Europäisches Patentamt *EP001084733A1* (19) European Patent Office

Office européen des brevets (11) EP 1 084 733 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication: (51) Int Cl.7: A61N 5/10, G21G 4/08, 21.03.2001 Bulletin 2001/12 A61K 51/12

(21) Application number: 99118544.8

(22) Date of filing: 20.09.1999

(84) Designated Contracting States: • Menuhr, Helmut, AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU c/o AEA Technology QSA GmbH MC NL PT SE 38110 Braunschweig (DE) Designated Extension States: • Hunt, Dave, Dr., c/o AEA Technology plc AL LT LV MK RO SI Oxfordshire OX11 ORA (GB)

(71) Applicant: AEA Technology QSA GmbH (74) Representative: Teipel, Susanne, Dr. 38110 Braunschweig (DE) Schwabe, Sandmair, Marx Patentanwälte (72) Inventors: Stuntzstrasse 16 • Fritz, Eberhard, Dr., 81677 München (DE) c/o AEA Technology QSA GmbH 38110 Braunschweig (DE)

(54) source for endovascular radiation treatment in form of a wire

(57) The present invention relates to a radioactive or then activated activatable material is a β-emitter, a γ- radiation source in form of a wire comprising a matrix of emitter or x-ray emitter. The source may further com- a ductile and/or plastic bindermaterial and a radioactive prise a means for containment. and/or activatable material. Preferably the elastic bind- The radioactive radiation source of the invention is ermaterial is a metal, a metal alloy or a radiation resist- preferably used in intravascular radiation treatment e.g. ant plastic material or mixture thereof. The radioactive to treat cancer, tumours, non-malign cell growth, or scar tissue or to prevent restenosis. EP 1 084 733 A1

Printed by Jouve, 75001 PARIS (FR) 1 EP 1 084 733 A1 2

Description general has been applied advantageously, the devices available for delivery of radiation sources and the radi- [0001] The present invention relates to a radiation ation sources themselves have certain drawbacks source for use in endovascular radiation treatment with which limit their usefulness. Typically, the devices in- fission product radioactivity and/or irradiation activated 5 clude a catheter, which is directed by way of a guide wire radioactivity, which radiation source is provided in the inserted therein to the site of treatment. The catheter is form of a wire and is suitable for being delivered in a then used to internally direct the radiation source to the catheter to the selected site to be treated within the vas- site of treatment. cular system of a patient. The invention further relates [0007] One typical problem encountered with the to use of said radiation source as well as a method of 10 catheter and/or the radiation source is related to stiff- treatment. ness of the source which is essentially proportional to its length. Thus shorter radiation sources are typically BACKGROUND OF THE INVENTION used to allow them to follow the tortuous anatomy of the heart. To irradiate the entire site of the vessel to be treat- [0002] Endovascular radiation treatment is the 15 ed a so-called "stepping-treatment" is then employed, present method of choice to prevent formation of scar wherein the radiation source is moved back and forth in tissue in a blood vessel which has been injured in vari- the vessel. Since, however, exact positioning is not pos- ous ways, for example, as trauma from surgical or diag- sible in a constantly moving vessel, irradiation is not pre- nostic procedures or for treatment of cancer and tu- cisely controllable in this "stepping-treatment". Thus, mours. One area of the vascular system of particular 20 long sources are desirable which allow for one-step concern with respect to such injury relates to coronary treatment of the site in its entire length. arteries that are subjected to procedures for removing [0008] For example, US-A-5,833,593 discloses