WO1997008568A1 - A detection method for radioactivity on support by direct detection of ionization - Google Patents

A detection method for radioactivity on support by direct detection of ionization Download PDF

Info

Publication number
WO1997008568A1
WO1997008568A1 PCT/FI1996/000458 FI9600458W WO9708568A1 WO 1997008568 A1 WO1997008568 A1 WO 1997008568A1 FI 9600458 W FI9600458 W FI 9600458W WO 9708568 A1 WO9708568 A1 WO 9708568A1
Authority
WO
WIPO (PCT)
Prior art keywords
radioactivity
gate
mosfet
support material
support
Prior art date
Application number
PCT/FI1996/000458
Other languages
French (fr)
Inventor
Timo Oikari
Jukka Kahilainen
Jukka Haaslahti
Juhani Aalto
Original Assignee
Hidex Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hidex Oy filed Critical Hidex Oy
Publication of WO1997008568A1 publication Critical patent/WO1997008568A1/en

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/24—Measuring radiation intensity with semiconductor detectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
    • H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by at least one potential-jump barrier or surface barrier, e.g. phototransistors
    • H01L31/115—Devices sensitive to very short wavelength, e.g. X-rays, gamma-rays or corpuscular radiation
    • H01L31/119—Devices sensitive to very short wavelength, e.g. X-rays, gamma-rays or corpuscular radiation characterised by field-effect operation, e.g. MIS type detectors

