not limited to any particular type of scanning unit, provided that it is capable of scanning the electron beam (10) according to a predetermined scanning pattern to form a scanned beam (10s). Upon collision with the bremsstrahlung converters, only a portion of the electron beam energy is converted into X-ray energy. The remainder is dissipated as heat. Scanning the electron beam on the converter ensures a flat beam distribution over the entire surface of the converter and reduces the concentration of beam power and heating in a small scanned area of ​​the converter.

[0026] The scanning unit (2) can be equipped with magnetic scanning coils (2 m) at the side of the electron beam (10). The magnetic scanning coils can be configured to linearly scan the electron beam along the first transverse direction (X), as illustrated in Fig. 1(c). Alternatively, the magnetic scanning coils can be configured to scan the electron beam over the scanned area along the first and second transverse directions (X, Y), as illustrated in Fig. 1(b).

[0027] In the first embodiment, the scanning unit (2) is configured to deflect the electron beam (10) along a predetermined scanning pattern extending only along the first transverse axis (X). Alternatively, in the second embodiment, the scanning unit (2) is configured to deflect the electron beam (10) along a predetermined scanning pattern extending along the first transverse axis (X) and the second transverse axis (Y), wherein X⊥Y⊥Z.

[0028] As discussed above, scanning the electron beam in the first and optionally second transverse directions into the converter facilitates cooling of the converter. However, this results in a wider geometric spread of the resulting photon beam. In some cases, when large targets are available, this can be an advantage. However, when target material is insufficient and it is necessary to use smaller targets, for example with 226 Ra, the wide geometric spread of X-rays can be a nuisance. For this reason, in this area of ​​technology, it has been proposed to use a focusing unit to converge the scanned beam (10s) to a single point for focusing the beam onto the transducer using focusing magnetic coils (3m).FOCUSING UNIT (3)

[0029] With smaller targets, the scanned beam (10s) as such cannot be effectively used, since the photon beams (11x) formed as a result of the interaction of the scanned electron beam with the converting unit (4) are also scattered. Refocusing of either the scanned beam (10s) or the photon beam (11x) is required for small targets. Focusing of the photon beam (11x) is described, for example, in WO 2012022491. In the present invention, the system comprises a focusing unit (4) located upstream of the converting unit (4) for focusing the scanned beam (10s) to form a focused beam (10f).

[0030] The focusing unit (3) is configured to focus the scanned beam (10s) over the first irradiation plane (X, Z) toward the first focal point (Fx) located on the irradiation axis (Z) to form a focused beam (10f). The first irradiation plane (X, Z) is defined by the irradiation axis (Z) and the first transverse axis (X), wherein X⊥Z. Focusing units of this type are well known in the art. The present invention is not limited to any particular type of focusing unit (3), provided that it is capable of focusing the scanned beam (10s) toward the first focal point (Fx) during scanning to form a focused beam (10f). For targets of smaller sizes, focusing points (Fx) of correspondingly smaller sizes are required.

[0031] As illustrated in Fig. 2, the focusing unit (3) of the scanned beam (10s) may comprise a lens formed by focusing magnetic coils (3m) forming a multipole lens, for example a quadrupole, hexapole or octupole lens. The focused beam (10f) formed in this way still scans in the first and optionally second transverse directions (X, Y), but, as illustrated in Fig. 5(b), from all points of the scanning pattern, the focused beam converges to the first focal point (Fx). Since the converter is located between the focusing unit (3) and the first focal point (Fx), the focused beam (10f) scans the scanned area of ​​the converting unit (4), thereby distributing the energy of the focused beam over a larger scanned area.

[0032] In the embodiment in which the scanning unit (2) is configured to deflect the electron beam (10) along a predetermined scanning pattern extending along the first transverse axis (X) and the second transverse axis (Y), the focusing unit (3) can be configured to focus the scanned beam (10s) also over the second irradiation plane (Y, Z) toward the second focusing point (Fy) located on the irradiation axis (Z). The second focusing point (Fy) can be the same as the first focusing point (Fx) or different from it.

