TECHNICAL FIELD

The invention relates to the production method of Pr-142 radioisotope source in line- and disc-source forms from monoisotopic Pr-141 praseodymium element, which is a rare-earth element (REE) through a research reactor neutron flux, suitable for use in brachytherapy applications in cancer treatment.

BACKGROUND

Brachytherapy is defined as the placement of small radioactive sources into the body to irradiate cancer cells directly. The main purpose of brachytherapy is to provide high doses of radiotherapy (radiation therapy) to the tumor region by protecting the surrounding normal healthy tissues from radiation. Brachytherapy is performed by placing radioactive sources in a body cavity or inserting in the relevant organ with the help of special applicators in contact with the tissue to be irradiated.

Different types of brachytherapy applications are currently applied in cancer treatment with the help of specific radioisotope sources with beta and gamma emitter. The mentioned types of brachytherapy can be listed as intracavitary, interstitial, superficial, intraluminal, intraoperative, and intravascular. Beta and gamma emitter radioisotope sources used in brachytherapy can be listed as Cs-137, lr-192, Pd-103, Sr-90/Y-90, Ru-106/Rh-106, 1-125, Co-60, Au-198, and Yb-168. The dose rates from the mentioned radioisotope sources are administered as low-dose rate (LDR: 0.4-2 Gy/h), medium-dose rate (MDR: 2-12Gy/h), and high-dose rate (HDR: >12Gy/h).

The radioisotope source to be used in brachytherapy is applied to the patient by direct application, pre-loading and after-loading source applicators, or by remotely loaded mechanical source application techniques. Currently, some radioisotope sources such as I- 125, lr-192, Co-60, Cs-137, Au-198, Yb-168, and Pd-103 are used in brachytherapy for temporary and permanent treatment. In permanent seed implants in prostate treatment, which is one of the cancer types in which brachytherapy is applied, 1-125 with an average energy of 28 keV or Pd-103 radioisotope source with 20.5 keV is selected. However, in temporary seed implants in prostate treatment, the relatively long-lived lr-192 radioisotope source is selected. 1-125 and Pd-103 radioisotope source plates with a half-life of 59.388 (28) days and a half-life of 16.964 (10) days are commonly used in ophthalmic (eye) cancers, which are among the cancer types in which brachytherapy is frequently applied, from intraocular tumors to uveal melanoma and retinoblastomas.

The treatment periods using the radioisotope sources mentioned in the state- of-the art take a very long time. In addition, in the said brachytherapy applications, undue doses can be given to the patient due to the ranges of photons. This causes photons to penetrate the tumor cell and cause to irradiate damage healthy tissues, and thus resulting in damage of them. For instance, when Cs-137 gamma-emitting radioisotope source (661.6 keV; gamma emission probability 85.1%), which has a half-life of 30.1 years, is used as a high-dose rate (HDR), some basic limitations arise. One is that Cs-137 gamma emitter used is the relatively long range of photons emitted by the radioisotope source. The long ranged photons causes unnecessary extra doses by exceeding the malignant prostate tumor and irradiating other healthy tissues. The dose conversion coefficient of Cs-137 gamma-emitting radioisotope source is D _v =0.531 MeV/(Bq-s) and is relatively high. The average beta energy of the betas emitted by Cs-137 is 0.187 MeV (intensity: 100%) and the corresponding average beta dose conversion coefficient is Dp=0.187 MeV/(Bq-s) and is quite low. This causes the patient to be exposed to a large amount of gamma dose in the treatment period.

Similarly, the average beta energy of the high-dose rate lr-192 radioisotope source used in brachytherapy is 0.179 MeV (intensity: 95.1 %) and the corresponding average beta dose conversion coefficient is Dp=0.170 MeV/(Bq-s). The said radioisotope source gives a lower dose when loaded into the prostate gland. This causes the treatment duration to be quite long. In addition, due to the longer duration of treatment, healthy tissues other than the target tissue are exposed to gamma doses for a longer period.

All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to the production method of Pr-142 radioisotope source in line- and disc- source forms in order to eliminate the above-mentioned disadvantages and to bring new advantages to the related technical field.

The aim of the present invention is to develop the production method of Pr-142 radioisotope source for use as a radioisotope source in prostate interstitial brachytherapy and ophthalmic(eye) episcleral brachytherapy applications.

The aim of the present invention is to develop the production method of the beta emitter (99.9836% beta decay branch) Pr-142 radioisotope source.

