CN109754890B - Method for manufacturing radioactive seed source core by utilizing electrohydrodynamic micro-droplet injection - Google Patents

Abstract

The invention discloses a manufacturing method of a radioactive seed source metal source core sprayed by electrohydrodynamic micro-droplets. A metal filament kept electrically grounded is placed under the spout, and a certain voltage is applied between the nozzle and the metal filament. The principle of electrohydrodynamics allows the creation of tiny droplets, which are charged and subjected to electrostatic forces, which tend to be collected by grounded metal filaments. The metal filaments can rotate in the axial direction and translate in the axial direction during the spraying process. Ensure that the droplets are sprayed evenly on the surface of the metal filament. This method can be used in the field of radiotherapy. The present invention combines electrohydrodynamic droplet generation technology and brachytherapy device manufacturing technology. And can effectively improve the speed of the adsorption reaction between radioactive substances and the surface. In addition, because the generated droplets are charged, under the action of the electric field, the droplets are more inclined to deposit on the metal filaments, preventing the adverse consequences caused by the splash of the solution. .

Description

Fabrication of a radioactive seed source core using electrohydrodynamic droplet ejection method

technical field

The invention relates to a technology for producing micron-diameter droplets by a micro-droplet generating device utilizing the principle of electrohydrodynamics, and the droplets are precisely applied to conductive filaments. It belongs to the technical field of micro liquid application.

Background technique

In general, electrohydrodynamic droplet generation devices are directed to liquids that have electrical conductivity. It is composed of a liquid supply module, a conductive nozzle and a conductive substrate. An electric field is generated by a voltage applied between the conductive nozzle and the conductive substrate. Under the traction of electrostatic force, the liquid at the conductive nozzle will be deformed and broken to form droplets. Under a certain liquid supply flow rate, by adjusting the applied voltage, a spraying state in which the size of the micro-droplets is uniform and the frequency of producing the micro-droplets is stable can be achieved. The diameter of the sprayed droplets can reach the micrometer level. This technology has broad application prospects in the fields of precise quantitative application of trace liquids, biomedical engineering, and tissue engineering.

Local treatment of tumors and other pathologies by intermittent implantation of radioactive material is an accepted treatment modality for long-term use. Radioactive implants are used to deliver radiation therapy to destroy tumors, or to slow or stop tumor growth. Radioactive implants are also used to stop the growth of metastatic microscopic deposits in lymph nodes draining from the tumor resection area. Implants are also used in post-radiation tumor beds after tumor resection. Implanting a radiation source directly into a solid tumor to destroy the tumor is called brachytherapy.

For example, US Patent No. 3,351,049 to Lawrence discloses the use of low energy X-ray emitting interstitial implants as a therapeutic source of brachytherapy. Such implants, especially those containing palladium (Pd-103) or iodine (I-125) as radioisotopes, have proven to be extremely effective against solid malignancies. There is good effect in the treatment of early stage prostate cancer with this device. These devices, or "seeds," must be small because they are typically placed in diseased tissue through a hollow needle. Once implanted in tissue, it is held in place by surrounding tissue or held in place by an associated suture. The typical size of a permanent implant is a cylinder 0.8 mm in diameter and 0.45 mm long. A temporary implant is generally inserted through a hollow needle or plastic sheath into the tissue to be treated and has the same outer diameter of about 0.8 mm as a permanent implant

In the invention patent "Fluid Jet Deposition of Radioactive Materials for Brachytherapy Devices", a method and device for precisely applying radioactive materials to substrates such as brachytherapy devices are disclosed. The rapidly solidifying radioactive fluid is deposited at the desired spot on a surface with a jet. However, when the deposited surface is a filament surface, the method mentioned in this invention still has some drawbacks in controlling the precise application of microdroplets. A number of factors, including changing hydrophilic properties at the nozzle, can cause droplets to deviate from the filament. It not only wastes precious radioactive liquid, but also affects the accuracy of radioactive measurement and pollutes the surrounding environment.

The present invention overcomes the above defects and adopts electrohydrodynamic technology to spray micro-droplets, which can not only control the size of micro-droplets by adjusting the voltage and flow rate, but also can control the size of micro-droplets by adjusting the voltage and flow rate. The guiding function of the droplet can precisely apply the droplet to the conductive filament, which can effectively prevent the droplet from deviating from the conductive filament.

