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84-474: Scintillography is an imaging method of nuclear events provoked by collisions or charged current interactions among nuclear particles or ionizing radiation and atoms which result in a brief, localised pulse of electromagnetic radiation , usually in the visible light range ( Cherenkov radiation ). This pulse ( scintillation ) is usually detected and amplified by a photomultiplier or charge-coupled device elements, and its resulting electrical waveform

168-425: A nuclear medicine scan, during one type of nuclear cardiac stress test . Soluble thallium salts (many of which are nearly tasteless) are highly toxic and they were historically used in rat poisons and insecticides . Because of their nonselective toxicity, use of these compounds has been restricted or banned in many countries. Thallium poisoning usually results in hair loss. Because of its historic popularity as

252-463: A basic and soluble thallium source in organic and organometallic chemistry. Organothallium compounds tend to be thermally unstable, in concordance with the trend of decreasing thermal stability down group 13. The chemical reactivity of the Tl–C bond is also the lowest in the group, especially for ionic compounds of the type R 2 TlX. Thallium forms the stable [Tl(CH 3 ) 2 ] ion in aqueous solution; like

336-429: A greater degree of objectivity to the study of these areas. One emerging technology is MALDI molecular imaging based on mass spectrometry . Many areas of research are being conducted in the field of molecular imaging. Much research is currently centered on detecting what is known as a predisease state or molecular states that occur before typical symptoms of a disease are detected. Other important veins of research are

420-671: A high index of refraction . Combined with sulfur or selenium and arsenic, thallium has been used in the production of high- density glasses that have low melting points in the range of 125 and 150 Celsius°. These glasses have room-temperature properties that are similar to ordinary glasses and are durable, insoluble in water and have unique refractive indices . Thallium(I) sulfide's electrical conductivity changes with exposure to infrared light , making this compound useful in photoresistors . Thallium selenide has been used in bolometers for infrared detection. Doping selenium semiconductors with thallium improves their performance, thus it

504-597: A large part of the work, especially the isolation of the metallic thallium was done by Lamy, Crookes tried to secure his own priority on the work. Lamy was awarded a medal at the International Exhibition in London 1862: For the discovery of a new and abundant source of thallium and after heavy protest Crookes also received a medal: thallium, for the discovery of the new element. The controversy between both scientists continued through 1862 and 1863. Most of

588-456: A murder weapon, thallium has gained notoriety as "the poisoner's poison" and "inheritance powder" (alongside arsenic ). A thallium atom has 81 electrons, arranged in the electron configuration [Xe]4f 5d 6s 6p ; of these, the three outermost electrons in the sixth shell are valence electrons. Due to the inert pair effect , the 6s electron pair is relativistically stabilised and it is more difficult to get these involved in chemical bonding than it

672-420: A notable green spectral line. Thallium, from Greek θαλλός , thallós , meaning "green shoot" or "twig", was named by Crookes. It was isolated by both Lamy and Crookes in 1862; Lamy by electrolysis and Crookes by precipitation and melting of the resultant powder. Crookes exhibited it as a powder precipitated by zinc at the international exhibition , which opened on 1 May that year. Thallium tends to form

756-474: A peptide probe that can binds to apoptotic and necrotic cells. A number of near-infrared (NIR) fluorophores have been employed for in vivo imaging, including Kodak X-SIGHT Dyes and Conjugates, Pz 247, DyLight 750 and 800 Fluors, Cy 5.5 and 7 Fluors, Alexa Fluor 680 and 750 Dyes, IRDye 680 and 800CW Fluors. Quantum dots, with their photostability and bright emissions, have generated a great deal of interest; however, their size precludes efficient clearance from

840-623: A radioaerosol invented in Australia by Dr Bill Burch and Dr Richard Fawdry) is inhaled by the patient through a mouthpiece or mask that covers the nose and mouth. The perfusion phase of the test involves the intravenous injection of radioactive technetium macro aggregated albumin (Tc99m-MAA). A gamma camera acquires the images for both phases of the study. For example, the ligand methylene-diphosphonate (MDP) can be preferentially taken up by bone. By chemically attaching technetium-99m to MDP, radioactivity can be transported and attached to bone via

