JP6368129B2 - How to remove radioactive material - Google Patents

Description

The present invention relates to a method for efficiently removing radioactive substances generated in a synthesis room for synthesizing an ¹⁸ F-labeled compound used as a diagnostic agent in a positron emission tomography diagnostic apparatus.

In medical institutions, due to the need for early detection and early treatment of cancerous sites, some elements of compounds that gather in tumors are replaced with radionuclides, administered to patients, radiation is measured outside the body, and tumor sites are identified. Specific radiodiagnosis (in vivo diagnosis) is performed. In recent years, in order to avoid unnecessary exposure to patients, compounds labeled with radionuclides having a short half-life and a high permeability to gamma rays have been sought, and 511 keV gamma rays per decay (β ⁺ decay) are directed in the opposite direction. Two labeled compounds with positron emitting nuclides are used. A diagnostic device using this labeling compound is called a positron emission tomography (PET), and can be found even in a small tumor site, and is installed in many medical institutions.

Radionuclides mainly used for labeling compounds are ¹¹ C, ¹³ N, ¹⁵ O, ¹⁸ F, and the like. Because of their short half-life (lifetime), these nuclides are produced by ultra-small cyclotrons that accelerate protons and deuterons mainly in medical institutions that actually perform diagnosis. After production, these nuclides are automatically sent to a synthesizer to become a medical diagnostic agent (labeled compound). The labeled compound is administered to the subject in the laboratory after adjusting the purity and dose. In recent years, a polysaccharide, ¹⁸ F FDG (fluorodeoxyglucose), which utilizes the high sugar content of tumor cells, has been frequently used. ¹⁸ F is obtained by irradiating protons accelerated by a cyclotron to H ₂ ¹⁸ O (target) in which oxygen which is a constituent atom of water (H ₂ O) is replaced by ¹⁸ O which is a non-radioactive isotope. ¹⁸ F FDG is synthesized through a process called fluorination by a dedicated automatic synthesizer placed in a small clean room called a synthesis room.

The automatic synthesizer is inspected for leaks with a helium leak detector or the like. However, there is a possibility of leakage from the connection part when the reagent, instrument, ion exchange resin column, etc. are exchanged or connected. Moreover, unreacted ¹⁸ F contained when the gas in the reaction system is released to the outside of the system is removed by an absorbent such as soda lime, but ¹⁸ F is released due to deterioration of the used absorbent. May be. Even if the leakage capacity is very small, the radiation dose is very large. If the production is stopped halfway, it must be disassembled and washed after waiting for the decay of radioactivity, and it is difficult to carry out production and synthesis again within the same day. In addition, if the amount of radioactive material in the exhaust gas is high and the concentration of radioactive substances in the exhaust gas is increased and exceeds the regulation values stipulated by related laws and regulations, it will be treated as a violation of laws and regulations, and the manufacturing and diagnosis of radiopharmaceuticals must be suspended for a while. Inconvenience. Therefore, the contaminated air generated by a slight leak from the automatic synthesizer installed in the synthesis chamber is carried to the exhaust purification equipment of the radiation facility by a duct connected to the synthesis chamber, where the granular activated carbon filter, HEPA filter or ULPA Purified by a filter.

On the other hand, when synthesizing ¹⁸ F FDG, a large amount of unreacted hydrogen fluoride (HF) is contained in the gas component, but the HEPA filter and ULPA filter do not support purification of the gas component. In order to cope with purification of gas components, a granular activated carbon filter is generally installed in an exhaust purification facility of a radiation facility. The granular activated carbon filter in the exhaust purification equipment adsorbs trace gases and moisture contained in the air, but this deteriorates (weathering) the collection performance of ¹⁸ F gas and intermediate products. In addition, because the exhaust purification equipment is connected with ducts so as to purify indoor air other than the synthesis room, the exhaust purification equipment is severely deteriorated and has a large amount of processing air and dust. Become.