a flex- or reducing blockages due to plaque within the arteries. ible source wire which is modified at its treatment end Partial and even complete blockage of the coronary ar- to receive a radioactive element. A plug seals the un- teries by the formation of an arteriosclerotic plaque is 25 modified section of the source from the lumen of the well known and a serious medical problem. Such block- modified segment or container which contains the radi- ages may be treated using arterectomy devices which oactive element. Both ends of the source wire are mechanically remove the plaque, hot or cold lasers sealed to prevent leakage of radioactivity. which vaporise the plaque, stents which hold the artery [0009] US-A-5,683,345 discloses an apparatus and a open and other devices and procedures well known in 30 method for . The radiation source used the art. The most common of them is the percutaneous according this document consists of individual treating transluminal coronary angioplasty (PTCA), more com- elements which may be joined together to form a train monly referred to as balloon angioplasty. of treating elements by use of several lengths of high [0003] Long term success of balloon angioplasty pro- tempered spring wire to prevent the treating elements cedures is largely limited due to restenosis or re-closing 35 from becoming too spaced apart while moving through of the intraluminal passageway through the artery by for- the catheter. mation of scar tissue. Restenosis is experienced in ap- [0010] Other typical drawbacks encountered with pri- proximately 30 to 50 % of the patients within six months or art radiation sources and devices for delivering the after balloon angioplasty. Apparently, restenosis is to a same to the site to be treated are related to the duration significant extent a natural healing response to the ves- 40 of exposure, controllability of the radiation exposure sel injury caused by inflation of the angioplasty balloon. (dosage, homogeneity of treatment), the necessity to [0004] Prior attempts to inhibit restenosis have includ- conduct a "stepping-treatment", or difficulties in com- ed the use of various light therapies, chemo-therapeu- pletely and controllably retracting the radiation source tical agents, stents, arterectomy devices, hot and cold from the catheter and therefore the risk of undesirable lasers and so on. The most promising approach to inhibit 45 exposure of both the patient and any medical personal restenosis after PTCA is the use of endovascular radi- "handling" the treatment device. ation therapy, i.e. the exposure of the potential or actual [0011] To solve this problem the European patent ap- restenotic site to ionising or radioactive radiation (brach- plication No. 99 111 100.6 discloses a radiation source ytherapy). comprising a deflectable container comprising at least [0005] Another important field for radiation treatment 50 two seeds or radiation emitting elements. The deflecta- is the localised, internal radiation treatment of cancer, ble container joins the relatively short and stiff seeds to tumours and/or non-malignant cell growth. The advan- form a flexible radiation source. Similarly EP 99 111 tage of a localised radiation treatment is that the healthy 099.0 teaches to form a flexible radiation source by di- tissue surrounding said tumour is exposed to the possi- rectly linking the individual seeds together while still al- bly hazardous radiation to only a very minor extent, 55 lowing relative movement. Still both radiation sources since the radiation can be directed specifically to the tar- have the problem that they are limited with respect to get region of the tumour. miniaturisation in that they either require the container [0006] Although endovascular in or require providing the linkage between the seeds. The