924-629: A sensitivity of around 10 mol/L to 10 mol/L which, compared to other types of imaging, can be very limiting. This problem stems from the fact that the difference between atoms in the high energy state and the low energy state is very small. For example, at 1.5 Tesla , a typical field strength for clinical MRI, the difference between high and low energy states is approximately 9 molecules per 2 million. Improvements to increase MR sensitivity include increasing magnetic field strength, and hyperpolarization via optical pumping, dynamic nuclear polarization or parahydrogen induced polarization . There are also

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1008-632: A trace element in iron pyrite , and thallium is extracted as a by-product of roasting this mineral for the production of sulfuric acid . Thallium can also be obtained from the smelting of lead and zinc ores. Manganese nodules found on the ocean floor contain some thallium. In addition, several other thallium minerals, containing 16% to 60% thallium, occur in nature as complexes of sulfides or selenides that primarily contain antimony , arsenic , copper, lead, and silver . These minerals are rare, and have had no commercial importance as sources of thallium. The Allchar deposit in southern North Macedonia

1092-550: A transportable generator, which is similar to the technetium-99m generator . The generator contains lead-201 (half-life 9.33 hours), which decays by electron capture to thallium-201. The lead-201 can be produced in a cyclotron by the bombardment of thallium with protons or deuterons by the (p,3n) and (d,4n) reactions. A thallium stress test is a form of scintigraphy in which the amount of thallium in tissues correlates with tissue blood supply. Viable cardiac cells have normal Na /K ion-exchange pumps . The Tl cation binds

1176-533: A variety of signal amplification schemes based on chemical exchange that increase sensitivity. To achieve molecular imaging of disease biomarkers using MRI, targeted MRI contrast agents with high specificity and high relaxivity (sensitivity) are required. To date, many studies have been devoted to developing targeted-MRI contrast agents to achieve molecular imaging by MRI. Commonly, peptides, antibodies, or small ligands, and small protein domains, such as HER-2 affibodies, have been applied to achieve targeting. To enhance

1260-453: Is a chemical element ; it has symbol Tl and atomic number 81. It is a silvery-white post-transition metal that is not found free in nature. When isolated, thallium resembles tin , but discolors when exposed to air. Chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861, in residues of sulfuric acid production. Both used the newly developed method of flame spectroscopy , in which thallium produces

1344-430: Is a nuclear medicine imaging technique which produces a three-dimensional image or picture of functional processes in the body. The theory behind PET is simple enough. First a molecule is tagged with a positron emitting isotope. These positrons annihilate with nearby electrons, emitting two 511 keV photons, directed 180 degrees apart in opposite directions. These photons are then detected by the scanner, which can estimate

1428-437: Is a black solid which decomposes above 800 °C, forming the thallium(I) oxide and oxygen. The simplest possible thallium compound, thallane (TlH 3 ), is too unstable to exist in bulk, both due to the instability of the +3 oxidation state as well as poor overlap of the valence 6s and 6p orbitals of thallium with the 1s orbital of hydrogen. The trihalides are more stable, although they are chemically distinct from those of

1512-400: Is a constituent of the alloy in the anode plates of magnesium seawater batteries . Soluble thallium salts are added to gold plating baths to increase the speed of plating and to reduce grain size within the gold layer. A saturated solution of equal parts of thallium(I) formate (Tl(HCO 2 )) and thallium(I) malonate (Tl(C 3 H 3 O 4 )) in water is known as Clerici solution . It

1596-470: Is a field of medical imaging that focuses on imaging molecules of medical interest within living patients. This is in contrast to conventional methods for obtaining molecular information from preserved tissue samples, such as histology . Molecules of interest may be either ones produced naturally by the body, or synthetic molecules produced in a laboratory and injected into a patient by a doctor. The most common example of molecular imaging used clinically today

1680-411: Is a mobile, odorless liquid which changes from yellowish to colorless upon reducing the concentration of the thallium salts. With a density of 4.25 g/cm at 20 °C, Clerici solution is one of the heaviest aqueous solutions known. It was used in the 20th century for measuring the density of minerals by the flotation method, but its use has discontinued due to the high toxicity and corrosiveness of