  In order to overcome such problems, an activated carbon fiber filter impregnated with an alkaline substance is installed at the exhaust port of the synthesis chamber, thereby removing a small amount of radioactive substance and reducing the amount of radioactive substance exhausted to the exhaust facility. A method has been proposed (see Patent Document 1). Such a method is extremely effective for removing radioactive substances, but the current situation is that sufficient exhaust facilities cannot be installed in recent synthesis facilities that are becoming smaller and cleaner.

JP 2010-127662 A

The present invention was devised in view of the current state of the prior art described above, and its purpose is to provide radioactive materials discharged from the ¹⁸ F-labeled compound synthesis chamber used in a miniaturized and cleaned positron emission tomography diagnostic apparatus. The object is to provide a method for efficiently removing substances.

  As a result of intensive studies on a method for removing a radioactive substance in order to achieve such an object, the present inventors have reduced the size by circulating air inside the synthesis chamber using a specific filter unit configuration and arrangement. It has been found that sufficient exhaust equipment can be installed in the synthesis room, and the present invention has been completed.

That is, the present invention has the following configurations (1) to ( 3 ).
(1) In a method of removing radioactive substances generated in a synthesis chamber when synthesizing an ¹⁸ F-labeled compound used as a diagnostic agent in a positron emission tomography diagnostic apparatus, the filter unit is disposed in the synthesis chamber. The filter unit is integrally provided with a blower fan, an activated carbon fiber filter, and a dust removal filter having a particle collection efficiency of 0.3 to 0.5 μm at a surface wind speed of 0.4 m / s of 90 to 99%. The activated air fiber fan is operated to remove the radioactive material by circulating the air in the synthetic chamber through the activated carbon fiber filter and the dust filter of the filter unit in this order , and the activated carbon fiber of the activated carbon fiber filter is radiation, characterized in that it consists of activated carbon fibers impregnated with an alkaline substance Method of removing the substance.
( 2 ) The method for removing a radioactive substance according to ( 1), wherein the activated carbon fiber filter and / or the dust removal filter can be removed from the filter unit and exchanged.
( 3 ) The method for removing a radioactive substance according to (1) or (2 ), wherein the filter unit has a gap for taking in air upstream of the blower fan.

According to the method of the present invention, the filter unit uses an activated carbon fiber filter with a small amount of dust generation and a relatively high-efficiency dust removal filter with a small pressure loss, so that the amount of dust generated from the filter unit is suppressed to a small amount. Sufficient air volume can be secured above. Furthermore, according to the method of the present invention, attaching the filter unit to the synthesis chamber portion, since the circulating air in the synthesis chamber portion by the blower fan, ^{18 F} gas and an intermediate without reducing the cleanliness of the synthesis chamber portion The product can be collected locally, and it is possible to perform exhaust treatment that is very efficient compared to the removal by the filter unit installed in the exhaust purification equipment of the entire radiology department.

Sectional drawing of the filter unit used for this invention is shown. The external appearance perspective view of the filter unit used for this invention is shown. The external appearance perspective view of the activated carbon fiber filter of the filter unit used for this invention is shown.

  The method for removing a radioactive substance of the present invention will be described below, but the present invention is not limited to this.

FIG. 1 shows a schematic cross-sectional view of a filter unit installed in the synthesis chamber of ¹⁸ F-labeled substance, and FIG. 2 shows an external perspective view of the filter unit. The filter unit includes a blower fan 1, an activated carbon fiber filter 2, and a dust filter 3 that is relatively highly efficient but has a low airflow resistance in this order, and is integrated in a metal housing 4. Is installed. The activated carbon fiber filter 2 and the dust removal filter 3 are fixed using a pressing frame 5 from the downstream side of the filter unit. On the upstream side of the blower fan 1, there is a gap 6 through which air can be sucked. When the blower fan 1 rotates, the air is taken in from the gap 6 and radioactive substances are removed through the activated carbon fiber filter 2 and the dust removal filter 3. The The filter unit is allowed to stand at one corner of the ¹⁸ F-labeled substance synthesis chamber, and the air inside the synthesis chamber circulates through the filter unit to remove the radioactive substance inside the synthesis chamber.

