Editing Positron emission tomography (section)

==== Neurology ====
[[File:PET-image.jpg|thumb|A PET scan of the human brain.]]
PET imaging with oxygen-15 indirectly measures blood flow to the brain. In this method, increased radioactivity signal indicates increased blood flow which is assumed to correlate with increased brain activity. Because of its two-minute [[half-life]], oxygen-15 must be piped directly from a medical [[cyclotron]] for such uses, which is difficult.<ref>{{cite book |last1=Cherry |first1=Simon R. |title=Physics in Nuclear Medicine |date=2012 |publisher=Saunders |location=Philadelphia |isbn=9781416051985 |page=60 |edition=4th |url=https://books.google.com/books?id=i794wmV6YQkC&pg=PA60}}</ref>

PET imaging with FDG takes advantage of the fact that the brain is normally a rapid user of glucose. Standard FDG PET of the brain measures regional glucose use and can be used in neuropathological diagnosis.

Brain pathologies such as [[Alzheimer's disease]] (AD) greatly decrease brain metabolism of both glucose and oxygen in tandem.  Therefore FDG PET of the brain may also be used to successfully differentiate Alzheimer's disease from other dementing processes, and also to make early diagnoses of Alzheimer's disease. The advantage of FDG PET for these uses is its much wider availability. In addition, some other fluorine-18 based radioactive tracers can be used to detect [[amyloid-beta]] plaques, a potential [[biomarker]] for Alzheimer's in the brain. These include [[Florbetapir (18F)|florbetapir]], [[Flutemetamol (18F)|flutemetamol]], [[Pittsburgh compound B]] (PiB) and [[Florbetaben (18F)|florbetaben]].<ref>{{cite journal |last1=Anand |first1=Keshav |last2=Sabbagh |first2=Marwan |title=Amyloid Imaging: Poised for Integration into Medical Practice |journal=Neurotherapeutics |date=January 2017 |volume=14 |issue=1 |pages=54–61 |doi=10.1007/s13311-016-0474-y |pmid=27571940 |pmc=5233621|doi-access=free}}</ref>

PET imaging with FDG can also be used for localization of "seizure focus". A seizure focus will appear as hypometabolic during an interictal scan.<ref>{{cite journal |last1=Stanescu |first1=Luana |last2=Ishak |first2=Gisele E. |last3=Khanna |first3=Paritosh C. |last4=Biyyam |first4=Deepa R. |last5=Shaw |first5=Dennis W. |last6=Parisi |first6=Marguerite T. |title=FDG PET of the Brain in Pediatric Patients: Imaging Spectrum with MR Imaging Correlation |journal=RadioGraphics |date=September 2013 |volume=33 |issue=5 |pages=1279–1303 |doi=10.1148/rg.335125152 |pmid=24025925|doi-access=free}}</ref> Several radiotracers (i.e. radioligands) have been developed for PET that are [[ligand (biochemistry)|ligands]] for specific [[neuroreceptor]] subtypes such as [<sup>11</sup>C][[raclopride]], [<sup>18</sup>F][[fallypride]] and [<sup>18</sup>F][[desmethoxyfallypride]] for [[dopamine]] [[Dopamine receptor D2|D<sub>2</sub>]]/[[Dopamine receptor D3|D<sub>3</sub>]] receptors; [<sup>11</sup>C][[McN5652]] and [<sup>11</sup>C][[DASB]] for [[serotonin transporter]]s; [<sup>18</sup>F][[mefway]] for serotonin [[5-HT1A receptor|5HT<sub>1A</sub> receptors]]; and [<sup>18</sup>F][[nifene]] for [[nicotinic acetylcholine receptor]]s or [[Enzyme|enzyme substrates]] (e.g. 6-[[FDOPA]] for the [[Aromatic L-amino acid decarboxylase|AADC enzyme]]). These agents permit the visualization of neuroreceptor pools in the context of a plurality of neuropsychiatric and neurologic illnesses.

