CN111063470A

CN111063470A - Preparation method of iridium-192 rear loading source and iridium-192 rear loading source

Info

Publication number: CN111063470A
Application number: CN201911183808.7A
Authority: CN
Inventors: 崔洪起; 李梅
Original assignee: Atom High Tech Co ltd; Beijing Shuangyuan Isotope Technology Co Ltd
Current assignee: Atom High Tech Co ltd; Beijing Shuangyuan Isotope Technology Co Ltd
Priority date: 2019-11-27
Filing date: 2019-11-27
Publication date: 2020-04-24

Abstract

The invention relates to a preparation method of an iridium-192 after-loading source and the iridium-192 after-loading source, wherein the method comprises the following steps: an iridium wire with the purity of more than 99.9 percent is selected as a target material and is made into an irradiation target. The raw material of iridium-192 is irradiated by using a reactor, and the irradiated raw material needs to be stored for a proper time in order to completely decay the 194Ir species in the raw material. Then processes such as target cutting, measurement, split charging, welding, inspection and the like are carried out. The iridium-192 prepared by the process is provided with a source welding spot in a semicircular shape, and has the advantages of good sealing property, no leakage and no pollution on the surface. The activity parallelism is good, and the maximum deviation is within +/-5%.

Description

Preparation method of iridium-192 rear loading source and iridium-192 rear loading source

Technical Field

The invention belongs to the field of nuclear technology application of medical equipment configuration products containing radioactive sources, and particularly relates to a preparation method of an iridium-192 rear loading source and an iridium-192 rear loading source, which adopt an argon arc welding sealing process.

Background

The radiation therapy is one of the main therapeutic means for treating tumor, and the iridium-192 after-loading source is applied to the after-loading machine after radiation therapy, so that the treatment range of the after-loading machine for tumor is expanded from the traditional gynecology to the esophagus, stomach, nasopharynx, lung, trachea, rectum, bladder and other cavities, and the after-loading machine can also be inserted into thyroid, mammary gland, liver, kidney, pancreas and other organs, and has unique characteristics for tumor treatment in operation forbidden areas. The traditional Chinese medicine composition is widely applied to treatment of cervical cancer, biliary tract tumor and other diseases, has special effects on gynecological cervical cancer, rhinitis cancer, rectal cancer and the like, and is irreplaceable. The high-activity micro iridium-192 radioactive source has the advantages of small volume, high activity and the like, and is very suitable for intracavity afterloading treatment. The energy of the iridium-192 is suitable for a human body, the average energy of gamma rays is only 380KeV, the iridium-192 can be loaded into the human body through the afterloader control, the iridium-192 can be used for focus site-specific treatment, cancer cells are killed, damage to normal tissues and organs such as viscera is reduced, and a remarkable effect is achieved. Iridium-192 also has the unique advantage that the gamma energy range of iridium-192 is such that its exponential decay in the medium is exactly compensated by the scatterometry factor, which makes the dose rate squared product approximately constant at any point over the 5cm range of clinical interest from the source. In addition, the half-value layer is only 2.4mm lead, the protection is simple, and the fund is saved. Meanwhile, the half-life period is short (74d), the waste source is easy to treat, the sealed radioactive source does not release gas and liquid radioactive effluents, and the radioactive influence on the environment can not be caused as long as the application is strictly carried out according to the radiation protection requirement. By combining the advantages, the modern intracavity afterloading therapeutic machine adopts the iridium-192 source.

The iridium-192 after-loading source prepared by the preparation method of the iridium-192 after-loading source in the prior art has poor tightness, low activity, poor activity parallelism and high cost, and occurs when leakage occurs.

Disclosure of Invention

In view of the problems in the background art, the invention aims to provide a method for preparing an iridium-192 after-loading source. The preparation method comprises the steps of target making, irradiation, welding, cleaning, inspection and the like, welding a stainless steel source shell on a stainless steel wire rope, and preparing iridium-192 after-loading source braids with the lengths of 1500mm, 1600mm, 1700mm, 2000mm and the like by tail end spot welding according to the requirements of different machines. And then the source braid is cleaned by electrochemical polishing clear water and dried for later use. Preparing a source core by irradiating an iridium wire with the purity of more than 99.9 percent by a reactor, filling the source core into a source shell with a source braid, sealing by argon arc welding to prepare iridium-192, and then filling the source.

In order to achieve the above purpose, the invention provides the following technical scheme:

the preparation method of the iridium 192 after-loading source provided by the invention comprises the following steps and contents:

(1) target making: an iridium wire with the purity of more than 99.9 percent is selected as a target material and is made into an irradiation target. The reactor is used for irradiation, and the 194Ir nuclide in the irradiated iridium source needs to be stored for a proper time in order to completely decay. 192Ir is mainly obtained by radiating 191Ir by neutrons, and the nuclear reaction formula for preparing 192Ir nuclide is as follows: 191Ir (n, γ) → 192 Ir.