1764-545: Is dangerous, and adequate ventilation is necessary when melting this metal. Thallium(I) compounds have a high aqueous solubility and are readily absorbed through the skin, and care should be taken to avoid this route of exposure, as cutaneous absorption can exceed the absorbed dose received by inhalation at the permissible exposure limit (PEL). Exposure by inhalation cannot safely exceed 0.1 mg/m in an eight-hour time-weighted average (40-hour work week). The Centers for Disease Control and Prevention (CDC) states, "Thallium

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1848-420: Is either extracted from the dusts from the smelter flues or from residues such as slag that are collected at the end of the smelting process. The raw materials used for thallium production contain large amounts of other materials and therefore a purification is the first step. The thallium is leached either by the use of an alkali or sulfuric acid from the material. The thallium is precipitated several times from

1932-440: Is estimated to be 0.7 mg/kg, mostly in association with potassium -based minerals in clays , soils , and granites . The major source of thallium for practical purposes is the trace amount that is found in copper , lead , zinc , and other heavy-metal- sulfide ores . Thallium is found in the minerals crookesite TlCu 7 Se 4 , hutchinsonite TlPbAs 5 S 9 , and lorándite TlAsS 2 . Thallium also occurs as

2016-432: Is for the heavier elements. Thus, very few electrons are available for metallic bonding, similar to the neighboring elements mercury and lead . Thallium, then, like its congeners, is a soft, highly electrically conducting metal with a low melting point, of 304 °C. A number of standard electrode potentials, depending on the reaction under study, are reported for thallium, reflecting the greatly decreased stability of

2100-449: Is formed. Sulfuric and nitric acids dissolve thallium rapidly to make the sulfate and nitrate salts, while hydrochloric acid forms an insoluble thallium(I) chloride layer. Thallium has 41 isotopes which have atomic masses that range from 176 to 216. Tl and Tl are the only stable isotopes and make up nearly all of natural thallium. The five short-lived isotopes Tl through Tl inclusive occur in nature, as they are part of

2184-459: Is not classifiable as a carcinogen, and it is not suspected to be a carcinogen. It is unknown whether chronic or repeated exposure to thallium increases the risk of reproductive toxicity or developmental toxicity. Chronic high level exposure to thallium through inhalation has been reported to cause nervous system effects, such as numbness of fingers and toes." For a long time thallium compounds were readily available as rat poison. This fact and that it

2268-591: Is ongoing to develop high-temperature superconducting materials for such applications as magnetic resonance imaging , storage of magnetic energy, magnetic propulsion , and electric power generation and transmission. The research in applications started after the discovery of the first thallium barium calcium copper oxide superconductor in 1988. Thallium cuprate superconductors have been discovered that have transition temperatures above 120 K. Some mercury-doped thallium-cuprate superconductors have transition temperatures above 130 K at ambient pressure, nearly as high as

2352-457: Is possible. Above 900 nm, water absorption can interfere with signal-to-background ratio. Because the absorption coefficient of tissue is considerably lower in the near infrared (NIR) region (700-900 nm), light can penetrate more deeply, to depths of several centimeters. Fluorescent probes and labels are an important tool for optical imaging. Some researchers have applied NIR imaging in rat model of acute myocardial infarction (AMI), using

2436-400: Is processed by computers to provide two- and three-dimensional images of a subject or region of interest . Scintillography is mainly used in scintillation cameras in experimental physics . For example, huge neutrino detection underground tanks filled with tetrachloroethylene are surrounded by arrays of photo detectors in order to capture the extremely rare event of a collision between

2520-409: Is produced not from potassium ores, but as a byproduct from refining of heavy-metal sulfide ores. Approximately 65% of thallium production is used in the electronics industry and the remainder is used in the pharmaceutical industry and in glass manufacturing . It is also used in infrared detectors . The radioisotope thallium-201 (as the soluble chloride TlCl) is used in small amounts as an agent in