PET may also be used for the diagnosis of [[hippocampal sclerosis]], which causes epilepsy. FDG, and the less common tracers [[flumazenil]] and [[MPPF]] have been explored for this purpose.<ref>{{cite journal |last1=la Fougère |first1=C. |last2=Rominger |first2=A. |last3=Förster |first3=S. |last4=Geisler |first4=J. |last5=Bartenstein |first5=P. |title=PET and SPECT in epilepsy: A critical review |journal=Epilepsy & Behavior |date=May 2009 |volume=15 |issue=1 |pages=50–55 |doi=10.1016/j.yebeh.2009.02.025 |pmid=19236949|doi-access=free}}</ref><ref>{{cite journal |last1=Hodolic |first1=Marina |last2=Topakian |first2=Raffi |last3=Pichler |first3=Robert |title=18 F-fluorodeoxyglucose and 18 F-flumazenil positron emission tomography in patients with refractory epilepsy |journal=Radiology and Oncology |date=1 September 2016 |volume=50 |issue=3 |pages=247–253 |doi=10.1515/raon-2016-0032 |pmid=27679539 |pmc=5024661}}</ref> If the sclerosis is unilateral (right hippocampus or left hippocampus), FDG uptake can be compared with the healthy side. Even if the diagnosis is difficult with MRI, it may be diagnosed with PET.<ref>{{cite journal |last1=Malmgren |first1=K |last2=Thom |first2=M |title=Hippocampal sclerosis – origins and imaging. |journal=Epilepsia |date=September 2012 |volume=53 |issue=Suppl 4 |pages=19–33 |doi=10.1111/j.1528-1167.2012.03610.x |pmid=22946718|doi-access=free}}</ref><ref>{{cite journal |last1=Cendes |first1=Fernando |title=Neuroimaging in Investigation of Patients With Epilepsy |journal=Continuum |date=June 2013 |volume=19 |issue=3 Epilepsy |pages=623–642 |doi=10.1212/01.CON.0000431379.29065.d3 |pmid=23739101|pmc=10564042 |s2cid=19026991 }}</ref>

The development of a number of novel probes for [[Non-invasive procedure|non-invasive]], [[In vivo|''in-vivo'']] PET imaging of neuroaggregate in human brain has brought amyloid imaging close to clinical use. The earliest [[amyloid]] imaging probes included [<sup>18</sup>F]FDDNP,<ref>{{cite journal | vauthors = Agdeppa ED, Kepe V, Liu J, Flores-Torres S, Satyamurthy N, Petric A, Cole GM, Small GW, Huang SC, Barrio JR | display-authors = 6 | title = Binding characteristics of radiofluorinated 6-dialkylamino-2-naphthylethylidene derivatives as positron emission tomography imaging probes for beta-amyloid plaques in Alzheimer's disease | journal = The Journal of Neuroscience | volume = 21 | issue = 24 | pages = RC189 | date = December 2001 | pmid = 11734604 | pmc = 6763047 | doi = 10.1523/JNEUROSCI.21-24-j0004.2001 }}</ref> developed at the [[University of California, Los Angeles]], and [[Pittsburgh compound B]] (PiB),<ref name="pmid11814781">{{cite journal |display-authors=6 |vauthors=Mathis CA, Bacskai BJ, Kajdasz ST, McLellan ME, Frosch MP, Hyman BT, Holt DP, Wang Y, Huang GF, Debnath ML, Klunk WE |date=February 2002 |title=A lipophilic thioflavin-T derivative for positron emission tomography (PET) imaging of amyloid in brain |journal=Bioorganic & Medicinal Chemistry Letters |volume=12 |issue=3 |pages=295–8 |doi=10.1016/S0960-894X(01)00734-X |pmid=11814781}}</ref> developed at the [[University of Pittsburgh]]. These probes permit the visualization of amyloid plaques in the brains of Alzheimer's patients and could assist clinicians in making a positive clinical diagnosis of AD pre-mortem and aid in the development of novel anti-amyloid therapies. [<sup>11</sup>C][[polymethylpentene]] (PMP) is a novel radiopharmaceutical used in PET imaging to determine the activity of the acetylcholinergic neurotransmitter system by acting as a substrate for [[acetylcholinesterase]]. Post-mortem examination of AD patients has shown decreased levels of acetylcholinesterase. [<sup>11</sup>C]PMP is used to map the acetylcholinesterase activity in the brain, which could allow for [[Stages of death|premortem]] diagnoses of AD and help to monitor AD treatments.<ref>{{cite journal | vauthors = Kuhl DE, Koeppe RA, Minoshima S, Snyder SE, Ficaro EP, Foster NL, Frey KA, Kilbourn MR | display-authors = 6 | title = In vivo mapping of cerebral acetylcholinesterase activity in aging and Alzheimer's disease | journal = Neurology | volume = 52 | issue = 4 | pages = 691–9 | date = March 1999 | pmid = 10078712 | doi = 10.1212/wnl.52.4.691 | s2cid = 11057426 }}</ref> [[Avid Radiopharmaceuticals]] has developed and commercialized a compound called [[florbetapir]] that uses the longer-lasting [[radionuclide]] fluorine-18 to detect amyloid plaques using PET scans.<ref>[[Gina Kolata|Kolata, Gina]]. [https://www.nytimes.com/2010/06/24/health/research/24scans.html "Promise Seen for Detection of Alzheimer's"], ''[[The New York Times]]'', June 23, 2010. Accessed June 23, 2010.</ref>