^Since the cleanliness of dust is kept high in the ¹⁸ F-labeled substance synthesis chamber, dust generation from the filter unit must be extremely limited. In the present invention, the activated carbon fiber filter 2 having a relatively small amount of dust generation is employed, and the dust removing filter 3 having a relatively high efficiency but a low airflow resistance is installed on the downstream side of the activated carbon fiber filter 2, thereby It is characterized by suppressing airflow resistance while preventing dust generation. As the dust removal filter 3, a HEPA filter or a ULPA filter used in an FFU (fan filter unit) in a general clean room or the like is not used. Although the HEPA filter and the ULPA filter have extremely high dust removal efficiency, the airflow resistance of the filter is high. Therefore, when a normal blower fan is used, the air volume is lowered, which is not preferable. HEPA filters and ULPA filters are used in combination with granular activated carbon filters that generate a large amount of dust, but there is still a problem that the air volume is reduced. For this reason, it is efficient to use a combination of an activated carbon fiber filter with less dust generation and a dust removal filter with low pressure loss and relatively high dust removal efficiency.

  The activated carbon fiber filter 2 used in the present invention is for collecting radioactive substances, and has a feature that the amount of dust generation is extremely small compared to a granular activated carbon filter. Activated carbon fiber has the property of adsorbing and removing organic substances, but it can also remove acidic radioactive substances by adding at least one alkaline substance. Further, when the activated carbon fiber is processed into a sheet shape, the activated carbon fiber hardly generates dust from the activated carbon due to the slight vibration during operation, which is found in a known granular carbon-filled filter. FIG. 3 shows an activated carbon fiber filter used in the present invention. After the activated carbon fiber 7 is formed into a sheet and folded in a zigzag shape, a corrugated separator 8 is inserted between the peaks to secure an air flow path, and the activated carbon fiber 7 is fixed by the frame body 9 to be activated carbon. It becomes the fiber filter 2. The activated carbon fiber filter 2 is installed on the downstream side of the blower fan 1 inside the housing 4 of the filter unit. As the alkaline substance to be attached to the activated carbon fiber, alkali, alkaline earth metal hydroxide or carbonate, or amines are preferably used.

  The dust removal filter 3 used in the present invention is provided mainly for removing fine dust that can be generated from the activated carbon fiber filter 2, and uses a filter with a low pressure loss in order to secure the air volume. Specifically, the dust removal filter 3 has a particle collection efficiency of 0.3 to 0.5 μm at a surface wind speed of 0.4 m / s of 90% or more, further 92% or more, and 99% or less, and further 98%. Preferably it has: The surface wind speed here refers to a value obtained by dividing the air volume set by the filter by the size of the opening of the filter. The filter pressure loss and the collection efficiency are in a complementary relationship at a constant surface wind speed. For example, if the collection efficiency is too high, the air volume cannot be secured, while if it is too low, a sufficient dust removal function cannot be performed. In general, a filter medium for a HEPA filter or a ULPA filter composed of a known glass fiber has a very high efficiency but is not preferable because of high ventilation resistance. Moreover, since the hydrogen fluoride which corrodes glass exists in the substance to be removed, it is not preferable. In the present invention, an activated carbon fiber filter with a small amount of dust generation is used to remove radioactive substances, so that it is not necessary to use a filter as highly efficient as a HEPA filter or ULPA filter on the downstream side, ensuring air volume. (Low ventilation resistance) can be prioritized. The dust removal filter 3 is not particularly limited as long as the above characteristics are satisfied, but a polymer filter medium is preferable, and a filter medium obtained by filtering an electrostatic filter medium charged with a known chemical-resistant polyolefin system by a known method. preferable. The dust removal filter 3 is installed on the downstream side of the activated carbon fiber filter. In this case, if the adhesion with the activated carbon fiber filter is improved, the leakage of fine dust can be effectively prevented. The housing 4 of the activated carbon fiber filter 2 and the dust filter 3 is made of a corrosion-resistant metal such as aluminum or stainless steel, and may be fixed with a packing made of chloroprene sandwiched between them. preferable.

