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textbook:nrctextbook:chapter13 [2025-01-23 00:41]
Merja Herzig 		textbook:nrctextbook:chapter13 [2025-04-24 17:04] (current)
Merja Herzig
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-Radiation imaging in used to locate, and in many cases also to quantify, radionuclide or a radionuclide-bearing compound from solid material. There are two basic types of imaging techniques: planar imaging giving information of radionuclide distribution at two dimensions and tomography giving three-dimensional information. The latter technique is only briefly described at the end of the chapter. Imaging techniques are typically used in biological and medical applications to locate target molecules. To enable the location of these molecules they have been labelled with a radionuclide, typically a beta-emitting radionuclide in planar imaging and a gamma-emitting  +Radiation imaging in used to locate, and in many cases also to quantify, [[textbook:nrctextbook:chapter4|radionuclide]] or a radionuclide-bearing compound from solid material. There are two basic types of imaging techniques: planar imaging giving information of radionuclide distribution at two dimensions and [[textbook:nrctextbook:chapter13#tomography|tomography]] giving three-dimensional information. The latter technique is only briefly described at the end of the chapter. Imaging techniques are typically used in biological and medical applications to locate target molecules. To enable the location of these molecules they have been labelled with a radionuclide, typically a [[textbook:nrctextbook:chapter5#beta|beta-emitting]] radionuclide in planar imaging and a [[textbook:nrctextbook:chapter5#gamma|gamma-emitting]] radionuclide in tomography. Radiation emitted by these radionuclides is then detected by [[textbook:nrctextbook:chapter13#autoradiography|autoradiography]] or using technique based on [[#13.3._ccd_camera_imaging|CCD camera filming]] in case of planar imaging and by an array of gamma detectors in case of [[#13.4._radiation_imaging_by_tomography|tomography]].
-radionuclide in tomography. Radiation emitted by these radionuclides is then detected by autoradiography or using technique based on [[#13.3._ccd_camera_imaging|CCD camera filming]] in case of planar imaging and by an array of gamma detectors in case of [[#13.4._radiation_imaging_by_tomography|tomography]].+
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 +{{anchor:autoradiography}}
 ### ###
-Autoradiography can be divided into two categories, [[#13.1._film_autoradiography|film autoradiography]] and [[#13.2._storage_phosphor_screen_autoradiography|storage phosphor screen autoradiography]]. The prefix auto means that the source of radiation is within the sample unlike in other types of radiographies in which the sample is exposed to an external radiation source, such as X-rays. Autoradiography dates back to late 19<sup>th</sup> century when [[textbook:nrctextbook:chapter1#1.1._the_invention_of_radioactivity|Henri Bequerel]] discovered in 1896 that uranium salts produced an image on photographic plates (Figure XIII.1).+Autoradiography can be divided into two categories, [[#13.1._film_autoradiography|film autoradiography]] and [[#13.2._storage_phosphor_screen_autoradiography|storage phosphor screen autoradiography]]. The prefix auto means that the source of radiation is within the sample unlike in other types of radiographies in which the sample is exposed to an external radiation source, such as [[textbook:nrctextbook:chapter5#x_rays|X-rays]]. Autoradiography dates back to late 19<sup>th</sup> century when [[textbook:nrctextbook:chapter1#henri_becquerel|Henri Becquerel]] discovered in 1896 that [[textbook:nrctextbook:chapter4#uranium|uranium]] salts produced an image on photographic plates (Figure XIII.1).
 ### ###
- 
 {{:textbook:nrctextbook:uranium_salt_on_photographic_plate_fig_13_1.png?200 |}} Figure XIII.1. Image of a uranium salt on a photographic plate (autoradiogram) determined by  {{:textbook:nrctextbook:uranium_salt_on_photographic_plate_fig_13_1.png?200 |}} Figure XIII.1. Image of a uranium salt on a photographic plate (autoradiogram) determined by 
 Henri Bequerel in 1896 (http://www.japanfocus.org/-elin_o_hara-lavick/3196/article.html).\\  Henri Bequerel in 1896 (http://www.japanfocus.org/-elin_o_hara-lavick/3196/article.html).\\ 
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 \\  \\ 
 \\  \\ 
 +
 +{{anchor:film_autoradiography}}
 ===== 13.1. Film autoradiography ===== ===== 13.1. Film autoradiography =====
  