Definitions

  • the present invention relates to detection of radioactivity on support materials, such as porous filters and various surfaces. More particularly, the present invention relates to detection of radioactivity on support by direct detection of ionization produced by radiation.
  • Radioactivity residing on various support materials and surfaces is a commonly performed procedure.
  • One on-support category are filter assays where radioactivity resides in a porous medium.
  • An example are wipe tests from various places to monitor their contamination.
  • objects to be studied are wiped with filter discs and their radioactivity detected with an appropriate technique.
  • Filters are also employed in bioanalytical assays utilizing radioactive isotopes as labels to quantify various biological phenomena.
  • harvesting assays where cells are grown with radioactively labeled substances and then harvested through a filter with a special harvester device. Radioactivity trapped within the filter is then determined. Also cell fragments can be harvested.
  • most harvesters have ability to simultaneously process several samples a ⁇ separate spots on a single filtermat; e.g. 96 spot ⁇ in a ⁇ tandardized 6 x 16 or 8 x 12 array.
  • Another on-support category is detection of radioactivity on inner walls of sample wells, test tubes, and other containers, used in many biological binding assays, for example radioimmunoas ⁇ ay ⁇ and nucleic acid hybridizations.
  • the containers are first coated with a substance (antibody, nucleic acid etc.) which can specifically bind the investigated compound from the solution to be then studied.
  • Radioactive labels are commonly employed to quantify binding.
  • unbound radioactivity is removed by washing with a suitable buffer solution and finally emptying, leaving a container with the true bound activity on inner walls.
  • multi-well sample plates made of plastic have become very common.
  • a typical plate, often called as a microplate has 96 sample wells in a standardized 8 x 12 array; each well having a sample volume of about 300 microliters.
  • Liquid scintillation counting is a known technique for detecting radioactivity on support.
  • a filter assay a filter disc i ⁇ put in a vial and liquid scintillator is added.
  • the energetic particles (betas, alphas) released in radioactive decay excite molecules of liquid scintillator causing them to emit light which i ⁇ detected with a liquid scntillation counter.
  • liquid scintillation counters which can have several (up to 12) detector units to ⁇ peed up detection.
  • liquid scintillator it i ⁇ al ⁇ o possible to use a ⁇ olid, meltable scintillator.
  • liquid scintillator is added therein and light output measured.
  • a drawback with liquid and meltable scintiilator ⁇ is that they produce costs and their addition is an extra working step. Al ⁇ o waste disposal with liquid scintillators can pre ⁇ ent regulatory problem ⁇ .
  • Another method for detecting radioactivity i ⁇ ga ⁇ counting is a gas filled cylindrical tube with two electrodes: the outer wall acting as a cathode and a fine wire along the cylinder axis acting as an anode. A high voltage is applied between the electrodes. Due to their structure, gas counters can be used only for filter applications and the like with a flat geometry. The filter to be studied is brought near the end of the tube so that particles from radioactive decays can ionize gas molecules . The ions are accelerated by the applied electric field and can, in turn, ionize other gas molecules resulting in an ion multiplication process.
  • Ga ⁇ multiplication require ⁇ ⁇ pecial gases, like noble gases (e.g. argon, xenon), methane, propane, carbon dioxide etc. and their mixtures. Air is not usable for multiplication.
  • noble gases e.g. argon, xenon
  • methane propane, carbon dioxide etc.
  • Air is not usable for multiplication.
  • a difficulty with gas counters is that optimal detection requires that the gas continuously flushes the support leading to incoveniences in maintenance of ga ⁇ ⁇ upply, producing costs and requiring handling of pressurized gas bottles.
  • the present invention discloses a new method for detecting radioactivity on support which does not employ scintillators or additional gases, thus avoiding problems associated with prior art.
  • the present invention also avoids high voltages needed in detectors of liquid scintillation counters and gas counters.
  • the present invention disclo ⁇ e ⁇ a method for detecting radioactivity on support materials.
  • Novel in the present invention is that radioactivity on the support is detected by a detector unit which employs a metal-oxide semiconductor type of field effect transi ⁇ tor (MOSFET) having a floating gate, the gate being ⁇ uitably charged before measurement.
  • MOSFET metal-oxide semiconductor type of field effect transi ⁇ tor
  • the gate charge attracts ions produced by radioactivity in the air.
  • ions neutralize charges thereon, thus causing a change in the gate potential.
  • the potential change being indicative to the amount of detected radioactivity, can be measured by registering the change in the conductivity of the source-drain channel of the MOSFET without destroying the gate charge itself.
  • radioactivity on flat supports like porous filters and non- porous plastic, glass, metal etc. surface ⁇ . It i ⁇ also possible to detect radioactivity residing on well-type supports, like on inner walls of various containers, e.g. multi-well sample plates.
  • the disclosed MOSFET unit does not necessarily need any electrical power.
  • Figure 1 shows one possible embodiment for a detector devis of the invention for measuring radioactivity on flat supports.
  • Figure 2 a detail of Figure i.
  • Figure 3 show ⁇ one po ⁇ ible embodiment for a detector unit of the invention for measuring radioactivity on well-type support ⁇ .
  • Radioactivity on a support ionizes air in its vicinity. It is characteristic to the invention that the generated ions are allowed to affect charges on the surface of the floating gate of a MOSFET (metal oxide semiconductor type of a field effect transistor). The charge is initially stored in the capacitance of the floating gate of the MOSFET before measurement, for example, by applying FN tunneling technique.
  • MOSFET metal oxide semiconductor type of a field effect transistor