[0033] The focusing half-angle (β) shown in Fig. 3, 4(a)-4(c) and 5(a)-5(c), and formed at the first focusing point (Fx) between the irradiation axis (Z) and the outer shell of the electron beam focused in this way, may be from 20 to 55°, preferably from 30 to 45°. If the scanning beam (10s) is scanned in both the first and second transverse directions (X, Y), the focusing half-angle (β) formed at the second focusing point (Fy), if it is different from the first focusing point (Fx), may be in the same ranges as defined above. CONVERTING UNIT (4)

[0034] As shown in Fig. 5(a), the conversion unit is traditionally formed by a series of bremsstrahlung converters (4.1-4.n) in the form of flat metal sheets with a high Z number, aligned one after another along the irradiation axis (Z) and separated from each other by cooling channels. There are two main problems with placing such a conversion unit downstream of the focusing unit (3).

[0035] Firstly, as shown in Fig. 4(a), it can be seen that the electrons placed maximally outward in the focused beam (10f) intersect the bremsstrahlung converter sheet (4.1) with an intersection angle (α) that is greater than 90°, while the electrons moving along the irradiation axis (Z) intersect the bremsstrahlung converter sheet (4.1) with an intersection angle (α) of 90°. As can be clearly seen in Fig. 4(a) and graphically depicted in Fig. 4(d), the length (Lα) of the bremsstrahlung material through which the electrons pass depends greatly on the intersection angle (α), with the minimum length (L90) at an intersection angle of α=90° (see Fig. 4(d)). This means that the outermost electrons, traveling a longer path (Lα) through the bremsstrahlung material, release more energy and hence more heat than electrons traveling closer to the irradiation axis (Z) with a path length close to or equal to L90.This is problematic because there is a temperature gradient in the scanned region of the bremsstrahlung converter, and also because the outermost electrons, having released more energy on the first bremsstrahlung sheet, have less energy to contribute to the following sheets than the innermost electrons passing closer to the (Z) axis of irradiation.

[0036] Second, as illustrated in Figs. 5(a), 5(c), and 5(d), the scanned area of ​​each bremsstrahlung sheet through which the focused beam (10f) passes is smaller when the bremsstrahlung sheets are flat than when they are curved. Fig. 5 shows side views or projections onto the (X, Z) plane, and the two-dimensional areas in the 3-dimensional system are reduced to one-dimensional lengths (hi, ci, with i=1-n) in the 2-dimensional projections of Fig. 5. Therefore, the term "area" is used when referring to the lengths hi or ci, allowing the reader to mentally multiply the lengths hi and ci by the corresponding length in the second transverse direction (Y) to obtain a quantity in [m 2 ].

[0037] In Fig. 5(a), the scanned area of ​​the bremsstrahlung sheet crossed by the focused electron beam (10f) is represented by the lengths (hi, i=1-n). Referring to Fig. 5(c), the lengths hi can be calculated as a function of the focusing half-angle (β) as hi=di×sinβ, where di is the distance separating the i-th bremsstrahlung converter (4.i) from the first focusing point (Fx) (measured along the irradiation axis (Z). It would be advantageous to increase the scanned area of ​​the bremsstrahlung crossed by the focused beam (10f), particularly if a large number (n) of bremsstrahlung sheets are used, since the scanned area decreases after each sheet, thus increasing the concentration of the beam energy on smaller scanned areas.

[0038] The present invention proposes to replace the bremsstrahlung converters in the form of flat sheets, which have been used so far in the given technical field, with curved bremsstrahlung converters (4.1-4.n) in the form of curved sheets, so that the focused beam (10f) intersects each of one or more bremsstrahlung converters at an intersection angle (α) equal to from 65° to 115° at all points, preferably from 75° to 105° at all points. Preferably, the intersection angle is 90°. An intersection angle of 90° at all points of the converting unit (4) can be obtained with bremsstrahlung converters in the form of sheets having a single curvature or optionally a double curvature of a radius (di), defined as the distance separating the curved sheets from the first and optionally second focal points (Fx, Fy).If the first and second focal points are the same, the bremsstrahlung sheets have a spherical cap geometry of radius (di). This simple solution solves the two problems discussed above, resulting in: • a more uniform heat distribution across the scanned area of ​​the bremsstrahlung sheets intersected by the focused beam (10f) and • a larger scanned area of ​​the bremsstrahlung sheets intersected by the focused beam (10f). More uniform heat distribution.