  The activated carbon fiber filter 2 and the dust removal filter 3 fixed in the casing 4 are fixed so as to be removed from the filter unit and exchanged with the pressing frame 5 from the most downstream side, and screwed to the casing 4 of the filter unit. Is done.

  The effects of the method of the present invention will be described below by way of examples. However, the following examples are not intended to limit the present invention and can be modified without departing from the spirit of the present invention.

Example 1
(Casing)
A case of SUS304 with a thickness of 1.5 mm and an outer size of 185 mm square and a depth of 220 mm is prepared, and a 160 mm square AC fan with a frame (rated air volume 7 m ³ / min) is distributed on the inside of the fan. It was attached as follows. An aluminum L-shaped bar having a length of 50 mm and a width of 20 mm was attached to the four corners on the upstream side of the fan, and an air inlet (gap) was secured when installed.

(Activated carbon fiber filter)
From fibrous activated carbon impregnated with 14% by weight of 1,4-diazabicyclo- (2,2,2) octane (DABCO), having a basis weight of 230 g / m ² , a thickness of 2.8 mm, a specific surface area of 1500 m ² / g, and a fiber diameter of 12 μm Two nonwoven fabric sheets to be formed were sandwiched from above and below with a polypropylene spunlace nonwoven fabric having a basis weight of 30 g / m ² and formed into a sheet by needle punching. Aluminum frame (180 mm square, 180 mm square, with a height of 130 mm, folded into zigzags at 7 peaks, slit into a width of 176 mm with a corrugated polyethylene coated paper between the peaks, and urethane resin applied inside An activated carbon fiber filter was prepared by setting the depth to 150 mm.

(Dust removal filter)
It is composed of a polyester / polypropylene nonwoven fabric having a basis weight of 145 g / m ² , a thickness of 0.5 mm, a pressure loss of 60 Pa at a wind speed of 10 cm / s, and a particle collection efficiency of 0.3 to 0.5 μm at a wind speed of 10 cm / s of 93%. An electrostatic filter medium was prepared, and a dust removal filter was prepared by a known method using an aluminum frame (180 mm square, 50 mm depth) having a mountain height of 45 mm and a mountain pitch of 5.0 mm. The produced filter had a pressure loss of 12 Pa at a surface wind speed of 0.4 m / s, and a particle collection efficiency of 0.3 to 0.5 μm at a surface wind speed of 0.4 m / s was 98.2%.

(Filter unit)
An activated carbon fiber filter in which chloroprene foam packing (10 mm width × 5 mm thickness) was attached to the frames on both sides was installed on the downstream side of the frame-equipped AC fan fixed to the housing, and installed in the housing. Furthermore, a dust removal filter is installed on the downstream side, a 180 square, 10 mm deep, 1.5 mm thick stainless steel frame is inserted into the housing from the most downstream side and screwed, the filter is fixed to the housing, and the filter unit is mounted. Created.

(Measurement of the number of dust particles on the downstream side and the wind speed of the filter unit)
The fan of the above filter unit is operated in clean air containing no dust from the upstream side, and the particle count (KC-01E manufactured by Lion Co., Ltd.) 0.3 L was collected and measured. The wind speed of the filter unit was measured with a propeller-type anemometer with a 250 mm hood attached downstream of the unit. The wind speed at this time was 1.7 m / s, and the number of dusts of 0.3 μm or more was not confirmed.

