Technetium-99m
Encyclopedia
Technetium-99m is a metastable nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...

 of technetium-99
Technetium-99
Technetium-99 is an isotope of technetium which decays with a half-life of 211,000 years to stable ruthenium-99, emitting soft beta rays, but no gamma rays....

, symbolized as 99mTc. The "m" indicates that this is a metastable nuclear isomer, i.e., that its half-life of 6 hours is considerably longer (by 14 orders of magnitude, at least) than most nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...

s that undergo gamma decay. The life-time of technetium-99m is very long in terms of average gamma-decay half-lives, though short in comparison with half-lives for other kinds of radioactive decay, and in comparison with radionuclides used in many kinds of nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...

 tests.

Technetium-99m is used as a radioactive tracer
Radioactive tracer
A radioactive tracer, also called a radioactive label, is a substance containing a radioisotope that is used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or tissue...

 that medical equipment can detect in the body. It is well suited to the role because it emits readily detectable 140 keV gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...

s (these are about the same wavelength emitted by conventional X-ray diagnostic equipment), and its half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 for gamma emission is 6.0058 hours (meaning that 93.7% of it decays to 99Tc in 24 hours). The "short" half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 of the isotope (in terms of human-activity and metabolism) allows for scanning procedures which collect data rapidly, but keep total patient radiation exposure low.

As in all gamma decay reactions, a metastable nuclear isomer does not change into another element (transmute
Nuclear transmutation
Nuclear transmutation is the conversion of one chemical element or isotope into another. In other words, atoms of one element can be changed into atoms of other element by 'transmutation'...

) upon its isomeric transition
Isomeric transition
An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer....

 or "decay"; thus 99mTc decays to technetium-99
Technetium-99
Technetium-99 is an isotope of technetium which decays with a half-life of 211,000 years to stable ruthenium-99, emitting soft beta rays, but no gamma rays....

 (Tc-99, the ground state of the same isotope) and remains technetium. The decay of technetium-99m is accomplished by rearrangement of nucleon
Nucleon
In physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...

s in its nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...

, a process that allows energy to be emitted as a gamma ray.

The resulting technetium-99 then decays to stable ruthenium
Ruthenium
Ruthenium is a chemical element with symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most chemicals. The Russian scientist Karl Ernst Claus discovered the element...

-99 with a half-life of 211,000 years. It emits soft beta particles (electrons) in this process, but no gamma rays (photons). All of these characteristics ensure that the technetium-99 produced from technetium-99m produces very little extra radiation burden on the body.

Due to its short half-life, technetium-99m for nuclear medicine purposes is usually extracted from technetium-99m generator
Technetium-99m generator
A technetium-99m generator, or colloquially a technetium cow or moly cow, is a device used to extract the metastable isotope 99mTc of technetium from a source of decaying molybdenum-99...

s which contain molybdenum-99 (Mo-99, half-life 2.75 days), which is the usual parent nuclide for this isotope. The majority of Mo-99 produced for Tc-99m medical use comes from fission of HEU (highly enriched uranium) from only five reactors around the world: NRU
National Research Universal Reactor
The National Research Universal reactor, located in Chalk River, Ontario, is one of Canada’s national science facilities. It is a multipurpose science facility that serves three main roles....

, Canada; BR2
SCK•CEN
SCK•CEN is the Belgian nuclear research centre located in Mol, Belgium. SCK•CEN is active in various areas of research and services in the nuclear sector.-Organisation profile:...

, Belgium; SAFARI-1
SAFARI-1
SAFARI-1 is a 20 MW research reactor, initially used for high level nuclear physics research programmes and was commissioned in 1965.The reactor is owned and operated by NECSA at their facility in Pelindaba, South Africa....

, South Africa; HFR
Petten nuclear reactor
The Petten nuclear reactors are nuclear research reactors in Petten, Netherlands. There are two reactors on the premises of the Petten research centre: a high flux reactor and a low flux reactor....