 ### ###
-In film autoradiography a film is apposed to a radionuclide-bearing sample. The sample should be flat and as smooth as possible, for example pressed plant or polished rock surface. The film consists of a 0.2 mm polymeric (polyester or cellulose acetate) support plate coated with an emulsion comprising fine silver halide (AgCl, AgI, AgBr) grains in gelatin. The outer surface facing the sample can have a very thin protective cover. Radiation, typically beta particles but also alpha particles, emitted from the sample pass the surface cover and ionize silver atoms in the emulsion layer, which is typically 10-20 µm thick. The released electrons travel in the emulsion and after  +In film autoradiography a film is apposed to a [[textbook:nrctextbook:chapter4|radionuclide]]-bearing sample. The sample should be flat and as smooth as possible, for example pressed plant or polished rock surface. The film consists of a 0.2 mm polymeric (polyester or cellulose acetate) support plate coated with an emulsion comprising fine silver halide (AgCl, AgI, AgBr) grains in gelatin. The outer surface facing the sample can have a very thin protective cover. Radiation, typically [[textbook:nrctextbook:chapter5#beta_particle|beta particles]] but also [[textbook:nrctextbook:chapter5#alpha_particle|alpha particles]], emitted from the sample pass the surface cover and ionize silver atoms in the emulsion layer, which is typically 10-20 µm thick. The released [[textbook:nrctextbook:chapter2#electron|electrons]] travel in the emulsion and after  
-losing their kinetic energy reduce Ag+ ions into metallic silver Ag forming a latent, invisible image of the radionuclide distribution on the sample. These latent metallic silver centers comprise only of a few silver atoms. When the film is developed in a reducing liquid, Ag<sup>+</sup> ions around the latent silver metal centres reduce and the amount of metallic silver in the crystal increases by a factor of 10<sup>8</sup>-10<sup>10</sup> making them visible either by eye (macro autoradiography) or by microscope (micro autoradiography).+losing their kinetic energy reduce Ag<sup>+</sup> ions into metallic silver Ag forming a latent, invisible image of the [[textbook:nrctextbook:chapter4|radionuclide]] distribution on the sample. These latent metallic silver centers comprise only of a few silver atoms. When the film is developed in a reducing liquid, Ag<sup>+</sup> ions around the latent silver metal centres reduce and the amount of metallic silver in the crystal increases by a factor of 10<sup>8</sup>-10<sup>10</sup> making them visible either by eye (macro autoradiography) or by microscope (micro autoradiography).
 ### ###
  
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 the reactive gel layer. the reactive gel layer.
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 +{{anchor:resolution_autoradiography}}
 ### ###
 An important parameter in autoradiography is the resolution, which means the ability of the system to differentiate two individual points in the sample. A typical resolution range is from 5 µm to 50 µm. The resolution is dependent on the following factors, in the order of importance: An important parameter in autoradiography is the resolution, which means the ability of the system to differentiate two individual points in the sample. A typical resolution range is from 5 µm to 50 µm. The resolution is dependent on the following factors, in the order of importance:
 ### ###
   - Distance between the film and the sample. Closer contact to the sample can be obtained by using a fluid silver halide emulsion without the polymeric support, which improves resolution by 5-7 times at maximum.   - Distance between the film and the sample. Closer contact to the sample can be obtained by using a fluid silver halide emulsion without the polymeric support, which improves resolution by 5-7 times at maximum.
-  - Energy of radiation. The lower the beta energy the better the resolution due to a shorter range of emitted beta particles. The resolution with the low energy beta emitter <sup>3</sup>H (E<sub>max</sub> = 18 keV) is about ten times better than with the high energy beta emitter <sup>32</sup>P (E<sub>max</sub> = 1710 keV). Resolution with the intermediate energy beta emitter <sup>14</sup>C (E<sub>max</sub> = 156 keV) is in between these two.+  - Energy of radiation. The lower the beta energy the better the resolution due to a shorter range of emitted beta particles. The resolution with the low energy beta emitter <sup>3</sup>H ([[textbook:nrctextbook:chapter5#emax_beta|E(max)]] = 18 keV) is about ten times better than with the high energy beta emitter <sup>32</sup>P (E<sub>max</sub> = 1710 keV). Resolution with the intermediate energy beta emitter <sup>14</sup>C (E<sub>max</sub> = 156 keV) is in between these two.
   - Thickness of the sample, the resolution being the better the thinner the sample is.   - Thickness of the sample, the resolution being the better the thinner the sample is.
  
