Array ( [0] => {{Short description|Isotope of iodine}} [1] => {{infobox isotope [2] => | alternate_names =radioiodine [3] => | symbol = I [4] => | mass_number =123 [5] => | mass ={{val|122.905589|(4)}} [6] => | num_neutrons =70 [7] => | num_protons =53 [8] => | abundance =0 [9] => | halflife = {{val|13.22|u=hours}} [10] => | image = [11] => | image_caption = [12] => | decay_mode1 =electron capture [13] => | decay_energy1 =0.159 (159 [[Electronvolt|keV]]) [14] => | decay_product =tellurium-123 [15] => | decay_symbol =123Te [16] => | decay_mass = [17] => | parent =Xenon-123 [18] => | parent_symbol =123Xe [19] => | parent_mass = [20] => }} [21] => '''Iodine-123''' (123I) is a [[radioactive decay|radioactive]] [[isotope]] of [[iodine]] used in [[nuclear medicine]] imaging, including [[single-photon emission computed tomography]] (SPECT) or SPECT/CT exams. The isotope's [[half-life]] is 13.2230 hours;{{cite journal | journal = Nuclear Data Sheets | volume = 174 | date = May–June 2021 | title = Nuclear Data Sheets for A=123 | doi = 10.1016/j.nds.2021.05.001 | author1 = Jun Chen | pages = 1–463| bibcode = 2021NDS...174....1C | osti = 1831118 | s2cid = 236557895 | doi-access = free }} the decay by [[electron capture]] to tellurium-123 emits [[gamma radiation]] with a predominant energy of 159 [[keV]] (this is the gamma primarily used for imaging). In medical applications, the radiation is detected by a [[gamma camera]]. The isotope is typically applied as [[iodide]]-123, the [[anion]]ic form. [22] => [23] => ==Production== [24] => [25] => Iodine-123 is produced in a [[cyclotron]] by [[proton]] irradiation of [[xenon]] in a capsule. [[Xenon-124]] absorbs a proton and immediately loses a neutron and proton to form [[xenon-123]], or else loses two neutrons to form [[caesium-123]], which decays to [[xenon-123]]. The xenon-123 formed by either route then decays to iodine-123, and is trapped on the inner wall of the irradiation capsule under refrigeration, then eluted with sodium hydroxide in a halogen [[disproportionation]] reaction, similar to collection of [[iodine-125]] after it is formed from xenon by [[neutron irradiation]] (see [[Iodine-125#Production|article on 125I]] for more details). [26] => [27] => :[[Xenon-124|{{chem|124|Xe}}]] (''p'',''pn'') {{chem|123|Xe}} → {{chem|123|I}} [28] => [29] => :[[Xenon-124|{{chem|124|Xe}}]] (''p'',''2n'') {{chem|123|Cs}} → {{chem|123|Xe}} → {{chem|123|I}} [30] => [31] => Iodine-123 is usually supplied as [{{chem|123|I}}]-sodium iodide in 0.1 M [[sodium hydroxide]] solution, at 99.8% isotopic purity.[https://www.nordion.com/wp-content/uploads/2014/10/MI_Iodine-123_Solution_Canada.pdf Nordion, I-123 fact sheet, accessed September 7, 2018] [32] => [33] => 123I for medical applications has also been produced at [[Oak Ridge National Laboratory]] by proton cyclotron bombardment of 80% isotopically enriched tellurium-123.{{cite journal |vauthors=Hupf HB, Eldridge JS, Beaver JE |title=Production of iodine-123 for medical applications |journal=Int J Appl Radiat Isot |volume=19 |issue=4 |pages=345–51 |date=April 1968 |pmid=5650883 |doi=10.1016/0020-708X(68)90178-6}} [34] => [35] => :[[Tellurium-123|{{chem|123|Te}}]] (''p'',''n'') {{chem|123|I}} [36] => [37] => ==Decay== [38] => [39] => The detailed decay mechanism is [[electron capture]] (EC) to form an [[excited state]] of the nearly-stable nuclide tellurium-123 (its half life is so long that it is considered stable for all practical purposes). This excited state of 123Te produced is not the [[metastable]] [[nuclear isomer]] 123mTe (the decay of 123I does not involve enough energy to produce 123mTe), but rather is a lower-energy [[nuclear isomer]] of 123Te that immediately [[gamma decay]]s to [[ground state]] 123Te at the energies noted, or else (13% of the time) decays by [[internal conversion]] electron emission (127 keV),{{cite book | vauthors = Sprawls P |chapter= Radioactive Transitions |chapter-url=http://www.sprawls.org/ppmi2/RADIOTRANS/ |year=1993 |title=The Physical Principles of Medical Imaging |publisher= Aspen Publishers |edition=2nd |isbn=978-0-8342-0309-9}} followed by an average of 11 [[Auger electron]]s emitted at very low energies (50-500 eV). The latter decay channel also produces ground-state 123Te. Especially because of the internal conversion decay channel, 123I is not an absolutely pure gamma-emitter, although it is sometimes clinically assumed to be one.