  • the ion ⁇ are collected by means of the electric field created by the gate charge. Upon hitting the gate, ion ⁇ neutralize charges thereon changing its potential which, in turn, change ⁇ conductivity of the source-drain channel of the MOSFET. Accordingly, by mea ⁇ uring the conductivity of the source-drain channel of the MOSFET, the amount of gate charge can be determined without destroying the charge itself. Thus, change in the gate charge (potential) in a selected time interval is indicative to the amount of radioactivity on the ⁇ upport. This type of "non-destructive" reading is analogou ⁇ to reading out the information ⁇ tored in an analog EEPROM memory.
  • MOSFETs with charged floating gate ⁇ have been u ⁇ ed in dosimeters, as shown in publication WO 95/12134.
  • FIG. 1 shows one example for a single MOSFET detector unit of the invention for measuring radioactivity on porous filters and on other flat supports. A detail of it is shown in Fig. 2.
  • the porous filter 10, having a radioactive sample 11 therein, is associated with a chamber 12. Particles (betas, alphas) released in radioactive decays in sample 11 ionize air of a chamber 12 which contains a MOSFET 13.
  • This component has three electrodes: source 14, drain 15 and gate 16.
  • surface area of gate 16 can be enlarged e.g. by attachment of a conducting ⁇ trip, di ⁇ c, plate or mesh into it. From here on in this text, the term "gate” includes also the gate enlarged in this way.
  • gate 16 (and it ⁇ po ⁇ ible enlargement) is left electrically unconnected to other parts of the structure, that i ⁇ , gate 16 is floating.
  • the invention is operated in the following way: After associating the filter 10 with the chamber 12 a voltage is applied via connectors 17 and 18 between source 14 and drain 15 of the MOSFET 13. This causes so called FN tunneling phenomenon where charges tunnel through the gate insulator onto the gate surface.
  • the sign of charges depends on MOSFET type. Charge retention properties of floating gates of MOSFET ⁇ are excellent ⁇ o that, after turning off the charging voltage, the charge on gate 16 remain ⁇ there for long period ⁇ , even for year ⁇ . Thi ⁇ property makes it also pos ⁇ ible to charge the gate 16 in advance, much before actual ea ⁇ urement.
  • the charge on gate 16 create ⁇ an electric field which attracts ions of opposite sign; i.e. negative gate charge attract ⁇ po ⁇ itive ion ⁇ and po ⁇ itive gate charge attracts negative ions.
  • ions neutralize charge thereon changing its potential.
  • the amount of gate charge can be read by determining the conductivity of the source-drain channel of the MOSFET 13. This can be done simply by applying a suitable voltage via connectors 17 and 18 and measuring the resulting current. The difference in the gate charge (i.e. in source-drain current) before and after detection interval is indicative to amount of radioactivity on the support.
  • the MOSFET unit of the invention does not necessarily require any electrical power. Naturally, it is also possible to apply an additional electrical field to enhance and optimize ion collection.
  • a very efficient detector unit is obtained by adding another chamber on the opposite side of the ⁇ upport. This is shown by the dashed lines in the Fig. 1. Its constitutional parts function in the same way a ⁇ explained above and are not repeated here. With this ⁇ tructure ion ⁇ can be collected more efficiently from porou ⁇ supports. For example, it is possible to charge the MOSFET gate on one side positively (to collect negative ion ⁇ ) and on the other side negatively (to collect positive ions).
  • the foil can be made either permanent or disposable.
  • a permanent foil enables fabrication of hermetically sealed chambers which can contain another gas than air, e.g. nitrogen, argon, methane, carbon dioxide etc.
  • pos ⁇ ible flat support ⁇ there are several pos ⁇ ible flat support ⁇ to be mea ⁇ ured with the above shown embodiment.
  • Perhap ⁇ the mo ⁇ t widespread are various porou ⁇ filter ⁇ .
  • Their material ⁇ include glass fiber, nylon, paper, nitrocellulose, polypropylene etc.
  • flat smooth supports such as plastic, glass or metal plates, sheets and surfaces are employed and can be measured with the invention.
  • Still another support types are chromatographic support ⁇ and gel ⁇ .
  • a final detecting device can have ⁇ everal units of Fig. 1 in a selected pattern or array, enabling detection of multiple spot ⁇ upport ⁇ .
  • the device can have 96 MOSFET units in a ⁇ tandardized 8 x 12 array to enable simultaneous mea ⁇ urement of all ⁇ pots in a typical filter.
  • a great number e.g. ten ⁇ of thousands
  • miniatyrized MOSFET units of the invention it is even possible to construct an imaging device.
  • the support is an inner wall of a container, such a ⁇ a well in a multi-well plate, it i ⁇ preferable to modify the above shown embodiment slightly. This is shown in Fig. 3. Many of it ⁇ construction units are the same as in Fig. 1 and same numerals are used for them.
  • the support is now a sample well 20 which has the radioactive sample 11 bound on its inner wall. Essential in this embodiment i ⁇ that the gate 16 of the MOSFET 13 is directed to the interior space of the .well 20 to be measured. This guarantees optimal ion collection.
  • Gate 16 can be of various shapes, e.g. stick, rod, strip, cylinder, mesh etc.
  • radioactive sample 11 ionizes air in the interior space of the sample well 20.
  • the gate 16 i ⁇ charged suitably so that it can collect generated ions. These neutralize gate charge causing a change in its potential which is mea ⁇ ured by measuring the conductivity of the source-drain channel of the MOSFET 13.
  • the final detection device can have several MOSFET units of Fig. 3.
  • the device can have 96 MOSFET units in a standardized 8 x 12 array to enable simultaneou ⁇ measurement of all wells of a typical microplate.
  • the system of this kind is very useful for radioimmunoassays and nucleic acid binding assays which are often performed in multi-well plates.
  • the present invention does not limit the ways the radioactive sample is disposed or attached on the support. These can include pipetting, harvesting, adsorption, chemical/biochemical binding reactions, evaporation, electrostatic mechanisms etc.
  • the radioactive sample can also be in particulate form, such as a powder, soil, microparticles etc., to be measured either with the embodiment of Fig. 1 (on a flat support) or Fig. 3 (in a well). For particulate sa ple ⁇ it i ⁇ also possible to use a sticky support to fix the sample thereon.