2604-446: Is significantly cheaper than either PET or fMRI. However it lacks good spatial (i.e., where exactly the particle is) or temporal (i.e., did the contrast agent signal happen at this millisecond, or that millisecond) resolution. Additionally, due to the radioactivity of the contrast agent, there are safety aspects concerning the administration of radioisotopes to the subject, especially for serial studies. Positron emission tomography (PET)

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2688-519: Is the most popular isotope used for thallium nuclear cardiac stress tests . Thallium(III) compounds resemble the corresponding aluminium(III) compounds. They are moderately strong oxidizing agents and are usually unstable, as illustrated by the positive reduction potential for the Tl /Tl couple. Some mixed-valence compounds are also known, such as Tl 4 O 3 and TlCl 2 , which contain both thallium(I) and thallium(III). Thallium(III) oxide , Tl 2 O 3 ,

2772-472: Is to be able to noninvasively monitor all of the biochemical processes occurring inside an organism in real time. Current research in molecular imaging involves cellular / molecular biology , chemistry , and medical physics , and is focused on: 1) developing imaging methods to detect previously undetectable types of molecules, 2) expanding the number and types of contrast agents available, and 3) developing functional contrast agents that provide information about

2856-426: Is to diagnose pulmonary embolism , e.g. with a ventilation/perfusion scan and may be appropriate for excluding PE in pregnancy. Less common indications include evaluation of lung transplantation , preoperative evaluation, evaluation of right-to-left shunts . In the ventilation phase of a ventilation/perfusion scan, a gaseous radionuclide xenon or technetium DTPA in an aerosol form (or ideally using Technegas,

2940-437: Is to inject a contrast agent (e.g., a microbubble , metal ion , or radioactive isotope) into a patient's bloodstream and to use an imaging modality (e.g., ultrasound , MRI , CT , PET ) to track its movement in the body. Molecular imaging originated from the field of radiology from a need to better understand fundamental molecular processes inside organisms in a noninvasive manner. The ultimate goal of molecular imaging

3024-405: Is transported into the cells. Exercise or dipyridamole induces widening ( vasodilation ) of normal coronary arteries. This produces coronary steal from areas of ischemia where arteries are already maximally dilated. Areas of infarct or ischemic tissue will remain "cold". Pre- and post-stress thallium may indicate areas that will benefit from myocardial revascularization . Redistribution indicates

3108-429: Is used in trace amounts in selenium rectifiers . Another application of thallium doping is the sodium iodide and cesium iodide crystals in gamma radiation detection devices. In these, the sodium iodide crystals are doped with a small amount of thallium to improve their efficiency as scintillation generators. Some of the electrodes in dissolved oxygen analyzers contain thallium. Research activity with thallium

3192-483: Is water-soluble and nearly tasteless led to frequent intoxication caused by accident or criminal intent. One of the main methods of removing thallium (both radioactive and stable) from humans is to use Prussian blue , a material which absorbs thallium. Up to 20 grams per day of Prussian blue is fed by mouth to the patient, and it passes through their digestive system and comes out in their stool. Hemodialysis and hemoperfusion are also used to remove thallium from

3276-536: The bile ducts by a gallstone ( cholelithiasis ), a tumor, or another cause. It can also diagnose gallbladder diseases , e.g. bile leaks of biliary fistulas . In cholescintigraphy, the injected radioactive chemical is taken up by the liver and secreted into the bile. The radiopharmaceutical then goes into the bile ducts, the gallbladder, and the intestines. The gamma camera is placed on the abdomen to picture these perfused organs. Other scintigraphic tests are done similarly. The most common indication for lung scintigraphy

3360-405: The hydroxyapatite for imaging. Any increased physiological function, such as a fracture in the bone, will usually mean increased concentration of the tracer. A thallium stress test is a form of scintigraphy, where the amount of thallium -201 detected in cardiac tissues correlates with tissue blood supply. Viable cardiac cells have normal Na/K ion exchange pumps . Thallium binds the K pumps and

3444-474: The +3 and +1 oxidation states. The +3 state resembles that of the other elements in group 13 ( boron , aluminium , gallium , indium ). However, the +1 state, which is far more prominent in thallium than the elements above it, recalls the chemistry of alkali metals and thallium(I) ions are found geologically mostly in potassium-based ores and (when ingested) are handled in many ways like potassium ions (K ) by ion pumps in living cells. Commercially, thallium