 (Petten), the Netherlands; and the OSIRIS reactor in Saclay, France. Production from LEU (low-enriched uranium) is possible, and is produced at the new OPAL
OPAL
OPAL is a 20 megawatt pool-type nuclear research reactor that was officially opened on 20 April 2007 at the Australian Nuclear Science and Technology Organisation Research Establishment at Lucas Heights, located in South Sydney, Australia.The main reactor uses are:* Irradiation of target...

 reactor, Australia, as well as other sites. Activation of Mo-98 is another, currently smaller, route of production.

Demand for medical use of Mo-99 to make Tc-99m began to overtake a dwindling supply, in the late 2000s.

Shortage

Global shortages of technetium-99m emerged in the late 2000s because two aging nuclear reactors (NRU
National Research Universal Reactor
The National Research Universal reactor, located in Chalk River, Ontario, is one of Canada’s national science facilities. It is a multipurpose science facility that serves three main roles....

 and HFR
Petten nuclear reactor
The Petten nuclear reactors are nuclear research reactors in Petten, Netherlands. There are two reactors on the premises of the Petten research centre: a high flux reactor and a low flux reactor....

) that provided about two-thirds of the world’s supply of molybdenum-99, which itself has a half-life of only 66 hours, were shut down repeatedly for extended maintenance periods. Two replacement Canadian reactors constructed in the 1990s were closed before beginning operation, for safety reasons.

Nuclear medicine overview

Technetium-99m or 99mTc ("m" indicates that this is a metastable nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...

) is used in radioactive isotope medical tests
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...

: for example, as a radioactive tracer
Radioactive tracer
A radioactive tracer, also called a radioactive label, is a substance containing a radioisotope that is used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or tissue...

 that medical equipment can detect in the human body. It is well-suited to the role because it emits readily detectable 140 keV
Electronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...

 gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...

s, and its half-life is only about six hours. It dissolves in aqua regia
Aqua regia
Aqua regia or aqua regis is a highly corrosive mixture of acids, fuming yellow or red solution, also called nitro-hydrochloric acid. The mixture is formed by freshly mixing concentrated nitric acid and hydrochloric acid, usually in a volume ratio of 1:3, respectively...

, nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

, and concentrated sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

, but it is not soluble in hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

 of any strength. Klaus Schwochau's book Technetium lists 31 radiopharmaceuticals based on 99mTc for imaging and functional studies of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

, myocardium, thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...

, lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

s, liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

, gallbladder
Gallbladder
In vertebrates the gallbladder is a small organ that aids mainly in fat digestion and concentrates bile produced by the liver. In humans the loss of the gallbladder is usually easily tolerated....

, kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

s, skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

, blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

, and tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

s.

Technetium-99m is used in 20 million diagnostic nuclear medical procedures every year. Approximately 85 percent of diagnostic imaging procedures in nuclear medicine use this isotope. Depending on the type of nuclear medicine procedure, the 99mTc is tagged (or bound to) a pharmaceutical that transports the Tc-99m to its required location. For example, when 99mTc is chemically bound to exametazime
Exametazime
Technetium exametazime is a drug used for the detection of altered regional cerebral perfusion in stroke and other cerebrovascular diseases, and for the labelling of leukocytes to localise intra-abdominal infections and inflammatory bowel disease.-Chemistry:The drug consists of two of the three...

, the drug is able to cross the blood-brain barrier and flow through the vessels in the brain for cerebral blood flow imaging. This combination is also used for labeling white blood cells to visualize sites of infection. 99mTc Sestamibi
Sestamibi
Technetium sestamibi is a pharmaceutical agent used in nuclear medicine imaging. The drug is a coordination complex of the radioisotope technetium-99m with the ligand methoxyisobutylisonitrile . The generic drug became available late September 2008...

 is used for myocardial perfusion imaging, which shows how well the blood flows through the heart. Imaging to measure renal function
Renal function
Renal function, in nephrology, is an indication of the state of the kidney and its role in renal physiology. Glomerular filtration rate describes the flow rate of filtered fluid through the kidney...

 is done by attaching 99mTc to Mercapto acetyl triglycine (informal acronym: MAG3); this procedure is known as a MAG3 scan.

Technetium-99m generators

Molybdenum-99 has a half-life of approximately 66 hours (2.75 days), and decays to 99mTc through beta decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...