Abstract

A method for detecting radioactivity, comprising the following steps: disposing at least one radioactive sample on a support material, associating with said support material a detecting device comprising at least one detector unit, each said detector unit containing a MOSFET having a floating gate, charging said gate to a suitable potential, allowing ions produced by said radioactivity to neutralize charge on the gate for a selected time, and registering a change in said potential, the change being indicative to amount of radioactivity on said support material.

Description

A DETECTION METHOD FOR RADIOACTIVITY ON SUPPORT BY DIRECT DETECTION OF IONIZATION
■The present invention relates to detection of radioactivity on support materials, such as porous filters and various surfaces. More particularly, the present invention relates to detection of radioactivity on support by direct detection of ionization produced by radiation.
BACKGROUND
Detection of radioactivity residing on various support materials and surfaces is a commonly performed procedure. One on-support category are filter assays where radioactivity resides in a porous medium. An example are wipe tests from various places to monitor their contamination. Typically, objects to be studied (tables, shelves etc.), are wiped with filter discs and their radioactivity detected with an appropriate technique.
Filters are also employed in bioanalytical assays utilizing radioactive isotopes as labels to quantify various biological phenomena. Among most common are harvesting assays where cells are grown with radioactively labeled substances and then harvested through a filter with a special harvester device. Radioactivity trapped within the filter is then determined. Also cell fragments can be harvested. To enable handling cf greater sample numberε, most harvesters have ability to simultaneously process several samples aε separate spots on a single filtermat; e.g. 96 spotε in a εtandardized 6 x 16 or 8 x 12 array.
Another on-support category is detection of radioactivity on inner walls of sample wells, test tubes, and other containers, used in many biological binding assays, for example radioimmunoasεayε and nucleic acid hybridizations. Typically, the containers are first coated with a substance (antibody, nucleic acid etc.) which can specifically bind the investigated compound from the solution to be then studied. Radioactive labels are commonly employed to quantify binding. After the binding reaction, unbound radioactivity is removed by washing with a suitable buffer solution and finally emptying, leaving a container with the true bound activity on inner walls. Instead of single wells or test tubes, multi-well sample plates made of plastic have become very common. A typical plate, often called as a microplate, has 96 sample wells in a standardized 8 x 12 array; each well having a sample volume of about 300 microliters.
Liquid scintillation counting is a known technique for detecting radioactivity on support. In case of a filter assay, a filter disc iε put in a vial and liquid scintillator is added. The energetic particles (betas, alphas) released in radioactive decay excite molecules of liquid scintillator causing them to emit light which iε detected with a liquid scntillation counter.
For multiple spot filters there exist special, εo called flat bed liquid scintillation counters which can have several (up to 12) detector units to εpeed up detection. Instead of liquid scintillator it iε alεo possible to use a εolid, meltable scintillator. When assaying sample wells containing bound radioactivity, liquid scintillator is added therein and light output measured. A drawback with liquid and meltable scintiilatorε is that they produce costs and their addition is an extra working step. Alεo waste disposal with liquid scintillators can preεent regulatory problemε.
Another method for detecting radioactivity iε gaε counting, either by proportional or Geiger-Muelier technique. Their typical construction unit is a gas filled cylindrical tube with two electrodes: the outer wall acting as a cathode and a fine wire along the cylinder axis acting as an anode. A high voltage is applied between the electrodes. Due to their structure, gas counters can be used only for filter applications and the like with a flat geometry. The filter to be studied is brought near the end of the tube so that particles from radioactive decays can ionize gas molecules . The ions are accelerated by the applied electric field and can, in turn, ionize other gas molecules resulting in an ion multiplication process. Finally, the generated ions are collected to the electrodes producing a detectable electronic signal. For multiple spot filters there exist devices having several tube units. Gaε multiplication requireε εpecial gases, like noble gases (e.g. argon, xenon), methane, propane, carbon dioxide etc. and their mixtures. Air is not usable for multiplication. A difficulty with gas counters is that optimal detection requires that the gas continuously flushes the support leading to incoveniences in maintenance of gaε εupply, producing costs and requiring handling of pressurized gas bottles.
