title: Glioma Recurrence Versus Radiation Necrosis: Single-Session Multiparametric Approach Using Simultaneous O-(2-18F-Fluoroethyl)-L-Tyrosine PET/MRI.
abstract: OBJECTIVE
  This study aimed to investigate the potential of hybrid gadolinium (Gd)-enhanced F-fluoroethyl-L-tyrosine (F-FET) PET/MRI in distinguishing recurrence from radiation necrosis using simultaneously acquired multiple structural and functional parameters.
  
  
  METHODS
  Twenty-six patients (5 female and 21 male patients; mean ± SD age, 51.58 ± 15.97 years) with single or multiple contrast-enhancing brain lesions (n = 32) on MRI after surgery and radiation therapy were evaluated with simultaneously acquired Gd-enhanced F-FET PET/MRI. They were then followed up with resurgery and histopathological diagnosis (n = 9) and/or clinical/MRI- or PET/MRI-based imaging follow-up (n = 17). PET/MR images were analyzed using manually drawn regions of interest over areas of maximal contrast enhancement and/or FET uptake. Maximum target-to-background ratio (TBRmax), mean target-to-background ratio (TBRmean), and choline-to-creatine (Cho/Cr) ratios as well as normalized mean relative cerebral blood volume (rCBVmean) and mean apparent diffusion coefficient (ADCmean) were determined. The accuracy of each parameter individually and in various possible combinations for differentiating recurrence versus radiation necrosis was evaluated using 2-tailed independent samples Student t test, multivariate analysis of variance, and multivariate receiver operating characteristic analysis. Positive histopathological finding and long-term imaging/clinical follow-up suggestive of disease progression served as criterion standard.
  
  
  RESULTS
  Of 26 patients, 19 were classified as recurrence, with 7 patients showing radiation necrosis. Individually, TBRmax, TBRmean, ADCmean, and Cho/Cr ratios as well as normalized rCBVmean was significant in differentiating recurrence from radiation necrosis, with an accuracy of 93.8% for TBRmax, 87.5% for TBRmean, 81.3% for ADCmean, 96.9% for Cho/Cr ratio, and 90.6% for normalized rCBVmean. The accuracy of both normalized rCBVmean and ADCmean was improved in combination with TBRmax or Cho/Cr ratio. However, TBRmax (or TBRmean) with Cho/Cr ratio yielded the highest accuracy, approaching up to 97%. Furthermore, maximum area under the curve is achieved with the combination of TBRmean, CBV, and Cho/Cr values.
  
  
  CONCLUSIONS
  Our findings suggest that FET uptake with Cho/Cr ratio and normalized rCBVmean could be most useful to distinguish primary glioma recurrence from radiation necrosis. Hybrid simultaneous multiparametric F-FET PET/MRI might play a significant role in the evaluation of patients with suspected glioma recurrence.
authors: From the *PET Suite, Department of Molecular Imaging and Nuclear Medicine, Indraprastha Apollo Hospitals, Sarita Vihar, New Delhi; †Molecular Imaging and Research Centre, Institute of Nuclear Medicine and Allied Sciences, Delhi; and ‡Institute of Radiation Oncology, and §Institute of Neuro Sciences, Indraprastha Apollo Hospitals, Sarita Vihar, New Delhi, India.
authors: Amarnath
authors: A
authors: Jena
authors: Sangeeta
authors: S
authors: Taneja
authors: Aashish
authors: A
authors: Gambhir
authors: Anil Kumar
authors: AK
authors: Mishra
authors: Maria Mathew
authors: MM
authors: Dʼsouza
authors: Sapna Manocha
authors: SM
authors: Verma
authors: Puja Panwar
authors: PP
authors: Hazari
authors: Pradeep
authors: P
authors: Negi
authors: Ganesh Krishna Rao
authors: GK
authors: Jhadav
authors: Shanti Kumar
authors: SK
authors: Sogani
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D005462:Fluorine Radioisotopes; D005682:Gadolinium; D005910:Glioma / Q000000981:diagnostic imaging*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D011832:Radiation Injuries / Q000000981:diagnostic imaging*; D019275:Radiopharmaceuticals
chemical_list: D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D005682:Gadolinium