2 3 EP 1 084 733 A1 4 latter radiation source further implies the risk that the vention is used in brachytherapy, preferably endovas- linkage between the seeds is interrupted during the cular brachytherapy, to treat restenosis, cancer, tu- treatment. In this case it may be difficult to retract the mours and non-malignant cell growth or scar tissues. entire radiation source out of the body to be treated. [0022] The present invention makes possible the ob- [0012] Further, in manufacture of the seeds or source 5 jects of (1) providing a radiation source having in- there is the constant demand for miniaturisation, since creased mechanical stability at sufficient flexibility of the only miniaturisation will provide sufficiently small sourc- source to follow the bends of a small vessel, of (2) pro- es to treat smaller vessels of the patient and thus to suc- viding improved security in view of leakage of radioac- cessfully allow for cancer or tumour therapy in other an- tive material in case the source is damaged or otherwise atomical sites. 10 manipulated during manufacture thereof e.g. by cutting [0013] It is the object of the invention to overcome or forming the same, of (3) providing a considerable sim- these and other drawbacks of prior art radiation sources. plification in manufacture of producing the radiation source, especially when activatable materials are used, and of (4) allowing for miniaturisation of the source in SUMMARY OF THE INVENTION 15 the sub-millimeter region.

[0014] This object is solved by the radiation source of DETAILED DESCRIPTION OF THE INVENTION the invention as disclosed in the appending claims. [0015] According to the present invention there is pro- [0023] The present invention provides a radioactive vided a radioactive radiation source in form of a wire 20 radiation source in form of a wire comprising a matrix of comprising a matrix of a ductile and/or plastic binderma- a ductile and/or plastic bindermaterial and a radioactive terial and a radioactive and/or activatable material. and/or activatable material. Said activatable material [0016] Preferably, the plastic bindermaterial has a low can be transformed into an activated material, usually capture cross-section for the method of activation of the in the form of an isotropically enriched stable , to activatable material and/or a low attenuation factor for 25 obtain the activated radiation source to be used in ther- the emitted radiation. More preferably the ductile and/or apy. plastic bindermaterial is of non-ceramic nature and com- [0024] The term "wire" as used herein is intended to prises a metal, a metal alloy or mixtures thereof or a ra- encompass any form of a radiation source having a ratio diation resistant plastic material, preferably a synthetic of its longitudinal axis (length) to its diameter of ≥ 2:1. rubber. 30 Thus, the radiation source is intended to have an elon- [0017] Preferably, the radioactive or then "activated" gated shape. Its cross-section needs not necessarily be material is selected from β-emitters, γ-emitters and/or x- circular, but may encompass any suitable cross-section ray emitting materials. More preferably the radioactive such as circular, oval, elliptic, polygonal, preferably material is a nuclear fission product or is an activatable quadratic or rectangular, hexagonal, octagonal or an ir- material activated by nuclear excitation by particles, 35 regular shape, provided this cross-section does not in- preferably , or . Most prefera- terfere with its use in a catheter and does not hamper bly the material has a maximum particle energy of β- advancing the radiation source through a catheter. The radiation of at least 500 keV, or a energy of γ- term "diameter" therefore refers to any axis normal to and/or x-ray radiation in the range of 20 to 100 keV. In the longitudinal axis. a preferred embodiment this radioactive and/or activat- 40 [0025] The term "wire" further implies the radiation ed material is selected from Sr/Y-90, Tm-170, Si/P-32, source having ductile or elastic or flexible properties to P-32, Cl-36, Zn-123, Ce-144, Tb-160, Ta-182, Tl-204, allow the radiation source to easily follow the bendings W/Rh-188, Ir-192 and Se-75 or mixtures thereof. of vessels within the body to be treated. Preferably the [0018] The radioactive and/or activatable material is plastic bindermaterial used as a matrix is therefore gen- preferably used in elemental form and/or in form of a 45 erally a non-ceramic material and comprises a metal, a compound insoluble under the prevailing compositions, metal alloy, mixtures thereof or a radiation resistant preferably in form of an oxide, fluoride, titanate, carbon- plastic material. ate, cermet or ceramic. [0026] Generally, the matrix bindermaterial is non-ce- [0019] The radiation source of the present invention ramic in nature to avoid the stiffness of this material. All generally has a ratio of length to diameter of ≥ 2:1, a 50 known metals and/or alloys which can be formed to length in the range of less than 1 to 25 mm and a diam- wires can be used as matrix material. Preferably the ma- eter in the range of 0.01 to 1 mm. trix or bindermaterial has a small capture cross section [0020] The radiation source of the invention may fur- so that the applied activation irradiation method only ac- ther comprise a means for containment which is prefer- tivates the activatable and when activated radioactivity ably a capsule or a coating. 55 emitting material to obtain the desired type of radiation. [0021] The radiation source of the invention can be Another preferred property of the matrix or bindermate- used for radiation treatment of a mammal, preferably a rial is a low attenuation factor for the emitted type of ra- human being. Preferably the radiation source of the in- diation. The latter property allows to reduce self-absorp-