SUMMARY OF THE INVENTION

In view of the defects existing in the prior art, the present invention provides a method for making a radioactive seed source core based on the jetting of electrohydrodynamic micro-droplets. Electrohydrodynamic droplet generation technology can generate droplets with diameters much smaller than the nozzles. Under proper working conditions, the diameter of microdroplets can reach below 10 microns, even submicron. The reduction of the diameter of the microdroplet increases the ratio of the surface of the microdroplet to the volume of the microdroplet, thereby effectively increasing the speed of the adsorption reaction between the radioactive substance and the surface. Because the generated droplets are charged, under the action of the electric field force, the droplets are more inclined to deposit on the conductive filaments, preventing the adverse consequences caused by the splash of the solution.

The present invention intends to place a conductive filament that is electrically connected (usually grounded) under the conductive nozzle, and apply a certain voltage between the conductive nozzle and the conductive filament. The principle of electrohydrodynamics enables the generation of tiny droplets, which are charged with electrostatic forces and tend to be collected by grounded conductive filaments. During the spraying process, the metal wire can rotate in the axial direction, and can translate along the axial direction to ensure that the microdroplets are sprayed evenly on the surface of the conductive filament. Promote the full contact of the liquid with the surface of the filament, thereby accelerating the adsorption or reaction of the radioactive material with the surface. At the same time, the influence of the local accumulation of liquid on the distribution of the electric field can be avoided, and the consistency and stability of the ejection of micro-droplets can be maintained. In particular, it relates to a method for precisely applying micron-sized droplets onto conductive filaments, which can be used in the field of radiotherapy. The present invention combines two hitherto unrelated technologies, namely electrohydrodynamic droplet generation technology and brachytherapy device fabrication technology.

The technical solution adopted in the present invention is a method for manufacturing a radioactive seed source metal source core using electro-hydrodynamic micro-droplet ejection. The electro-hydrodynamic micro-droplet ejection device for realizing the manufacturing method comprises a liquid supply module 2, a micro-droplet ejection device Droplet generation system, clamping device 6 , CCD image acquisition module 7 , and control chip 3 .

The micro-droplet generation system includes a power supply 1, a conductive nozzle 4 and a conductive filament 5. The power supply 1 is respectively connected with the conductive nozzle 4 and the conductive filament 5, and the conductive nozzle 4 corresponds to the position of the conductive filament 5; the liquid supply module 2 Connected to the conductive nozzle 4 , the liquid supply amount of the liquid supply module 2 is controlled by the control chip 3 . The liquid supply module 2 is filled with radioactive fluid.

The conductive filament 5 is installed on the clamping device 6 ; the CCD image acquisition system 7 is facing the axial direction 5 of the conductive filament. The clamping device can realize the axial translation and the rotational movement of the conductive filament 5 .

The liquid supply module 2 is a syringe pump with the working principle of pushing the needle tube piston (as shown in Fig. 2), or a Poiseuille fluid (as shown in Fig. 3) which is realized by maintaining a pressure difference at both ends of the thin tube. The liquid supply volume of the liquid supply module 2 is calculated by the piston propulsion speed and the piston cross-sectional area; the liquid supply volume of Poiseuille fluid is obtained by maintaining a certain pressure at both ends of the thin tube, and the flow rate of the liquid supply volume can be obtained according to the Poiseuille formula.

The power supply 1 is an adjustable regulated power supply, or a pulse power supply.

The voltage of the power supply 1 is determined by the distance between the conductive nozzle 4 and the conductive filament 5 . In order to improve the spraying stability and consistency of the conductive nozzle 4, the distance between the conductive nozzle 4 and the conductive filament 5 is 1mm-10mm. The voltage of power supply 1 is 100V–10000V.

The clamping device 6 can ensure that the conductive filaments can rotate in the axial direction and translate in the axial direction. At the same time, the conductive filament is kept in electrical contact with the power supply electrode (usually set as the ground terminal).

The consistency and stability of the ejection of the micro-droplets and whether the micro-droplets reach the conductive filaments accurately can be confirmed by the CCD image acquisition system under the control of the control chip 3 . The specific implementation technology does not fall within the protection scope of the present invention.