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 {{:textbook:nrctextbook:autoradiogram_of_the_surface_of_a_rock_fig_13_3.png?200 |}} Figure XIII.3. An autoradiogram of the surface of a rock impregnated with polymethylmetacrylate labelled with <sup>14</sup>C. Standard series with varying <sup>14</sup>C activities are at the bottom. {{:textbook:nrctextbook:autoradiogram_of_the_surface_of_a_rock_fig_13_3.png?200 |}} Figure XIII.3. An autoradiogram of the surface of a rock impregnated with polymethylmetacrylate labelled with <sup>14</sup>C. Standard series with varying <sup>14</sup>C activities are at the bottom.
  
 +{{anchor:storage_phosphor_screen_autoradiography}}
 +{{anchor:digital_autoradiography}}
 ===== 13.2. Storage phosphor screen autoradiography ===== ===== 13.2. Storage phosphor screen autoradiography =====
  
 ### ###
-In storage phosphor screen autoradiography, also known as digital autoradiography, the radiation emitted from the sample excites molecules in a phosphor screen apposed to the sample. The excitations are relaxed by scanning with a laser beam, the light emitted in de-excitation is detected and an image is created in a computer based on detected light intensities at all scanned points. The storage term in the name of the process means that the energy from the emitted radiation hitting phosphor molecules is stored in the phosphor crystal as excitation energy. Phosphor is a general name of compounds, which are able to emit light in de-excitation processes.+In storage phosphor screen autoradiography, also known as digital autoradiography, the radiation emitted from the sample [[textbook:nrctextbook:chapter7#excitation|excites]] molecules in a phosphor screen apposed to the sample. The excitations are relaxed by scanning with a laser beam, the light emitted in de-excitation is detected and an image is created in a computer based on detected light intensities at all scanned points. The storage term in the name of the process means that the energy from the emitted radiation hitting phosphor molecules is stored in the phosphor crystal as excitation energy. Phosphor is a general name of compounds, which are able to emit light in de-excitation processes.
 ### ###
 +{{anchor:europium}}
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 The phosphor screen, also known as an imaging plate, consists of a polymer support; polyester for example, over which there is a thin layer (150 μm) of phosphor compound bariumfluorobromide BaFBr doped with trace amounts of divalent Eu<sup>2+</sup> which replace Ba<sup>2+</sup> ions in the crystal. The crystal size of BaFBr:Eu<sup>2+</sup> is very small, at about 5 µm. Since the typical oxidation state of europium is  The phosphor screen, also known as an imaging plate, consists of a polymer support; polyester for example, over which there is a thin layer (150 μm) of phosphor compound bariumfluorobromide BaFBr doped with trace amounts of divalent Eu<sup>2+</sup> which replace Ba<sup>2+</sup> ions in the crystal. The crystal size of BaFBr:Eu<sup>2+</sup> is very small, at about 5 µm. Since the typical oxidation state of europium is 
-+III, Eu<sup>2+</sup> is readily ionized to Eu3+ when a beta particle from the sample hits the phosphor molecules. The electrons originating from the ionization are trapped in barium vacancies resulting in the excitation of the BaFBr molecules. After exposure, the excitation points are located on points where the radionuclide was present in the sample. To make this “latent” image visible the excitations are relaxed by scanning the image plate with a laser beam and light intensity emitted in ++III, Eu<sup>2+</sup> is readily ionized to Eu<sup>3+</sup> when a beta particle from the sample hits the phosphor molecules. The electrons originating from the ionization are trapped in barium vacancies resulting in the excitation of the BaFBr molecules. After exposure, the excitation points are located on points where the radionuclide was present in the sample. To make this “latent” image visible the excitations are relaxed by scanning the image plate with a laser beam and light intensity emitted in 
 the de-excitations at all scanned points (pixels) are detected with a photomultiplier tube. Laser beam moves the trapped electrons to conduction band where they finally combine with Eu<sup>3+</sup> ions to regain Eu<sup>2+</sup> ions (Figure XIII.4). This process is called photostimulated luminescence (PSL). Typically the scanning resolution, pixel size, in digital autoradiography varies from 5 to 500 μm. After scanning the plate, it is erased from excitations by intensive light after which the plate can be reused. the de-excitations at all scanned points (pixels) are detected with a photomultiplier tube. Laser beam moves the trapped electrons to conduction band where they finally combine with Eu<sup>3+</sup> ions to regain Eu<sup>2+</sup> ions (Figure XIII.4). This process is called photostimulated luminescence (PSL). Typically the scanning resolution, pixel size, in digital autoradiography varies from 5 to 500 μm. After scanning the plate, it is erased from excitations by intensive light after which the plate can be reused.
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 {{:textbook:nrctextbook:optimal_densities_and_light_intensity_autoradiography_fig_13_6.png?200 |}} Figure XIII.6. Optical densities and light intensity response (PSL) as a function of detected activity for film (black) and for phosphor screen (white). {{:textbook:nrctextbook:optimal_densities_and_light_intensity_autoradiography_fig_13_6.png?200 |}} Figure XIII.6. Optical densities and light intensity response (PSL) as a function of detected activity for film (black) and for phosphor screen (white).
  