(Example 2)
It was composed of a polyester / polypropylene nonwoven fabric having a basis weight of 115 g / m ² , a thickness of 0.9 mm, a pressure loss of 40 Pa at a wind speed of 10 cm / s, and a particle collection efficiency of 0.3 to 0.5 μm at a wind speed of 10 cm / s of 78%. An electrostatic filter medium was prepared, and a dust removal filter was prepared by a known method using an aluminum frame (180 mm square, 50 mm depth) having a mountain height of 45 mm and a mountain pitch of 5.0 mm. The produced filter had a pressure loss of 22 Pa at a surface wind speed of 0.4 m / s, and a particle collection efficiency of 0.3 to 0.5 μm at a surface wind speed of 0.4 m / s was 92.2%. A filter unit was prepared and evaluated in the same manner as in Example 1 except for the preparation of the dust removal filter. The wind speed at this time was 1.8 m / s, and the number of dusts of 0.3 μm or more was not confirmed.

(Comparative Example 1)
The dust filter is a fluorine membrane ULPA filter (180 mm square, depth 50 mm, pressure loss 150 Pa at a surface wind speed of 0.4 m / s, particle collection efficiency of 0.3 to 0.5 μm at a surface wind speed of 0.4 m / s is 99. A filter unit was prepared and evaluated in the same manner as in the above example, except that it was changed to 9995%). Although the number of dusts of 0.3 μm or more was not confirmed, the wind speed was 0.4 m / s.

(Comparative Example 2)
The dust removal filter is a fluorine membrane HEPA filter (180 mm square, depth 50 mm, pressure loss 70 Pa at a surface wind speed of 0.4 m / s, and particle collection efficiency of 0.3 to 0.5 μm at a surface wind speed of 0.4 m / s is 99.99 μm. A filter unit was prepared and evaluated in the same manner as in the above example except that it was changed to 997%. Although the number of dusts of 0.3 μm or more was not confirmed, the wind speed was 0.6 m / s.

(Comparative Example 3)
An electrostatic capacity composed of a polypropylene nonwoven fabric having a basis weight of 97 g / m ² , a thickness of 1.0 mm, a pressure loss of 40 Pa at a wind speed of 10 m / s, and a particle collection efficiency of 0.3 to 0.5 μm at a wind speed of 10 m / s of 63%. A filter medium was prepared, and a dust removal filter was prepared by a known method using an aluminum frame (180 mm square, 50 mm depth) having a mountain height of 45 mm and a mountain pitch of 5.0 mm. The produced filter had a pressure loss of 20 Pa at a surface wind speed of 0.4 m / s and a particle collection efficiency of 0.3 to 0.5 μm at a surface wind speed of 0.4 m / s of 83.1%. A filter unit was prepared and evaluated in the same manner as in Example 1 except for the preparation of the dust removal filter. The wind speed at this time was 1.8 m / s, and five dust counts of 0.3 μm or more were confirmed.

According to the method of the present invention, the radioactive substance discharged from the ¹⁸ F-labeled compound synthesis chamber used in the miniaturized and cleaned positron emission tomography diagnostic apparatus can be efficiently removed.

DESCRIPTION OF SYMBOLS 1 Blower fan 2 Activated carbon fiber filter 3 Dust removal filter 4 Case 5 Holding frame 6 Cavity 7 Activated carbon fiber filter material 8 Separator 9 Outer frame

Claims (3)

In a method for removing radioactive substances generated in a synthesis chamber with a filter unit when synthesizing an ¹⁸ F-labeled compound used as a diagnostic agent in a positron emission tomography diagnostic apparatus, the filter unit is disposed in the synthesis chamber, and the filter unit Is integrally equipped with a blower fan, an activated carbon fiber filter, and a dust removal filter having a particle collection efficiency of 0.3 to 0.5 μm at a surface wind speed of 0.4 m / s of 90 to 99%. The radioactive carbon is removed by circulating the air in the synthesis chamber through the activated carbon fiber filter and the dust filter in the order of the filter unit, and the activated carbon fiber of the activated carbon fiber filter removes the alkaline substance. radioactive material characterized by comprising the impregnated the activated carbon fiber Removal method. 2. The method for removing a radioactive substance according to claim 1, wherein the activated carbon fiber filter and / or the dust filter can be removed from the filter unit and exchanged. Method of removing radioactive material according to claim 1 or 2 filter unit is characterized by having a gap for taking in air at the upstream side of the blower fan.