document: Image fusion between / sup 18/FDG-PET and MRI/CT for radiotherapy planning of oropharyngeal and nasopharyngeal carcinomas Accurate diagnosis of tumor extent is important in three-dimensional conformal radiotherapy . This study reports the use of image fusion between -LRB- 18 -RRB- F-fluoro-2-deoxy-D-glucose positron emission tomography -LRB- / sup 18/FDG-PET -RRB- and magnetic resonance imaging/computed tomography -LRB- MRI/CT -RRB- for better targets delineation in radiotherapy planning of head-and-neck cancers . The subjects consisted of 12 patients with oropharyngeal carcinoma and 9 patients with nasopharyngeal carcinoma -LRB- NPC -RRB- who were treated with radical radiotherapy between July 1999 and February 2001 . Image fusion between / sup 18/FDG-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 -LRB- GTV -RRB- was determined based on clinical examination and / sup 18/FDG uptake on the fusion images . Clinical target volume -LRB- CTV -RRB- was determined following the usual pattern of lymph node spread for each disease entity along with the clinical presentation of each patient . Except for 3 cases with superficial tumors , all the other primary tumors were detected by / sup 18/FDG-PET . The GTV volumes for primary tumors were not changed by image fusion in 19 cases -LRB- 89 % -RRB- , 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 -LRB- 71 % -RRB- whose upper neck areas near the parotid glands were tumor-free by / sup 18/FDG-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 . In conclusion , this preliminary study showed that image fusion between / sup 18/FDG-PET and MRI/CT was useful in GTV and CTV determination in conformal RT , thus sparing normal tissues
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extractive_keyphrases: image fusion radiotherapy planning nasopharyngeal carcinomas parotid glands simultaneous primary site recurrence superficial tumors primary tumors
abstractive_keyphrases: /sup 18/fdg-pet mri/ct oropharyngeal carcinomas normal tissues sparing f