, emitting an electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

 and an antineutrino in the process (see equation below). This is a useful life since once molybdenum-99 is created, it can be transported to any hospital in the world and still is able to produce its decay product technetium-99m over the next week. The electrons produced from the decay of Mo-99 are easily absorbed, and Mo-99 generators are only minor radiation hazards, mostly due to secondary X-rays produced by the electrons (also known as bremsstrahlung
Bremsstrahlung
Bremsstrahlung is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typically an electron by an atomic nucleus. The moving particle loses kinetic energy, which is converted into a photon because energy is conserved. The term is...

).

The decay process that produces 99mTc:
99Mo → 99mTc + +

can also be written as
99Mo → 99mTc + +

where (or ) denotes the electron (beta particle) emitted from the nucleus, and denotes the emitted antineutrino (or more specifically, an electron antineutrino).

Most commercial 99Mo/99mTc generators use column chromatography
Column chromatography
Column chromatography in chemistry is a method used to purify individual chemical compounds from mixtures of compounds. It is often used for preparative applications on scales from micrograms up to kilograms.The main advantage of column chromatography is the relatively low cost and disposability...

, in which 99Mo in the form of molybdate, MoO42- is adsorbed onto acid alumina (Al2O3). When the 99Mo decays it forms pertechnetate
Pertechnetate
The pertechnetate ion is an oxoanion with the chemical formula TcO4−. It is often used as a convenient water-soluble source of isotopes of the radioactive element technetium...

 TcO4-, which because of its single charge is less tightly bound to the alumina. Pulling normal saline solution through the column of immobilized 99Mo elutes the soluble 99mTc, resulting in a saline solution containing the 99mTc as the dissolved sodium salt of the pertechnetate.

99mTc will then undergo an isomeric transition
Isomeric transition
An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer....

 to yield 99Tc and a monoenergetic gamma emission:
99mTc → 99Tc + γ


This is the process that happens inside the patient, and which is picked up by the gamma camera.

When a hospital receives a technetium-99m generator
Technetium-99m generator
A technetium-99m generator, or colloquially a technetium cow or moly cow, is a device used to extract the metastable isotope 99mTc of technetium from a source of decaying molybdenum-99...

 containing molybdenum-99, the technetium-99m that forms through 99Mo decay can be chemically extracted easily. One technetium-99m generator
Technetium-99m generator
A technetium-99m generator, or colloquially a technetium cow or moly cow, is a device used to extract the metastable isotope 99mTc of technetium from a source of decaying molybdenum-99...

, holding only a few micrograms of 99Mo, can potentially diagnose ten thousand patients because it will be producing 99mTc strongly for over a week. The short half-life of the isotope allows for scanning procedures that collect data rapidly. The isotope is also of a very low energy level for a gamma emitter. Its ~140 keV of energy make it safer for use because of the substantially-reduced ionization
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...

 compared with other gamma emitters. The energy of gammas from 99mTc is about the same as the radiation from a commercial diagnostic X-ray machine, although the number of gammas emitted results in radiation doses more comparable to X-ray studies like computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

.

Dose

Typical quantities of technetium administered for immunoscintigraphy tests, such as SPECT
Single photon emission computed tomography
Single-photon emission computed tomography is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera. However, it is able to provide true 3D information...

 tests, range from 10 to 30 mCi for adults. These doses result in radiation exposures to the patient around 10 mSv
Sievert
The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...

, the equivalent of about 500 chest X-ray exposures.

Exposure, contamination, and elimination

Radiation exposure
Radioactive contamination
Radioactive contamination, also called radiological contamination, is radioactive substances on surfaces, or within solids, liquids or gases , where their presence is unintended or undesirable, or the process giving rise to their presence in such places...

 due to diagnostic treatment involving technetium-99m can be kept low. Because technetium-99m has a short half-life and emits primarily a gamma ray (allowing small amounts to be easily detected), its quick decay into the far-less radioactive technetium-99 results in relatively low total radiation dose to the patient per unit of initial activity after administration, as compared to other radioisotopes. In the form administered in these medical tests (usually pertechnetate), technetium-99m and technetium-99 are eliminated from the body within a few days. Technetium for nuclear medicine purposes is extracted from technetium-99m generator
Technetium-99m generator
A technetium-99m generator, or colloquially a technetium cow or moly cow, is a device used to extract the metastable isotope 99mTc of technetium from a source of decaying molybdenum-99...

s, because of its short 6-hour half-life.

