View source for Physics:Technetium-99m

{{Short description|Metastable nuclear isomer of technetium-99}}
{{Infobox isotope
| alternate_names =
| symbol =Tc
| mass_number =99m
| m=m
| mass =98.9063
| num_neutrons =56
| num_protons =43
| abundance =
| halflife = {{val|6.0067|u=hours}}<ref>{{cite web|title=<sup>99m</sup>Tc tables|url=http://www.nucleide.org/DDEP_WG/Nuclides/Tc-99m_tables.pdf|work=Nucleide.org|publisher=Laboratoire National Henri Becquerel|access-date=23 May 2012|date=17 January 2012|archive-date=4 August 2016|archive-url=https://web.archive.org/web/20160804083942/http://www.nucleide.org/DDEP_WG/Nuclides/Tc-99m_tables.pdf|url-status=dead}}</ref>
| image = First technetium-99m generator - 1958.jpg
| image_caption = The first [[Physics:Technetium-99m generator|technetium-99m generator]], 1958.<br/>A <sup>99m</sup>Tc pertechnetate solution is<br/>being eluted from <sup>99</sup>Mo molybdate<br/>bound to a chromatographic substrate
| decay_product =Technetium-99
| decay_symbol =Tc
| decay_mass =99
| decay_mode1 =Isomeric transition<br/>γ emission 87.87%
| decay_energy1 =98.6%: 0.1405 MeV<br/> 1.4%: 0.1426
| decay_mode2 =[[Physics:Internal conversion|Internal conversion]] <br/>K-shell (9.13%)<br/> L-shell (1.18%)<br/> M-shell (0.39%)
| decay_energy2 =
| decay_mode3 =
| decay_energy3 =
| decay_mode4 =
| decay_energy4 =
| parent = Molybdenum-99
| parent_symbol = Mo
| parent_mass = 99
| parent_decay = 65.976 h
| parent2 =
| parent2_symbol =
| parent2_mass =
| parent2_decay =
| spin =1/2−
| excess_energy = −87327.195
| binding_energy = 8613.603
}}
'''Technetium-99m''' (<sup>99m</sup>Tc) is a metastable [[Physics:Nuclear isomer|nuclear isomer]] of [[Physics:Technetium-99|technetium-99]] (itself an isotope of [[Chemistry:Technetium|technetium]]), symbolized as <sup>99m</sup>Tc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used [[Biology:Radiopharmacology|medical radioisotope]] in the world.

Technetium-99m is used as a [[Biology:Radioactive tracer|radioactive tracer]] and can be detected in the body by medical equipment ([[Physics:Gamma camera|gamma camera]]s). It is well suited to the role, because it emits readily detectable [[Physics:Gamma ray|gamma ray]]s with a [[Physics:Photon energy|photon energy]] of 140&nbsp;[[Physics:Kiloelectronvolt|keV]] (these 8.8&nbsp;pm [[Physics:Photon|photon]]s are about the same wavelength as emitted by conventional X-ray diagnostic equipment) and its [[Physics:Half-life|half-life]] for gamma emission is 6.0058 hours (meaning 93.7% of it decays to <sup>99</sup>Tc in 24 hours). The relatively "short" physical [[Physics:Half-life|half-life]] of the isotope and its [[Biology:Biological half-life|biological half-life]] of 1 day (in terms of human activity and metabolism) allows for scanning procedures which collect data rapidly but keep total patient radiation exposure low. The same characteristics make the isotope unsuitable for therapeutic use.

Technetium-99m was discovered as a product of [[Physics:Cyclotron|cyclotron]] bombardment of [[Chemistry:Molybdenum|molybdenum]]. This procedure produced [[Physics:Molybdenum-99|molybdenum-99]], a radionuclide with a longer half-life (2.75 days), which decays to <sup>99m</sup>Tc. This longer decay time allows for <sup>99</sup>Mo to be shipped to medical facilities, where <sup>99m</sup>Tc is extracted from the sample as it is produced. In turn, <sup>99</sup>Mo is usually created commercially by fission of highly enriched uranium in a small number of research and material testing nuclear reactors in several countries.

==History==
===Discovery===
In 1938, [[Biography:Emilio Segrè|Emilio Segrè]] and [[Biography:Glenn T. Seaborg|Glenn T. Seaborg]] isolated for the first time the metastable isotope technetium-99m, after bombarding natural molybdenum with 8 MeV [[Physics:Deuteron|deuteron]]s in the {{convert|37|inch|adj=on}} [[Physics:Cyclotron|cyclotron]] of Ernest Orlando Lawrence's [[Organization:Lawrence Berkeley National Laboratory|Radiation laboratory]].<ref>{{cite journal |last1=Segrè |first1=Emilio |last2=Seaborg |first2=Glenn T. |date=1 November 1938 |title=Nuclear Isomerism in Element 43 |journal=Physical Review |volume=54 |issue=9 |pages=772 |bibcode=1938PhRv...54..772S |doi=10.1103/PhysRev.54.772.2}}</ref> In 1970 Seaborg explained that:<ref>{{harvnb|Hoffmann|Ghiorso|Seaborg|2000 |pp =15–16}}</ref>

{{Blockquote|we discovered an isotope of great scientific interest, because it decayed by means of an isomeric transition with emission of a line spectrum of electrons coming from an almost completely internally converted gamma ray transition. [actually, only 12% of the decays are by internal conversion] (...) This was a form of radioactive decay which had never been observed before this time. Segrè and I were able to show that this radioactive isotope of the element with the atomic number 43 decayed with a half-life of 6.6&nbsp;h [later updated to 6.0&nbsp;h] and that it was the daughter of a 67-h [later updated to 66&nbsp;h] molybdenum parent radioactivity. This chain of decay was later shown to have the mass number 99, and (...) the 6.6-h activity acquired the designation ‘technetium-99m.}}

Later in 1940, Emilio Segrè and [[Biography:Chien-Shiung Wu|Chien-Shiung Wu]] published experimental results of an analysis of fission products of uranium-235, including molybdenum-99, and detected the presence of an isomer of element 43 with a 6-hour half life, later labelled as technetium-99m.<ref>{{harvnb|Schwochau|2000|p=4}}</ref><ref>{{cite journal|last=Segrè|first=Emilio|author2=Wu, Chien-Shiung |title=Some Fission Products of Uranium|journal=Physical Review|year=1940|volume=57|issue=6|pages=552 |doi=10.1103/PhysRev.57.552.3|bibcode = 1940PhRv...57..552S }}</ref>

===Early medical applications in the United States===
[[File:Tc99minjektion.jpg|thumb|right|A technetium injection contained in a shielded syringe]]
<sup>99m</sup>Tc remained a scientific curiosity until the 1950s when Powell Richards realized the potential of technetium-99m as a medical radiotracer and promoted its use among the medical community. While Richards was in charge of the radioisotope production at the Hot Lab Division of the [[Organization:Brookhaven National Laboratory|Brookhaven National Laboratory]], Walter Tucker and Margaret Greene were working on how to improve the separation process purity of the short-lived [[Chemistry:Elution|eluted]] daughter product [[Physics:Iodine-132|iodine-132]] from its parent, [[Physics:Tellurium-132|tellurium-132]] (with a half life of 3.2 days), produced in the Brookhaven Graphite Research Reactor.<ref>{{cite web|title=Brookhaven Graphite Research Reactor|url=http://www.bnl.gov/bnlweb/history/BGRR.asp|work=bnl.gov|access-date=3 May 2012}}</ref> They detected a trace contaminant which proved to be <sup>99m</sup>Tc, which was coming from <sup>99</sup>Mo and was following tellurium in the chemistry of the separation process for other fission products. Based on the similarities between the chemistry of the tellurium-iodine parent-daughter pair, Tucker and Greene developed the first [[Physics:Technetium-99m generator|technetium-99m generator]] in 1958.<ref>{{cite book|last=Richards|first=Powell|title=Technetium-99m: The Early Days|year=1989|publisher=Brookhaven National Laboratory|location=New York|url= http://www.osti.gov/bridge/servlets/purl/5612212-IkoOXK/5612212.pdf|volume=BNL-43197 CONF-8909193-1|access-date=3 May 2012}}</ref><ref>{{cite journal|last1=Tucker|first1= W. D.|last2= Greene|first2= M. W.|last3= Weiss|first3=A. J.|last4= Murrenhoff |first4=A.|title=Methods of preparation of some carrier-free radioisotopes involving sorption on alumina|journal=Transactions American Nuclear Society|year=1958|volume=1|pages=160–161}}</ref> It was not until 1960 that Richards became the first to suggest the idea of using technetium as a medical tracer.<ref>{{cite journal|last=Richards|first=Powell|title=A survey of the production at Brookhaven National Laboratory of radioisotopes for medical research|year=1960|journal=VII Rassegna Internazionale Elettronica e Nucleare Roma|pages=223–244}}</ref><ref>{{cite web|url=http://www.bnl.gov/bnlweb/history/tc-99m.asp|work=Bnl.gov|title=The Technetium-99m Generator}}</ref><ref>{{cite journal|last1=Richards|first1=P.|last2=Tucker|first2= W. D.|last3=Srivastava|first3= S. C.|title=Technetium-99m: an historical perspective|journal=The International Journal of Applied Radiation and Isotopes|date=October 1982|volume=33|issue=10 |pages=793–9 |pmid=6759417|doi=10.1016/0020-708X(82)90120-X}}</ref><ref>{{cite journal|last1=Stang|first1=Louis G.|last2=Richards|first2= Powell|title=Tailoring the isotope to the need|journal=Nucleonics|year=1964|volume=22|issue=1|issn=0096-6207}}</ref>

The first US publication to report on medical scanning of <sup>99m</sup>Tc appeared in August 1963.<ref name="ncbi.nlm.nih.gov">{{cite journal|last1=Herbert|first1=R.|last2=Kulke|first2= W.|last3= Shepherd|first3= R. T.|title=The use of technetium 99m as a clinical tracer element.|journal=Postgraduate Medical Journal|date=November 1965|volume=41|issue=481|pages=656–62|pmid=5840856|pmc=2483197|doi=10.1136/pgmj.41.481.656}}</ref><ref name=sor>{{cite journal|last1=Sorensen|first1=Leif|last2=Archambault|first2=Maureen|title=Visualization of the liver by scanning with Mo99 (molybdate) as tracer|year=1963|journal=The Journal of Laboratory and Clinical Medicine|pages=330–340|pmid=14057883|volume=62}}</ref> Sorensen and Archambault demonstrated that intravenously injected carrier-free <sup>99</sup>Mo selectively and efficiently concentrated in the liver, becoming an internal generator of <sup>99m</sup>Tc. After build-up of <sup>99m</sup>Tc, they could visualize the liver using the 140 keV gamma ray emission.