3 5 EP 1 084 733 A1 6 tion of the radiation source thereby providing a more ho- particles, preferably neutrons, protons or photons. Pre- mogenous or uniform radiation field. The first property ferred activatable materials are materials activatable by reduces the likelihood of activating the bindermaterial of the above nuclear reactions. More preferably these ma- the matrix, which will therefore preferably be non-active. terials have a maximum particle energy of beta radiation [0027] The bindermaterial used as the matrix further 5 of at least 500 keV and a photon energy for γ-radiation preferably forms radioactive activation having and/or x-ray radiation between 20 keV and 100 keV. a short half-live (preferably less than one day), in cases These radioactive materials are soft emitters which are where the bindermaterial is activated by the activation most desirably used in treatment of biologic materials treatment to activate the radiation emitting element at due to their short attenuation distance, more in detail all. More preferably the bindermaterial is not activated 10 these materials are desirably due to their local ionizing during activation of the radiation emitting element. effect and thus localized biological/medical effect. [0028] Examples of the metal to be used as the ductile [0034] By choice of the above emitters, the probability bindermaterial include metals selected from the group for emission of γ-energies greater than 100 keV is pref- consisting of Al, Ag, Au, Pb, Cd, Ce, Cr, Co, Cu, Fe, Hg, erably reduced to a better tolerable degree. By use of Hf, Bi, In, Mg, Mn, Mo, Nb, Ni, Pd, Pt, Pr, Re, Rh, Sn, 15 these preferred β-emitters and/or γ-emitters and x-ray Si, Ta, Ti, Tb, Th, V, W, Y, Yb, Zn, Zr or their alloys and nuclides the necessary amount of radiation can further mixtures thereof. easily be introduced into the radiation source of the in- [0029] The ductile and/or plastic bindermaterial may vention in form of a wire even in case this wire has very also comprise a metal alloy selected from the group con- small dimensions in the sub-millimeter region. sisting of aluminum alloys such as Al/Mg, Al/Cu, Al/Cu/ 20 [0035] In a preferred embodiment the radioactive (fis- Mg, Al/Mg/Si, Al/Cr, Tinal alloy BB, copper alloys such sion product) or activated material is selected from the as brass, bronzes, iron alloys such as Fe/Cr, Fe/Ni, Fe/ group consisting of Sr/Y-90, Tm-170, Si/P-32, P-32, Cl- Cr/Ni, Fe/Cr/Al, nickel alloys such as Ni/Ti, Ni/Cr, nitinol, 36, Zn-123, Ce-144, Tb-160, Ta-182, Tl-204, and W/Rh- platinum alloys, titanium alloys such as Ti/Al, Ti/Al/V, Ti/ 188, Ir-192 and Se-75 or mixtures thereof. More prefer- Mo, Woods alloy, Inconel, and amalgams. 25 ably, the activatable material comprises Tm-170. [0030] More preferably, the bindermaterial is one or a [0036] In all circumstances the radioactive or activat- mixture of materials selected from the group Ag, Cu, Al, able/activated material differs from the bindermaterial Ti, Ni, the amalgams and Woods alloy. Most preferably used as the matrix. Depending on the type of material the plastic bindermaterial is aluminum or an alloy there- used, the radioactive and/or activatable material is used of. 30 in an elemental form and/or in form of a compound in- [0031] The plastic bindermaterial may also comprise soluble under the prevailing conditions, preferably in a radiation resistant plastic material selected from syn- form of an oxide, fluoride, titanate, carbonate, cermet or thetic rubbers such as polyethylene, polypropylene, co- ceramic. polymers thereof, silicon rubber or (meth)acrylics or [0037] For producing the radiation source of the in- mixtures thereof. The plastic bindermaterial may also 35 vention the radioactive and/or activatable material is comprise a mixture of such radiation resistant plastic provided in fine divided form, preferably in form of a pow- material(s) with one or more of the above metals or met- der or granules and is mixed with the bindermaterial of al alloys. The matrix material may be modified by use of the matrix. magnetic or other magnetisable materials to provide [0038] After mixing the wire is formed by conventional magnetic radiation sources which can e.g. magnetically 40 techniques to the desired dimensions, e.g. by rolling, be linked to a transfer wire used to advance and retract casting, forging etc. In case an activatable material is the radiation source within a catheter lumen. used, the production process to make the radiation [0032] The radiation emitting element or of the invention is simplified as all the fabrication material can be a β-emitter, γ-emitter and/or an x-ray steps to make the wire can be done using the inactive emitting . The radiation emitter can be a fission 45 isotope. Namely, there are no radiological dangers to product or can be an irradiation activated activatable ra- personnel during manufacture and use of the inactive diation emitter. The term "activatable material" means a isotope removes the requirement for complex equip- non-radioactive material, which can be transformed into ment and handling procedures e.g. in enclosed boxes, a radioactive emitter e.g. by particle irradiation. The term necessary for the manufacture and processing of radi- "activated material" refers to the material obtained from 50 oactive materials. said activation. [0039] The radioactive radiation source of the present [0033] Activatable materials are preferred, since the invention may further comprise a means for contain- radiation source of the invention can be formed by rou- ment. This means for containment is preferably a sealed tine steps without requiring appropriate equipment to capsule preferably in tubular form to contain the wire shield the manufacturing personal and equipment from 55 comprising the matrix and the radioactive material. In radiation. The final radiation source is then activated for another embodiment the means for containment may be example by excitation of an activatable material or nu- a coating which prevents leakage of radioactivity from cleus by bombardment with charged and uncharged the wire.