[0039] As shown in Fig. 4(b) and 4(c), the intersection angle (α) can be made close to or even equal to 90° by locally tilting the bremsstrahlung sheet relative to the irradiation direction parallel to the irradiation axis (Z) by an angle γ. With a sufficiently curved bremsstrahlung sheet, the intersection angle (α) can be reduced to a range of 65° to 115° at all points, preferably 75° to 105° at all points. Referring to Fig. 4(d), it can be seen that in the range of the intersection angle (α) from 65° to 115° at all points, represented by the light shaded area, the standard thickness (Lα / L90=1 / sinα) of the bremsstrahlung material through which two electrons of the focused beam (10f) pass can vary by no more than approximately 10% (Lα / L90≈1.1). When the range of the intersection angle (α) is reduced to the range from 75 to 105°, represented by the dark shaded area in Fig.4(d), the standard thickness (Lα / L90) changes by less than 4% for any two electrons of the focused beam (10f) (Lα / L90=1.04). If the intersection angle α=90° at all points, the standard thickness (Lα / L90=1) is constant for all electrons of the focused beam, and the thermal energy transferred to the bremsstrahlung converters (4.1-4.i) is distributed uniformly over the entire scanned area of ​​the converting unit (4), through which the focused beam (10f) passes, without localized areas of higher temperatures.

[0040] For comparison, the focused beam (10f) passing through the flat bremsstrahlung sheet as shown in Fig. 4(a), with an intersection angle of, for example, α=135°, which corresponds to a focusing half-angle of β=α-90°=45°, the standard thickness of the flat sheet through which the focused beam passes changes by more than 40% (Lα / L90=1.4 in Fig. 4(d)), which results in a proportionally comparable thermal gradient in the scanned region of the flat sheet through which the focused beam (10f) passes.

[0041] The use of bremsstrahlung converters (4.1-4.n) curved in such a way that the focused beam (10f) intersects each of one or more bremsstrahlung converters (4.1-4.n) at an intersection angle (α) of 65° to 115° at all points clearly promotes homogenization of the heat generated by interaction with the focused beam over the scanned area of ​​the bremsstrahlung converter. This makes cooling of the converter unit easier than for flat sheets, and conventional cooling systems (4c) can be successfully used. Large scanned area

[0042] Referring to Fig. 5(a) and 5(c), it can be seen that the scanned region represented by the height (hi) of the conversion unit formed by flat sheets may be characterized by the value hi:=di×sinβ, while the scanned region represented by the curved height (ci) of the conversion unit formed by curved sheets of radius (di) may be characterized by the value ci:=di×β; the height ratio (ci / hi) of the curved height (ci) according to the present invention to the height (hi) according to the prior art can be expressed as ci / hi=β / sinβ. The height ratio (ci / hi) is graphically depicted in Fig. 5(d) as a function of the focusing half-angle (β). It can be seen that at a focal half-angle of, for example, β = 45°, curved bremsstrahlung converters have a scanned area (ci) that is 10% larger than that of flat sheets. The scanned area is approximately 15% larger at a focal half-angle of β = 50°.This increase in the scanned area allows the focused beam energy to be distributed over a larger scanned area with curved bremsstrahlung converters than with flat ones. Thus, the heat generated during the interaction between the focused beam and the scanned area of ​​the converter unit is correspondingly reduced, further facilitating cooling of the converter unit (4). Geometries of bremsstrahlung converters (4.1-4.n).

[0043] One or more bremsstrahlung converters (4.1-4.n) may have the shape of a cylindrical cross-section defined by a curved cross-section in the first transverse plane (X, Z) and generating surfaces extending along the second transverse axis (Y), wherein X⊥Y⊥Z. This geometry is preferable in the case where the scanning unit (2) is designed to deflect the electron beam (10) along a given scanning pattern extending only along the first transverse axis (X). This may also be preferable in the case where the target (5) has a length defining an elongated shape, and there is no need to focus the scanned beam into a plane having the length of the elongated target. The converting unit (4) of this type is illustrated in Fig. (c).