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3528-552: The +3 oxidation state: Thallium is the first element in group 13 where the reduction of the +3 oxidation state to the +1 oxidation state is spontaneous under standard conditions. Since bond energies decrease down the group, with thallium, the energy released in forming two additional bonds and attaining the +3 state is not always enough to outweigh the energy needed to involve the 6s-electrons. Accordingly, thallium(I) oxide and hydroxide are more basic and thallium(III) oxide and hydroxide are more acidic, showing that thallium conforms to

3612-538: The 1970s allowed mapping of the distribution of the radioisotopes in the organ or tissue, and led to the technique now called single photon emission computed tomography (SPECT). The imaging agent used in SPECT emits gamma rays, as opposed to the positron emitters (such as F ) used in PET. There are a range of radiotracers (such as Tc , In , I , Tl ) that can be used, depending on

3696-434: The K pumps and is transported into the cells. Exercise or dipyridamole induces widening ( vasodilation ) of arteries in the body. This produces coronary steal by areas where arteries are maximally dilated. Areas of infarct or ischemic tissue will remain "cold". Pre- and post-stress thallium may indicate areas that will benefit from myocardial revascularization . Redistribution indicates the existence of coronary steal and

3780-508: The Physikalisch-Medizinische Gesellschaft für Neuroradiologie (The Physics and Medical Society for Neuroradiology) instituted the ‘Ziedses des Plantes Medal'. It was first awarded to W. Oldendorf en G. Hounsfield in 1974 for Computer Tomography (CT) . Later, in 1985, the medal was awarded to Ziedses des Plantes himself. In 1977 he received The Roentgen Medal. Molecular imaging Molecular imaging

3864-503: The blood serum. At later stages of the treatment, additional potassium is used to mobilize thallium from the tissues. According to the United States Environmental Protection Agency (EPA), artificially-made sources of thallium pollution include gaseous emission of cement factories , coal-burning power plants, and metal sewers. The main source of elevated thallium concentrations in water is

3948-458: The circulatory and renal systems while exhibiting long-term toxicity. . Several studies have demonstrated the use of infrared dye-labeled probes in optical imaging. It is important to note that addition of an NIR probe to any vector can alter the vector's biocompatibility and biodistribution. Therefore, it can not be unequivocally assumed that the conjugated vector will behave similarly to the native form. The development of computed tomography in

4032-475: The composition of minerals and chemical products. Crookes and Lamy both started to use the new method. Crookes used it to make spectroscopic determinations for tellurium on selenium compounds deposited in the lead chamber of a sulfuric acid production plant near Tilkerode in the Harz mountains . He had obtained the samples for his research on selenium cyanide from August Hofmann years earlier. By 1862, Crookes

4116-410: The density of positron annihilations in a specific area. When enough interactions and annihilations have occurred, the density of the original molecule may be measured in that area. Typical isotopes include C , N , O , F , Cu , Cu , I , Br , Rb , Zr and Ga , with F being the most clinically utilized. One of

4200-468: The description of the human genome. New paths in fundamental research, as well as in applied and industrial research, render the task of scientists more complex and increase the demands on them. Therefore, a tailor-made teaching program is in order. Molecular imaging differs from traditional imaging in that probes known as biomarkers are used to help image particular targets or pathways. Biomarkers interact chemically with their surroundings and in turn alter

4284-400: The diagnosis of diseases such as cancer, and neurological and cardiovascular diseases. This technique also contributes to improving the treatment of these disorders by optimizing the pre-clinical and clinical tests of new medication. They are also expected to have a major economic impact due to earlier and more precise diagnosis. Molecular and Functional Imaging has taken on a new direction since

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4368-689: The discussion ended after Crookes was elected Fellow of the Royal Society in June 1863. The dominant use of thallium was the use as poison for rodents. After several accidents the use as poison was banned in the United States by Presidential Executive Order 11643 in February 1972. In subsequent years several other countries also banned its use. Thallium concentration in the Earth's crust