===Worldwide expansion===
The production and medical use of <sup>99m</sup>Tc rapidly expanded across the world in the 1960s, benefiting from the development and continuous improvements of the [[Physics:Gamma camera|gamma camera]]s.

==== Americas ====
Between 1963 and 1966, numerous scientific studies demonstrated the use of <sup>99m</sup>Tc as radiotracer or diagnostic tool.<ref>{{cite journal|last1=Harper|first1=Paul V |last2=Andros | first2=GJ |first3= KC |last3=Lathop |title=Preliminary observations on the use of six-hour <sup>99m</sup>Tc as a tracer in biology and medicine|journal= Argonne Cancer Research Hospital |volume=18|pages=76–87|year= 1962}}</ref><ref>{{cite journal|last1=Harper|first1=PV |last2=Beck | first2=R |last3=Charleston|first3=D|last4=Lathrop|first4=KA|title=Optimization of a scanning method using <sup>99m</sup>Tc|journal=Nucleonics|year=1964|volume=22|pages=54|issn=0096-6207}}</ref><ref>{{cite journal|last=Smith|first=E. M.|title=Properties, uses, radiochemical purity and calibration of <sup>99m</sup>Tc|journal=Journal of Nuclear Medicine|date=November 1964|volume=5|pages=871–82|pmid=14247783|url=http://jnm.snmjournals.org/content/5/11/871.full.pdf|access-date=6 May 2012|issue=11}}</ref><ref>{{cite journal|last=Smith|first=E. M.|title=Internal dose calculation for 99mtc|journal=Journal of Nuclear Medicine|date=April 1965|volume=6|pages=231–51|pmid=14291076|url=http://jnm.snmjournals.org/content/6/4/231.full.pdf|access-date=6 May 2012|issue=4}}</ref> As a consequence the demand for <sup>99m</sup>Tc grew exponentially and by 1966, [[Organization:Brookhaven National Laboratory|Brookhaven National Laboratory]] was unable to cope with the demand. Production and distribution of <sup>99m</sup>Tc generators were transferred to private companies. ''"TechneKow-CS generator"'', the first commercial <sup>99m</sup>Tc generator, was produced by Nuclear Consultants, Inc. (St. Louis, Missouri) and Union Carbide Nuclear Corporation (Tuxedo, New York).<ref>{{cite book|editor1-first=W. C. |editor1-last=Eckelman|editor2-first= B. M.|editor2-last=Coursey|title=Technetium - 99m : generators, chemistry and preparation of radiopharmaceuticals|year=1982|publisher=Pergamon |location=Oxford|isbn=978-0-08-029144-4}}</ref><ref>{{cite journal|author= Nuclear Consultants Inc|title= Injectable sodium pertechnetate 99mTc from your own compact production facilities|page=36A|date=December 1966 |url=http://radiology.rsna.org/content/87/6/local/front-matter.pdf|journal=Radiology |volume=87|issue=6|doi=10.1148/87.6.1128}}</ref> From 1967 to 1984, <sup>99</sup>Mo was produced for Mallinckrodt Nuclear Company at the [[Organization:University of Missouri Research Reactor Center|Missouri University Research Reactor]] (MURR).

Union Carbide actively developed a process to produce and separate useful isotopes like <sup>99</sup>Mo from mixed fission products that resulted from the irradiation of highly enriched uranium (HEU) targets in nuclear reactors developed from 1968 to 1972 at the Cintichem facility (formerly the Union Carbide Research Center built in the Sterling forest in Tuxedo, New York ({{coord|41|14|6.88|N|74|12|50.78|W |type:landmark_scale:10000_region:US |display=inline}})).<ref>{{cite patent|country=US|number=3799883|title=Silver coated charcoal step|invent1=Hirofumi Arino|assign1= Union Carbide Corporation|gdate=26 March 1974}}</ref> The Cintichem process originally used 93% highly enriched U-235 deposited as UO<sub>2</sub> on the inside of a cylindrical target.<ref>{{cite patent|country=US|number=3940318 |title=Preparation of a primary target for the production of fission products in a nuclear reactor|invent1=Hirofumi Arino|assign1= Union Carbide Corporation|gdate=24 February 1974}}</ref><ref>{{cite journal|last1=Arino|first1=Hirofumi|last2=Kramer|first2= Henry H.|title=Fission product 99mTc generator|journal=The International Journal of Applied Radiation and Isotopes|date=May 1975|volume=26|issue=5|pages=301–303|doi=10.1016/0020-708X(75)90165-9|pmid=1184215}}</ref>

At the end of the 1970s, {{convert|200000|Ci|Bq|abbr=on}} of total fission product radiation were extracted weekly from 20 to 30 reactor bombarded HEU capsules, using the so-called "Cintichem [chemical isolation] process."<ref>{{cite web|title=Decommissioning ALARA Programs Cintichem Decommissioning Experience|year=1994 |url=http://hps.ne.uiuc.edu/natcisoe/brookhaven/2057.pdf |first1=Joseph J.|last1=Adler |first2=Thomas |last2=LaGuardia}}</ref> The research facility with its 1961 5-MW pool-type research reactor was later sold to Hoffman-LaRoche and became Cintichem Inc.<ref>{{cite book|last=Botshon|first=Ann|title=Saving Sterling Forest the epic struggle to preserve New York's highlands|year=2007|publisher=State Univ. of New York Press|location=Albany, NY|isbn=978-0-7914-6939-2|pages=86|url=https://books.google.com/books?id=YSmJzn6Bl_0C&q=cintichem&pg=PA86}}</ref> In 1980, Cintichem, Inc. began the production/isolation of <sup>99</sup>Mo in its reactor, and became the single U.S. producer of <sup>99</sup>Mo during the 1980s. However, in 1989, Cintichem detected an underground leak of radioactive products that led to the reactor shutdown and decommissioning, putting an end to the commercial production of <sup>99</sup>Mo in the USA.<ref>{{cite book|editor =National Research Council of the National Academies|author=Committee on Medical Isotope Production Without Highly Enriched Uranium|title=Medical isotope production without highly enriched uranium|year=2009|publisher=National Academies Press|location=Washington, D.C.|isbn=978-0-309-13039-4|url=http://www.nap.edu/catalog.php?record_id=12569|doi=10.17226/12569|pmid=25009932}}</ref>

The production of <sup>99</sup>Mo started in Canada in the early 1970s and was shifted to the NRU reactor in the mid-1970s.<ref>{{harvnb|Atomic Energy of Canada Limited|1997|pp=108–109}}</ref> By 1978 the reactor provided technetium-99m in large enough quantities that were processed by AECL's radiochemical division, which was privatized in 1988 as Nordion, now MDS Nordion.<ref>{{harvnb|Litt|2000|p=224 }}</ref> In the 1990s a substitution for the aging NRU reactor for production of radioisotopes was planned. The [[Engineering:Multipurpose Applied Physics Lattice Experiment|Multipurpose Applied Physics Lattice Experiment]] (MAPLE) was designed as a dedicated isotope-production facility. Initially, two identical MAPLE reactors were to be built at [[Organization:Chalk River Laboratories|Chalk River Laboratories]], each capable of supplying 100% of the world's medical isotope demand. However, problems with the MAPLE 1 reactor, most notably a positive [[Physics:Nuclear chain reaction|power co-efficient of reactivity]], led to the cancellation of the project in 2008.

The first commercial <sup>99m</sup>Tc generators were produced in {{wipe|Argentina}} in 1967, with <sup>99</sup>Mo produced in the [[Organization:National Atomic Energy Commission|CNEA]]'s [[Physics:RA-1 Enrico Fermi|RA-1 Enrico Fermi]] reactor.<ref>{{cite journal|last1=Karpeles|first1=Alfredo|last2=Palcos|first2=María Cristina|title=Obtención de Generadores de <sup>99m</sup>Tc|year=1970|volume=CNEA-267|url=http://www.cnea.gov.ar/cac/ci/CICACInformes/cicacInformeCNEA168.pdf|access-date=6 May 2012|language=es}}</ref><ref>{{cite web|title=El Reactor RA - 1|url=http://www.cnea.gov.ar/xxi/reactores/RA1.asp|work=CNEA.gob.ar|access-date=26 April 2012|language=es|url-status=dead|archive-url=https://web.archive.org/web/20120208023628/http://www.cnea.gov.ar/xxi/reactores/RA1.asp|archive-date=8 February 2012}}</ref> Besides its domestic market CNEA supplies <sup>99</sup>Mo to some South American countries.<ref>{{harvnb|National Research Council|2009}}</ref>

==== Asia ====
In 1967, the first <sup>99m</sup>Tc procedures were carried out in [[Place:Auckland|Auckland]], [[Earth:New Zealand|New Zealand]].<ref>{{cite book|editor-last=Jamieson|editor-first=Hugh |title=The development of medical physics and biomedical engineering in New Zealand hospitals, 1945-1995 some personal overviews|year=2006|publisher=H.D. Jamieson|location=Dannevirke, New Zealand|isbn=978-0-473-11900-3|url=http://www.acpsem.org.au/index.php/home/governance-/branches/nz-branch/nzbranch-documents/doc_view/196-historyofmedicalphysicsinnz1945-95|page=14}}</ref> <sup>99</sup>Mo was initially supplied by Amersham, UK, then by the Australian Nuclear Science and Technology Organisation (ANSTO) in Lucas Heights, Australia.<ref>{{cite book|editor-last=Jamieson|editor-first=Hugh |title=The development of medical physics and biomedical engineering in New Zealand hospitals, 1945-1995 some personal overviews|year=2006|publisher=H.D. Jamieson|location=Dannevirke, New Zealand|isbn=978-0-473-11900-3|url=http://www.acpsem.org.au/index.php/home/governance-/branches/nz-branch/nzbranch-documents/doc_view/196-historyofmedicalphysicsinnz1945-95|page=78}}</ref>

==== Europe ====
In May 1963, Scheer and Maier-Borst were the first to introduce the use of <sup>99m</sup>Tc for medical applications.<ref name="ncbi.nlm.nih.gov"/><ref>{{cite journal|last1=Scheer|first1=K. E.|last2=Maier-Borst|first2= W.|title=On the production of Tc99 m for medical purposes|journal=Nuclear-Medizin|date=15 May 1963|volume=3|pages=214–7|pmid=13986994|language=de}}</ref>
In 1968, [[Company:Philips#Spinouts|Philips-Duphar]] (later Mallinckrodt, today Covidien) marketed the first technetium-99m generator produced in Europe and distributed from Petten, the Netherlands.

