title: A new brain positron emission tomography scanner with semiconductor detectors for target volume delineation and radiotherapy treatment planning in patients with nasopharyngeal carcinoma.
abstract: OBJECTIVE
  We compared two treatment planning methods for stereotactic boost for treating nasopharyngeal carcinoma (NPC): the use of conventional whole-body bismuth germanate (BGO) scintillator positron emission tomography (PET(CONV)WB) versus the new brain (BR) PET system using semiconductor detectors (PET(NEW)BR).
  
  
  METHODS
  Twelve patients with NPC were enrolled in this study. [(18)F]Fluorodeoxyglucose-PET images were acquired using both the PET(NEW)BR and the PET(CONV)WB system on the same day. Computed tomography (CT) and two PET data sets were transferred to a treatment planning system, and the PET(CONV)WB and PET(NEW)BR images were coregistered with the same set of CT images. Window width and level values for all PET images were fixed at 3000 and 300, respectively. The gross tumor volume (GTV) was visually delineated on PET images by using either PET(CONV)WB (GTV(CONV)) images or PET(NEW)BR (GTV(NEW)) images. Assuming a stereotactic radiotherapy boost of 7 ports, the prescribed dose delivered to 95% of the planning target volume (PTV) was set to 2000 cGy in 4 fractions.
  
  
  RESULTS
  The average absolute volume (±standard deviation [SD]) of GTV(NEW) was 15.7 ml (±9.9) ml, and that of GTV(CONV) was 34.0 (±20.5) ml. The average GTV(NEW) was significantly smaller than that of GTV(CONV) (p = 0.0006). There was no statistically significant difference between the maximum dose (p = 0.0585) and the mean dose (p = 0.2748) of PTV. The radiotherapy treatment plan based on the new gross tumor volume (PLAN(NEW)) significantly reduced maximum doses to the cerebrum and cerebellum (p = 0.0418) and to brain stem (p = 0.0041).
  
  
  CONCLUSIONS
  Results of the present study suggest that the new brain PET system using semiconductor detectors can provide more accurate tumor delineation than the conventional whole-body BGO PET system and may be an important tool for functional and molecular radiotherapy treatment planning.
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan. noriwokatoh@med.hokudai.ac.jp
authors.forename: Norio
authors.initials: N
authors.lastname: Katoh
authors.forename: Koichi
authors.initials: K
authors.lastname: Yasuda
authors.forename: Tohru
authors.initials: T
authors.lastname: Shiga
authors.forename: Masakazu
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Rikiya
authors.initials: R
authors.lastname: Onimaru
authors.forename: Shinichi
authors.initials: S
authors.lastname: Shimizu
authors.forename: Gerard
authors.initials: G
authors.lastname: Bengua
authors.forename: Masayori
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Nagara
authors.initials: N
authors.lastname: Tamaki
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
mesh_terms: D000328:Adult; D000368:Aged; D001729:Bismuth; D001921:Brain / Q000000981:diagnostic imaging*; D002277:Carcinoma; D005260:Female; D019788:Fluorodeoxyglucose F18; D005857:Germanium; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000295:instrumentation / Q000379:methods; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000379:methods; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D005857:Germanium; D019788:Fluorodeoxyglucose F18; C042364:bismuth germanium oxide; D001729:Bismuth