[0044] In an alternative embodiment, one or more bremsstrahlung converters (4.1-4.n) have the shape of an ovoid cap, preferably a spherical cap, defined by a first curved cross-section in a first irradiation plane (X, Z) and a second curved cross-section in a second irradiation plane (Y, Z). This type of converter unit is illustrated in Fig. 1(b) and is particularly suitable in the case where the scanning unit (2) is designed to deflect the electron beam (10) along a given scanning pattern passing along the first transverse axis (X) and the second transverse axis (Y), wherein X⊥Y⊥Z, and the focusing unit (3) is designed to focus the scanned beam (10s) also above the second irradiation plane (Y, Z) in the direction of the second focusing point (Fy) located on the irradiation axis (Z), wherein the second focusing point (Fy) may be the same as the first focusing point (Fx) or different from it.In a preferred embodiment, the first and second focus points (Fx, Fy) are the same focus point (i.e. Fx=Fy).

[0045] In both embodiments (i.e., with single or double curvature), it is preferable that the radius of curvature of the curved sections be constant, i.e., defining an arc of a circle or a spherical cap, respectively. The radius of curvature should preferably be close to the distance (di) separating the bremsstrahlung converter (4.1-4.n) from the first focal point (Fx).

[0046] In a preferred embodiment, each of the one or more bremsstrahlung converters (4.1-4.n) has a first curved cross-section in the first irradiation plane (X, Z), defined substantially by an arc of a circle of radius (d1-dn) centered at the first focal point (Fx). "Substantially an arc of a circle" is defined herein as a curved segment having a radius of curvature that varies by no more than 10% along the length of the curved arc. With this geometry, the focused beam (10h) reaches the bremsstrahlung converters with an intersection angle equal to 90° along the first irradiation plane (X, Z).

[0047] In a preferred embodiment, each of the one or more bremsstrahlung converters (4.1-4.n) has a second curved cross-section in the second irradiation plane (Y, Z), defined essentially by an arc of a circle of radius (d1-dn) with a center at the second focal point (Fy). It is preferable that the second focal point (Fy) is the same as the first focal point (Fx) (i.e. Fx=Fy), defining the geometry of a spherical cap with a center at a separate focal point (Fx=Fy).

[0048] As shown in Fig. 3, the converter unit (4) comprises from 1 to n bremsstrahlung converters (4.1-4.n) separated from each other by cooling channels, wherein n is from 2 to 8, preferably from 3 to 5. The converter cooling system (4c) may provide for gas or liquid forced cooling, wherein the cooling fluid flows through the cooling channels to remove heat from the bremsstrahlung converters generated during interaction with the focused beam (10f). This configuration defines what is referred to in this document as a "conventional cooling system", which is well known to those skilled in the art.

[0049] Each of the one or more bremsstrahlung converters (4.1-4.n) has a thickness (L90), measured along the radius of curvature, of no more than 3 mm, preferably the thickness (L90) is from 0.2 to 2.5 mm, more preferably from 0.5 to 1.5 mm. The radius of curvature at one point of the bremsstrahlung converter is defined as the radius of a circle that touches the bremsstrahlung converter at this point and has the same tangent and curvature at this point. Thus, the radius of curvature is perpendicular to the tangent of the bremsstrahlung converter at this point. This is illustrated in Fig. 4(a)-4(c), as indicated by L90. The thickness (L90) is also the shortest straight line intersecting the bremsstrahlung converter from one surface to the opposite surface.