===Shortage===
Global shortages of technetium-99m emerged in the late 2000s because two aging nuclear reactors (NRU and [[Physics:Petten nuclear reactor|HFR]]) 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.<ref name="nyt09">{{Cite news |url=https://www.nytimes.com/2009/07/24/science/24isotope.html |newspaper={{wipe|New York Times}} |title=Radioactive Drug for Tests Is in Short Supply |first=Matthew L. |last=Wald |date=23 July 2009 }}.</ref><ref>{{Cite web|url=http://www.medpagetoday.com/Radiology/NuclearMedicine/18495|title=Looming Isotope Shortage Has Clinicians Worried|last=Smith|first=Michael|date=16 February 2010|access-date=25 February 2010|work=[[Medicine:MedPage Today|MedPage Today]]}}</ref><ref>{{cite journal|last=Ruth|first=Thomas|title=Accelerating production of medical isotopes|journal=Nature|date=29 January 2009|volume=457|issue=7229|pages=536–537|doi=10.1038/457536a|pmid=19177112|bibcode = 2009Natur.457..536R |s2cid=29861596|doi-access=free}}</ref> In May 2009 the Atomic Energy of Canada Limited announced the detection of a small leak of [[Chemistry:Heavy water|heavy water]] in the NRU reactor that remained out of service until completion of the repairs in August 2010. After the observation of gas bubble jets released from one of the deformations of primary cooling water circuits in August 2008, the HFR reactor was stopped for a thorough safety investigation. [[Company:Nuclear Research and Consultancy Group|NRG]] received in February 2009 a temporary license to operate HFR only when necessary for medical radioisotope production. HFR stopped for repairs at the beginning of 2010 and was restarted in September 2010.<ref>{{cite journal|last=de Widt|first=Eric Jan|title=The High Flux Reactor in Petten resumes the vital roles of production of medical radioisotopes and nuclear research|journal=Tijdschrift voor Nucleaire Geneeskunde|year=2010|volume=32|issue=4|pages=586–591|url=http://www.tijdschriftvoornucleairegeneeskunde.nl/files/Archief/TvNG0410.pdf|access-date=27 April 2012|issn=1381-4842}}</ref>

Two replacement Canadian reactors (see [[Engineering:Multipurpose Applied Physics Lattice Experiment|MAPLE Reactor]]) constructed in the 1990s were closed before beginning operation, for safety reasons.<ref name="nyt09" /><ref>{{cite journal|last1=Thomas|first1=G. S.|last2=Maddahi|first2= J.|title=The Technetium Shortage|journal=Journal of Nuclear Cardiology|date=December 2010|volume=17|issue=6|pages=993–8|pmid=20717761|doi=10.1007/s12350-010-9281-8|s2cid=2397919}}</ref>  A construction permit for a new production facility to be built in Columbia, MO was issued in May 2018.<ref>{{Cite web|url=http://www.columbiatribune.com/news/20180810/business-seeks-tax-break-to-build-108m-facility|title=Business seeks tax break to build $108M facility|access-date=27 September 2018|archive-date=28 September 2018|archive-url=https://web.archive.org/web/20180928044358/http://www.columbiatribune.com/news/20180810/business-seeks-tax-break-to-build-108m-facility|url-status=dead}}</ref>

==Nuclear properties==
Technetium-99m is a metastable [[Physics:Nuclear isomer|nuclear isomer]], as indicated by the "m" after its [[Chemistry:Mass number|mass number]] 99. This means it is a nuclide in an excited (metastable) state that lasts much longer than is typical. The nucleus will eventually relax (i.e., de-excite) to its [[Physics:Ground state|ground state]] through the emission of [[Physics:Gamma ray|gamma ray]]s or [[Physics:Internal conversion|internal conversion electron]]s. Both of these decay modes rearrange the [[Physics:Nucleon|nucleon]]s without [[Physics:Nuclear transmutation|transmuting]] the technetium into another element.

<sup>99m</sup>Tc decays mainly by gamma emission, slightly less than 88% of the time. (<sup>99m</sup>Tc → <sup>99</sup>Tc + γ) About 98.6% of these gamma decays result in 140.5 keV gamma rays and the remaining 1.4% are to gammas of a slightly higher energy at 142.6 keV. These are the radiations that are picked up by a gamma camera when <sup>99m</sup>Tc is used as a [[Biology:Radioactive tracer|radioactive tracer]] for [[Medicine:Medical imaging|medical imaging]]. The remaining approximately 12% of <sup>99m</sup>Tc decays are by means of [[Physics:Internal conversion|internal conversion]], resulting in ejection of high speed internal conversion electrons in several sharp peaks (as is typical of electrons from this type of decay) also at about 140 keV (<sup>99m</sup>Tc → <sup>99</sup>Tc<sup>+</sup> + e<sup>−</sup>). These conversion electrons will [[Physics:Ionizing radiation|ionize]] the surrounding matter like beta radiation electrons would do, contributing along with the 140.5 keV and 142.6 keV gammas to the total deposited dose.

Pure gamma emission is the desirable decay mode for medical imaging because other particles deposit more energy in the patient body (radiation dose) than in the camera. Metastable isomeric transition is the only nuclear decay mode that approaches pure gamma emission.

<sup>99m</sup>Tc's [[Physics:Half-life|half-life]] of 6.0058 hours is considerably longer (by 14 orders of magnitude, at least) than most nuclear isomers, though not unique. This is still a short half-life relative to many other known modes of [[Physics:Radioactive decay|radioactive decay]] and it is in the middle of the range of half lives for [[Medicine:Radiopharmaceutical|radiopharmaceutical]]s used for [[Medicine:Medical imaging|medical imaging]].

After gamma emission or internal conversion, the resulting ground-state technetium-99 then decays with a half-life of 211,000 years to [[Physics:Stable isotope|stable]] [[Physics:Ruthenium-99|ruthenium-99]]. This process emits soft beta radiation without a gamma. Such low radioactivity from the daughter product(s) is a desirable feature for radiopharmaceuticals.
:<chem>^{99\!m}_{43}Tc ->[\ce{\gamma\ 141 keV}][\ce{6 h}] {}^{99}_{43}Tc ->[\ce{\beta^-\ 249 keV}][211,000\ \ce{y}] \overbrace{\underset{(stable)}{^{99}_{44}Ru}}^{ruthenium-99}</chem>

==Production==
===Production of <sup>99</sup>Mo in nuclear reactors===
==== Neutron irradiation of uranium-235 targets ====
The parent nuclide of <sup>99m</sup>Tc, <sup>99</sup>Mo, is mainly extracted for medical purposes from the fission products created in neutron-irradiated [[Physics:Uranium-235|uranium-235]] targets, the majority of which is produced in five nuclear [[Physics:Research reactor|research reactor]]s around the world using [[Physics:Enriched uranium#Highly enriched uranium .28HEU.29|highly enriched uranium]] (HEU) targets.<ref>{{harvnb|National Research Council|2009|p=34}} [http://books.nap.edu/openbook.php?record_id=12569&page=34]</ref><ref>{{cite journal | url = http://www.sciencenews.org/view/feature/id/47185/title/Desperately_Seeking_Moly | title = Desperately Seeking Moly | first = Janet | last = Raloff | year = 2009 | volume = 176 | issue = 7 | pages = 16–20 | journal = Science News | doi=10.1002/scin.5591760717}}</ref> Smaller amounts of <sup>99</sup>Mo are produced from [[Physics:Enriched uranium#Low-enriched uranium .28LEU.29|low-enriched uranium]] in at least three reactors.