{{citation needed|date=July 2013}} [40] => [41] => The Auger electrons from the radioisotope have been found in one study to do little cellular damage, unless the radionuclide is directly incorporated chemically into cellular [[DNA]], which is not the case for present [[radiopharmaceutical]]s which use 123I as the radioactive label nuclide. The [[Radiation damage|damage]] from the more penetrating gamma radiation and 127 keV internal conversion electron radiation from the initial decay of 123Te is moderated by the relatively short [[half-life]] of the [[isotope]].{{cite journal |vauthors=Narra VR, Howell RW, Harapanhalli RS, Sastry KS, Rao DV |title=Radiotoxicity of some iodine-123, iodine-125 and iodine-131-labeled compounds in mouse testes: implications for radiopharmaceutical design |journal=J. Nucl. Med. |volume=33 |issue=12 |pages=2196–201 |date=December 1992 |pmid=1460515 |url=http://jnm.snmjournals.org/cgi/pmidlookup?view=long&pmid=1460515}} [42] => [43] => ==Medical applications== [44] => {{main|Ioflupane (123I) |Iofetamine (123I) |Iomazenil (123I)|Iobenguane|Sodium iodohippurate}} [45] => {{Drugbox [46] => | IUPAC_name = [47] => | image = [48] => | alt = [49] => | caption = [50] => [51] => [52] => | tradename = [53] => | pregnancy_AU = [54] => | pregnancy_US = X [55] => | pregnancy_category = [56] => | legal_AU = [57] => | legal_CA = [58] => | legal_UK = [59] => | legal_US = Rx-only [60] => | legal_status = [61] => | routes_of_administration = [62] => [63] => [64] => | bioavailability = [65] => | protein_bound = [66] => | metabolism = [67] => | elimination_half-life = [68] => | excretion = [69] => [70] => [71] => | CAS_number_Ref = {{cascite|correct|CAS}} [72] => | CAS_number = 2052213-29-1 [73] => | UNII_Ref = {{fdacite|correct|FDA}} [74] => | UNII = 8YWR746RPQ [75] => | ATCvet = [76] => | ATC_prefix = V09 [77] => | ATC_suffix = AB [78] => | PubChem = 135300 [79] => | DrugBank = [80] => | ChEMBL = 1249 [81] => | index2_label = iodide ion [82] => | CAS_number2_Ref = {{cascite|correct|CAS}} [83] => | CAS_number2 = 69239-56-1 [84] => | UNII2_Ref = {{fdacite|correct|FDA}} [85] => | UNII2 = 98QPV8670C [86] => [87] => [88] => | chemical_formula = 123I− [89] => | molecular_weight = 122.91 [90] => | molecular_weight_comment = g/mol [91] => | smiles = [123I-] [92] => | StdInChI = 1S/HI/h1H/p-1/i1-4 [93] => | StdInChIKey = XMBWDFGMSWQBCA-AHCXROLUSA-M [94] => }} [95] => [96] => 123I is the most suitable isotope of iodine for the diagnostic study of [[thyroid]] diseases. The half-life of approximately 13.2 hours is ideal for the 24-hour [[Radioactive iodine uptake test|iodine uptake test]] and 123I has other advantages for diagnostic imaging thyroid tissue and thyroid cancer [[metastasis]]. The energy of the photon, 159 keV, is ideal for the NaI ([[sodium iodide]]) [[crystal detector]] of current [[gamma camera]]s and also for the pinhole [[collimator]]s. It has much greater photon flux than 131I. It gives approximately 20 times the counting rate of 131I for the same administered dose, while the radiation burden to the thyroid is far less (1%) than that of 131I. Moreover, scanning a thyroid remnant or metastasis with 123I does not cause "stunning" of the tissue (with loss of uptake), because of the low radiation burden of this isotope.{{cite journal |author=Park HM |title=123I: almost a designer radioiodine for thyroid scanning |journal=J. Nucl. Med. |volume=43 |issue=1 |pages=77–8 |date=January 2002 |pmid=11801707 |url=http://jnm.snmjournals.org/cgi/pmidlookup?view=long&pmid=11801707}} For the same reasons, 123I is never used for thyroid cancer or [[Graves disease]] ''treatment'', and this role is reserved for [[Iodine-131|131I]]. [97] => [98] => 123I is supplied as [[sodium iodide]] (NaI), sometimes in basic solution in which it has been dissolved as the free element. This is administered to a patient by ingestion under capsule form, by [[intravenous injection]], or (less commonly due to problems involved in a spill) in a drink. The iodine is taken up by the [[thyroid gland]] and a [[gamma camera]] is used to obtain functional images of the [[thyroid]] for diagnosis. Quantitative measurements of the thyroid can be performed to calculate the iodine uptake (absorption) for the diagnosis of [[hyperthyroidism]] and [[hypothyroidism]]. [99] => [100] => Dosing can vary; {{convert|7.5|-|25|MBq|μCi|lk=on}} is recommended for thyroid imaging{{cite web|title=Society of Nuclear Medicine Procedure Guideline for Thyroid Scintigraphy|url=http://snmmi.files.cms-plus.com/docs/Thyroid_Scintigraphy_V3.pdf|website=SNMMI|date=10 September 2006}}{{cite web|title=Radionuclide Thyroid Scans Clinical Guidelines|url=https://www.bnms.org.uk/procedures-guidelines/bnms-clinical-guidelines/radionuclide-thyroid-scans.html|website=BNMS|language=en-gb|date=February 2003|access-date=2017-08-31|archive-url=https://web.archive.org/web/20170831133446/https://www.bnms.org.uk/procedures-guidelines/bnms-clinical-guidelines/radionuclide-thyroid-scans.html|archive-date=2017-08-31|url-status=dead}} and for total body while an uptake test may use {{convert|3.7|-|11.1|MBq|μCi|abbr=on}}.{{Cite journal|author=Venturi, Sebastiano|title=Evolutionary significance of iodine|journal=Current Chemical Biology|volume=5 |pages=155–162|year=2011|issn=1872-3136|doi=10.2174/187231311796765012|issue=3}}{{cite web|title=Society of Nuclear Medicine Procedure Guideline for Thyroid Uptake Measurement|url=http://snmmi.files.cms-plus.com/docs/Thyroid%20Uptake%20Measure%20v3%200.pdf|website=SNMMI|date=5 September 2006}} There is a study that indicates a given dose can effectively result in effects of an otherwise higher dose, due to impurities in the preparation.{{cite journal |doi=10.1016/0020-708X(76)90046-6 |title=Absorbed radiation dose by the thyroid from radioiodine impurities found in 123I |year=1976 | vauthors = Colombetti LG, Johnston AS |journal=The International Journal of Applied Radiation and Isotopes |volume=27 |issue=11 |pages=656–9}} The dose of radioiodine 123I is typically tolerated by individuals who cannot tolerate [[contrast medium]]s containing larger concentration of stable iodine such as used in [[X-ray computed tomography|CT scan]], [[intravenous pyelogram]] (IVP) and similar imaging diagnostic procedures. Iodine is not an [[allergen]].{{cite journal | vauthors = Schabelman E, Witting M | title = The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed | journal = The Journal of Emergency Medicine | volume = 39 | issue = 5 | pages = 701–707 | date = November 2010 | pmid = 20045605 | doi = 10.1016/j.jemermed.2009.10.014 }} [101] => [[File:Sequence of 123-iodide total body human scintiscans.jpg|thumb|Sequence of 123-iodide human scintiscans after an intravenous injection, (from left) after 30 minutes, 20 hours, and 48 hours. A high and rapid concentration of radio-iodide is evident in [[cerebrospinal fluid]] (left), gastric and oral [[mucosa]], [[salivary gland]]s, [[arterial wall]]s, [[ovary]] and [[thymus]]. In the thyroid gland, I-concentration is more progressive, as in a reservoir (from 1% after 30 minutes, and after 6, 20 h, to 5.8% after 48 hours, of the total injected dose).(Venturi, 2011)]] [102] => [103] => 123I is also used as a label in other imaging [[radiopharmaceuticals]], such as [[metaiodobenzylguanidine]] (MIBG) and [[ioflupane]]. [104] => [105] => ==Precautions== [106] => Removal of radioiodine contamination can be difficult and use of a decontaminant specially made for radioactive iodine removal is advised. Two common products designed for institutional use are Bind-It{{cite web |url=http://www.labtechinc.com/Bind-It.html |title=Bind-It Decontamination Products |publisher=Laboratory Technologies |year=2009}} and I-Bind.{{citation needed|date=July 2013}} General purpose radioactive decontamination products are often unusable for iodine, as these may only spread or volatilize it.{{citation needed|date=July 2013}} [107] => [108] => == See also == [109] => * [[Isotopes of iodine]] [110] => * [[Iodine-125]] [111] => * [[Iodine-129]] [112] => * [[Iodine-131]] [113] => * [[Iodine in biology]] [114] => [115] => ==References== [116] => {{reflist|30em}} [117] => [118] => {{Radiopharmaceuticals}} [119] => [120] => [[Category:Diagnostic endocrinology]] [121] => [[Category:Isotopes of iodine]] [122] => [[Category:Medical isotopes]] [] => )
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Iodine-123

Iodine-123 (123I) is a radioactive isotope of iodine used in nuclear medicine imaging, including single-photon emission computed tomography (SPECT) or SPECT/CT exams. The isotope's half-life is 13.

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