[0050] In a preferred embodiment, the n-th bremsstrahlung converter (4.n) in a sequence of n bremsstrahlung converters, which is located closest to the target holder (5h), has a greater thickness (L90) than the first bremsstrahlung converter (4.1) located closest to the focusing unit (3). Preferably, each bremsstrahlung converter (4.i) in the sequence is thicker than the adjacent bremsstrahlung converter (4.(i-1)) located upstream, i.e. L90(4.i)>L90(4.(i-1)). Since the scanned area of ​​the bremsstrahlung converters decreases as the bremsstrahlung converters approach the first focusing point (Fx), an increase in the thickness of the bremsstrahlung converters located downstream in the sequence makes it possible to homogenize the volume of the bremsstrahlung converter material interacting with the focused beam (10f).Thus, all bremsstrahlung converters contribute equally to X-ray production. The heat generated during interaction, which must be removed, is also distributed more evenly among the various bremsstrahlung converters in the conversion unit (4), thus facilitating their cooling.

[0051] Bremsstrahlung converters (4.1-4.n) from 1 to n can be made of tantalum (Ta) or tungsten (W), or titanium (Ti).TARGET (5) AND HOLDER (5H) OF THE TARGET

[0052] By using a focusing unit, the system of the present invention is particularly suitable for small-sized targets (5). The target (5) can be 226 Ra for production 225 Ac, commonly used for diagnostic imaging. Other examples of targets that can be used with the system of the present invention to generate isotopes for diagnostic imaging include a target100 Mo for the formation of 99mTc or target 186 W for production 187 Re, or 134 He for education 131 I, or 68 Zn for production 67 Cu and the like.

[0053] Since the transmutation reaction caused by the interaction of X-rays (11x) with the target generates heat, a target cooling system (5c) is provided, which is designed to cool the target (5) when it is held in the target holder (5h). Similar to the converter cooling system (4c) discussed above, the target cooling system (5c) can provide gas or liquid forced cooling, with the cooling fluid flowing through cooling channels in thermal contact with the target (5). Of course, it is important to maintain the temperature of the target (5) below the destruction temperature.

[0054] If the first and second focal points are the same (i.e. Fx=Fy) and the X-rays thus produced by the transducer unit (4) converge to a small convergence area around the focal point (Fx), the sample holder can be designed to move the target (5) so that the focal point (which is static) scans a larger area of ​​the target. This is especially interesting in the case of large targets whose open area is larger than the convergence area of ​​the X-rays, so that transmutation occurs over a larger area / volume of the target than if it remained static. METHOD FOR PRODUCING A RADIOISOTOPE

[0055] The system according to the present invention can be used in the process of producing a radioisotope by irradiating a target with X-rays. The method includes providing a system as described above. After loading the target (5) onto the target holder (5h), scanning and focusing the accelerated electron beam into the converting unit (4) for producing X-rays involves irradiating the target with the X-rays thus produced.

[0056] The target could be, for example, 226 Ra for production 225 Ace or target 100 Mo for the formation of 99mTc, or target 186 W for production 187 Re, or 134 He for education 131 I, or 68 Zn for production 67 Cu and the like.

Claims

1. A system for producing radioisotopes, comprising: an electron accelerator (1) designed to generate a beam (10) of electrons, which are accelerated electrons, along the irradiation axis (Z), a scanning unit (2) designed to deflect a beam (10) of electrons according to a given scanning pattern to form a scanned beam (10s), a focusing unit (3) comprising one or more magnets configured to focus the scanned beam (10s) over the first irradiation plane (X, Z) towards the first focusing point (Fx) located on the irradiation axis (Z) to form a focused beam (10f), wherein the first irradiation plane (X, Z) is defined by the irradiation axis (Z) and the first transverse axis (X), wherein X⊥Z, a converting unit (4) located between the focusing unit (3) and the first focusing point (Fx) and containing one or more converters (4.1-4.n) of bremsstrahlung designed to convert the focused beam (10f) into a beam (11x) of photons, a converter cooling system (4c) designed to cool one or more bremsstrahlung converters (4.1-4.n), a target holder (5h) designed to hold a target (5), wherein all of the electron accelerator (1), scanning unit (2), focusing unit (3), converting unit (4) and target holder (5h) are aligned along the irradiation axis (Z) and are located downstream relative to each other in this sequence, wherein “downstream” is defined relative to the direction of the electron beam, characterized in that one or more bremsstrahlung converters (4.1-4.n) are bent in such a way that the focused beam (10f) intersects each of the one or more bremsstrahlung converters (4.1-4.n) at an intersection angle (α) of from 65 to 115° at all points, preferably from 75 to 105° at all points.