The present invention discloses a new method for detecting radioactivity on support which does not employ scintillators or additional gases, thus avoiding problems associated with prior art. The present invention also avoids high voltages needed in detectors of liquid scintillation counters and gas counters.
SUMMARY OF THE INVENTION
The present invention discloεeε a method for detecting radioactivity on support materials. Novel in the present invention is that radioactivity on the support is detected by a detector unit which employs a metal-oxide semiconductor type of field effect transiεtor (MOSFET) having a floating gate, the gate being εuitably charged before measurement. The gate charge attracts ions produced by radioactivity in the air. Upon hitting the gate, ions neutralize charges thereon, thus causing a change in the gate potential. The potential change, being indicative to the amount of detected radioactivity, can be measured by registering the change in the conductivity of the source-drain channel of the MOSFET without destroying the gate charge itself.
According to the invented method, it is possible to detect radioactivity on flat supports, like porous filters and non- porous plastic, glass, metal etc. surfaceε. It iε also possible to detect radioactivity residing on well-type supports, like on inner walls of various containers, e.g. multi-well sample plates.
For multiple spot filters and multi-well sample plates it is possible to construct a device comprising several MOSFET detector units.
It is noteworthy that during the ion collection phase the disclosed MOSFET unit does not necessarily need any electrical power.
DESCRIPTION OF THE DRAWINGS
Figure 1 shows one possible embodiment for a detector unii of the invention for measuring radioactivity on flat supports. Figure 2 a detail of Figure i.
Figure 3 showε one poεεible embodiment for a detector unit of the invention for measuring radioactivity on well-type supportε.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Radioactivity on a support ionizes air in its vicinity. It is characteristic to the invention that the generated ions are allowed to affect charges on the surface of the floating gate of a MOSFET (metal oxide semiconductor type of a field effect transistor). The charge is initially stored in the capacitance of the floating gate of the MOSFET before measurement, for example, by applying FN tunneling technique.
The ionε are collected by means of the electric field created by the gate charge. Upon hitting the gate, ionε neutralize charges thereon changing its potential which, in turn, changeε conductivity of the source-drain channel of the MOSFET. Accordingly, by meaεuring the conductivity of the source-drain channel of the MOSFET, the amount of gate charge can be determined without destroying the charge itself. Thus, change in the gate charge (potential) in a selected time interval is indicative to the amount of radioactivity on the εupport. This type of "non-destructive" reading is analogouε to reading out the information εtored in an analog EEPROM memory. Previously, MOSFETs with charged floating gateε have been uεed in dosimeters, as shown in publication WO 95/12134.
There are obviously εeveral poεεible wayε to construct an apparatus for performing the invented method. Fig. 1 shows one example for a single MOSFET detector unit of the invention for measuring radioactivity on porous filters and on other flat supports. A detail of it is shown in Fig. 2.
The porous filter 10, having a radioactive sample 11 therein, is associated with a chamber 12. Particles (betas, alphas) released in radioactive decays in sample 11 ionize air of a chamber 12 which contains a MOSFET 13. This component has three electrodes: source 14, drain 15 and gate 16. To enable more efficient ion collection geometry, surface area of gate 16 can be enlarged e.g. by attachment of a conducting εtrip, diεc, plate or mesh into it. From here on in this text, the term "gate" includes also the gate enlarged in this way. Crucial in the invention is that gate 16 (and itε poεεible enlargement) is left electrically unconnected to other parts of the structure, that iε, gate 16 is floating. The invention is operated in the following way: After associating the filter 10 with the chamber 12 a voltage is applied via connectors 17 and 18 between source 14 and drain 15 of the MOSFET 13. This causes so called FN tunneling phenomenon where charges tunnel through the gate insulator onto the gate surface. The sign of charges (positive or negative) depends on MOSFET type. Charge retention properties of floating gates of MOSFETε are excellent εo that, after turning off the charging voltage, the charge on gate 16 remainε there for long periodε, even for yearε. Thiε property makes it also posεible to charge the gate 16 in advance, much before actual eaεurement.