{| class="wikitable" style="margin: 1em auto 1em auto;"
|+ Nuclear reactors producing <sup>99</sup>Mo from <sup>235</sup>U targets. The year indicates the date of the first [[Physics:Nuclear fission|criticality]] of the reactor.
|-
! scope="col" |Type
! scope="col" |Reactor
! scope="col" |Location
! scope="col" |Target/Fuel
! scope="col" |Year
|-
|rowspan="5" |Large-scale producers|| NRU (Decommissioned) || Canada || HEU/LEU ||1957
|-
|| [[Organization:SCK•CEN|BR2]]|| Belgium|| HEU/HEU||1961
|-
|| [[Physics:SAFARI-1|SAFARI-1]]||South Africa|| LEU/LEU||1965
|-
|| [[Physics:Petten nuclear reactor|HFR]]|| the Netherlands|| HEU/LEU||1961
|-
|| Osiris reactor|| France|| LEU/HEU||1966
|-
|rowspan="5" |Regional producers||[[Physics:Open-pool Australian lightwater reactor|OPAL]]|| Australia|| LEU/LEU||2006
|-
|| [[Physics:Reaktor Serba Guna G.A. Siwabessy|MPR RSG-GAS]]<ref>{{cite web|title=The Licensing for Decommissioning of Research Reactors in Indonesia of Research Reactors in Indonesia|url=http://www-ns.iaea.org/downloads/rw/projects/r2d2/workshop3/national-presentations/indonesia-licensing-for-decomm-of-rr.pdf|work=Iaea.org|access-date=26 April 2012}}</ref>|| Indonesia|| LEU/LEU||1987
|-
|| [[Organization:National Atomic Energy Commission|RA-3]]<ref>{{cite web|title=Centro Atómico Ezeiza|url=http://www.cnea.gob.ar/xxi/cnea_info/cae.asp|work=CNEA.gob.ar|access-date=26 April 2012}}</ref>|| Argentina|| LEU/LEU||1961
|-
|| [[Physics:Maria reactor|MARIA]] 			||Poland||HEU/HEU||1974
|-
|| LVR-15<ref>{{cite web|title=REAKTOR LVR-15|url=http://www.nri.cz/web/ujv-800/reaktor-lvr-15|access-date=11 May 2012|language=cs|archive-date=25 February 2011|archive-url=https://web.archive.org/web/20110225050122/http://www.nri.cz/web/ujv-800/reaktor-lvr-15|url-status=dead}}</ref>||Czech Republic||HEU/HEU||1957
|}

==== Neutron activation of <sup>98</sup>Mo ====
Production of <sup>99</sup>Mo by [[Physics:Neutron activation|neutron activation]] of natural molybdenum, or molybdenum enriched in <sup>98</sup>Mo,<ref>{{cite patent|country=US|number=3382152|title=Production of high purity radioactive isotopes|invent1=Ephraim Lieberman|assign1= Union Carbide Corporation|gdate=7 May 1968}}</ref> is another, currently smaller, route of production.<ref>[http://www.iaea.org/OurWork/ST/NE/NEFW/nfcms_researchreactors_Mo99.html Our Work: Nuclear Fuel Cycle and Materials Section]</ref>

===Production of <sup>99m</sup>Tc/<sup>99</sup>Mo in particle accelerators===
==== Production of "Instant" <sup>99m</sup>Tc ====
The feasibility of <sup>99m</sup>Tc production with the 22-MeV-proton bombardment of a <sup>100</sup>Mo target in medical cyclotrons was demonstrated in 1971.<ref>{{cite journal|last1=Beaver|first1=J. E.|author2=Hupf, H.B. |title=Production of <sup>99m</sup>Tc on a Medical Cyclotron: a Feasibility Study|journal=Journal of Nuclear Medicine|date=November 1971|volume=12|issue=11|pages=739–41|pmid=5113635 |url=http://jnm.snmjournals.org/content/12/11/739.full.pdf}}</ref> The recent shortages of <sup>99m</sup>Tc reignited the interest in the production of "instant" 99mTc by proton bombardment of isotopically enriched <sup>100</sup>Mo targets (>99.5%) following the reaction <sup>100</sup>Mo(p,2n)<sup>99m</sup>Tc.<ref>{{cite journal|last1=Guérin|first1=B.|last2=Tremblay|first2= S. |last3=Rodrigue|first3= S. |last4=Rousseau|first4= J. A. |last5=Dumulon-Perreault|first5= V. |last6=Lecomte|first6= R. |last7=van Lier|first7= J. E. |last8=Zyuzin|first8=A. |last9=van Lier|first9= E. J.|title=Cyclotron production of 99mTc: an approach to the medical isotope crisis|journal=Journal of Nuclear Medicine |date=April 2010|volume=51|issue=4|pages=13N–6N|pmid=20351346|url=http://jnm.snmjournals.org/content/51/4/13N.full.pdf|access-date=11 May 2012}}</ref> Canada is commissioning such cyclotrons, designed by [[Company:Advanced Cyclotron Systems|Advanced Cyclotron Systems]], for <sup>99m</sup>Tc production at the University of Alberta and the Université de Sherbrooke, and is planning others at the University of British Columbia, [[Organization:TRIUMF|TRIUMF]], [[Organization:University of Saskatchewan|University of Saskatchewan]] and Lakehead University.<ref>{{cite journal | last1=Schaffer | first1=P. | last2=Bénard | first2=F. | last3=Bernstein | first3=A. | last4=Buckley | first4=K. | last5=Celler | first5=A. | last6=Cockburn | first6=N. | last7=Corsaut | first7=J. | last8=Dodd | first8=M. | last9=Economou | first9=C. | last10=Eriksson | first10=T. | last11=Frontera | first11=M. | last12=Hanemaayer | first12=V. | last13=Hook | first13=B. | last14=Klug | first14=J. | last15=Kovacs | first15=M. | last16=Prato | first16=F.S. | last17=McDiarmid | first17=S. | last18=Ruth | first18=T.J. | last19=Shanks | first19=C. | last20=Valliant | first20=J.F. | last21=Zeisler | first21=S. | last22=Zetterberg | first22=U. | last23=Zavodszky | first23=P.A. | title=Direct Production of 99mTc via 100Mo(p,2n) on Small Medical Cyclotrons | journal=Physics Procedia | volume=66 | year=2015 | issn=1875-3892 | doi=10.1016/j.phpro.2015.05.048 | pages=383–395 | bibcode =2015PhPro..66..383S | doi-access =free }}</ref><ref>{{cite web| last =Alary| first =Bryan| title =Cyclotron facility revolutionizes medical isotope manufacturing| publisher =University of Alberta| date =2 July 2013| url =http://news.ualberta.ca/newsarticles/2013/july/cyclotron-facility-revolutionizes-medical-isotope-manufacturing| access-date =6 July 2013| archive-date =6 June 2014| archive-url =https://web.archive.org/web/20140606221137/http://news.ualberta.ca/newsarticles/2013/july/cyclotron-facility-revolutionizes-medical-isotope-manufacturing| url-status =dead}}</ref><ref>{{cite journal| last =Lougheed| first =Tim| title =Cyclotron production of medical isotopes scales up| journal =CMAJ| volume =185| issue =11| pages =947| publisher =Canadian Medical Association| location =Ottawa| date =20 June 2013| url =http://www.cmaj.ca/site/earlyreleases/20june13_cyclotron_production_of_medical_isotopes_scales_up.xhtml| archive-url =https://archive.today/20130706181010/http://www.cmaj.ca/site/earlyreleases/20june13_cyclotron_production_of_medical_isotopes_scales_up.xhtml| url-status =dead| archive-date =6 July 2013| issn =1488-2329| doi =10.1503/cmaj.109-4525| pmid =23798456| access-date =6 July 2013| pmc =3735742}}</ref>

A particular drawback of cyclotron production via (p,2n) on <sup>100</sup>Mo is the significant co-production of  <sup>99g</sup>Tc. The preferential in-growth of this nuclide occurs due to the larger reaction cross-section pathway leading to the ground state, which is almost five times higher at the cross-section maximum in comparison with the metastable one at the same energy. Depending on the time required to process the target material and recovery of <sup>99m</sup>Tc, the amount of <sup>99m</sup>Tc  relative to <sup>99g</sup>Tc will continue to decrease, in turn reducing the specific activity of <sup>99m</sup>Tc available. It has been reported that ingrowth of <sup>99g</sup>Tc as well as the presence of other Tc isotopes can negatively affect subsequent labelling and/or imaging;<ref>{{Cite journal|last1=Qaim|first1=S. M.|last2=Sudár|first2=S.|last3=Scholten|first3=B.|last4=Koning|first4=A. J.|last5=Coenen|first5=H. H.|date=1 February 2014|title=Evaluation of excitation functions of 100Mo(p,d+pn)99Mo and 100Mo (p,2n)99mTc reactions: Estimation of long-lived Tc-impurity and its implication on the specific activity of cyclotron-produced 99mTc|url=http://www.sciencedirect.com/science/article/pii/S0969804313003928|journal=Applied Radiation and Isotopes|language=en|volume=85|pages=101–113|doi=10.1016/j.apradiso.2013.10.004|pmid=24389533|issn=0969-8043}}</ref> however, the use of high purity <sup>100</sup>Mo targets, specified proton beam energies, and appropriate time of use have shown to be sufficient for yielding <sup>99m</sup>Tc from a cyclotron comparable to that from a commercial generator.<ref>{{Cite journal|date=1 September 2018|title=In-house cyclotron production of high-purity Tc-99m and Tc-99m radiopharmaceuticals|url=https://www.sciencedirect.com/science/article/abs/pii/S0969804317312125|journal=Applied Radiation and Isotopes|language=en|volume=139|pages=325–331|doi=10.1016/j.apradiso.2018.05.033|issn=0969-8043|last1=Martini|first1=Petra|last2=Boschi|first2=Alessandra|last3=Cicoria|first3=Gianfranco|last4=Zagni|first4=Federico|last5=Corazza|first5=Andrea|last6=Uccelli|first6=Licia|last7=Pasquali|first7=Micòl|last8=Pupillo|first8=Gaia|last9=Marengo|first9=Mario|last10=Loriggiola|first10=Massimo|last11=Skliarova|first11=Hanna|last12=Mou|first12=Liliana|last13=Cisternino|first13=Sara|last14=Carturan|first14=Sara|last15=Melendez-Alafort|first15=Laura|last16=Uzunov|first16=Nikolay M.|last17=Bello|first17=Michele|last18=Alvarez|first18=Carlos Rossi|last19=Esposito|first19=Juan|last20=Duatti|first20=Adriano|pmid=29936404|hdl=11392/2393270 |s2cid=49417395|hdl-access=free}}</ref><ref>{{Cite journal|last1=Uzunov|first1=N M|last2=Melendez-Alafort|first2=L|last3=Bello|first3=M|last4=Cicoria|first4=G|last5=Zagni|first5=F|last6=De Nardo|first6=L|last7=Selva|first7=A|last8=Mou|first8=L|last9=Rossi-Alvarez|first9=C|last10=Pupillo|first10=G|last11=Di Domenico|first11=G|date=19 September 2018|title=Radioisotopic purity and imaging properties of cyclotron-produced 99mTc using direct 100Mo(p,2n) reaction|url=https://doi.org/10.1088/1361-6560/aadc88|journal=Physics in Medicine & Biology|volume=63|issue=18|pages=185021|doi=10.1088/1361-6560/aadc88|pmid=30229740|bibcode=2018PMB....63r5021U|issn=1361-6560|hdl=11577/3286327|s2cid=52298185|hdl-access=free}}</ref>  Liquid metal molybdenum-containing targets have been proposed that would aid in streamlined processing, ensuring better production yields.<ref>{{Cite journal|date=1 October 2012|title=Radiometals from liquid targets: 94mTc production using a standard water target on a 13 MeV cyclotron|url=https://www.sciencedirect.com/science/article/abs/pii/S0969804312003697|journal=Applied Radiation and Isotopes|language=en|volume=70|issue=10|pages=2308–2312|doi=10.1016/j.apradiso.2012.06.004|issn=0969-8043|last1=Hoehr|first1=Cornelia|last2=Morley|first2=Tom|last3=Buckley|first3=Ken|last4=Trinczek|first4=Michael|last5=Hanemaayer|first5=Victoire|last6=Schaffer|first6=Paul|last7=Ruth|first7=Thomas|last8=Bénard|first8=François|pmid=22871432}}</ref> A particular problem associated with the continued reuse of recycled, enriched <sup>100</sup>Mo targets is unavoidable transmutation of the target as other Mo isotopes are generated during irradiation and cannot be easily removed post-processing.