 +{{anchor:cdd_camera_imaging}}
 ===== 13.3. CCD camera imaging ===== ===== 13.3. CCD camera imaging =====
  
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 autoradiography can be avoided. autoradiography can be avoided.
 ### ###
 +{{anchor:tomography}} 
 +{{anchor:pet_tomography}} 
 +{{anchor:spect_tomography}}
 ===== 13.4. Radiation imaging by tomography ===== ===== 13.4. Radiation imaging by tomography =====
 ### ###
 If a three-dimensional picture of the radionuclide distribution in a sample is needed one could cut thin slices of the sample, determine their autoradiograms and superimpose them to get the three-dimensional picture. This would, however, be very laborious and not suitable to determine distribution of a short-lived radionuclide, and particularly to distribution in a human body. For this purpose tomographic methods are the choice and they are widely used in the development and clinical use of radiopharmaceuticals. Depending on the type of radionuclide either single photon  If a three-dimensional picture of the radionuclide distribution in a sample is needed one could cut thin slices of the sample, determine their autoradiograms and superimpose them to get the three-dimensional picture. This would, however, be very laborious and not suitable to determine distribution of a short-lived radionuclide, and particularly to distribution in a human body. For this purpose tomographic methods are the choice and they are widely used in the development and clinical use of radiopharmaceuticals. Depending on the type of radionuclide either single photon 
-emission tomography (SPECT) or positron emission tomography (PET) are two choices. In the SPECT mode a radiopharmaceutical labelled with a gamma-emitting radionuclide, most typically <sup>99m</sup>Tc, is injected into a body of a test animal or human. In PET mode the label is a positron emitter, most typically 18F. Thereafter the distribution of the radiopharmaceutical in the body is followed with a gamma camera in case of SPECT and with a PET camera in case of PET, both detecting gamma rays outside the body. Gamma camera comprise an array of collimated Na(I) detectors capable to separate gamma rays emitting from various parts of the body. PET camera makes use of two 511 keV gamma rays emitted in opposite directions in the annihilation of positron particles. PET camera consist of an array of Na(I) detectors in a ring. The target is positioned inside the ring and the camera detects pulses in coincidence mode, i.e. when two gamma rays hit detectors on opposite sides of the ring a pulse is registered while in case of only one gamma ray the pulse is rejected. Both SPECT and PET tomographies are powerful tools in medical imaging and they are increasingly used also in the preclinical development.+emission tomography (SPECT) or positron emission tomography (PET) are two choices. In the SPECT mode a radiopharmaceutical labelled with a [[textbook:nrctextbook:chapter5#gamma|gamma-emitting radionuclide]] , most typically <sup>99m</sup>Tc, is injected into a body of a test animal or human. In PET mode the label is a positron emitter, most typically 18F. Thereafter the distribution of the radiopharmaceutical in the body is followed with a gamma camera in case of SPECT and with a PET camera in case of PET, both detecting gamma rays outside the body. Gamma camera comprise an array of collimated Na(I) detectors capable to separate gamma rays emitting from various parts of the body. PET camera makes use of two 511 keV gamma rays emitted in opposite directions in the annihilation of positron particles. PET camera consist of an array of Na(I) detectors in a ring. The target is positioned inside the ring and the camera detects pulses in coincidence mode, i.e. when two gamma rays hit detectors on opposite sides of the ring a pulse is registered while in case of only one gamma ray the pulse is rejected. Both SPECT and PET tomographies are powerful tools in medical imaging and they are increasingly used also in the preclinical development.
 ### ###
  