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[0040] In case of a capsule this is preferably provided the scope of protection. in form of a tube sealed on both ends. The capsule may be made from metals or alloys such as , preferably Example 1 Thulium170 wire stainless steel, V, Ti, Ni, Au, Pt and mixtures and alloys thereof. In case of a coating this may comprise Ni, Cr, 5 [0047] The present example refers to a small thulium Co, Au, Pt, C or mixtures thereof. Such coating may oxide/aluminium wire as the radiation source. 169 have a thickness of several nm to several 10 µm to pre- [0048] In the first step naturally occurring Tm 2O3 vent leakage of activity. A coating may further be made in form of small particles is mixed with aluminium pow- from radiation resistant plastic materials or mixtures der to obtain an evenly distributed mixture of the two thereof with one of the above materials, if desired. 10 materials. The mixing ration of thulium oxide to alumin- [0041] In general the means for containment is made ium is 15 wt% to 85 wt%. from a material which has like the bindermaterial of the [0049] After mixing the material is pressed in and matrix a small capture cross section for the method used formed according to known procedures into a small wire to activate the activatable material and/or has a low at- of approximately 0.3 mm diameter and 2.5 mm length. tenuation factor for the emitted radiation. Preferably it 15 The wire is fitted into a thin welded pure vanadium cap- forms radioactive or activation nuclides having sule which capsule is subsequently sealed to encapsu- a short half-life (preferably less than one day), in case late the thulium oxide/aluminium wire insert. the radiation source is activated after manufacture, if it [0050] The entire capsule is then placed on a nuclear is activated at all. reactor to undergo activation. This creates ac- [0042] The amount of radioactivity provided by the ra- 20 tive Tm170 from Tm169 and the fabrication process of the diation source of the present invention is typically in the source is complete, and a radiation source of 0.4 mm range of up to 25,000 mCi per centimeter of vessel to outer diameter and 3.0 mm length can be obtained. be treated, depending on the radioactive and/or activat- [0051] In case pure vanadium is used as the encap- ed material used. The emitted radiation should be suf- sulating material, this capsule like the aluminium as the ficient to deliver a desired dosage from 100 to about 25 bindermaterial of the matrix develops no long-living ra- 10.000 rads, preferably about 700 to 5.000 rads in about dioactive isotopes during neutron bombardment. There- 2 to 10 minutes to the tissue to be treated. fore, both the outer encapsulation and the wire binder- [0043] The radiation source of the invention prefera- matrix remain non-radioactive. bly has a ratio of length to diameter in the range of ≥ 2: 1, preferably 5:1 to 25:1, more preferably 8:1 to 17:1. It 30 Example 2 Strontium90 wire further may have a length in the range of less than 1 to 25 mm, preferably 1 to 15 mm, more preferably 2.0 to [0052] The second example refers to a small stron- 10 mm and most preferably 2.5 to 5 mm and may also tium fluoride/aluminium wire. 90 have a diameter in the range of 0.01 to 1 mm, preferably [0053] In this case radioactive Sr F2 in form of a pow- 0.1 to 0.8 mm, more preferably 0.1 to 0.5 mm and most 35 der is mixed with aluminium powder in an enclosed box. preferably 0.2 to 0.3 mm. The mixing ratio is 10 wt% SrF2 to 90 wt% Al. The mix- [0044] The radiation source of the invention can be ture is then pressed and processed to a wire according used in intravascular radiation treatment of a mammal, to known proceedings, although all these proceedings preferably of a human being. More precisely the radia- have to be carried out under containment conditions to tion source of the invention can be used to treat cancer, 40 prevent irradiation of personnel and equipment. tumours and other non-malignant cell growth, scar tis- [0054] The finally obtained wire has dimensions of 0.5 sue and most preferably to prevent restenosis after bal- mm diameter and 2,5 mm length. loon angioplasty. [0055] According to another embodiment the alumin- [0045] The radiation source of the invention can be ium matrix was replaced by a copper matrix. In this case, used with any known device or apparatus to position the 45 a wire of 0.3 mm diameter and 2.3 mm length was ob- same within the body to be treated. Such apparatus typ- tained, which was encapsulated in a sealed tube 0.4 mm ically comprises a catheter to securely advance the ra- in diameter and 2.5 mm in length. diation source within the vessels of the body to be treat- [0056] Although being described with respect to the ed. The radiation source of the invention can be used preferred embodiments above, this description is not to as such or can be used as a seed to form a train of ra- 50 be considered limiting in that the skilled worker will ap- diation emitting elements or seeds. In a preferred em- preciate the possibility of several variations of the inven- bodiment at least two radiation sources of the present tion as defined in the appending claims, without depart- invention are used as seeds to form a train of radiation ing from its scope. element as disclosed in the European patent applica- tions 99 111 100.6 and 99 111 099.0. 55 [0046] The invention will now be further disclosed by Claims way of specific examples. These examples are given for purpose of illustration only and are not intended to limit 1. Radioactive radiation source in form of a wire com-

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prising a matrix of a ductile and/or plastic binderma- 188, Ir-192 and Se-75 and mixtures thereof. trial and a radioactive and/or activatable material. 11. Radiation source of claims 7 to 10, wherein the ra- 2. Radiation source of claim 1, wherein the ductile dioactive and/or activated material is used in ele- and/or plastic bindermaterial comprises a metal, a 5 mental form and/or in form of an insoluble com- metal alloy or a radiation resistant plastic material, pound thereof, preferably in form of an oxide, fluo- or mixtures thereof. ride, titanate, carbonate, cermet or a ceramic.