==== Indirect routes of production of <sup>99</sup>Mo ====

Other particle accelerator-based isotope production techniques have been investigated. The supply disruptions of <sup>99</sup>Mo in the late 2000s and the ageing of the producing nuclear reactors forced the industry to look into alternative methods of production.<ref>{{Cite journal|last1=Wolterbeek|first1=Bert|last2=Kloosterman|first2=Jan Leen|last3=Lathouwers|first3=Danny|last4=Rohde|first4=Martin|last5=Winkelman|first5=August|last6=Frima|first6=Lodewijk|last7=Wols|first7=Frank|date=1 November 2014|title=What is wise in the production of 99Mo? A comparison of eight possible production routes|url=https://doi.org/10.1007/s10967-014-3188-9|journal=Journal of Radioanalytical and Nuclear Chemistry|language=en|volume=302|issue=2|pages=773–779|doi=10.1007/s10967-014-3188-9|s2cid=97298803|issn=1588-2780}}</ref> The use of cyclotrons or electron accelerators to produce <sup>99</sup>Mo from <sup>100</sup>Mo via (p,pn)<ref>{{cite journal|last1=Scholten|first1=Bernhard|last2=Lambrecht|first2=Richard M.|last3=Cogneau|first3=Michel|last4=Vera Ruiz|first4=Hernan|last5=Qaim|first5=Syed M.|date=25 May 1999|title=Excitation functions for the cyclotron production of 99mTc and 99Mo|journal=Applied Radiation and Isotopes|volume=51|issue=1|pages=69–80|doi=10.1016/S0969-8043(98)00153-5}}</ref><ref>{{cite journal|last1=Takács|first1=S.|last2=Szűcs|first2=Z.|last3=Tárkányi|first3=F.|last4=Hermanne|first4=A.|last5=Sonck|first5=M.|date=1 January 2003|title=Evaluation of proton induced reactions on <sup>100</sup>Mo: New cross sections for production of <sup>99m</sup>Tc and <sup>99</sup>Mo|journal=Journal of Radioanalytical and Nuclear Chemistry|volume=257|issue=1|pages=195–201|doi=10.1023/A:1024790520036|s2cid=93040978}}</ref><ref>{{cite journal|last1=Celler|first1=A.|last2=Hou|first2=X.|last3=Bénard|first3=F.|last4=Ruth|first4=T.|date=7 September 2011|title=Theoretical modeling of yields for proton-induced reactions on natural and enriched molybdenum targets|journal=Physics in Medicine and Biology|volume=56|issue=17|pages=5469–5484|bibcode=2011PMB....56.5469C|doi=10.1088/0031-9155/56/17/002|pmid=21813960|s2cid=24231457 }}</ref> or (γ,n)<ref>{{Cite journal|last1=Martin|first1=T. Michael|last2=Harahsheh|first2=Talal|last3=Munoz|first3=Benjamin|last4=Hamoui|first4=Zaher|last5=Clanton|first5=Ryan|last6=Douglas|first6=Jordan|last7=Brown|first7=Peter|last8=Akabani|first8=Gamal|date=1 November 2017|title=Production of 99Mo/99mTc via photoneutron reaction using natural molybdenum and enriched 100Mo: part 1, theoretical analysis|url=https://doi.org/10.1007/s10967-017-5455-z|journal=Journal of Radioanalytical and Nuclear Chemistry|language=en|volume=314|issue=2|pages=1051–1062|doi=10.1007/s10967-017-5455-z|s2cid=104119040|issn=1588-2780}}</ref> reactions, respectively, has been further investigated. The (n,2n) reaction on <sup>100</sup>Mo yields a higher reaction cross-section for high energy neutrons than of (n,γ) on <sup>98</sup>Mo with thermal neutrons.<ref>{{Cite journal|last1=Nagai|first1=Yasuki|last2=Hatsukawa|first2=Yuichi|date=10 March 2009|title=Production of 99Mo for Nuclear Medicine by 100Mo(n,2n)99Mo|journal=Journal of the Physical Society of Japan|volume=78|issue=3|pages=033201|doi=10.1143/JPSJ.78.033201|bibcode=2009JPSJ...78c3201N|issn=0031-9015|doi-access=free}}</ref>  In particular, this method requires accelerators that generate fast neutron spectrums, such as ones using D-T<ref>{{Cite journal|title=14 MeV neutrons for medical application: a scientific case for 99Mo/99Tcm production|year=2018|doi=10.1088/1742-6596/1021/1/012038|last1=Capogni|first1=M.|last2=Pietropaolo|first2=A.|last3=Quintieri|first3=L.|last4=Fazio|first4=A.|last5=Pillon|first5=M.|last6=De Felice|first6=P.|last7=Pizzuto|first7=A.|journal=Journal of Physics: Conference Series|volume=1021|issue=1|page=012038|bibcode=2018JPhCS1021a2038C|doi-access=free}}</ref> or other fusion-based reactions,<ref>{{Cite journal|date=1 May 2018|title=Investigation of <sup>99</sup>Mo radioisotope production by d-Li neutron source|journal=Nuclear Materials and Energy|language=en|volume=15|pages=261–266|doi=10.1016/j.nme.2018.05.017|issn=2352-1791|last1=Ohta|first1=Masayuki|last2=Kwon|first2=Saerom|last3=Sato|first3=Satoshi|last4=Ochiai|first4=Kentaro|last5=Suzuki|first5=Hiromitsu|doi-access=free}}</ref> or high energy spallation or knock out reactions.<ref>{{Cite journal|last1=Takahashi|first1=Naruto|last2=Nakai|first2=Kozi|last3=Shinohara|first3=Atsushi|last4=Htazawa|first4=Jun|last5=Nakamura|first5=Masanobu|last6=Fukuda|first6=Mitsuhiro|last7=Hatanaka|first7=Kichiji|last8=Morikawa|first8=Yasumasa|last9=Kobayashi|first9=Masaaki|last10=Yamamoto|first10=Asaki|date=1 May 2012|title=Production of <sup>99</sup>Mo-<sup>99m</sup>Tc by using spallation neutron|url=http://jnm.snmjournals.org/content/53/supplement_1/1475|journal=Journal of Nuclear Medicine|language=en|volume=53|issue=supplement 1|pages=1475|issn=0161-5505}}</ref> A disadvantage of these techniques is the necessity for enriched <sup>100</sup>Mo targets, which are significantly more expensive than natural isotopic targets and typically require recycling of the material, which can be costly, time-consuming, and arduous.<ref>{{Cite journal|last1=Gagnon|first1=K.|last2=Wilson|first2=J. S.|last3=Holt|first3=C. M. B.|last4=Abrams|first4=D. N.|last5=McEwan|first5=A. J. B.|last6=Mitlin|first6=D.|last7=McQuarrie|first7=S. A.|date=1 August 2012|title=Cyclotron production of 99mTc: Recycling of enriched 100Mo metal targets|url=http://www.sciencedirect.com/science/article/pii/S0969804312002941|journal=Applied Radiation and Isotopes|language=en|volume=70|issue=8|pages=1685–1690|doi=10.1016/j.apradiso.2012.04.016|pmid=22750197|issn=0969-8043}}</ref><ref>{{Cite journal|last1=Tkac|first1=Peter|last2=Vandegrift|first2=George F.|date=1 April 2016|title=Recycle of enriched Mo targets for economic production of 99Mo/99mTc medical isotope without use of enriched uranium|url=https://doi.org/10.1007/s10967-015-4357-1|journal=Journal of Radioanalytical and Nuclear Chemistry|language=en|volume=308|issue=1|pages=205–212|doi=10.1007/s10967-015-4357-1|osti=1399098|s2cid=99424811|issn=1588-2780}}</ref>

===Technetium-99m generators===
{{Main|Physics:Technetium-99m generator}}
Technetium-99m's short half-life of 6 hours makes storage impossible and would make transport very expensive. Instead, its parent nuclide <sup>99</sup>Mo is supplied to hospitals after its extraction from the neutron-irradiated uranium targets and its purification in dedicated processing facilities.{{#tag:ref|The <sup>99</sup>Tc formed by decay of <sup>99</sup>Mo and <sup>99m</sup>Tc during the time of the processing is removed, together its isomer <sup>99m</sup>Tc, at the end of the manufacturing process of the generator.<ref>{{cite journal|last=Moore|first=P. W.|title=Technetium-99 in generator systems.|journal=Journal of Nuclear Medicine|date=April 1984|volume=25|issue=4|pages=499–502|pmid=6100549|url=http://jnm.snmjournals.org/content/25/4/499.full.pdf|access-date=11 May 2012}}</ref>|group=notes}}<ref name="Dilw">{{cite journal| first1=Jonathan R.|last1=Dilworth|last2=Parrott|first2=Suzanne J.|title=The biomedical chemistry of technetium and rhenium|journal=Chemical Society Reviews|year= 1998|volume=27|pages=43–55|doi=10.1039/a827043z}}</ref> It is shipped by specialised radiopharmaceutical companies in the form of [[Physics:Technetium-99m generator|technetium-99m generator]]s worldwide or directly distributed to the local market. The generators, colloquially known as moly cows, are devices designed to provide radiation shielding for transport and to minimize the extraction work done at the medical facility. A typical dose rate at 1 metre from the <sup>99m</sup>Tc generator is 20-50&nbsp;μSv/h during transport.<ref>{{cite news|last=Shaw|first=Ken B.|title=Worker Exposures: How Much in the UK?|url=http://www.iaea.org/Publications/Magazines/Bulletin/Bull271/27104592527.pdf|access-date=19 May 2012|newspaper=IAEA Bulletin|date=Spring 1985|url-status=dead|archive-url=https://web.archive.org/web/20110905103646/http://www.iaea.org/Publications/Magazines/Bulletin/Bull271/27104592527.pdf|archive-date=5 September 2011}}</ref> These generators' output declines with time and must be replaced weekly, since the half-life of <sup>99</sup>Mo is still only 66 hours.