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 (http://www.cellsighttech.com/technology/pet.html) and scheme of PET camera (right)  (http://www.cellsighttech.com/technology/pet.html) and scheme of PET camera (right) 
 (http://www.lookfordiagnosis.com/mesh_info.php?term=Positron-Emission+Tomography&lang=1). (http://www.lookfordiagnosis.com/mesh_info.php?term=Positron-Emission+Tomography&lang=1).
 +{{anchor:applications_autoradiography}}
 ===== 13.5. Applications of autoradiography ===== ===== 13.5. Applications of autoradiography =====
  
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 ### ###
-In environmental radioactivity studies it is a common way to identify and localize particles with higher than typical activities. These particles are present in the environment from fallouts from the nuclear weapons tests in the 1950' to 1970's and from the Chernobyl accident, as well as from releases from nuclear facilities. Particles can be found from air sampling filters and from soils and sediments. Figure XIII.8 shows a film autoradiogram of an air filter taken from a nuclear power  +In environmental radioactivity studies it is a common way to identify and localize particles with higher than typical [[textbook:nrctextbook:chapter6#activity|activities]]. These particles are present in the environment from fallouts from the nuclear weapons tests in the 1950' to 1970's and from the Chernobyl accident, as well as from releases from nuclear facilities. Particles can be found from air sampling filters and from soils and sediments. Figure XIII.8 shows a film autoradiogram of an air filter taken from a nuclear power  
-plant during maintenance work. The points seen as dark spots in the autoradiogram represent individual particles or their agglomerates removed from the air by filtration (pore size typically about 0.2 μm); the darker the spots are the larger the particles and the higher is their activity. The activity of the largest particle in this autoradiogram was 25 Bq.  Based on the information obtained from the autoradiogram larger particles can be localized and further also isolated with the aid of a microscope. The isolated particle can then be characterized with respect to elemental, radionuclide and isotopic composition using a variety of methods, such as scanning electron microscopy, gamma spectrometry, XANES/EXAFS spectroscopy, as well as alpha and mass spectroscopy.+plant during maintenance work. The points seen as dark spots in the autoradiogram represent individual particles or their agglomerates removed from the air by filtration (pore size typically about 0.2 μm); the darker the spots are the larger the particles and the higher is their activity. The [[textbook:nrctextbook:chapter6#activity|activity]] of the largest particle in this autoradiogram was 25 Bq.  Based on the information obtained from the autoradiogram larger particles can be localized and further also isolated with the aid of a microscope. The isolated particle can then be characterized with respect to elemental, [[textbook:nrctextbook:chapter4|radionuclide]] and [[textbook:nrctextbook:chapter2#isotope|isotopic]] composition using a variety of methods, such as scanning electron microscopy, [[textbook:nrctextbook:chapter9|gamma spectrometry]], XANES/EXAFS spectroscopy, as well as [[textbook:nrctextbook:chapter11#semiconductor_detectors_alpha|alpha spectrometry]] and [[textbook:nrctextbook:chapter8#mass_spectrometry|mass spectroscopy]].
 ### ###
  
-{{:textbook:nrctextbook:autoradiogram_of_an_air_filter_fig_13_8.png?400|}} Figure XIII.8. Autoradiogram of an air filter sample taken from a nuclear power plant during  +{{:textbook:nrctextbook:autoradiogram_of_an_air_filter_fig_13_8.png?400|}}  
-maintenance (http://www.stuk.fi/julkaisut_maaraykset/kirjasarja/fi_FI/kirjasarja2/). The diameter of the image is about 10 cm.+ 
 +Figure XIII.8. Autoradiogram of an air filter sample taken from a nuclear power plant during maintenance (http://www.stuk.fi/julkaisut_maaraykset/kirjasarja/fi_FI/kirjasarja2/). The diameter of the image is about 10 cm.
  
