title: Comparative evaluation of 18F-FDOPA, 13N-AMMONIA, 18F-FDG PET/CT and MRI in primary brain tumors - A pilot study.
abstract: OBJECTIVE
  To determine the diagnostic reliability of 18F-FDOPA, 13N-Ammonia and 18F-FDG PET/CT in primary brain tumors and comparison with magnetic resonance imaging (MRI).
  
  
  METHODS
  A total of 23 patients, 8 preoperative and 15 postoperative, undergoing evaluation for primary brain tumors were included in this study. Of them, 9/15 were operated for high grade gliomas (7/9 astrocytomas and 2/9 oligodendrogliomas) and 6/15 for low grade gliomas (5/6 astrocytomas and 1/6 oligodendroglioma). After PET study, 2 of 8 preoperative cases were histopathologically proven to be of benign etiology. 3 low grade and 2 high grade postoperative cases were disease free on 6 months follow-up. Tracer uptake was quantified by standardized uptake values (SUV(max)) and the SUV max ratio of tumor to normal symmetrical area of contra lateral hemisphere (T/N). 18F-FDOPA uptake was also quantified by SUV(max) ratio of tumor to striatum (T/S). Conventional MR studies were done in all patients.
  
  
  RESULTS
  Both high-grade and low-grade tumors were well visualized with 18F-FDOPA PET. Sensitivity of 18F-FDOPA PET was substantially higher (6/6 preoperative, 3/3 low grade postoperative, 7/7 high grade postoperative) than with 18F-FDG (3/6 preoperative, 1/3 low grade postoperative, 3/7 high grade postoperative) and 13N-Ammonia PET (2/6 preoperative, 1/3 low grade postoperative, 1/7 high grade postoperative). FDOPA was equally specific as FDG and Ammonia PET in operated cases but was falsely positive in two preoperative cases. Sensitivity of FDOPA (16/16) was more than MRI (13/16).
  
  
  CONCLUSIONS
  18F-FDG uptake correlates with tumor grade. Though 18F-FDOPA PET cannot distinguish between tumor grade, it is more reliable than 18F-FDG and 13N-Ammonia PET for evaluating brain tumors. 18F-FDOPA PET may prove to be superior to MRI in evaluating recurrence and residual tumor tissue. 13N-Ammonia PET did not show any encouraging results.
authors.affiliation: Department of Nuclear Medicine, Army Hospital, Research and Referral, Delhi Cantt, New Delhi, India.
authors.forename: Charu
authors.initials: C
authors.lastname: Jora
authors.forename: Jacob J
authors.initials: JJ
authors.lastname: Mattakarottu
authors.forename: Pandit G
authors.initials: PG
authors.lastname: Aniruddha
authors.forename: Ravina
authors.initials: R
authors.lastname: Mudalsha
authors.forename: Dhananjay K
authors.initials: DK
authors.lastname: Singh
authors.forename: Harish C
authors.initials: HC
authors.lastname: Pathak
authors.forename: Nitin
authors.initials: N
authors.lastname: Sharma
authors.forename: Arti
authors.initials: A
authors.lastname: Sarin
authors.forename: Arvind
authors.initials: A
authors.lastname: Prince
authors.forename: Giriraj
authors.initials: G
authors.lastname: Singh