The aim of the present invention is to develop the production method of Pr-142 radioisotope source, which shortens the cancer treatment time achieved with conventional radioisotope sources currently used in brachytherapy by approximately 4.5-5 times and minimizes the undue dose given to risky organs adjacent to the target organ. In this way, healthy tissues are preserved more during cancer treatment.

The aim of the present invention is to improve the production method of Pr-142 radioisotope source in line- and disc- source forms with a shorter average beta range in tissue and a relatively shorter life.

Another object of the present invention is to improve the production method of Pr-142 radioisotope source, which can be used as a radioisotope source in brachytherapy applications for the treatment of gynecological cancers such as the cervix and the uterus (endometrium), head, and neck cancers such as the nasopharynx, and skin and breast cancers.

Another object of the present invention is to develop the production method of Pr-142 radioisotope source with relatively high dose efficacy when compared to that of either Cs-137 or lr-192 gamma sources, which enables the desired level of treatment dose to be given more effectively to the malignant tumor region.

Another object of the present invention is to improve the production method of a new brachytherapy-oriented Pr-142 radioisotope source that offers the advantage of dose giving to the selected target organ as a medium-dose rate(MDR) or high-dose rate (HDR) radioisotope source. Another object of the present invention is to improve the production method of the Pr-142 radioisotope source, which can be reproduced in the reactor by irradiation after a certain time (e.g. about 30 days) has elapsed from the same target material.

Another object of the present invention is to improve the production method of the Pr-142 radioisotope source, which has the desired dosimetric properties (such as dose rate, and dose homogeneity) at the desired level when elapsed 10-14 hours after its production.

In order to achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to the production method of Pr-142 radioisotope source in line-source and/or disc-source forms suitable for use in brachytherapy applications in cancer treatment. The novelty of the invention is that it comprises the steps of preparing the praseodymium metallic form or praseodymium oxide in at least one form; irradiating for a first time in approximately 2.5x10 ¹² n/cm ² /s ^_ thermal neutron flux in one reactor and producing Pr-142 radioisotope source in MBq levels from net amounts of Pr element.

A possible embodiment of the invention is characterized in that it comprises the step of filling at least one capsule or placing it in at least one source applicator having a wall thickness through which at least 90% of the betas emitted from the Pr-142 radioisotope source can transmit for use it in medium-dose rate (MDR) and high-dose rate (HDR) brachytherapy applications.

A possible embodiment of the invention is characterized in that it comprises the step of irradiating it in the reactor for a certain period in approximately 2.5x10 ¹² n/cm ² /s' thermal neutron flux after the said Pr-142 radioisotope source is completely decayed and making it reusable.

Another possible embodiment of the invention is characterized in that for producing the Pr- 142 radioisotope source in the solid line form, it comprises the steps of filling at least one praseodymium oxide form into at least one sheath (capsule); sealing this sheath; inserting the filled sheath into at least one magazine, also called a line-source irradiation magazine, and sealing it with at least one sealing material such as Teflon; placing the said magazine in at least one irradiation tube having a cylindrical form, preferably made of Teflon/HDPE material, having a bare standard Au-AI foil, preferably 12.7 mm in diameter, and a standard Au-AI foil in a 0.5-1 mm thick Cd sheath outside; irradiating said irradiation tube by placing it in at least one Al-irradiation tube in the reactor and producing at least one Pr-142 radioactive source in solid line-form within its capsule.

Another possible embodiment of the invention is characterized in that it comprises the step of filling at least one praseodymium oxide powder form in the amount of 95-120 mg and at least 99.9% purity into at least one sheath of thin-aluminum or plastic with one end closed.

Another possible embodiment of the invention is characterized in that it comprises the step of filling at least one praseodymium glass microspheres powder form containing an average of 40% Pr into at least one thin sheath.

Another possible embodiment of the invention is characterized in that it comprises the step of placing the rod in the form of at least one praseodymium glass having a thickness in the range of 0.2-0.3 mm and a maximum length of 30 mm into at least one sheath.

Another possible embodiment of the invention is characterized in that it comprises the steps of filling the said praseodymium oxide powder form or at least one praseodymium glass microsphere powder form into a thin sheath with one end closed, filling the window wall thickness with a capillary plastic equivalent to 25-50 pm Aluminum thickness or 18-50 pm mylar thickness or with a powder filling mechanism specific to a gold tube with <25-50 pm wall thickness and sealing the "open end" part of the tube automatically.