4452-603: The existence of coronary steal and the presence of ischemic coronary artery disease . Tc99m- sestamibi is used to detect parathyroid adenomas . To detect metastases/function of thyroid, the isotopes technetium-99m or iodine-123 are generally used, and for this purpose the iodide isotope does not need to be attached to another protein or molecule, because thyroid tissue takes up free iodide actively. Examples are gallium scans , indium white blood cell scans , iobenguane scan (MIBG) and octreotide scans . The MIBG scan detects adrenergic tissue and thus can be used to identify

4536-457: The field. In this way, a European Master Programme "EMMI" is being set up to train a new generation of professionals in molecular imaging. Recently the term molecular imaging has been applied to a variety of microscopy and nanoscopy techniques including live-cell microscopy, Total Internal Reflection Fluorescence (TIRF)-microscopy, STimulated Emission Depletion (STED)-nanoscopy and Atomic Force Microscopy (AFM) as here images of molecules are

4620-417: The fluid's atoms and a neutrino . Another extensive use of scintillography is in medical imaging techniques which use gamma ray detectors called gamma cameras . Detectors coated with materials which scintillate when subjected to gamma rays are scanned with optical photon detectors and scintillation counters . The subjects are injected with special radionuclides which irradiate in the gamma range inside

4704-418: The gamma camera around the patient, a three-dimensional image of the distribution of the radiotracer can be obtained by employing filtered back projection or other tomographic techniques. The radioisotopes used in SPECT have relatively long half lives (a few hours to a few days) making them easy to produce and relatively cheap. This represents the major advantage of SPECT as a molecular imaging technique, since it

4788-439: The general rule of elements being more electropositive in their lower oxidation states. Thallium is malleable and sectile enough to be cut with a knife at room temperature. It has a metallic luster that, when exposed to air, quickly tarnishes to a bluish-gray tinge, resembling lead. It may be preserved by immersion in oil. A heavy layer of oxide builds up on thallium if left in air. In the presence of water, thallium hydroxide

4872-516: The image according to molecular changes occurring within the area of interest. This process is markedly different from previous methods of imaging which primarily imaged differences in qualities such as density or water content. This ability to image fine molecular changes opens up an incredible number of exciting possibilities for medical application, including early detection and treatment of disease and basic pharmaceutical development. Furthermore, molecular imaging allows for quantitative tests, imparting

4956-551: The imaging of gene expression and the development of novel biomarkers. Organizations such as the SNMMI Center for Molecular Imaging Innovation and Translation (CMIIT) have formed to support research in this field. In Europe, other "networks of excellence" such as DiMI (Diagnostics in Molecular Imaging) or EMIL (European Molecular Imaging Laboratories) work on this new science, integrating activities and research in

5040-521: The isoelectronic Hg(CH 3 ) 2 and [Pb(CH 3 ) 2 ] , it is linear. Trimethylthallium and triethylthallium are, like the corresponding gallium and indium compounds, flammable liquids with low melting points. Like indium, thallium cyclopentadienyl compounds contain thallium(I), in contrast to gallium(III). Thallium ( Greek θαλλός , thallos , meaning "a green shoot or twig") was discovered by William Crookes and Claude Auguste Lamy , working independently, both using flame spectroscopy (Crookes

5124-424: The legal limit ( permissible exposure limit ) for thallium exposure in the workplace as 0.1 mg/m skin exposure over an eight-hour workday. The National Institute for Occupational Safety and Health (NIOSH) also set a recommended exposure limit (REL) of 0.1 mg/m skin exposure over an eight-hour workday. At levels of 15 mg/m , thallium is immediately dangerous to life and health . Contact with skin

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5208-473: The lighter group 13 elements and are still the least stable in the whole group. For instance, thallium(III) fluoride , TlF 3 , has the β-BiF 3 structure rather than that of the lighter group 13 trifluorides, and does not form the TlF 4 complex anion in aqueous solution. The trichloride and tribromide disproportionate just above room temperature to give the monohalides, and thallium triiodide contains