Radiation exposure with technetium-99m is associated with a potential, small, risk of inducing cancer in the patient later in life and is higher in younger patients.

3-D scanning technique: SPECT

Single photon emission computed tomography
Single photon emission computed tomography
Single-photon emission computed tomography is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera. However, it is able to provide true 3D information...

 (SPECT) is a nuclear medicine imaging technique using gamma rays. It may be used with any gamma-emitting isotope, including Tc-99m. In the use of technetium-99m, the radioisotope is administered to the patient and the escaping gamma rays are incident upon a moving gamma camera
Gamma camera
A gamma camera, also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy...

 which computes and processes the image. To acquire SPECT images, the gamma camera is rotated around the patient. Projections are acquired at defined points during the rotation, typically every 3-6 degrees. In most cases, a full 360 degree rotation is used to obtain an optimal reconstruction. The time taken to obtain each projection is also variable, but 15–20 seconds is typical. This gives a total scan time of 15–20 minutes. The technetium-99m radioisotope is used predominantly in both bone and brain scans to check for any irregularities. Although Tc-99m is used for diagnostic nuclear medicine imaging procedures, it is not used for any therapeutic procedures.

Common nuclear medicine techniques using technetium-99m

Technetium comes off the generator in the form of the pertechnetate ion, TcO4-. The oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...

 of Tc in this compound is +7. This is not suitable for medical applications. In medical practice, a reducing agent
Reducing agent
A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...

 is added to the pertechnetate solution to bring the oxidation state down to +3 or +4. Secondly a ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...

 is added to form a coordination complex
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...

. The ligand is chosen to have an affinity for the specific organ to be targeted. For example, the exametazime
Exametazime
Technetium exametazime is a drug used for the detection of altered regional cerebral perfusion in stroke and other cerebrovascular diseases, and for the labelling of leukocytes to localise intra-abdominal infections and inflammatory bowel disease.-Chemistry:The drug consists of two of the three...

 complex of Tc in oxidation state +3 is able to cross the blood-brain barrier and flow through the vessels in the brain for cerebral blood flow imaging. Other ligands include Sestamibi
Sestamibi
Technetium sestamibi is a pharmaceutical agent used in nuclear medicine imaging. The drug is a coordination complex of the radioisotope technetium-99m with the ligand methoxyisobutylisonitrile . The generic drug became available late September 2008...

 for myocardial perfusion imaging and Mercapto Acetyl TRIGlycine for MAG3 scan to measure renal function.

Bone scan

The nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...

 technique commonly called the bone scan
Bone scan
A bone scan or bone scintigraphy is a nuclear scanning test to find certain abnormalities in bone which are triggering the bone's attempts to heal. It is primarily used to help diagnose a number of conditions relating to bones, including: cancer of the bone or cancers that have spread to the bone,...

 usually uses Tc-99m. It is not to be confused with the different "bone density scan," DEXA, which is a low exposure X-ray test measuring bone density to look for osteoporosis and other diseases where bones lose mass without re-building activity. The nuclear medicine technique is sensitive to areas of unusual bone re-building activity, since the radiopharmaceutical is taken up by osteoblast
Osteoblast
Osteoblasts are mononucleate cells that are responsible for bone formation; in essence, osteoblasts are specialized fibroblasts that in addition to fibroblastic products, express bone sialoprotein and osteocalcin.Osteoblasts produce a matrix of osteoid, which is composed mainly of Type I collagen...

 cells which build bone. The technique therefore is sensitive to fractures and bone reaction to bone tumors, including metastases. For a bone scan, the patient is injected with a small amount of radioactive material
Technetium
Technetium is the chemical element with atomic number 43 and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature...

 such as 20-30 mCi of technetium-99m-MDP
Methylene diphosphonate
Technetium medronic acid is a pharmaceutical product used in nuclear medicine to localize bone metastases as well as other diseases that can alter the natural turn-over in the bone.-Chemistry:...

 and then scanned with a gamma camera
Gamma camera
A gamma camera, also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy...