Another possible embodiment of the invention is characterized in that it comprises the steps of carefully filling the powder or microspheres powder form containing the stable P-141 target isotope into at least one thin capillary gold or aluminum tube and plugging it with 25 pm Al foil and sealing the "open end" part in an appropriate way and sending it to the reactor for irradiation as it is for filling the said praseodymium oxide powder form or at least one praseodymium glass microspheres powder form into a thin sheath with one end closed.

Another possible embodiment of the invention is characterized in that for producing Pr-142 radioisotope source in solid disc form, it comprises the step of homogeneous mixing of the powder form of the praseodymium oxide in the amount of 205-260 mg containing the praseodymium element in the amount of 175-210 mg on average with at least one cellulose- binding material at the rate of 30%; pressing the mixture at a pressure of approximately 9-10 tons/cm ² in the range of 1 .02-1 .20 mm thickness with the help of at least one pressing device into the form of a disc; placing in a pre-made 25 pm-AI window HDPE(high density polyethylene) source applicator, the back of which is supported by a suitable plastic or cotton; irradiating the HDPE source applicator for a third time with a neutron flux of approximately 2.5x10 ¹² n/cm ² /s ^_ by placing it in the Al-irradiation tube in the mentioned reactor and producing Pr-142 radioisotope source in disc form.

Another possible embodiment of the invention is characterized in that for producing Pr-142 radioisotope source in solid disc form, it comprises the steps of cutting the metallic praseodymium foil of at least 99% purity circularly with a diameter of 13 mm with at least one disc cutter (puncher); adhering the cut foil to the substrate and placing it in a pre-made 25 pm Al-window HDPE source applicator with 14 mm diameter; irradiating the HDPE source applicator for a third time by placing it in the Al-irradiation tube in the mentioned reactor with a neutron flux of approximately 2.5x10 ¹² n/cm ² /s' and producing Pr-142 radioisotope source in the form of a disc.

Another possible embodiment of the invention is characterized in that it comprises the steps of bending the 13 mm diameter, at least 99% purity metallic praseodymium foil by giving a concave radius of curvature (for example, 84.72mm, 42.69mm, 28.32mm, 22.00 mm, 15.40mm or 7.80mm, respectively) to give a first value (for example, 0.25mm or 0.5mm or 0.75mm or 1 mm or 1.5mm or 2mm) of deflection; irradiating the neutron flux into an Al- irradiation tube in the mentioned reactor for a third time so that the neutron flux is about 2.5x10 ¹² n/cm ² /s' and producing Pr-142 radioisotope in the form of a concave disc. In this way, it is ensured that metallic praseodymium foil is a more suitable superficial plaque source for ophthalmic (eye) brachytherapy.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows a representative side view of the metallic praseodymium foil used in the radioisotope source production method of the invention with a value of 0.25 mm deflection and 84.72 mm radius of curvature.

Figure 2 shows a representative side view of the metallic praseodymium foil used in the radioisotope source production method of the invention with a value of 0.5 mm deflection and 42.69 mm radius of curvature. Figure 3 shows a representative side view of the metallic praseodymium foil with a deflection value of 0.75 mm and a radius of curvature of 28.82 mm used in the radioisotope source production method of the invention.

Figure 4 shows a representative side view of the metallic praseodymium foil with a deflection of 1.0 mm and a radius of curvature of 22.00 mm used in the radioisotope source production method of the invention.

Figure 5 shows a representative side view of the metallic praseodymium foil used in the radioisotope source production method of the invention with a 1.5 mm deflection and 15.40 mm radius of curvature.

Figure 6 shows a representative side view of the metallic praseodymium foil used in the radioisotope source production method, which is the subject of the invention, with a 2mm deflection and 7.80mm radius of curvature.

DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, the subject of the invention is explained with examples that do not have any limiting effect only for a better understanding of the subject.

The invention relates to the production method of Pr-142 radioisotope source in line- and/or disc- source form suitable for use in brachytherapy applications in cancer treatment. The called production method includes the steps of preparing the praseodymium metallic form or praseodymium oxide (PrsOs) in at least one form, irradiating it in the reactor at about 2.5x10 ¹² n/cm ² /s' thermal neutron flux for a first time and producing Pr-142 radioisotope beta source at MBq levels from net praseodymium (Pr) amounts. The first period is preferably in the period of 20-30 minutes.

