11C PBR28 positron emission tomography [Neurosurgery Wiki]

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====== 11C PBR28 positron emission tomography ======

[11C]-[[PBR28]] is a [[positron emission tomography]] ([[PET]]) [[radiotracer]] that binds to a 18pkD translocator protein (TSPO)8, which is expressed in activated [[microglia]], reactive [[astrocyte]]s, vascular endothelium, and to a much lower degree in neurons.
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Tran et al. performed a feasibility study to prospectively evaluate [[11C methionine positron emission tomography]] and [11C]PBR28 using PET in 5 patients with 7 previously SRS-treated [[brain metastases]] demonstrating regrowth to differentiate [[tumor regrowth]] (TR) from [[radiation necrosis]] (RN).

Sequential imaging with dual tracers was well-tolerated. [11C]methionine was accurate for detecting pathologically confirmed TR in 7/7 lesions, whereas [11C]PBR28 was only accurate in 3/7 lesions. Tumor [[PBR]]-[[TSPO]] expression was elevated in both [[melanoma]] and [[lung cancer]] cells, contributing to lack of [[specificity]] of [11C]PBR28-PET.

Sequential use of PET tracers is safe and effective. [11C]Methionine was a reliable TR marker, but [11C]PBR28 was not a reliable marker of RN. Studies are needed to determine the causes of post-radiation inflammation and identify specific markers of RN to improve diagnostic imaging
((Tran TT, Gallezot JD, Jilaveanu LB, Zito C, Turcu G, Lim K, Nabulsi N, Huang H, Huttner A, Kluger HM, Chiang VL, Carson R. [11C]Methionine and [11C]PBR28 as PET Imaging Tracers to Differentiate Metastatic Tumor Recurrence or Radiation Necrosis. Mol Imaging. 2020 Jan-Dec;19:1536012120968669. doi: 10.1177/1536012120968669. PMID: 33147119.)).