3. Radiation source of claims 1 or 2, wherein the bind- 12. Radiation source of one of the preceding claims ermaterial has a low capture cross-section for the 10 having a ratio of length to diameter in the range of method of activation of the activatable material and/ ≥ 2:1, preferably 5:1 to 25:1, more preferably 8:1 to or a low attenuation-factor for the emitted radiation. 17:1.

4. Radiation source of claim 2 or 3, wherein the ductile 13. Radiation source of one of the preceding claims bindermaterial is selected from the group consisting 15 having a length in the range of less than 1 to 25 mm, of Al, Ag, Au, Pb, Cd, Ce, Cr, Co, Cu, Fe, Hg, Hf, preferably 1 to 15 mm, more preferably 2.0 to 10 Bi, In, Mg, Mn, Mo, Nb, Ni, Pd, Pt, Pr, Re, Rh, Sn, mm and most preferably 2.5 to 5 mm. Si, Ta, Ti, Tb, Th, V, W, Y, Yb, Zn, Zr or their alloys and mixtures thereof, preferably Ag, Cu, Al, Ti, Ni, 14. Radiation source of one of the preceding claims amalgams and Woods alloy. 20 having a diameter in the range of 0.01 to 1 mm, pref- erably 0.1 to 0.8 mm, more preferably 0.1 to 0.5 mm 5. Radiation source of claim 4, wherein the ductile and most preferably 0.2 to 0.3 mm. and/or plastic binder material comprises a metal al- loy selected from the group consisting of aluminium 15. Radiation source of claim 1 further comprising a alloys such as Al/Mg, Al/Cu, Al/Cu/Mg, Al/Mg/Si, Al/ 25 means for containment. Cr, Tinal alloy BB, copper alloys such as brass, bronzes, iron alloys such as Fe/Cr, Fe/Ni, Fe/Cr/Ni, 16. Radiation source of claim 15, wherein the means Fe/Cr/Al, nickel alloys such as Ni/Ti, Ni/Cr, nitinol, for containment is a capsule or a coating. platinum alloys, titanium alloys such as Ti/Al, Ti/Al/ V, Ti/Mo, Woods alloy, Inconel, and amalgams. 30 17. Radiation source of claims 15 or 16, wherein the means for containment comprises a metal, prefer- 6. Radiation source of claims 1 and 2, wherein the ably selected from Fe, V, Ti, Ni, Au, Pt, Cr, Co or plastic bindermaterial comprises a radiation resist- their alloys, or C or a radiation resistant plastic ma- ant plastic material selected from synthetic rubbers terial, and their mixtures. such as polyethylene, polypropylene, copolymers 35 thereof, silicon rubber or (meth) acrylics or mixtures 18. Use of a radiation source according to one of claims thereof. 1 to 17 for radiation treatment of a mammal, prefer- ably a human being. 7. Radiation source of claims 1 to 6, wherein the radi- oactive and/or activated material is selected from β- 40 19. Use of claim 18 in brachytherapy, preferably en- emitters, γ-emitters and/or x-ray emitting materials. dovascular brachytherapy.

8. Radiation source of claim 7 wherein the radioactive 20. Use of claim 18 for treatment of cancer, tumours and/or activated material is a nuclear fission prod- and non-malign cell growth or scar tissue. uct or is activated by nuclear excitation of an acti- 45 vatable material by particles, preferably neutrons, protons or photons.

9. Radiation source of claim 8 wherein the material has a maximum particle energy of β-radiation 50 (Eβmax) of at least 500 keV and/or a photon energy of γ- and/or x-ray radiation in the range of 20 to 100 keV.

10. Radiation source of claim 7, wherein the radioactive 55 or activatable material is selected from the group consisting of Sr/Y-90, Tm-170, Si/P-32, P-32, Cl-36, Zn-123, Ce-144, Tb-160, Ta-182, Tl-204, W/Rh-

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