In a preferred embodiment of the invention, the described production method comprises the step of filling it into at least one capsule having a wall thickness through which at least 90% of the betas emitted from the Pr-142 radioisotope source can pass through or placing it in at least one source applicator for use it in medium-dose rate (MDR) and high-dose rate (HDR) brachytherapy applications. The produced Pr-142 radioisotope source becomes available for brachytherapy applications within 10 hours at the latest from production. Pr-142 radioisotope source can be used with a dose optimization/dose program (Gy/fraction) suitable for brachytherapy 10-14 hours after its production Pr-142 radioisotope is completely depleted after its decay of 8 days from source production. At the end of this period, the residue dose effect remains minimal. The residue activity can vary if the recommended analytical impurity (99.9%) of the target material is not applied.

In a preferred embodiment of the invention, the said production method comprises the step of irradiating and reusable in the reactor for a first time at about 2.5x10 ¹² n/cm ² /s ^_ thermal neutron flux after the mentioned Pr-142 radioisotope source is completely depleted.

The forms of the mentioned praseodymium oxide (PrsOs) are prepared by cutting the smallsized (<13mm in diameter) disc and thin metallic praseodymium foil (wherein the praseodymium foil contains at least 99.9% Pr element) of the praseodymium oxide powder form containing 84.5% Pr element or solid line- source from the praseodymium glass microsphere and metallic praseodymium foil form. In order to be suitable for episcleral plaque brachytherapy in ophthalmic eye cancer treatments, preferably said metallic foil with a diameter of 13 mm can be given a concave to deflect at a first value (said first value preferably being in the range of 0.25-2 mm with an increase of 0.25 mm).

The particle size of the said praseodymium glass microsphere is preferably in the range of 10-35 pm.

Praseodymium (Pr-141) is a rare earth element with atomic number Z=59, atomic weight M= 140.90765 g/mol, periodic table F block, group 3, and 6th period, with a metallic density of 6.64-6.77 g/cm ³ , monoisotopic (100% Pr-141).

In order for said Pr-142 beta sources to have a usable level of activity for brachytherapy, the minimum thermal neutron flux of the relevant reactor is preferably in the order of (<|)th)~10 ¹² n/cm ² /s' and the epithelial neutron flux is preferably in the order of (<|>epi)~10 ¹¹ n/cm ² /s'.

In a preferred embodiment of the invention, for producing Pr-142 radioisotope source in solid line-source form, the described production method comprises the following steps: filling at least one praseodymium oxide form into at least one suitable sheath; sealing the mentioned sheath; - inserting the filled sheath into at least one source holding magazine, also called a line-source irradiation magazine, and sealing it with at least one sealing material such as Teflon;

- placing the source holding magazine in at least one irradiation tube having a cylindrical form, preferably made of Teflon/HDPE material, having a bare standard Au-AI foil, preferably 12.7 mm in diameter, and a standard Au-AI foil in a 1 mm Cd sheath outside;

- irradiating said irradiation tube by placing it in at least one Al-irradiation tube in the reactor and producing at least one Pr-142 radioactive source in solid line-source form.

Since the irradiation tube is kept in the reactor site for a second period to decay the residue activity after irradiation, the high radiation dose due to 1778.97 keV gamma radiation emitted from ²⁸ AI (2.2414 min) residue activity in the Al-sheath and Al-irradiation tube is ensured to be kept waiting before loading to the transport vehicle due to radiation protection measures.

In a preferred embodiment of the invention, the said production method comprises the following steps:

- filling at least one praseodymium oxide (PrsOs) powder form in the amount of 95-120 mg (preferably, on average, 100 mg in weight ) and with a purity of at least 99.9% into at least one sheath of thin aluminum or plastic closed at one end; or

- filling at least one praseodymium glass micro urea powder form with an average Pr of 40% in weight (preferably with diameters of 10-35 pm) in at least one thin sheath; or

- placing at least one Pr glass rod with a thickness in the range of 0.2-0.3 mm and a maximum length of 30 mm in at least one outer sheath.