Molybdenum-99 spontaneously decays to excited states of <sup>99</sup>Tc through [[Physics:Beta decay|beta decay]]. Over 87% of the decays lead to the {{val|142|u=keV}} excited state of <sup>99m</sup>Tc. A {{Subatomic particle|Beta-}} [[Physics:Electron|electron]] and a {{math|{{Subatomic particle|Electron antineutrino}}}} electron antineutrino are emitted in the process (<sup>99</sup>Mo → <sup>99m</sup>Tc + {{Subatomic particle|Beta-}} + {{math|{{Subatomic particle|Electron antineutrino}}}}). The {{Subatomic particle|Beta-}} electrons are easily shielded for transport, and <sup>99m</sup>Tc generators are only minor radiation hazards, mostly due to secondary X-rays produced by the electrons (also known as ''[[Physics:Bremsstrahlung|Bremsstrahlung]]'').

At the hospital, the <sup>99m</sup>Tc that forms through <sup>99</sup>Mo decay is chemically extracted from the technetium-99m generator. Most commercial <sup>99</sup>Mo/<sup>99m</sup>Tc generators use [[Column chromatography|column chromatography]], in which <sup>99</sup>Mo in the form of water-soluble molybdate, MoO<sub>4</sub><sup>2−</sup> is [[Chemistry:Adsorption|adsorbed]] onto acid alumina (Al<sub>2</sub>O<sub>3</sub>). When the <sup>99</sup>Mo decays, it forms [[Chemistry:Pertechnetate|pertechnetate]] TcO<sub>4</sub><sup>−</sup>, which, because of its single charge, is less tightly bound to the alumina. Pulling normal saline solution through the column of immobilized <sup>99</sup>MoO<sub>4</sub><sup>2−</sup> elutes the soluble <sup>99m</sup>TcO<sub>4</sub><sup>−</sup>, resulting in a saline solution containing the <sup>99m</sup>Tc as the dissolved [[Chemistry:Sodium pertechnetate|sodium salt of the pertechnetate]]. One technetium-99m generator, holding only a few micrograms of <sup>99</sup>Mo, can potentially diagnose 10,000 patients{{citation needed|date=May 2012}} because it will be producing <sup>99m</sup>Tc strongly for over a week.

[[File:Basedow-vor-nach-RIT.jpg|thumb|right|Technetium [[Medicine:Nuclear medicine|scintigraphy]] of a neck of a Graves' disease patient]]

===Preparation===
Technetium exits the generator in the form of the pertechnetate ion, TcO<sub>4</sub><sup>−</sup>. The [[Chemistry:Oxidation state|oxidation state]] of Tc in this compound is +7. This is directly suitable for medical applications only in bone scans (it is taken up by osteoblasts) and some thyroid scans (it is taken up in place of iodine by normal thyroid tissues). In other types of scans relying on <sup>99m</sup>Tc, a [[Chemistry:Reducing agent|reducing agent]] is added to the pertechnetate solution to bring the oxidation state of the technecium down to +3 or +4. Secondly, a [[Chemistry:Ligand|ligand]] is added to form a [[Chemistry:Complex|coordination complex]]. The ligand is chosen to have an affinity for the specific organ to be targeted. For example, the exametazime 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 for myocardial perfusion imaging and mercapto acetyl triglycine for MAG3 scan to measure renal function.<ref name=eck>{{cite journal|last=Eckelman|first=William C.|title=Unparalleled Contribution of Technetium-99m to Medicine Over 5 Decades|journal=JACC: Cardiovascular Imaging|year=2009|volume=2|issue=3|pages=364–368|doi=10.1016/j.jcmg.2008.12.013|pmid=19356582|doi-access=}} Historical perspective, full text</ref>

==Medical uses==
In 1970, Eckelman and Richards presented the first "kit" containing all the ingredients required to release the <sup>99m</sup>Tc, "milked" from the generator, in the chemical form to be administered to the patient.<ref name=eck/><ref>{{cite journal|last1=Eckelman|first1=William C.|last2=Richards|first2= Powell|title=Instant 99mTc-DTPA.|journal=Journal of Nuclear Medicine |date=December 1970|volume=11|issue=12|pages=761|pmid=5490410|access-date=21 July 2012|url=http://jnm.snmjournals.org/content/11/12/761.full.pdf}}</ref><ref>{{cite journal|last=Molinski|first=Victor J.|title=A review of 99mTc generator technology|journal=The International Journal of Applied Radiation and Isotopes|date=1 October 1982|volume=33|issue=10|pages=811–819|doi=10.1016/0020-708X(82)90122-3}}</ref><ref name=Agency2008>{{cite book | title = Technetium-99m Radiopharmaceuticals: Manufacture of Kits | url = http://www-pub.iaea.org/mtcd/publications/pdf/trs466_web.pdf | year = 2008 | author = International Atomic Energy Agency|  isbn = 9789201004086 | access-date = 21 July 2012|location=Vienna}}</ref>

Technetium-99m is used in 20 million diagnostic [[Medicine:Nuclear medicine|nuclear medical]] procedures every year. Approximately 85% of diagnostic imaging procedures in nuclear medicine use this isotope as [[Biology:Radioactive tracer|radioactive tracer]]. Klaus Schwochau's book ''Technetium'' lists 31 radiopharmaceuticals based on <sup>99m</sup>Tc for imaging and functional studies of the [[Biology:Brain|brain]], myocardium, [[Biology:Thyroid|thyroid]], [[Medicine:Lung|lung]]s, [[Biology:Liver|liver]], [[Biology:Gallbladder|gallbladder]], kidneys, [[Biology:Skeleton|skeleton]], [[Biology:Blood|blood]], and tumors.<ref>{{Harvnb|Schwochau|2000|p=414}}</ref> A more recent review is also available.<ref>{{cite book|first1=Roger |last1=Alberto|first2=Qaisar|last2=Nadeem|title=Metal Ions in Bio-Imaging Techniques|publisher=Springer|year=2021|pages=195–238|chapter=Chapter 7. <sup>99m</sup> Technetium-Based Imaging Agents and Developments in <sup>99</sup>Tc Chemistry|doi=10.1515/9783110685701-013|s2cid=233684677}}</ref>

Depending on the procedure, the <sup>99m</sup>Tc is tagged (or bound to) a pharmaceutical that transports it to its required location. For example, when <sup>99m</sup>Tc is chemically bound to exametazime (HMPAO), 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 ('''<sup>99m</sup>Tc labeled WBC''') to visualize sites of infection. [[Chemistry:Technetium (99mTc) sestamibi|<sup>99m</sup>Tc sestamibi]] is used for myocardial perfusion imaging, which shows how well the blood flows through the heart. Imaging to measure [[Medicine:Renal function|renal function]] is done by attaching <sup>99m</sup>Tc to mercaptoacetyl triglycine (MAG3); this procedure is known as a MAG3 scan.

Technetium-99m (Tc-99m) can be readily detected in the body by medical equipment because it emits 140.5&nbsp;[[Physics:Kiloelectronvolt|keV]] [[Physics:Gamma ray|gamma ray]]s (these are about the same wavelength as emitted by conventional X-ray diagnostic equipment), and its [[Physics:Half-life|half-life]] for gamma emission is six hours (meaning 94% of it decays to <sup>99</sup>Tc in 24 hours). Besides, it emits virtually no beta radiation, thus keeping radiation dosage low. Its decay product, <sup>99</sup>Tc, has a relatively long half-life (211,000 years) and emits little radiation. The short physical [[Physics:Half-life|half-life]] of <sup>99m</sup>Tc and its [[Biology:Biological half-life|biological half-life]] of 1 day with its other favourable properties allows scanning procedures to collect data rapidly and keep total patient radiation exposure low. Chemically, technetium is selectively concentrated in thyroid, salivary glands, and stomach and excluded from [[Biology:Cerebrospinal fluid|cerebrospinal fluid]]. Combination with perchlorate abolishes its selectiveness.<ref>{{Cite journal |last1=Harper |first1=P. V. |last2=Lathrop |first2=K. A. |last3=Jiminez |first3=F. |last4=Fink |first4=R. |last5=Gottschalk |first5=A. |date=July 1965 |title=Technetium 99m as a Scanning Agent |url=http://pubs.rsna.org/doi/10.1148/85.1.101 |journal=Radiology |language=en |volume=85 |issue=1 |pages=101–109 |doi=10.1148/85.1.101 |pmid=14303054 |issn=0033-8419}}</ref>