Radioactivity from εa ple 11 ionizeε air molecules in the chamber 12. The charge on gate 16 createε an electric field which attracts ions of opposite sign; i.e. negative gate charge attractε poεitive ionε and poεitive gate charge attracts negative ions. Upon hitting the gate 16, ions neutralize charge thereon changing its potential. After a selected time, the amount of gate charge (potential) can be read by determining the conductivity of the source-drain channel of the MOSFET 13. This can be done simply by applying a suitable voltage via connectors 17 and 18 and measuring the resulting current. The difference in the gate charge (i.e. in source-drain current) before and after detection interval is indicative to amount of radioactivity on the support.
It is noteworthy that during the ion collection phase the MOSFET unit of the invention does not necessarily require any electrical power. Naturally, it is also possible to apply an additional electrical field to enhance and optimize ion collection.
A very efficient detector unit is obtained by adding another chamber on the opposite side of the εupport. This is shown by the dashed lines in the Fig. 1. Its constitutional parts function in the same way aε explained above and are not repeated here. With this εtructure ionε can be collected more efficiently from porouε supports. For example, it is possible to charge the MOSFET gate on one side positively (to collect negative ionε) and on the other side negatively (to collect positive ions).
Optionally, it is also posεible to include a thin foil between the support and the chamber to prevent itε contamination. Care εhould then be taken that the foil iε not too thick and abεorptive for particleε emitted in radioactive decays from the sample. The foil can be made either permanent or disposable. A permanent foil enables fabrication of hermetically sealed chambers which can contain another gas than air, e.g. nitrogen, argon, methane, carbon dioxide etc.
There are several posεible flat supportε to be meaεured with the above shown embodiment. Perhapε the moεt widespread are various porouε filterε. Their materialε include glass fiber, nylon, paper, nitrocellulose, polypropylene etc. In some special biological binding asεays also flat smooth supports, such as plastic, glass or metal plates, sheets and surfaces are employed and can be measured with the invention. Still another support types are chromatographic supportε and gelε.
It εhould be noted that a final detecting device can have εeveral units of Fig. 1 in a selected pattern or array, enabling detection of multiple spot εupportε. For example, the device can have 96 MOSFET units in a εtandardized 8 x 12 array to enable simultaneous meaεurement of all εpots in a typical filter. By using a great number (e.g. tenε of thousands) of miniatyrized MOSFET units of the invention it is even possible to construct an imaging device.
When the support is an inner wall of a container, such aε a well in a multi-well plate, it iε preferable to modify the above shown embodiment slightly. This is shown in Fig. 3. Many of itε construction units are the same as in Fig. 1 and same numerals are used for them. The support is now a sample well 20 which has the radioactive sample 11 bound on its inner wall. Essential in this embodiment iε that the gate 16 of the MOSFET 13 is directed to the interior space of the .well 20 to be measured. This guarantees optimal ion collection. Gate 16 can be of various shapes, e.g. stick, rod, strip, cylinder, mesh etc.
The embodiment of Fig. 3 operates in the same way as explained above: radioactive sample 11 ionizes air in the interior space of the sample well 20. The gate 16 iε charged suitably so that it can collect generated ions. These neutralize gate charge causing a change in its potential which is meaεured by measuring the conductivity of the source-drain channel of the MOSFET 13.
As above, the final detection device can have several MOSFET units of Fig. 3. For example, the device can have 96 MOSFET units in a standardized 8 x 12 array to enable simultaneouε measurement of all wells of a typical microplate. The system of this kind is very useful for radioimmunoassays and nucleic acid binding assays which are often performed in multi-well plates.
The present invention does not limit the ways the radioactive sample is disposed or attached on the support. These can include pipetting, harvesting, adsorption, chemical/biochemical binding reactions, evaporation, electrostatic mechanisms etc. The radioactive sample can also be in particulate form, such as a powder, soil, microparticles etc., to be measured either with the embodiment of Fig. 1 (on a flat support) or Fig. 3 (in a well). For particulate sa pleε it iε also possible to use a sticky support to fix the sample thereon.