(2) Measurement before loading: after the iridium source is properly decayed, the small amount of 194Ir contained therein does not affect the measurement and use, and then the measurement and use are carried out. To ensure the activity of each iridium-192 afterload is accurate, each iridium charge is pre-measured in a lead chamber using an activity meter and recorded.

(3) Preparing a source braid: and welding a stainless steel source shell on a stainless steel wire rope, and preparing an iridium-192 rear loading source braid by tail-end spot welding according to different requirements of rear loading machines. And then the source braid is cleaned by electrochemical polishing clear water and dried for later use.

(4) Assembling and welding sealing: and (3) placing a stainless steel source shell into a fixed base in a lead chamber by means of a mechanical arm, placing a source core into the source shell with a source braid by using the mechanical arm, welding and sealing to prepare iridium-192, and then loading the source.

As a preferred aspect, the method further comprises:

(5) quality inspection: the appearance of the source is checked by an imaging method, the outside diameter and the length of the back source are respectively measured by a micrometer and a vernier caliper which are calibrated by a metering department, a liveness meter is calibrated by a standard source which is calibrated by the metering department, the activity of the back source is measured under the same condition, the outer surface of the source is cleaned in the water solution by an ultrasonic cleaner, and the surface pollution and the leakage of the source are checked by a method of measuring the activity of the water solution by a gamma counter.

Preferably, the diameter of the iridium wire in the step (1) is phi 0.5-1 mm, and the length of the iridium wire is 0.6-4.5 mm.

As a preferable scheme, the irradiation time of the pile in the step (1) is 10-20 days, and the storage time after irradiation is 1-5 days.

As a preferable scheme, the measurement result of the activity of the source core in the step (2) is 1-20 Ci.

As a preferable scheme, the length of the source braid in the step (3) is 1500-2500 mm.

As a preferable scheme, the source core loading tool in the step (4) is a special tool funnel.

Preferably, the welding method in the step (4) adopts argon arc welding for sealing.

As a preferable scheme, the welding conditions in the step (4): the current is 5-20A.

In the preparation method, the external dimension of the post-assembled source in the step (4) is phi 0.9-phi 1.3 multiplied by 3.5-6.5 mm.

In the preparation method, the back loading source welding spot in the step (5) is smooth and has no burr to form a semicircle, and the deviation of the external dimension of the back loading source is less than 5 percent.

In the above preparation method, the activity of the feed after the step (5) is 1 to 20 Ci.

In the above production method, the contamination and leakage level in the step (5) is less than 200 Bq.

In the above preparation method, in the step (1), since the medical iridium-192 post-loading source introduces the radiation source into the tumor in vivo, the dose rate and the uniformity of the radiation energy at the same position from the radiation source are particularly important problems; in addition, during the irradiation, the neutron self-shielding effect of the iridium material is obvious, so that the self-shielding effect is reduced by reducing the volume of the target material. In the step (4), the sealing is achieved by spot welding because the diameter of the source is small. In the step (5), because the source has a small shape and surface pollution and leakage are not easy to detect, the method of filling the source after ultrasonic cleaning is adopted to detect the surface pollution and leakage.

A second object of the invention is to provide an iridium-192 afterloader source comprising a source shell, a source core, and a source braid, the source shell being wrapped around the outside of the source core, the source braid being used to connect the source shell to a steel wire rope;

the length of the source braid is 1500-2500 mm.

As a preferable scheme, the diameter of the iridium-192 after-loading source is 0.9-1.3 mm; the length of the iridium-192 rear source is 3.5-6.5 mm.

Preferably, the welding point of the iridium-192 after-loading source is semicircular.

The invention has the beneficial effects that:

the diameter of the iridium-192 after-loading source prepared by the method is between phi 0.9 and phi 1.3mm, and the length of the source is between 3.5 and 6.5 mm. The source welding spot is semicircular, has good sealing performance, no leakage, no surface pollution and good activity parallelism, and the maximum deviation is within +/-5 percent. The method has the advantages of high specific activity of raw materials, safety, reliability and the like.

The medical iridium-192 with high specific activity prepared by the method is afterloaded, the activity is 1-20Ci, the size of an active region is phi 0.5-phi 1 multiplied by 1-5 mm, the length of a source braid is 1500-2500 mm, and the performance index of the product meets the use requirement of most medical afterloaders in China.

Drawings

FIG. 1 is a schematic structural diagram of an Ir-192 afterloader prepared in EXAMPLE 1 of the present invention;

wherein, 1-source shell; 2-source core; 3-source braid.

Detailed Description

The following detailed description of the embodiments of the present invention will be made with reference to the accompanying drawings and examples.

Example 1:

in this embodiment, taking 1 piece of iridium-192 with an external dimension of Φ 1.1 × 6.5mm, a source braid length of 1500mm and an activity of 10Ci as an example, and then loading the source, the preparation can be performed according to the following steps:

(1) target making: an iridium wire with the purity of more than 99.9 percent is selected as a target material and is made into an irradiation target. The reactor is used for irradiation, and the 194Ir nuclide in the irradiated iridium source needs to be stored for a proper time in order to completely decay. The diameter of the iridium wire is phi 0.7mm, and the length of the iridium wire is 3.5 mm. The time of stacking is 15 days, and the storage time after stacking is 3 days.

