18F FET PET [Neurosurgery Wiki]

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====== 18F FET PET ======

===== Indications =====

18F-FET PET may provide additional diagnostic information compared to standard MRI in neuro-oncology
((Muoio B, Giovanella L, Treglia G. Recent Developments of 18F-FET PET in
Neuro-oncology. Curr Med Chem. 2017 Nov 23. doi:
10.2174/0929867325666171123202644. [Epub ahead of print] PubMed PMID: 29173147.
)).

The addition of [[18F FET PET]] to MRI helped discriminate tumor from non-tumor lesions in the largest consecutive cohort of pediatric CNS tumor patients
((Marner L, Lundemann M, Sehested A, Nysom K, Borgwardt L, Mathiasen R, Wehner PS, Henriksen OM, Thomsen C, Skjøth-Rasmussen J, Broholm H, Østrup O, Forman JL, Højgaard L, Law I. Diagnostic Accuracy and Clinical Impact of [ 18F]FET PET in Childhood CNS tumors. Neuro Oncol. 2021 Apr 17:noab096. doi: 10.1093/neuonc/noab096. Epub ahead of print. PMID: 33864083.))

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[[18F]]-[[FET]] [[PET]] may be useful in the [[differential diagnosis]] between [[brain tumor]]s and non-neoplastic lesions and between low-grade and [[high-grade glioma ]]s. Integration of 18F-FET PET into surgical planning allows better delineation of the [[extent of resection]] beyond margins visible with standard MRI. For biopsy planning, 18F-FET PET is particularly useful in identifying malignant foci within non-contrast-enhancing gliomas. 18F-FET PET may improve the radiation therapy planning in patients with gliomas. This metabolic imaging method may be useful to evaluate treatment response in patients with gliomas and it improves the differential diagnosis between brain tumours recurrence and post-treatment changes. 18F-FET PET may provide useful prognostic information in high-grade gliomas. 




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For quantification of standard PET-derived parameters such as the tumor-to-background ratio, the background activity is assessed using a region of interest (ROI) or volume of interest (VOI) in unaffected brain tissue. However, there is no standardized approach regarding the assessment of the background reference
((Unterrainer M, Vettermann F, Brendel M, Holzgreve A, Lifschitz M, Zähringer M,
Suchorska B, Wenter V, Illigens BM, Bartenstein P, Albert NL. Towards
standardization of (18)F-FET PET imaging: do we need a consistent method of
background activity assessment? EJNMMI Res. 2017 Dec;7(1):48. doi:
10.1186/s13550-017-0295-y. Epub 2017 May 30. PubMed PMID: 28560582.)).


(18)F-Fluoroethyl-l-thyrosine (FET) is a [[positron emission tomography]] (PET) radiopharmaceutical applicable for widespread use because of its long half-life [[radionuclide]]. 

[[Fluoroethyl]] [[Tyrosine]] [[Positron Emission Tomography]] for patients with gliomas undergoing multimodal treatment or various forms of irradiation is a powerful tool to improve the differential diagnosis
((Rachinger W, Goetz C, Pöpperl G, Gildehaus FJ, Kreth FW, Holtmannspötter M,
Herms J, Koch W, Tatsch K, Tonn JC. Positron emission tomography with
O-(2-[18F]fluoroethyl)-l-tyrosine versus magnetic resonance imaging in the
diagnosis of recurrent gliomas. Neurosurgery. 2005 Sep;57(3):505-11; discussion
505-11. PubMed PMID: 16145529.
)).

[[FET]] [[PET]] reliably distinguishes between post-therapeutic benign lesions and tumour recurrence after initial treatment of low- and high-grade gliomas
((Pöpperl G, Götz C, Rachinger W, Gildehaus FJ, Tonn JC, Tatsch K. Value of
O-(2-[18F]fluoroethyl)- L-tyrosine PET for the diagnosis of recurrent glioma. Eur
J Nucl Med Mol Imaging. 2004 Nov;31(11):1464-70. Epub 2004 Jul 10. PubMed PMID:
15248032.
)).

Maps of (18)FET uptake kinetics strongly correlated with histopathology in suspected grade II gliomas. Anaplastic foci can be accurately identified, and this finding has implications for prognostic evaluation and treatment planning
((Kunz M, Thon N, Eigenbrod S, Hartmann C, Egensperger R, Herms J, Geisler J, la
Fougere C, Lutz J, Linn J, Kreth S, von Deimling A, Tonn JC, Kretzschmar HA,
Pöpperl G, Kreth FW. Hot spots in dynamic (18)FET-PET delineate malignant tumor
parts within suspected WHO grade II gliomas. Neuro Oncol. 2011 Mar;13(3):307-16. 
doi: 10.1093/neuonc/noq196. Epub 2011 Feb 3. PubMed PMID: 21292686; PubMed
Central PMCID: PMC3064604.
)).

Dynamic 18F-FET PET in suspected WHO grade II gliomas defines distinct biological subgroups with different clinical courses
((Thon N, Kunz M, Lemke L, Jansen NL, Eigenbrod S, Kreth S, Lutz J, Egensperger 
R, Giese A, Herms J, Weller M, Kretzschmar H, Tonn JC, la Fougère C, Kreth FW.
Dynamic 18F-FET PET in suspected WHO grade II gliomas defines distinct biological
subgroups with different clinical courses. Int J Cancer. 2015 May
1;136(9):2132-45. doi: 10.1002/ijc.29259. Epub 2014 Nov 3. PubMed PMID: 25311315.)).

In [[Low-grade glioma]]s [[5-aminolevulinic acid ]] fluorescence is the exception and FET PET is more sensitive. High grade areas in diffuse gliomas with anaplastic foci usually fluoresce, if they are FET PET positive. As a result, FET PET appears valuable for pre-operative identification of anaplastic foci and hot spots are strongly predictive for ALA-derived fluorescence, which highlight anaplastic foci during resection
((Ewelt C, Floeth FW, Felsberg J, Steiger HJ, Sabel M, Langen KJ, Stoffels G,
Stummer W. Finding the anaplastic focus in diffuse gliomas: the value of Gd-DTPA 
enhanced MRI, FET-PET, and intraoperative, ALA-derived tissue fluorescence. Clin 
Neurol Neurosurg. 2011 Sep;113(7):541-7. doi: 10.1016/j.clineuro.2011.03.008.
Epub 2011 Apr 20. PubMed PMID: 21507562.
)).

Age, tumor volume, and [[Fluoroethyl Tyrosine Positron Emission Tomography]] uptake are factors predicting 5-ALA-induced fluorescence in gliomas without typical glioblastoma imaging features. Fluorescence was associated with an increased [[Ki67]]/[[MIB-1 index]] and high-grade pathology. Whether fluorescence in grade II gliomas identifies a subtype with worse prognosis remains to be determined
((Jaber M, Wölfer J, Ewelt C, Holling M, Hasselblatt M, Niederstadt T, Zoubi T, 
Weckesser M, Stummer W. The Value of 5-Aminolevulinic Acid in Low-grade Gliomas
and High-grade Gliomas Lacking Glioblastoma Imaging Features: An Analysis Based
on Fluorescence, Magnetic Resonance Imaging, 18F-Fluoroethyl Tyrosine Positron
Emission Tomography, and Tumor Molecular Factors. Neurosurgery. 2016
Mar;78(3):401-11. doi: 10.1227/NEU.0000000000001020. PubMed PMID: 26366972;
PubMed Central PMCID: PMC4747980.
)).

===== Case series =====

[[18F FET PET case series]].