2. The system according to paragraph 1, characterized in that the scanning unit (2) is designed to deflect the electron beam (10) according to a given scanning pattern passing along the first transverse axis (X) and the second transverse axis (Y), wherein X⊥Y⊥Z, the focusing unit (3) is designed to focus the scanned beam (10s) also above the second plane (Y, Z) of irradiation in the direction of the second focusing point (Fy) located on the axis (Z) of irradiation, wherein the second focusing point (Fy) can be the same as the first focusing point (Fx) or different from it, and one or more bremsstrahlung converters (4.1-4.n) have the shape of an ovoid cap, preferably a spherical cap, defined by a first curved cross-section in a first irradiation plane (X, Z) and a second curved cross-section in a second irradiation plane (Y, Z).

3. The system according to paragraph 1, characterized in that the scanning unit (2) is designed to deflect the electron beam (10) according to a given scanning pattern, passing only along the first transverse axis (X), and one or more bremsstrahlung converters (4.1-4.n) have the shape of a cylindrical cross-section defined by a curved cross-section in the first transverse plane (X, Z) and generating surfaces passing along the second transverse axis (Y), where X⊥Y⊥Z.

4. A system according to any of the preceding paragraphs, characterized in that the focusing unit (3) is designed to form a focused beam (10f), wherein the focusing half-angle (β) is formed at the first focusing point (Fx) with the irradiation axis (Z) in the first irradiation plane (X, Z) and is from 20 to 55°, preferably from 30 to 45°.

5. A system according to any one of the preceding claims, characterized in that each of the one or more bremsstrahlung converters (4.1-4.n) has a first curved cross-section in the first plane (X, Z) of irradiation, defined essentially by an arc of a circle of radius (d1-dn) with a center at the first point (Fx) of focus, wherein "essentially an arc of a circle" is defined as a curved segment having a radius of curvature that varies by no more than 10% along the length of the curved cross-section.

6. The system according to claim 5, characterized in that each of the one or more bremsstrahlung converters (4.1-4.n) has a second curved cross-section in the first plane (Y, Z) of irradiation, defined essentially by an arc of a circle of radius (d1-dn) with a center at the second focal point (Fy), wherein the second focal point (Fy) is preferably the same as the first focal point (Fx) (i.e. Fx=Fy).

7. A system according to any of the preceding claims, characterized in that each of the one or more bremsstrahlung transducers (4.1-4.n) has a thickness (L90), measured along the radius of curvature, of no more than 3 mm, preferably the thickness (L90) is from 0.2 to 2.5 mm, more preferably from 0.5 to 1.5 mm.

8. A system according to any of the preceding paragraphs, characterized in that the n-th bremsstrahlung converter (4.n), located closest to the target holder (5h), has a greater thickness (L90) than the first bremsstrahlung converter (4.1), located closest to the focusing unit (3).

9. A system according to any of the preceding paragraphs, characterized in that the converting unit (4) contains from 1 to n bremsstrahlung converters (4.1-4.n), separated from each other by cooling channels, wherein n is from 2 to 8, preferably from 3 to 5.

10. A system according to any of the preceding paragraphs, characterized in that the converter cooling system (4c) provides for gas or liquid forced cooling.

11. The system according to the previous paragraph, characterized in that one or more converters (4.1-4.n) of bremsstrahlung are made of tantalum (Ta), or tungsten (W), or titanium (Ti).

12. A method for producing a radioisotope by irradiating a target with X-rays, comprising: provision of a system under any of the preceding paragraphs, loading the target (5) onto the target holder (5h), scanning and focusing the accelerated electron beam into the conversion unit (4) to produce X-rays, irradiation of the target with the X-rays produced in this way.

13. The method according to the previous paragraph, characterized in that the target (5) is selected from one of 226 Ra for production 225 Ace or 100 Mo for education 99m Tc, or 186 W for production 187 Re, or 134 He for education 131 I, or 68 Zn for production 67 Cu.

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