Claims

1. A method for detecting radioactivity, comprising the steps of: disposing at least one radioactive sample on a support material, associating with said support material a detecting device comprising at least one detector unit, each said detector unit containing a MOSFET having a floating gate, charging said gate to a suitable potential, - allowing ionε produced by εaid radioactivity to neutralize charge on the gate for a εelected time, and registering a change in εaid potential, the change being indicative to amount of radioactivity on said support material.
2. The method according to claim 1, wherein said step of charging is performed by applying a voltage between source and drain of said MOSFET.
3. The method according to claim 1, wherein said step of registering is performed by applying a voltage between source and drain of said MOSFET and meaεuring the resulting source-drain current.
4. A method for detecting radioactivity, comprising the steps of:
- disposing at least one radioactive sample on a support material, associating with said εupport material a detecting device comprising at least one detector unit, each said detector unit containing a MOSFET having a floating gate, said gate being charged to a suitable potential, - allowing ions produced by said radioactivity to neutralize the charge on the gate for a εelected time, and registering a change in said potential, the change being indicative to amount of radioactivity on said support material.
PCT/FI1996/000458 1995-08-28 1996-08-28 A detection method for radioactivity on support by direct detection of ionization WO1997008568A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI954041A FI954041A0 (en) 1995-08-28 1995-08-28 Foerfarande Foer detection of radioactivity and stoedmaterial genome direct detection of ionization
FI954041 1995-08-28

Publications (1)

Publication Number Publication Date
WO1997008568A1 true WO1997008568A1 (en) 1997-03-06

Family

ID=8543928

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1996/000458 WO1997008568A1 (en) 1995-08-28 1996-08-28 A detection method for radioactivity on support by direct detection of ionization

Country Status (2)

Country Link
FI (1) FI954041A0 (en)
WO (1) WO1997008568A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009126582A3 (en) * 2008-04-07 2010-02-18 Mirion Technologies, Inc. Dosimetry apparatus, systems, and methods
US9151848B2 (en) 2010-12-15 2015-10-06 Mirion Technologies, Inc. Dosimetry system, methods, and components

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4788581A (en) * 1984-04-10 1988-11-29 Hahn-Meitner-Institut Berlin Gmbh MOS dosimeter
WO1995012134A1 (en) * 1993-10-28 1995-05-04 Rados Technology Oy Radiation detector
WO1996029820A1 (en) * 1995-03-20 1996-09-26 Sarad Gesellschaft Für Komplexe Leistungen Zur Sanierung Radiologisch Belasteter Objekte Mbh Radiation sensor arrangement for detecting the frequency of radiation impinging thereon