. MDP is a phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

 derivative which can exchange place with bone phosphate in regions of active bone growth, so anchoring the radioisotope to that specific region. In order to view small lesions (less than 1 cm) especially in the spine, the SPECT imaging technique may be required, but currently in the United States, most insurance companies require separate authorization for SPECT imaging.

Myocardial perfusion imaging

Myocardial perfusion imaging (MPI) is a form of functional cardiac imaging, used for the diagnosis of ischemic heart disease. The underlying principle is that under conditions of stress, diseased myocardium receives less blood flow than normal myocardium. MPI is one of several types of cardiac stress test
Cardiac stress test
Cardiac stress test is a test used in medicine and cardiology to measure the heart's ability to respond to external stress in a controlled clinical environment....

.

Several radiopharmaceuticals and radionuclides may be used for this, each giving different information. In the myocardial perfusion scans using Tc-99m, the radiopharmaceuticals 99mTc-tetrofosmin
Tetrofosmin
Technetium tetrofosmin is a drug used in nuclear medicine cardiac imaging. It is sold under the brand name Myoview...

 (Myoview, GE Healthcare
GE Healthcare
GE Healthcare is a division of GE Technology Infrastructure, which is itself a division of General Electric . It employs more than 46,000 people worldwide and is headquartered in Little Chalfont, Buckinghamshire, United Kingdom. GE Healthcare is the first GE business segment to be headquartered...

) or 99mTc-sestamibi
Sestamibi
Technetium sestamibi is a pharmaceutical agent used in nuclear medicine imaging. The drug is a coordination complex of the radioisotope technetium-99m with the ligand methoxyisobutylisonitrile . The generic drug became available late September 2008...

 (Cardiolite, Bristol-Myers Squibb
Bristol-Myers Squibb
Bristol-Myers Squibb , often referred to as BMS, is a pharmaceutical company, headquartered in New York City. The company was formed in 1989, following the merger of its predecessors Bristol-Myers and the Squibb Corporation...

) are used. Following this, the heart rate is raised to induce myocardial stress, either by exercise or pharmacologically with adenosine, dobutamine
Dobutamine
Dobutamine is a sympathomimetic drug used in the treatment of heart failure and cardiogenic shock. Its primary mechanism is direct stimulation of β1 receptors of the sympathetic nervous system. Dobutamine was developed by a laboratory led by Drs...

 or dipyridamole
Dipyridamole
Dipyridamole is a drug that inhibits thrombus formation when given chronically and causes vasodilation when given at high doses over a short time.-Mechanism and effects:...

 (aminophylline
Aminophylline
Aminophylline is a bronchodilator. It is a compound of the bronchodilator theophylline with ethylenediamine in 2:1 ratio. The ethylenediamine improves solubility, and the aminophylline is usually found as a dihydrate-Properties:...

 can be used to reverse the effects of dipyridamole). Scanning may then be performed with a conventional gamma camera, or with SPECT.

Cardiac ventriculography

In cardiac ventriculography
Cardiac ventriculography
Cardiac Ventriculography is a medical imaging test used to determine a patient's cardiac function in the right, or more typically, left ventricle. Cardiac ventriculography involves injecting contrast media into the heart's ventricle to measure the volume of blood pumped...

, a radionuclide, which usually is 99mTc, is injected, and the heart is imaged to evaluate the flow through it. This test is done to evaluate coronary artery disease (CAD), valvular heart disease
Valvular heart disease
Valvular heart disease is any disease process involving one or more of the valves of the heart . Valve problems may be congenital or acquired...

, congenital heart diseases, cardiomyopathy
Cardiomyopathy
Cardiomyopathy, which literally means "heart muscle disease," is the deterioration of the function of the myocardium for any reason. People with cardiomyopathy are often at risk of arrhythmia or sudden cardiac death or both. Cardiomyopathy can often go undetected, making it especially dangerous to...