In a preferred embodiment of the invention, the described production method comprises the steps of filling the said praseodymium oxide (PrsOs) powder form or at least one praseodymium glass microsphere powder form into a thin sheath with one end closed, filling the window wall thickness with a capillary plastic equivalent to 25-50 pm Aluminum thickness or 18-50 pm Mylar thickness or with a powder filling mechanism specific to a golden tube with a wall thickness of < 25-50 pm and sealing the "open end" part of the tube automatically. In a preferred embodiment of the invention, the described production method comprises the steps of carefully filling the powder or microsphere powder form containing the stable P-141 target isotope into a thin capillary glass, gold, or aluminum tube (with a diameter of 1 .75 mm; maximum wall thickness of 0.2 mm and a maximum length of 50 mm) and plugging it with 25 pm Al foil and sealing the "open end" part of it in a suitable way and sending it to the reactor for irradiation as it is, in order to fill the powder form of the said praseodymium oxide (PrsOs) or at least one praseodymium glass microsphere powder form into a thin sheath with one end closed.

In a preferred embodiment of the invention, the said production method comprises the step of wrapping said irradiation tube preferably with parafilm and fine stretch nylon to prevent possible contamination.

In a preferred embodiment of the invention, the described production method comprises the step of keeping the irradiation tube at the reactor site for at least a second time period (preferably between 25-40 minutes) to decay the residue activity(e.g. ²⁸ AI radioisotope) after irradiation.

In a preferred embodiment of the invention, the described production method includes the step of handling the produced Pr-142 radioactive source from the reactor and sending it to the application area.

The praseodymium oxide used in the described production method should be sufficient analytical grade impurity and the weight percentage of Na and Zn elements among the impurity elements should be below 0.01%.

The activities of the Pr-142 radioisotope solid line sources in the form of produced glass rods measured with HPGe detector and the waste ²⁴ Na activity values (2nd irradiation session in the presently used reactor) arising from the glass structure are given in Table 1 below.

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Table - 1

The activities of the Pr-142 radioisotope solid line- sources in the form of produced glass rods measured with an HPGe detector and the waste ²⁴ Na activity values arising from the glass structure (3rd irradiation session in the presently used reactor) are given in Table 2 below.

Table - 2

The activities of microspheres Pr-142 radioisotope sources in the form of produced glass rods measured with HPGe detector and the activity values of residue ²⁴ Na arising from glass structure (3rd irradiation session in the presently used reactor) are given in Table-3 below.

Table - 3

Before use Pr-142 brachytherapy source, the Pr-142 radioisotope source activity produced by the described production method can be measured by using either a dose calibrator or a gamma spectrometer with LaBr3:Ce scintillation or HPGe semiconductor detector. For the mentioned gamma spectrometric measurements, the Al-Au foils placed in said irradiation tube are separated and stored in a lead box(domus).

For the dose homogeneity and/or dose strength (mGy/h) in air of the Pr-142 radioisotope source in solid line-source form produced by the described production method, each Pr-142 radioisotope source in solid line-source form on the EBT3 film piece is irradiated for a short time and then measured by Radiochromic Film Dosimetry (RFD) technique. In practice, the Pr-142 solid line source strengths are measured in real-time by either a suitable Plastic Scintillator Dosimetry (PSD) technique or a suitable ion chamber based dosimeter in terms of dose rate units such as mGy/h.

For all dosimetric tests required for the application of brachytherapy to the Pr-142 radioisotope in solid line-source form produced by the described production method, cumulative dose determination, and homogeneity test is performed by means of radiochromic film technique with use of EBT3 film, which will be scanned by a three channel (RGB) flatbed scanner and for instantaneous dose rate measurement in accordance with the radiotherapy dose range, measurement is made with a dosimeter system with thin cylindrical ion chamber or plastic scintillator detector. According to any of the NCS 14, AAPTG 60, or ICRU72 brachytherapy protocols of the Pr- 142 radioisotope source in solid line- source form produced by the said production method, the minimum dose homogeneity in all source effective lengths (ASL) is tested to be at least 90% and above.

In a preferred embodiment of the invention, said production method comprises the steps of homogeneously mixing the powder form of praseodymium oxide (at least 99.99% purity) in the amount of 205-260 mg containing an average of 175-210 mg mass of praseodymium element in order to produce the Pr-142 radioisotope source in the form of a solid disc with at least preferably 13 mm (0.5 inch) in diameter in the solid form of a disc-source that we need to use 30% cellulose binding material, the PrsOs mixture by pressing about 9-10 tons/cm ² with the help of at least one press device made of steel material, resulting in the range of 1.02-1.20 mm thick pellet, placing in a pre-made 25 pm-AI window HDPE source applicator, the back of which is supported by a suitable plastic or cotton, irradiating the HDPE source applicator for a third time (preferably in the period of 20-30 minutes) with a neutron flux of approximately 2.5x10 ¹² n/cm ² /s' by placing it in the Al-irradiation tube in the mentioned reactor and producing Pr-142 radioisotope source in disc form.