The usual working steps of this method are as follows:

One pole (positive pole) of the power supply 1 is connected to the conductive nozzle 4, the other pole of the power supply 1 is connected to the conductive filament 5 and grounded, a voltage is applied, and the conductive nozzle 4 is filled with a radioactive fluid, due to the radioactive fluid (usually NaI) It has good electrical conductivity, an electric field is generated between the radioactive fluid and the conductive filaments 5, the surface of the radioactive fluid accumulates electric charges, and the electric charges are forced in the electric field, so that the radioactive fluid is deformed under the combined action of electric field force, surface tension and gravity, Solution deformation at the tip: from a hemispherical or elliptical liquid to a conical liquid. When the electric field is large enough, the electrostatic force and gravity exceed the surface tension, and the tip of the conical liquid breaks to form tiny droplets. The diameter of the tiny droplets is smaller than the diameter of the nozzle, and the tiny droplets are charged. Under the action of the electric field between, the tiny droplets will be accurately collected on the conductive filament 5 .

The radioactive liquid (usually NaI) undergoes an adsorption reaction with the surface-treated conductive filaments 5. After the adsorption reaction, most of the radioactive substances are combined with the conductive filaments 5, and there is almost no radioactive material in the liquid phase. as "residue".

The removal of the residual liquid can be carried out after the adsorption reaction of the radioactivity and the conductive filament 5 is completed.

The cutting and dividing of the conductive filaments 5 is performed after the residual liquid is removed.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention solves the defect that the isotope solution will splash out in the prior art, can realize the accurate collection of the solution on the conductive filament 5, and reduce waste and radioactive pollution. Improve the accuracy of the radioactivity measurement of the source core.

The present invention can control the size of the droplet by adjusting the voltage, and for the conductive filament 5 with a small diameter, it can prevent the droplet from being too large and unable to adhere to the surface of the conductive filament. Reducing the diameter of the droplet increases the relative volume of the surface area of the droplet. Since the combination of the radioactive liquid (usually NaI) and the conductive filament is an adsorption reaction, reducing the diameter of the droplet helps to improve the efficiency of the adsorption reaction.

The grounding conductor closest to the conductive nozzle is a conductive filament, and the conductive filament can be rotated to a set angle in the axial direction under the driving mechanism, and can be translated to a set distance in the axial direction. The radioactive source core can also be obtained after the conductive filament is cut, and the source core is filled into the thin tube and sealed. That is, the radioactive seed source is obtained. The present invention does not include the technology of adding the cut and segmented source core into the thin tube and automatically sealing it.

Description of drawings

FIG. 1 is a schematic diagram of the structure of the device of the present invention.

In the figure: 1. Power supply, 2. Liquid supply module, 3. Control chip, 4. Conductive nozzle, 5. Conductive filament, 6. Clamping device 7, CCD image acquisition system.

Figure 2 is a liquid supply module based on a syringe pump, and the liquid supply module is controlled by a control chip

Figure 3 is a liquid supply module that uses differential pressure to drive liquid flow, and the liquid supply module is controlled by a control chip

FIG. 4 is a clamping device for realizing the axial rotation and translation of the conductive filament, and the conductive filament is kept connected to the power supply electrode (usually the power supply ground electrode) through the clamping device.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments and the accompanying drawings

As shown in Figure 1, a syringe pump is used to control the supply of radioactive solution under the control of a computer or other controller. The positive electrode of the power supply 1 is applied to the conductive nozzle 4, and the negative electrode is applied to the conductive filament 5, and an electrostatic potential difference is introduced by applying a voltage. As the voltage increases, the solution on the conductive nozzle 4 will become hemispherical or ellipsoid meniscus droplets; as the voltage of the power supply 1 increases gradually, the surface charge density of the solution on the conductive nozzle 4 increases, and the electric field force increases big. When the power supply 1 continues to increase and the electrostatic force and gravity exceed the surface tension, the droplets will leave the conductive nozzle 4. Since the conductive filament is the closest conductive object to the conductive nozzle, the electric field is mainly distributed between the conductive nozzle and the conductive filament. , the droplets are charged, and under the action of the electric field, the droplets will be accurately collected on the conductive filament 5 . This feature prevents microdroplets from not depositing on the conductive filaments due to droplet ejection deviations, resulting in radioactive fluid loss and environmental contamination. Improve the radioactive dose accuracy of the source core.

The present invention can also adjust the liquid supply volume by adjusting the moving speed of the liquid supply module 2, so that the setting of the voltage 1 and the flow rate of the liquid supply reach a matching state. Under the interaction between the power supply 1 and the liquid supply, the droplets are uniform in size and stable in frequency.