, and other cardiac disorders. It exposes patients to less radiation than do comparable chest x-ray
Chest X-ray
In medicine, a chest radiograph, commonly called a chest X-ray , is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures...

 studies.

Functional brain imaging

Usually the gamma-emitting tracer used in functional brain imaging is 99mTc-HMPAO (hexamethylpropylene amine oxime, exametazime). The similar 99mTc-EC tracer may also be used. These molecules are preferentially distributed to regions of high brain blood flow, and act to assess brain metabolism regionally, in an attempt to diagnose and differentiate the different causal pathologies of dementia
Dementia
Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...

. When used with the 3-D SPECT
Single photon emission computed tomography
Single-photon emission computed tomography is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera. However, it is able to provide true 3D information...

 technique, they compete with brain FDG-PET
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...

 scans and fMRI
Functional magnetic resonance imaging
Functional magnetic resonance imaging or functional MRI is a type of specialized MRI scan used to measure the hemodynamic response related to neural activity in the brain or spinal cord of humans or other animals. It is one of the most recently developed forms of neuroimaging...

 brain scans as techniques to map the regional metabolic rate of brain tissue.

Sentinel-node identification

The radioactive properties of 99mTc can be used to identify the predominant lymph nodes draining a cancer, such as breast cancer
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...

 or malignant melanoma. This is usually performed at the time of biopsy
Biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...

 or resection
Resection
Resection may refer to:*Segmental resection , the partial removal of an organ or other body structure*Resection , a means of establishing a location...

. 99mTc-labelled isosulfan blue dye
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

 is injected intradermally around the intended biopsy site. The general location of the sentinel node is determined with the use of a handheld scanner with a gamma-sensor probe that detects the technetium-99m–labeled sulfur colloid that was previously injected around the biopsy site. An incision is then made over the area of highest radionuclide accumulation, and the sentinel node is identified within the incision by inspection; the isosulfan blue dye will usually stain any draining nodes blue.

Immunoscintigraphy

Immunoscintigraphy
Immunoscintigraphy
Immunoscintigraphy is a procedure used to find cancer cells in the body by injecting a radioactively labeled antibody, which binds predominantly to cancer cells and then scanning for concentrations of radioactive emissions.-See also:...

 incorporates 99mTc into a monoclonal antibody
Monoclonal antibodies
Monoclonal antibodies are monospecific antibodies that are the same because they are made by identical immune cells that are all clones of a unique parent cell....

, an immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

 protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

, capable of binding to cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 cells. A few hours after injection, medical equipment is used to detect the gamma rays emitted by the 99mTc; higher concentrations indicate where the tumor is. This technique is particularly useful for detecting hard-to-find cancers, such as those affecting the intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...

. These modified antibodies are sold by the German company Hoechst
Hoechst AG
Hoechst AG was a German chemicals then life-sciences company that became Aventis Deutschland after its merger with France's Rhône-Poulenc S.A. in 1999...

 (now part of Sanofi-Aventis
Sanofi-Aventis
Sanofi S.A. is a multinational pharmaceutical company headquartered in Paris, France, the world's fourth-largest by prescription sales. Sanofi engages in the research and development, manufacturing and marketing of pharmaceutical products for sale principally in the prescription market, but the...

) under the name "Scintium".

Blood pool labeling

When 99mTc is combined with a tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...

 compound it binds to red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...

s and can therefore be used to map circulatory system
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

 disorders. It is commonly used to detect gastrointestinal bleeding sites.

Pyrophosphate for heart damage

A pyrophosphate
Pyrophosphate
In chemistry, the anion, the salts, and the esters of pyrophosphoric acid are called pyrophosphates. Any salt or ester containing two phosphate groups is called a diphosphate. As a food additive, diphosphates are known as E450.- Chemistry :...

 ion with 99mTc adheres to calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 deposits in damaged heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 muscle, making it useful to gauge damage after a heart attack
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

.

Sulfure colloid for spleen scan

The sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

 colloid of 99mTc is scavenged by the spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...

, making it possible to image the structure of the spleen.

Further reading

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