In a preferred embodiment of the invention, for producing Pr-142 radioisotope source in solid line-source form, the described production method comprises the steps of cutting the metallic praseodymium foil of at least 99% purity, preferably 0.5 mm thick, with at least one disc cutter (puncher), preferably 13 mm in diameter; adhering the cut foil to the substrate and placing it in a pre-made 25 pm Al-window HDPE source applicator with 14 mm diameter; irradiating the HDPE source applicator for a third time (preferably in the range of the said third time, 20-30 min) by placing it in the Al-irradiation tube in the mentioned reactor with a neutron flux of approximately 2.5x10 ¹² n/cm ² /s ^_ and producing Pr-142 radioisotope source in the form of a disc.

Here, it is determined that each praseodymium foil formed by cutting with a puncher is metallic foil containing a maximum of 440 mg Pr.

In a preferred embodiment of the invention, the said production method comprises the step of pre-discharging the metallic praseodymium foil to make it concave so that the Pr-142 radioisotope source in the form of the said solid disc is suitable for use in ophthalmic eye cancer brachytherapy. For ophthalmic eye brachytherapy, the metallic praseodymium foil is bended at a given a radius of curvature (R) of 84.72mm, 42.69mm, 28.82mm, 22.00mm, 15.40mm and 7.80mm, respectively, with an increment of 0.25 in the range of 0.25mm to 2mm, that is, with respect to the deflection value determined as 0.25mm, 0.5mm, 0.75mm, 1.0mm, 1.5mm or 2mm. Example views of the metallic praseodymium foil with the radius of curvature (R) values are given in Figures 1 -6.

In a preferred embodiment of the invention, the described production method comprises the step of wrapping at least one bare standard Au-AI foil (preferably 12.7 mm in diameter) on the said HDPE applicator, which is used to measure the neutron flux during irradiation in the said reactor, and bare Au-AI foil in a 1 mm Cd-box sheath on the opposite outer surface of another HDPE applicator that does not correspond to its window.

In the mentioned reactor, four HDPE source applicators can be irradiated simultaneously. The outer surface of said HDPE source applicators is also wrapped with parafilm and thin stretch nylon to prevent possible contamination.

In a preferred embodiment of the invention, the said production method comprises the step of keeping the aluminum tube sheath removed from at least one irradiation channel of the reactor at the reactor site after irradiation for at least a fourth time (preferably the said fourth time, in the period of 25-40 minutes) to decay the residue ²⁸ AI activity.

In a preferred embodiment of the invention, the described production method includes the step of handling the Pr-142 radioisotope source from the mentioned reactor and sending it to the application area in the form of a disc.

Before using the Pr-142 radioisotope source in the form of a solid disc produced by the described production method, its activity is determined roughly in a dose calibrator, or its activity and radionuclide impurity are determined more precisely in the LaBr3:Ce scintillation detector gamma spectrometer. For the said gamma spectrometric measurements, the Al-Au foils in described irradiation tube are separated and stored in a suitable lead box(domus)

The source strength (mGy/h) of the Pr-142 radioisotope source in the form of a solid disc produced by the described production method is irradiated for a short time on the EBT3 film piece for determination of its source effective radius and dose homogeneities, and then EBT3 film pieces are measured by means of RFD and PSD technique. According to the NCS 14 or ICRU72 brachytherapy protocol, the Pr-142 radioisotope source in the form of a solid disc produced by the described production method is tested in the range of 0.80xR50 radii and verified the dose homogeneity that should be meet within the minimum 78-80%.

The radionuclide impurity of the Pr-142 radioisotope source in solid line-source form produced by the described production methods is tested with use of an HPGe detector or LaBr3:Ce detector based-gamma spectrometer for at least one of a group of sources prepared from the same target material and contained in the same sheath material.

The activities of the produced Pr-142 radioisotope sources in the form of solid discs measured with HPGe and LaBr3:Ce detectors (2nd irradiation session in the presently used reactor) are given in Table-4 below.