===Radiation side-effects===
Diagnostic treatment involving technetium-99m will result in radiation exposure to technicians, patients, and passers-by. Typical quantities of technetium administered for immunoscintigraphy tests, such as [[Biology:Single-photon emission computed tomography|SPECT]] tests, range from {{convert|400|to|1100|MBq|mCi|abbr=on}} ([[Physics:Curie (unit)|millicurie]] or mCi; and Mega-[[Becquerel]] or MBq) for adults.<ref name=Cardialite>{{cite web|url=http://www.accessdata.fda.gov/drugsatfda_docs/label/2008/019785s018lbl.pdf|title = Cardialite kit for the preparation of Technetium 99m Sestamibi for injection, Prescribing information, April 2008|access-date = 3 September 2009|publisher = Food and Drug Administration|last=Squibb|first= B.-M.}}</ref><ref>{{cite web|url=http://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=3709|title=Neurolite (bicisate dihydrochloride)|access-date=11 November 2009|publisher=National Institutes of Health}}</ref> These doses result in radiation exposures to the patient around 10&nbsp;m[[Physics:Sievert|Sv]] (1000&nbsp;mrem), the equivalent of about 500 chest X-ray exposures.<ref name=Bedetti>{{cite journal|journal=J Am Coll Radiol|volume=5|issue=2|pages=126–31|year=2008|last1=Bedetti |first1=G. |last2=Pizzi |first2=C. |last3=Gavaruzzi |first3=G. |last4=Lugaresi |first4=F. |last5=Cicognani |first5=A. |last6=Picano |first6=E.|title=Suboptimal awareness of radiologic dose among patients undergoing cardiac stress scintigraphy|pmid=18242529|doi = 10.1016/j.jacr.2007.07.020}}</ref> This level of radiation exposure is estimated by the [[Physics:Linear no-threshold model|linear no-threshold model]] to carry a 1 in 1000 lifetime risk of developing a solid cancer or leukemia in the patient.<ref>Committee to Assess the Health Risks from Exposure to Low Levels of Ionizing Radiation, BEIR VII, National Research Council.
[https://nap.nationalacademies.org/resource/11340/beir_vii_final.pdf Health Risks From Exposure to Low Levels of Ionizing Radiation.] Washington, DC: National Academies Press; 2006</ref> The risk is higher in younger patients, and lower in older ones.<ref>{{cite journal|last1=Fahey|first1=Frederic H.|last2=Treves|first2= S. Ted|last3=Adelstein|first3= S. James |title=Minimizing and Communicating Radiation Risk in Pediatric Nuclear Medicine|journal=Journal of Nuclear Medicine Technology|date=1 August 2011|volume=52|issue=8|pages=1240–1251|doi=10.2967/jnumed.109.069609|pmid=21764783 |s2cid=2890364|url=http://jnm.snmjournals.org/content/52/8/1240.full.pdf|doi-access=free}}</ref> Unlike a chest x-ray, the radiation source is inside the patient and will be carried around for a few days, exposing others to second-hand radiation. A spouse who stays constantly by the side of the patient through this time might receive one thousandth of patient's radiation dose this way.

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&nbsp;keV of energy make it safer for use because of the substantially reduced [[Physics:Ionizing radiation|ionization]] compared with other gamma emitters. The energy of gammas from <sup>99m</sup>Tc 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.

Technetium-99m has several features that make it safer than other possible isotopes. Its gamma decay mode can be easily detected by a camera, allowing the use of smaller quantities. And because technetium-99m has a short half-life, 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 with 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.{{citation needed|date=January 2016}}

===3-D scanning technique: SPECT===
{{Main|Biology:Single-photon emission computed tomography}}
[[Biology:Single-photon emission computed tomography|Single-photon emission computed tomography]] (SPECT) is a nuclear medicine imaging technique using gamma rays. It may be used with any gamma-emitting isotope, including <sup>99m</sup>Tc. In the use of technetium-99m, the radioisotope is administered to the patient and the escaping gamma rays are incident upon a moving [[Physics:Gamma camera|gamma camera]] 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 three to six degrees. In most cases, a full 360° rotation is used to obtain an optimal reconstruction. The time taken to obtain each projection is also variable, but 15–20 seconds are typical. This gives a total scan time of 15–20 minutes.

The technetium-99m radioisotope is used predominantly in bone and brain scans. For bone scans, the pertechnetate ion is used directly, as it is taken up by osteoblasts attempting to heal a skeletal injury, or (in some cases) as a reaction of these cells to a tumor (either primary or metastatic) in the bone. In brain scanning, <sup>99m</sup>Tc is attached to the chelating agent HMPAO to create [[Chemistry:Technetium (99mTc) exametazime|technetium (<sup>99m</sup>Tc) exametazime]], an agent which localizes in the brain according to region blood flow, making it useful for the detection of stroke and dementing illnesses that decrease regional brain flow and metabolism.

Most recently, technetium-99m scintigraphy has been combined with CT coregistration technology to produce SPECT/CT scans. These employ the same radioligands and have the same uses as SPECT scanning, but are able to provide even finer 3-D localization of high-uptake tissues, in cases where finer resolution is needed. An example is the sestamibi parathyroid scan which is performed using the <sup>99m</sup>Tc radioligand sestamibi, and can be done in either SPECT or SPECT/CT machines.

===Bone scan===
The [[Medicine:Nuclear medicine|nuclear medicine]] technique commonly called the bone scan usually uses <sup>99m</sup>Tc. It is not to be confused with the "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 rebuilding activity. The nuclear medicine technique is sensitive to areas of unusual bone rebuilding activity, since the radiopharmaceutical is taken up by [[Biology:Osteoblast|osteoblast]] 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, such as {{convert|700|-|1100|MBq|mCi|abbr=on}} of [[Chemistry:Technetium (99mTc) medronic acid|<sup>99m</sup>Tc-medronic acid]] and then scanned with a [[Physics:Gamma camera|gamma camera]]. Medronic acid is a [[Chemistry:Phosphate|phosphate]] derivative which can exchange places with bone phosphate in regions of active bone growth, so anchoring the radioisotope to that specific region. To view small lesions (less than {{convert|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===
{{Main|Chemistry: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, under conditions of stress, diseased myocardium receives less blood flow than normal myocardium. MPI is one of several types of [[Medicine:Cardiac stress test|cardiac stress test]]. As a nuclear stress test, the average radiation exposure is 9.4 mSv, which when compared with a typical 2 view chest X-ray (.1 mSv) is equivalent to 94 Chest X-rays.<ref name=xrayrisk.com>{{Cite web|url=http://www.xrayrisk.com/calculator/calculator-normal-studies.php|title = X-Ray Risk}}</ref>

Several radiopharmaceuticals and radionuclides may be used for this, each giving different information. In the myocardial perfusion scans using <sup>99m</sup>Tc, the radiopharmaceuticals <sup>99m</sup>Tc-tetrofosmin (Myoview, [[Company:GE Healthcare|GE Healthcare]]) or <sup>99m</sup>Tc-sestamibi (Cardiolite, [[Company:Bristol-Myers Squibb|Bristol-Myers Squibb]]) are used. Following this, myocardial stress is induced, either by exercise or pharmacologically with [[Chemistry:Adenosine|adenosine]], [[Chemistry:Dobutamine|dobutamine]] or [[Chemistry:Dipyridamole|dipyridamole]](Persantine), which increase the heart rate or by [[Chemistry:Regadenoson|regadenoson]](Lexiscan), a vasodilator. ([[Chemistry:Aminophylline|Aminophylline]] can be used to reverse the effects of dipyridamole and regadenoson). Scanning may then be performed with a conventional gamma camera, or with SPECT/CT.

===Cardiac ventriculography===
In [[Physics:Cardiac ventriculography|cardiac ventriculography]], a radionuclide, usually <sup>99m</sup>Tc, is injected, and the heart is imaged to evaluate the flow through it, to evaluate [[Medicine:Coronary artery disease|coronary artery disease]], [[Medicine:Valvular heart disease|valvular heart disease]], congenital heart diseases, [[Medicine:Cardiomyopathy|cardiomyopathy]], and other cardiac disorders. As a nuclear stress test, the average radiation exposure is 9.4 mSv, which when compared with a typical 2 view chest X-ray (.1 mSv) is equivalent to 94 Chest X-Rays.<ref name="xrayrisk.com"/><ref name=merck/> It exposes patients to less radiation than comparable chest X-ray studies.<ref name=merck>[http://www.merck.com/mmpe/sec07/ch070/ch070i.html Merck manuals &gt; Radionuclide Imaging] Last full review/revision May 2009 by Michael J. Shea, MD. Content last modified May 2009</ref>

===Functional brain imaging===
Usually the gamma-emitting tracer used in functional brain imaging is <sup>99m</sup>Tc-HMPAO (hexamethylpropylene amine oxime, [[Chemistry:Technetium (99mTc) exametazime|exametazime]]). The similar <sup>99m</sup>Tc-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 [[Medicine:Dementia|dementia]]. When used with the 3-D [[Biology:Single-photon emission computed tomography|SPECT]] technique, they compete with brain [[Physics:Positron emission tomography|FDG-PET]] scans and [[Physics:Functional magnetic resonance imaging|fMRI]] brain scans as techniques to map the regional metabolic rate of brain tissue.