5292-552: The linear triiodide anion ( I 3 ) and is actually a thallium(I) compound. Thallium(III) sesquichalcogenides do not exist. The thallium(I) halides are stable. In keeping with the large size of the Tl cation, the chloride and bromide have the caesium chloride structure, while the fluoride and iodide have distorted sodium chloride structures. Like the analogous silver compounds, TlCl, TlBr, and TlI are photosensitive and display poor solubility in water. The stability of thallium(I) compounds demonstrates its differences from

5376-476: The location of tumors such as pheochromocytomas and neuroblastomas . Certain tests, such as the Schilling test and urea breath test , use radioisotopes but are not used to produce a specific image. Scintigraphic scanning was invented and proven by Neurologist and Radiologist professor Bernard George Ziedses des Plantes. He presented the results in 1950 under the name 'indirect Autoradiograph ’. In 1970,

5460-438: The major disadvantages of PET is that most of the probes must be made with a cyclotron. Most of these probes also have a half life measured in hours, forcing the cyclotron to be on site. These factors can make PET prohibitively expensive. PET imaging does have many advantages though. First and foremost is its sensitivity: a typical PET scanner can detect between 10 mol/L to 10 mol/L concentrations. Thallium Thallium

5544-480: The natural decay chains of heavier elements. Tl is the most stable radioisotope , with a half-life of 3.78 years. It is made by the neutron activation of stable thallium in a nuclear reactor . The most useful radioisotope, Tl (half-life 73 hours), decays by electron capture, emitting X-rays (~70–80 keV), and photons of 135 and 167 keV in 10% total abundance; therefore, it has good imaging characteristics without an excessive patient-radiation dose. It

5628-486: The presence of ischemic coronary artery disease . A mercury–thallium alloy, which forms a eutectic at 8.5% thallium, is reported to freeze at −60 °C, some 20 °C below the freezing point of mercury. This alloy is used in thermometers and low-temperature switches. In organic synthesis, thallium(III) salts, as thallium trinitrate or triacetate, are useful reagents for performing different transformations in aromatics, ketones and olefins, among others. Thallium

5712-424: The production if a new application, such as a thallium-containing high-temperature superconductor , becomes practical for widespread use outside of the laboratory. The odorless and tasteless thallium sulfate was once widely used as rat poison and ant killer. Since 1972 this use has been prohibited in the United States due to safety concerns. Many other countries followed this example. Thallium salts were used in

5796-411: The readout. There are many different modalities that can be used for noninvasive molecular imaging. Each have their different strengths and weaknesses and some are more adept at imaging multiple targets than others. MRI has the advantages of having very high spatial resolution and is very adept at morphological imaging and functional imaging. MRI does have several disadvantages though. First, MRI has

5880-549: The region of interest, such as the heart or the brain . A special type of gamma camera is the SPECT (Single Photon Emission Computed Tomography). Another medical scintillography technique, the Positron-emission tomography (PET), which uses the scintillations provoked by electron-positron annihilation phenomena. Scintigraphy of the biliary system is called cholescintigraphy and is done to diagnose obstruction of

5964-456: The rest of the group: a stable oxide , hydroxide , and carbonate are known, as are many chalcogenides. The double salt Tl 4 (OH) 2 CO 3 has been shown to have hydroxyl-centred triangles of thallium, [Tl 3 (OH)] , as a recurring motif throughout its solid structure. The metalorganic compound thallium ethoxide (TlOEt, TlOC 2 H 5 ) is a heavy liquid (ρ 3.49 g·cm , m.p. −3 °C), often used as

6048-520: The sensitivity of the contrast agents, these targeting moieties are usually linked to high payload MRI contrast agents or MRI contrast agents with high relaxivities. In particular, the recent development of micron-sized particles of iron oxide (MPIO) allowed to reach unprecedented levels of sensitivity to detect proteins expressed by arteries and veins. There are a number of approaches used for optical imaging. The various methods depend upon fluorescence , bioluminescence , absorption or reflectance as

6132-436: The solution to remove impurities. At the end it is converted to thallium sulfate and the thallium is extracted by electrolysis on platinum or stainless steel plates. The production of thallium decreased by about 33% in the period from 1995 to 2009 – from about 15 metric tonnes to about 10 tonnes. Since there are several small deposits or ores with relatively high thallium content, it would be possible to increase

