title: Comparison of 18F-FET PET and perfusion-weighted MR imaging: a PET/MR imaging hybrid study in patients with brain tumors.
abstract: PET using O-(2-(18)F-fluoroethyl)-L-tyrosine ((18)F-FET) provides important diagnostic information in addition to that from conventional MR imaging on tumor extent and activity of cerebral gliomas. Recent studies suggest that perfusion-weighted MR imaging (PWI), especially maps of regional cerebral blood volume (rCBV), may provide similar diagnostic information. In this study, we directly compared (18)F-FET PET and PWI in patients with brain tumors.
  
  
  METHODS
  Fifty-six patients with gliomas were investigated using static (18)F-FET PET and PWI. For comparison, 8 patients with meningiomas were included. We generated a set of tumor and reference volumes of interest (VOIs) based on morphologic MR imaging and transferred these VOIs to the corresponding (18)F-FET PET scans and PWI maps. From these VOIs, tumor-to-brain ratios (TBR) were calculated, and normalized histograms were generated for (18)F-FET PET and rCBV maps. Furthermore, in rCBV maps and in (18)F-FET PET scans, tumor volumes, their spatial congruence, and the distance between the local hot spots were assessed.
  
  
  RESULTS
  For patients with glioma, TBR was significantly higher in (18)F-FET PET than in rCBV maps (TBR, 2.28 ± 0.99 vs. 1.62 ± 1.13; P < 0.001). Histogram analysis of the VOIs revealed that (18)F-FET scans could clearly separate tumor from background. In contrast, deriving this information from rCBV maps was difficult. Tumor volumes were significantly larger in (18)F-FET PET than in rCBV maps (tumor volume, 24.3 ± 26.5 cm(3) vs. 8.9 ± 13.9 cm(3); P < 0.001). Accordingly, spatial overlap of both imaging parameters was poor (congruence, 11.0%), and mean distance between the local hot spots was 25.4 ± 16.1 mm. In meningioma patients, TBR was higher in rCBV maps than in (18)F-FET PET (TBR, 5.33 ± 2.63 vs. 2.37 ± 0.32; P < 0.001) whereas tumor volumes were comparable.
  
  
  CONCLUSIONS
  In patients with cerebral glioma, tumor imaging with (18)F-FET PET and rCBV yields different information. (18)F-FET PET shows considerably higher TBRs and larger tumor volumes than rCBV maps. The spatial congruence of both parameters is poor. The locations of the local hot spots differ considerably. Taken together, our data show that metabolically active tumor tissue of gliomas as depicted by amino acid PET is not reflected by rCBV as measured with PWI.
authors.affiliation: Institute of Neuroscience and Medicine (INM-3, -4, -5), Research Center Jülich, Jülich, Germany.
authors.forename: Christian P
authors.initials: CP
authors.lastname: Filss
authors.forename: Norbert
authors.initials: N
authors.lastname: Galldiks
authors.forename: Gabriele
authors.initials: G
authors.lastname: Stoffels
authors.forename: Michael
authors.initials: M
authors.lastname: Sabel
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Wittsack
authors.forename: Bernd
authors.initials: B
authors.lastname: Turowski
authors.forename: Gerald
authors.initials: G
authors.lastname: Antoch
authors.forename: Ke
authors.initials: K
authors.lastname: Zhang
authors.forename: Gereon R
authors.initials: GR
authors.lastname: Fink
authors.forename: Heinz H
authors.initials: HH
authors.lastname: Coenen
authors.forename: Nadim J
authors.initials: NJ
authors.lastname: Shah
authors.forename: Hans
authors.initials: H
authors.lastname: Herzog
authors.forename: Karl-Josef
authors.initials: KJ
authors.lastname: Langen
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D003627:Data Interpretation, Statistical; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000134:cerebrospinal fluid; D005910:Glioma / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008579:Meningioma / Q000000981:diagnostic imaging / Q000473:pathology; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000134:cerebrospinal fluid; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: O-(2-18F-fluoroethyl)-l-tyrosine; PET/MR imaging; PWI; glioma; histogram; rCBV