===Sentinel-node identification===
The radioactive properties of <sup>99m</sup>Tc can be used to identify the predominant lymph nodes draining a cancer, such as [[Medicine:Breast cancer|breast cancer]] or malignant melanoma. This is usually performed at the time of [[Medicine:Biopsy|biopsy]] or [[Medicine:Segmental resection|resection]].<sup>99m</sup>Tc-labelled filtered sulfur colloid or [[Chemistry:Technetium (99mTc) tilmanocept|Technetium (99mTc) tilmanocept]] are 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 tracer that was previously injected around the biopsy site. An injection of [[Chemistry:Methylene blue|Methylene blue]] or [[Chemistry:Isosulfan blue|isosulfan blue]] is done at the same time to dye any draining nodes visibly blue.  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 lymph nodes blue that are draining from the area around the tumor.<ref>{{Cite journal| doi = 10.1056/NEJMct1002967| issn = 0028-4793
| volume = 364| issue = 18| pages = 1738–1745| last1 = Gershenwald| first1 = J. E.| last2= Ross |first2=M. I.| title = Sentinel-Lymph-Node Biopsy for Cutaneous Melanoma | journal = New England Journal of Medicine| date = 5 May 2011| pmid = 21542744}}</ref>

===Immunoscintigraphy===
Immunoscintigraphy incorporates <sup>99m</sup>Tc into a monoclonal antibody, an [[Biology:Immune system|immune system]] [[Biology:Protein|protein]], capable of binding to [[Medicine:Cancer|cancer]] cells. A few hours after injection, medical equipment is used to detect the gamma rays emitted by the <sup>99m</sup>Tc; higher concentrations indicate where the tumor is. This technique is particularly useful for detecting hard-to-find cancers, such as those affecting the [[Chemistry:Intestine|intestine]]s. These modified antibodies are sold by the German company Hoechst (now part of Sanofi-Aventis) under the name [[Chemistry:Besilesomab|Scintimun]].<ref name=blocks>{{harvnb|Emsley |2001| pp =422–425}}</ref>

===Blood pool labeling===
When <sup>99m</sup>Tc is combined with a [[Chemistry:Tin|tin]] compound, it binds to [[Biology:Red blood cell|red blood cell]]s and can therefore be used to map [[Biology:Circulatory system|circulatory system]] disorders. It is commonly used to detect gastrointestinal bleeding sites as well as [[Medicine:Ejection fraction|ejection fraction]], heart wall motion abnormalities, abnormal shunting, and to perform [[Physics:Cardiac ventriculography|ventriculography]].

===Pyrophosphate for heart damage===
A [[Chemistry:Pyrophosphate|pyrophosphate]] ion with <sup>99m</sup>Tc adheres to [[Chemistry:Calcium|calcium]] deposits in damaged [[Biology:Heart|heart]] muscle, making it useful to gauge damage after a [[Medicine:Myocardial infarction|heart attack]].{{citation needed|date=January 2016}}

===Sulfur colloid for spleen scan===
The [[Chemistry:Sulfur|sulfur]] colloid of <sup>99m</sup>Tc is scavenged by the [[Biology:Spleen|spleen]], making it possible to image the structure of the spleen.<ref name=enc>{{Harvnb|Rimshaw| 1968| pp= 689–693}}</ref>

===Meckel's diverticulum===
[[Chemistry:Pertechnetate|Pertechnetate]] is actively accumulated and secreted by the mucoid cells of the gastric mucosa,<ref>{{cite web | title=Nuclear Imaging of Meckel's Diverticulum: A Pictorial Essay of Pitfalls | website=University of Texas Houston | date=13 March 2003 | url=http://www.uth.tmc.edu/radiology/publish/meckel_diverticulum/index.html | archive-url=https://web.archive.org/web/20140101203234/http://www.uth.tmc.edu/radiology/publish/meckel_diverticulum/index.html | archive-date=1 January 2014 | url-status=dead | access-date=4 October 2023}}</ref> and therefore, technetate(VII) radiolabeled with Tc99m is injected into the body when looking for ectopic gastric tissue as is found in a [[Medicine:Meckel's diverticulum|Meckel's diverticulum]] with Meckel's Scans.<ref>{{cite journal | vauthors = Diamond RH, Rothstein RD, Alavi A | title = The role of cimetidine-enhanced technetium-99m-pertechnetate imaging for visualizing Meckel's diverticulum | journal = Journal of Nuclear Medicine | volume = 32 | issue = 7 | pages = 1422–4 | date = July 1991 | pmid = 1648609 | url = http://jnm.snmjournals.org/cgi/reprint/32/7/1422.pdf}}</ref>

=== Pulmonary ===
Carbon inhalation aerosol labeled with technetium-99m (Technegas) is indicated for the visualization of pulmonary ventilation and the evaluation of pulmonary embolism.<ref>https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/022335s000lbl.pdf</ref><ref>{{cite journal | vauthors = Currie GM, Bailey DL | title = A Technical Overview of Technegas as a Lung Ventilation Agent | journal = Journal of Nuclear Medicine Technology | volume = 49 | issue = 4 | pages = 313–319 | date = December 2021 | pmid = 34583954 | doi = 10.2967/jnmt.121.262887 | s2cid = 238218763 | doi-access = free }}</ref><ref>https://investor.cyclopharm.com/site/pdf/4113810c-e2ca-4455-a50e-ad50f4e613f2/Cyclopharm-Receives-USFDA-Approval-for-Technegas.pdf</ref>

== See also ==
* Cholescintigraphy
* [[Physics:Isotopes of technetium|Isotopes of technetium]]
* [[Physics:Transient equilibrium|Transient equilibrium]]

== Notes ==
{{reflist|group=notes}}

== References ==
;Citations
{{reflist|30em}}
;Bibliography
{{refbegin|2}}
*{{cite book|title=Canada enters the nuclear age a technical history of Atomic Energy of Canada Limited|year=1997|publisher=McGill-Queen's University Press|location=Montréal|isbn=978-0-7735-1601-4|url=https://books.google.com/books?id=SkrVDKMconIC&pg=PA109|author=Atomic Energy of Canada Limited|access-date=18 April 2012}}
*{{cite book| title = Nature's Building Blocks: An A-Z Guide to the Elements| first = John| last = Emsley| location = New York| publisher = Oxford University Press| year = 2001| isbn = 978-0-19-850340-8| url-access = registration| url = https://archive.org/details/naturesbuildingb0000emsl}}
*{{cite book|first1=Darleane|last1=Hoffmann|first2=Albert|last2=Ghiorso|first3=Glenn T.|last3=Seaborg|title=The Transuranium People: The Inside Story|publisher=University of California, Berkeley & Lawrence Berkeley National Laboratory|year=2000|chapter=Chapter 1.2: Early Days at the Berkeley Radiation Laboratory|chapter-url=http://www.worldscibooks.com/etextbook/p074/p074_chap1_2.pdf|isbn=978-1-86094-087-3|bibcode=2000tpis.book.....H|access-date=18 April 2012|archive-date=17 April 2022|archive-url=https://web.archive.org/web/20220417204434/http://www.worldscibooks.com/etextbook/p074/p074_chap1_2.pdf|url-status=dead}}
*{{cite book|last=Litt|first=Paul|title=Isotopes and innovation MDS Nordion's first fifty years, 1946-1996|year=2000|publisher=McGill-Queen's University Press|location=Montreal|isbn=978-0-7735-2082-0|url=https://books.google.com/books?id=DOQscmCAdFoC&pg=PA224|access-date=18 April 2012}}
*{{cite book | author = National Research Council |  isbn = 978-0-309-13039-4 | url = http://www.nap.edu/catalog.php?record_id=12569 | publisher = National Academies Press | year = 2009 | title = Medical Isotope Production Without Highly Enriched Uranium }}
*{{cite book| title = The Encyclopedia of the Chemical Elements| url = https://archive.org/details/encyclopediaofch00hamp| url-access = registration| editor-first = Cifford A.| editor-last = Hampel| first = S. J.| last = Rimshaw| location = New York| publisher = Reinhold Book Corporation| year = 1968}}
*{{cite book |last=Schwochau |first=Klaus |title=Technetium: Chemistry and Radiopharmaceutical Applications |publisher=Wiley |location=New York |year=2000 |isbn=978-3-527-29496-1}}
{{refend}}

==Further reading==

*{{cite journal|author=P. Saraswathy, A.C. Dey, S.K. Sarkar, C. Koth, alkar, P. Naskar, G. Arjun, S.S. Arora, A.K.Kohli, V. Meera, V.Venugopal and N.Ramamoorthy|title=99mTc generators for clinical use based on zirconium molybdate gel and (n, gamma) produced 99 Mo: Indian experience in the development and deployment of indigenous technology and processing facilities|year=2007|url=http://www.rertr.anl.gov/RERTR29/PDF/9-5_Saraswathy.pdf|journal=Proceedings of the 2007 International RERTR Meeting}}
*{{cite journal|last=Iturralde|first=Mario P.|title=Molybdenum-99 production in South Africa|journal=European Journal of Nuclear Medicine|date=1 December 1996|volume=23|issue=12|pages=1681–1687|doi=10.1007/BF01249633|s2cid=28154691}}
*{{cite journal|last=Hansell|first=Cristina|title=Nuclear Medicine's Double Hazard: Imperiled Treatment and the Risk of Terrorism|journal=The Nonproliferation Review|date=1 July 2008|volume=15|issue=2|pages=185–208|doi=10.1080/10736700802117270|s2cid=8559456|access-date=24 May 2012|url=http://kms1.isn.ethz.ch/serviceengine/Files/ISN/113475/ichaptersection_singledocument/d20f8cfd-9e01-4309-af3e-413c95d59f56/en/Special+Section+01+Hansell.pdf|archive-date=18 July 2013|archive-url=https://web.archive.org/web/20130718145855/http://kms1.isn.ethz.ch/serviceengine/Files/ISN/113475/ichaptersection_singledocument/d20f8cfd-9e01-4309-af3e-413c95d59f56/en/Special+Section+01+Hansell.pdf|url-status=dead}}

== External links ==
*[http://www-nds.iaea.org/mib <sup>99m</sup>Tc production simulator – IAEA ]

{{Isotope sequence
|element=technetium
|lighter=[[Physics:Technetium-99|technetium-99]]
|heavier=[[Physics:Technetium-100|technetium-100]]
|before=[[Physics:Molybdenum-99|molybdenum-99]]
|after=[[Physics:Technetium-99|technetium-99]]
}}

{{Radiopharmaceuticals}}

{{DEFAULTSORT:Technetium-099m}}
[[Category:Technetium-99m| ]]
[[Category:Metastable isotopes]]
[[Category:Medical physics]]
[[Category:Radiochemistry]]
[[Category:Medicinal radiochemistry]]
[[Category:Medical isotopes]]

{{Sourceattribution|Technetium-99m}}