6216-489: The solution. Thallium iodide is frequently used as an additive in metal-halide lamps , often together with one or two halides of other metals. It allows optimization of the lamp temperature and color rendering, and shifts the spectral output to the green region, which is useful for underwater lighting. Thallium and its compounds are extremely toxic, with numerous recorded cases of fatal thallium poisoning. The Occupational Safety and Health Administration (OSHA) has set

6300-400: The source of contrast. Optical imaging's most valuable attribute is that it and ultrasound do not have strong safety concerns like the other medical imaging modalities. The downside of optical imaging is the lack of penetration depth, especially when working at visible wavelengths. Depth of penetration is related to the absorption and scattering of light, which is primarily a function of

6384-426: The specific application. Xenon ( Xe ) gas is one such radiotracer. It has been shown to be valuable for diagnostic inhalation studies for the evaluation of pulmonary function; for imaging the lungs; and may also be used to assess rCBF. Detection of this gas occurs via a gamma camera —which is a scintillation detector consisting of a collimator, a NaI crystal, and a set of photomultiplier tubes. By rotating

6468-602: The treatment of ringworm , other skin infections and to reduce the night sweating of tuberculosis patients. This use has been limited due to their narrow therapeutic index , and the development of improved medicines for these conditions. Thallium(I) bromide and thallium(I) iodide crystals have been used as infrared optical materials, because they are harder than other common infrared optics, and because they have transmission at significantly longer wavelengths. The trade name KRS-5 refers to this material. Thallium(I) oxide has been used to manufacture glasses that have

6552-433: The various activities that cells and tissues perform in both health and disease. Molecular imaging emerged in the mid twentieth century as a discipline at the intersection of molecular biology and in vivo imaging. It enables the visualisation of the cellular function and the follow-up of the molecular process in living organisms without perturbing them. The multiple and numerous potentialities of this field are applicable to

6636-447: The wavelength of the excitation source. Light is absorbed by endogenous chromophores found in living tissue (e.g. hemoglobin, melanin, and lipids). In general, light absorption and scattering decreases with increasing wavelength. Below ~700 nm (e.g. visible wavelengths), these effects result in shallow penetration depths of only a few millimeters. Thus, in the visible region of the spectrum, only superficial assessment of tissue features

6720-411: The world-record-holding mercury cuprates. Before the widespread application of technetium-99m in nuclear medicine , the radioactive isotope thallium-201 , with a half-life of 73 hours, was the main substance for nuclear cardiography . The nuclide is still used for stress tests for risk stratification in patients with coronary artery disease (CAD). This isotope of thallium can be generated using

6804-399: Was able to isolate small quantities of the new element and determine the properties of a few compounds. Claude-Auguste Lamy used a spectrometer that was similar to Crookes' to determine the composition of a selenium-containing substance which was deposited during the production of sulfuric acid from pyrite . He also noticed the new green line in the spectra and concluded that a new element

6888-480: Was first to publish his findings, on March 30, 1861). The name comes from thallium's bright green spectral emission lines derived from the Greek 'thallos', meaning a green twig. After the publication of the improved method of flame spectroscopy by Robert Bunsen and Gustav Kirchhoff and the discovery of caesium and rubidium in the years 1859 to 1860, flame spectroscopy became an approved method to determine

6972-561: Was present. Lamy had received this material from the sulfuric acid plant of his friend Frédéric Kuhlmann and this by-product was available in large quantities. Lamy started to isolate the new element from that source. The fact that Lamy was able to work ample quantities of thallium enabled him to determine the properties of several compounds and in addition he prepared a small ingot of metallic thallium which he prepared by remelting thallium he had obtained by electrolysis of thallium salts. As both scientists discovered thallium independently and

7056-408: Was the only area where thallium was actively mined. This deposit still contains an estimated 500 tonnes of thallium, and it is a source for several rare thallium minerals, for example lorándite. The United States Geological Survey (USGS) estimates that the annual worldwide production of thallium is 10 metric tonnes as a by-product from the smelting of copper, zinc, and lead ores. Thallium

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