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4788581A (en) * 1984-04-10 1988-11-29 Hahn-Meitner-Institut Berlin Gmbh MOS dosimeter
WO1995012134A1 (en) * 1993-10-28 1995-05-04 Rados Technology Oy Radiation detector
WO1996029820A1 (en) * 1995-03-20 1996-09-26 Sarad Gesellschaft Für Komplexe Leistungen Zur Sanierung Radiologisch Belasteter Objekte Mbh Radiation sensor arrangement for detecting the frequency of radiation impinging thereon

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009126582A3 (en) * 2008-04-07 2010-02-18 Mirion Technologies, Inc. Dosimetry apparatus, systems, and methods
US8841622B2 (en) 2008-04-07 2014-09-23 Mirion Technologies, Inc. Dosimetry apparatus, systems, and methods
US9134430B2 (en) 2008-04-07 2015-09-15 Mirion Technologies Inc. Dosimetry apparatus, systems, and methods
US10545248B2 (en) 2008-04-07 2020-01-28 Mirion Technologies, Inc. Dosimetry apparatus, systems, and methods
US9151848B2 (en) 2010-12-15 2015-10-06 Mirion Technologies, Inc. Dosimetry system, methods, and components
US9746564B2 (en) 2010-12-15 2017-08-29 Mirion Technologies, Inc. Dosimetry system, methods, and components

Also Published As

Publication number Publication date
FI954041A0 (en) 1995-08-28

Similar Documents

Publication Publication Date Title
US6406604B1 (en) Multi-dimensional electrophoresis apparatus
US4389670A (en) Electronic method for autofluorography of macromolecules on two-D matrices
US4707235A (en) Electrophoresis method and apparatus having continuous detection means
US5246869A (en) Method for the simultaneous assay of ligands
US20030211637A1 (en) Single particle electrochemical sensors and methods of utilization
EP1644095B1 (en) Method and apparatus for detecting chemical binding
US7687257B2 (en) Device for separating and/or analyzing several molecular targets dissolved in a complex mixture
WO2001068225A1 (en) Micropreparative isoelectric focussing
WO1997008568A1 (en) A detection method for radioactivity on support by direct detection of ionization
US4019057A (en) Device for determining the spatial distribution of radioactivity within an object
Sweedler et al. Novel detection schemes for the trace analysis of amino acids and peptides using capillary electrophoresis
JPH03501057A (en) Device for monitoring the radioactivity of multiple liquid scintillation samples in a multi-well sample plate
US2916626A (en) Electrostatic precipitator sample counter
DE3620235A1 (en) SYSTEM FOR DETERMINING THE SIZE OF ORGANIC MACROMOLECULES
CN111257302B (en) Liquid sample pool for detecting aerobic or facultative anaerobic pathogenic microorganisms by micro-Raman spectrum
Buchtela Gas ionization detectors
JP2002107458A (en) Radioactive ion detector
US4808831A (en) Container for wet and dry radioactive samples
EP0329720A1 (en) Method of scintillation counting using a solid scintillator
Gruner et al. A method for rapid, continuous monitoring of solute uptake and binding
JPS5882176A (en) Continuous radiation flow monitor device
FI96067C (en) Method and apparatus for counting scintillation light pulses
Cosma et al. Simultaneous measurement of radon and thoron exhalation rate from soil and building materials
Kuc et al. A small volume teflon-copper vial for 14C low level liquid scintillation counting
Pathak Measurement of Radiation

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): CA JP NO US

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LU MC NL PT SE

CFP Corrected version of a pamphlet front page
CR1 Correction of entry in section i

Free format text: PAT.BUL.11/97 UNDER INID(54)"TITLE",REPLACE THE EXISTING TEXT BY"A DETECTION METHOD FOR RADIOACTIVITY ON SUPPORT BY DIRECT DETECTION OF IONIZATION"

DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: CA