The invention has simple operation and low cost, and only needs to act on the electric field, so that the solution can be accurately collected on the conductive filaments to prevent the solution from splashing;

The conductive filament clamping device 6 can realize axial rotation and axial translation of the conductive filament 5 .

The consistency and stability of the ejection of micro-droplets, and whether the micro-droplets reach the conductive filaments accurately are all under the control of the control chip 3 and confirmed by the CCD image acquisition system.

Claims (6)

1. A method for making a radioactive seed metal source core utilizing electrohydrodynamic droplet ejection, the electrohydrodynamic droplet ejection device for realizing the fabrication method comprises a liquid supply module (2), a droplet generation system and a clamp a holding device (6), a CCD image acquisition system (7); It is characterized in that: the droplet generating system comprises a power source (1), a nozzle (4) and a metal filament (5), the power source (1) is respectively connected with the nozzle (4) and the metal filament (5), and the nozzle (4) Corresponding to the position of the metal filament (5); the liquid supply module (2) is connected to the nozzle (4), and the liquid supply amount of the liquid supply module (2) is controlled by the control chip (3); filled with radioactive fluid; One pole of the power supply (1) is connected to the nozzle (4), the other pole of the power supply (1) is connected to the metal filament (5) and grounded, a voltage is applied, and the nozzle (4) is filled with a radioactive fluid, due to the radioactive fluid That is, NaI has good electrical conductivity, an electric field is generated between the radioactive fluid and the metal filament (5), the surface of the radioactive fluid accumulates electric charges, and the electric charges are forced in the electric field, so that the radioactive fluid has a combined effect of electric field force, surface tension and gravity. Under the deformation, the solution at the tip is deformed: from a hemispherical or elliptical liquid to a cone-shaped liquid; when the electric field is large enough, the electrostatic force and gravity exceed the surface tension, and the tip of the cone-shaped liquid breaks, forming tiny droplets, tiny liquids The diameter of the droplet is smaller than the diameter of the nozzle, the tiny droplets are charged, and under the action of the electric field between the nozzle (4) and the metal filament (5), the tiny droplet will be accurately collected on the metal filament (5); The metal filament (5) is installed on the clamping device; the CCD image acquisition system (7) is facing the metal filament (5); the clamping device can realize the axial translation and the rotational movement of the metal filament (5) ; The liquid supply module (2) is a syringe pump whose working principle is to push a needle tube piston, or a Poiseuille fluid realized by maintaining a pressure difference at both ends of the thin tube; the liquid supply amount of the liquid supply module (2) is determined by the piston advancing speed and the cross-sectional area of the piston; the liquid supply of Poiseuille fluid can be obtained by maintaining a certain pressure at both ends of the thin tube, and the flow rate of the liquid supply can be obtained according to the Poiseuille formula. 2 . The method for manufacturing a radioactive seed metal source core using electrohydrodynamic droplet spraying according to claim 1 , wherein the power source (1) is a constant voltage power source or a pulse power source. 3 . 3. The method for making a radioactive seed metal source core utilizing electrohydrodynamic droplet spraying according to claim 1, wherein the voltage of the power supply (1) is determined by the nozzle (4) and the metal filament ( 5) The distance is determined; in order to improve the spraying stability and consistency of the nozzle (4), the distance between the nozzle (4) and the metal filament (5) is 1mm-10mm; the voltage of the power supply (1) is 100V-10000V. 4. a kind of manufacture method of the radioactive seed source metal source core that utilizes electrohydrodynamic droplet spraying according to claim 1, it is characterized in that: NaI by and the metal filament (5) through surface treatment generation adsorption reaction , after the adsorption reaction, most of the NaI is combined with the metal filaments (5), and there is almost no NaI component in the liquid phase. 5 . The method for manufacturing a radioactive seed metal source core using electrohydrodynamic droplet spraying according to claim 1 , wherein the cutting and dividing of the metal filaments ( 5 ) is performed after the residual liquid is removed. 6 . 6. The method for making a radioactive seed metal source core utilizing electrohydrodynamic droplet spraying according to claim 1, wherein the consistency and stability of droplet spraying, and whether the droplet is sprayed Accurately reaching the conductive filaments is all under the control of the control chip (3) and confirmed by the CCD image acquisition system.

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