 ==== 13.5.2. Determination of rock porosities ==== ==== 13.5.2. Determination of rock porosities ====
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 ### ###
  
-{{:textbook:nrctextbook:14cpmma_fig_13_9.png?400|}} Figure XIII.9. Photograph of a polished rock piece surface (left) and an autoradiogram from the same surface (right) after impregnating the rock with <sup>14</sup>C labeled MMA and polymerizing it into <sup>14</sup>C-PMMA.+{{:textbook:nrctextbook:14cpmma_fig_13_9.png?400|}}  
 + 
 +Figure XIII.9. Photograph of a polished rock piece surface (left) and an autoradiogram from the same surface (right) after impregnating the rock with <sup>14</sup>C labeled MMA and polymerizing it into <sup>14</sup>C-PMMA.
  
 +{{anchor:imaging_radiopharmaceuticals}}
 ==== 13.5.3 Radionuclide imaging in radiopharmaceutical research ==== ==== 13.5.3 Radionuclide imaging in radiopharmaceutical research ====
  
 ### ###
-In the development of a radiopharmaceutical the product needs to pass preclinical tests prior to human tests. An essential part of the preclinical tests are imaging studies to reveal distribution of the product into various organs. These imaging studies are carried out by animals, either with living animals or with specific organs/tissues of dead animals. Both autoradiography and PET/SPECT imaging are used in these studies. The autoradiography tests can be divided into //in vivo// and //ex vivo// tests. In the former an organ or tissue is equilibrated with a radiopharmaceutical-bearing solution and in the latter radiopharmaceutical is injected into a living animal. After desired contact time the animal is sacrificed and the distribution of the radiopharmaceutical in the body is determined by measuring radioactivity of various organs separated from the carcass. More detailed distribution can be observed by freezing the organ/tissue or the whole body, by taking thin slices with microtome and by making autoradiograms from the slices. An example of a series of slices taken from a rat’s brain incubated with a solution containing a 18F-labelled radiopharmaceutical <sup>18</sup>F-CTF-FP is shown in Figure XIII.10. The autoradiograms show the spatial distribution of the <sup>18</sup>F radioactivity (red  +In the development of a radiopharmaceutical the product needs to pass preclinical tests prior to human tests. An essential part of the preclinical tests are imaging studies to reveal distribution of the product into various organs. These imaging studies are carried out by animals, either with living animals or with specific organs/tissues of dead animals. Both [[textbook:nrctextbook:chapter13#autoradiography|autoradiography]] and [[textbook:nrctextbook:chapter13#pet_tomography|PET]]/[[textbook:nrctextbook:chapter13#spect_tomography|SPECT]] imaging are used in these studies. The autoradiography tests can be divided into //in vivo// and //ex vivo// tests. In the former an organ or tissue is equilibrated with a radiopharmaceutical-bearing solution and in the latter radiopharmaceutical is injected into a living animal. After desired contact time the animal is sacrificed and the distribution of the radiopharmaceutical in the body is determined by measuring radioactivity of various organs separated from the carcass. More detailed distribution can be observed by freezing the organ/tissue or the whole body, by taking thin slices with microtome and by making autoradiograms from the slices. An example of a series of slices taken from a rat’s brain incubated with a solution containing a 18F-labelled radiopharmaceutical <sup>18</sup>F-CTF-FP is shown in Figure XIII.10. The autoradiograms show the spatial distribution of the <sup>18</sup>F radioactivity (red indicates the highest levels, blue the lowest levels), with nonspecific uptake partly subtracted. STR indicates striatum; AMY, amygdala; HIP, hippocampus; LC, locus coeruleus; RAP, raphe nuclei; SN, substantia nigra; CTX, frontal cortex; and CERE, cerebellum.
-indicates the highest levels, blue the lowest levels), with nonspecific uptake partly subtracted. STR indicates striatum; AMY, amygdala; HIP, hippocampus; LC, locus coeruleus; RAP, raphe nuclei; SN, substantia nigra; CTX, frontal cortex; and CERE, cerebellum.+
 ### ###
  
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 Figure XIII.10. Autoradiograms of ex vivo rat brain sections at 15 min after injection of dopamine transporter (DAT) radioligand [<sup>18</sup>F]β-CFT-FP. The upper row depicts a control rat, and the lower row depicts a rat pretreated with the DAT inhibitor GBR12909 (Koivula, T. et al. Nucl. Med. Biol. 35 (2):177-183). Figure XIII.10. Autoradiograms of ex vivo rat brain sections at 15 min after injection of dopamine transporter (DAT) radioligand [<sup>18</sup>F]β-CFT-FP. The upper row depicts a control rat, and the lower row depicts a rat pretreated with the DAT inhibitor GBR12909 (Koivula, T. et al. Nucl. Med. Biol. 35 (2):177-183).
  