Table - 4

The activities (3rd irradiation session in the presently used reactor) of Pr-142 radioisotope sources in the form of produced solid discs measured in three different counting geometries in 44.8% relatively efficient well-type HPGe detector are given in Table 5 below.

Total 2127.3±4.6%

* Disc source was measured on the detector end cap surface which was placed at a height of 4.1 cm from the bottom of the well of HPGe detector.

** Disc source was measured using a 3.15 cm thick spacer (PP plastic spacer) on the detector end cap surface which is at a height of 7.25 cm from the bottom of the well of HPGe detector.

*** Disc source was measured using two 6.3 cm thick distance holders (PP plastic spacer) placed on the detector end cap surface which is at a height of 10.8 cm high from the bottom of the well of HPGe detector.

Disc source activity reference date: October 1 , 2020, Time 11 :48 (End time of irradiation) and Irradiation time duration: tirr =20 min.

PP: plastic spacer: Annular plastic disc fitted on the end cap and the distance is adjusts with an insert made of polypropylene(PP).

Table - 5

In the state-of- the art, when the dose rate values given by the commercial Ru-106/Rh-106 source are converted into the SI unit system; 9.48 Gy/h, 7.08 Gy/h, 7.44 Gy/h, and 10.56 Gy/h. However, as a result of the tests carried out in this invention, the dose rate of Pr-142 radioisotope source (HDPE applicator window 25pmAI) in the form of a disc produced by the invention was measured with the ExradinWI polystyrene-based PSD technique at intervals of 2.5-3.7 Gy/h, 7.02-8.57 Gy/h and at some points 28.5-42.1 Gy/h in an eye phantom (on the sclera surface) according to the strength of the source used, when the 10-hour decay time of Pr-142 radioisotope source in the form of the disc in the reactor after production was taken into account. Since the dose rate obtained at this level given by the disc-form Pr-142 radioisotope source is within the dose rate range of the sources in the known state of the commercially used technique, the disc-form Pr-142 radioisotope source falls into a high-dose rate (HDR) source class and is shown to be a novel radioactive beta source that is at least a candidate for prostate interstitial brachytherapy and ophthalmic episcleral brachytherapy applications.

The pelvic group (prostate+bladder+rectum) phantom produced from tissue equivalent PLA material with the help of 3D printinf for Interstitial Prostate Brachytherapy Application, which is an object of the invention, is measured with RFD and PSD techniques and it is shown that with Pr-142 radioisotope solid line-source, a minimum dose rate of 7 Gy/h can be given in the urethra after 10 hours decay after its production, the Pr-142 activities can be produced and therefore these sources have the dose transfer strength. This means that these new radioisotope source can be used as MDR beta source in prostate cancer treatment.

Similarly, for Ophthalmic Episcleral (Superficial) Brachytherapy Application, it is determined by using an eye phantom (eye sclera filled with pure water +lens+optic nerve), EBT3 film RFD and ExradinWI polystyrene-based PSD dose measurement techniques; it is applied on the phantom of the eye by producing activities that can be given at different points in the range of 11 .3-42.1 Gy/h dose rates according to the assumption that the tumor is in the eye apex with a single disc Pr-142 radioisotope source encapsulated with a HDPE applicator afterl O hours elapsed after its production. However, dosimetric tests in the phantom revealed that unnecessary doses in the lens and optic nerve remained minimal. Therefore, it has been determined that these sources have good dosimetric properties in view of brachytherapy. This demonstrated that Pr-142 disc sources can be used as HDR beta sources in plaque brachytherapy of ophthalmic eye cancers.

In the production of the Pr-142 radioisotope source produced by the invention, the source production processes are carried out by employing the appropriate shielding measures and using protective equipment in such a way that the legal maximum dose limits are not exceeded and it is a must to obey the necessary radiation protection measures. Pr-142 radioisotope source production requires the implementation of the specific processes in which the recommended radiation protection procedures will be professionally applied within a scheduled time schedule of minutes and hours after certain preparations have been made and the irradiation program in the reactor has been determined.

The scope of protection of the invention is specified in the attached claims and cannot be limited to those explained for sampling purposes in this detailed description. It is evident that a person skilled in the technique may exhibit similar embodiments in light of the above- mentioned facts without drifting apart from the main theme of the invention. REFERENCE NUMBERS GIVEN IN THE FIGURE

R Radius of curvature