(2) Measurement before loading: the target material was cut open with a cutter in the work box and the activity of each iridium material was measured with a liveness meter and recorded.

(3) Preparing a source braid: and cleaning the source shell and the source braid together, placing aside for later use, and welding the source shell and the source braid by argon arc welding for later use.

(4) Assembling and welding sealing: iridium raw material with a measured activity of 10Ci is loaded into a source housing with a source braid in a work box by a robot with the aid of special tools. And welding the source shell by argon arc welding at a current of 5-20A.

(5) Quality inspection: and cleaning the welded finished product source for 1 minute by using ultrasonic waves, and measuring the activity of the cleaning solution by using a gamma counter, wherein the activity is less than 200Bq, which indicates that the welding machine is free from pollution and leakage.

And (4) placing the qualified finished product source into a specific packaging container, and labeling for delivery.

The structure of the prepared iridium-192 after-loading source is shown in figure 1, the after-loading source comprises a source shell 1, a source core 2 and a source braid 3, the source shell is wrapped outside the source core, and the source braid is used for connecting the source shell and a steel wire rope.

Example 2:

in this example, 1 piece of iridium-192 with an external dimension of Φ 0.9 × 3.5mm, a source braid length of 2000mm and an activity of 5Ci is prepared and then source-loaded.

In the step (1), the iridium wire has a diameter of Φ 0.5mm and a length of 2.0 mm. The time of stacking is 10 days, and the storage time after stacking is 1 day.

Other steps and conditions were the same as in example 1.

Example 3:

in this example, 1 piece of iridium-192 with the external dimension of Φ 1.3 × 5.0mm, the length of the source braid of 2500mm and the activity of 20Ci is prepared and then loaded.

In the step (1), the iridium wire has a diameter of Φ 1mm and a length of 4.5 mm. The time of illumination is 20 days, and the storage time after illumination is 5 days.

Other steps and conditions were the same as in example 1.

The above description is specific to the present invention and is not intended to limit the present invention to the specific embodiments. It will be apparent to those skilled in the art that a number of simple derivations and modifications can be made without departing from the inventive concept, and these are intended to be within the scope of the present invention.

Claims

1. A method of preparing an iridium-192 afterload source, the method comprising the steps of:

the method comprises the following steps: selecting iridium wire with purity of more than 99.9% as a target material to prepare an irradiation target; irradiating the irradiation target with a reactor; storing for a proper time until the decay of the 194Ir nuclide in the irradiated iridium source is complete;

step two: in order to ensure the accuracy of the activity of each iridium-192 rear source, each iridium raw material is pre-measured and recorded in a lead chamber by using an activity meter;

step three: welding a source shell on a wire rope, and preparing an iridium-192 post-loading source braid by tail end spot welding according to different post-loading machine requirements; loading iridium-192 into a source braid, performing electrochemical polishing, cleaning, and drying for later use;

step four: and (3) putting the source shell into a fixed base in a lead chamber, putting the source core into the source shell with a source braid, welding and sealing to prepare iridium-192, and then putting the source into a source.

2. The method of making an iridium-192 post-source as claimed in claim 1, further comprising:

step five: the appearance of the iridium-192 afterload source is checked by an imaging method; respectively measuring the outer diameter and the length of the rear loading source by using a micrometer and a vernier caliper; calibrating an activity meter by using a standard source, and measuring the activity of the iridium-192 post-loading source under the same condition; the outer surface of the iridium-192 afterload source was cleaned and a gamma counter was used to check for surface contamination and leakage of the iridium-192 afterload source.

3. The method of producing an iridium-192 aftersource as claimed in claim 1 wherein in step one, the iridium wire has a diameter of Φ 0.5 to Φ 1mm and a length of 0.6 to 4.5 mm.

4. The method of claim 1, wherein in step one, the irradiation time is 10 to 20 days and the storage time after irradiation is 1 to 5 days.

5. The method for preparing iridium-192 post-loading source as claimed in claim 1, wherein in step four, the source core loading tool is a special tooling funnel.

6. The method of claim 1, wherein in step four, the welding process uses argon arc welding for sealing.

7. The method of claim 6, wherein in step four, the welding conditions are as follows: the current is 5-20A.

8. An iridium-192 back-loading source, comprising a source shell, a source core and a source braid, wherein the source shell is wrapped outside the source core, and the source braid is used for connecting the source shell with a steel wire rope;

the length of the source braid is 1500-2500 mm.

9. The iridium-192 post-load source of claim 8, wherein the iridium-192 post-load source has a diameter of 0.9 to 1.3 mm; the length of the iridium-192 rear source is 3.5-6.5 mm.

10. The iridium-192 post-source of claim 8 wherein the welds of the iridium-192 post-source are semicircular.