 +{{anchor:hplc}}
 +{{anchor:tlc}}
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 For the quality control of radiopharmaceutical products HPLC (high performance liquid  For the quality control of radiopharmaceutical products HPLC (high performance liquid 
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 ### ###
  
 +{{anchor:solid_state_nuclear_track_detectors}}
 ===== 13.6. Solid state nuclear track detectors ===== ===== 13.6. Solid state nuclear track detectors =====
  
 ### ###
-Nuclear track methods are based on tracks created by charged particles (from H<sup>+</sup> up) in solid state nuclear track detector (SSNTD) apposed to the sample emitting the particles. SSNTD can be used to locate particles with elevated alpha activity or fissile material and quantify their amounts by the number of detected tracks. SSNTDs are typically made of plastics. Also other detector materials, such as mica and glass, are used but they are not discussed here. The plastic detectors are made of cellulose nitrate, polycarbonate, polethyleneterephthalate and polyallyldiglycol carbonate, of which the latter has the best sensitivity, i.e. it can produce detectable tracks most effectively. Polyallyldiglycol carbonate is also known with a code name CR-39. It is also able to register tracks from alpha particles, which are not the case with polycarbonate detector. Plastic SSNT detectors are thin foils with thickness varying in the range of 100-1000 µm. The tracks created in the detector are so small, tens of nanometers, that they cannot be seen by eye. They can be detected directly with transmission electron microscopy (TEM) and their number can be counted by eye or computer programs developed for this purpose. Alternatively, the size of the tracks can be enlarged by etching, typically with 2-6M NaOH, which enables detection and counting of the tracks with an optical microscope. Etching is carried at a slightly elevated temperature (50-60 ºC) for about an hour. Furthermore, the tracks can be widened by electrical methods after chemical etching and detected by image analysis techniques. Figure XIII.11 presents a scanned Makrofol film for +Nuclear track methods are based on tracks created by charged particles (from H<sup>+</sup> up) in solid state nuclear track detector (SSNTD) apposed to the sample emitting the particles. SSNTD can be used to locate particles with elevated [[textbook:nrctextbook:chapter5#alpha|alpha activity]] or [[textbook:nrctextbook:chapter3#fission|fissile]] material and quantify their amounts by the number of detected tracks. SSNTDs are typically made of plastics. Also other detector materials, such as mica and glass, are used but they are not discussed here. The plastic detectors are made of cellulose nitrate, polycarbonate, polethyleneterephthalate and polyallyldiglycol carbonate, of which the latter has the best sensitivity, i.e. it can produce detectable tracks most effectively. Polyallyldiglycol carbonate is also known with a code name CR-39. It is also able to register tracks from [[textbook:nrctextbook:chapter5#alpha_particle|alpha particles]], which are not the case with polycarbonate detector. Plastic SSNT detectors are thin foils with thickness varying in the range of 100-1000 µm. The tracks created in the detector are so small, tens of nanometers, that they cannot be seen by eye. They can be detected directly with transmission electron microscopy (TEM) and their number can be counted by eye or computer programs developed for this purpose. Alternatively, the size of the tracks can be enlarged by etching, typically with 2-6M NaOH, which enables detection and counting of the tracks with an optical microscope. Etching is carried at a slightly elevated temperature (50-60 ºC) for about an hour. Furthermore, the tracks can be widened by electrical methods after chemical etching and detected by image analysis techniques. Figure XIII.11 presents a scanned Makrofol film for 
 determination of radon content in the indoor air by counting the number of tracks on the film and magnified image of the tracks by optical microscope. determination of radon content in the indoor air by counting the number of tracks on the film and magnified image of the tracks by optical microscope.
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textbook/nrctextbook/chapter13.1737589266.txt.gz · Last modified: 2025-01-23 00:41 by Merja Herzig

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