title: Image fusion between 18FDG-PET and MRI/CT for radiotherapy planning of oropharyngeal and nasopharyngeal carcinomas.
abstract: OBJECTIVE
  Accurate diagnosis of tumor extent is important in three-dimensional conformal radiotherapy. This study reports the use of image fusion between (18)F-fluoro-2-deoxy-D-glucose positron emission tomography (18FDG-PET) and magnetic resonance imaging/computed tomography (MRI/CT) for better targets delineation in radiotherapy planning of head-and-neck cancers.
  
  
  METHODS
  The subjects consisted of 12 patients with oropharyngeal carcinoma and 9 patients with nasopharyngeal carcinoma (NPC) who were treated with radical radiotherapy between July 1999 and February 2001. Image fusion between 18FDG-PET and MRI/CT was performed using an automatic multimodality image registration algorithm, which used the brain as an internal reference for registration. Gross tumor volume (GTV) was determined based on clinical examination and 18FDG uptake on the fusion images. Clinical target volume (CTV) was determined following the usual pattern of lymph node spread for each disease entity along with the clinical presentation of each patient.
  
  
  RESULTS
  Except for 3 cases with superficial tumors, all the other primary tumors were detected by 18FDG-PET. The GTV volumes for primary tumors were not changed by image fusion in 19 cases (89%), increased by 49% in one NPC, and decreased by 45% in another NPC. Normal tissue sparing was more easily performed based on clearer GTV and CTV determination on the fusion images. In particular, parotid sparing became possible in 15 patients (71%) whose upper neck areas near the parotid glands were tumor-free by 18FDG-PET. Within a mean follow-up period of 18 months, no recurrence occurred in the areas defined as CTV, which was treated prophylactically, except for 1 patient who experienced nodal recurrence in the CTV and simultaneous primary site recurrence.
  
  
  CONCLUSIONS
  This preliminary study showed that image fusion between 18FDG-PET and MRI/CT was useful in GTV and CTV determination in conformal RT, thus sparing normal tissues.
authors.affiliation: Division of Radiation Oncology, Department of Radiology, School of Medicine, Hokkaido University, Sapporo, Japan. trout@radi.med.hokudai.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishioka
authors.forename: Tohru
authors.initials: T
authors.lastname: Shiga
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
authors.forename: Eriko
authors.initials: E
authors.lastname: Tsukamoto
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Tsuchiya
authors.forename: Takashi
authors.initials: T
authors.lastname: Kato
authors.forename: Keiichi
authors.initials: K
authors.lastname: Ohmori
authors.forename: Akira
authors.initials: A
authors.lastname: Yamazaki
authors.forename: Hidefumi
authors.initials: H
authors.lastname: Aoyama
authors.forename: Seiko
authors.initials: S
authors.lastname: Hashimoto
authors.forename: Ta-Chen
authors.initials: TC
authors.lastname: Chang
authors.forename: Kazuo
authors.initials: K
authors.lastname: Miyasaka
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001921:Brain / Q000473:pathology; D002277:Carcinoma / Q000532:radiotherapy*; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D009959:Oropharyngeal Neoplasms / Q000532:radiotherapy*; D020266:Radiotherapy, Conformal / Q000379:methods*; D013997:Time Factors; D014055:Tomography, Emission-Computed / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*