title: Contribution of 68Ga-DOTATOC PET/CT to target volume delineation of skull base meningiomas treated with stereotactic radiation therapy.
abstract: OBJECTIVE
  To investigate the potential impact of 68Ga-DOTATOC positron emission tomography (68Ga-DOTATOC-PET) in addition to magnetic resonance imaging (MRI) and computed tomography (CT) for retrospectively assessing the gross tumor volume (GTV) delineation of meningiomas of the skull base in patients treated with fractionated stereotactic radiation therapy (FSRT).
  
  
  METHODS
  The study population consisted of 48 patients with 54 skull base meningiomas, previously treated with FSRT. After scans were coregistered, the GTVs were first delineated with MRI and CT data (GTVMRI/CT) and then by PET (GTVPET) data. The overlapping regions of both datasets resulted in the GTVcommon, which was enlarged to the GTVfinal by adding volumes defined by only one of the complementary modalities (GTVMRI/CT-added or GTVPET-added). We then evaluated the contribution of conventional imaging modalities (MRI, CT) and 68Ga-DOTATOC-PET to the GTVfinal, which was used for planning purposes.
  
  
  RESULTS
  Forty-eight of the 54 skull base lesions in 45 patients showed increased 68Ga-DOTATOC uptake and were further analyzed. The mean GTVMRI/CT and GTVPET were approximately 21 cm3 and 25 cm3, with a common volume of approximately 15 cm3. PET contributed a mean additional GTV of approximately 1.5 cm3 to the common volume (16%±34% of the GTVcommon). Approximately 4.5 cm3 of the GTVMRI/CT was excluded from the contribution to the common volume. The resulting mean GTVfinal was significantly smaller than both the GTVMRI/CT and the GTVPET. Compared with the initial GTVMRI/CT, the addition of 68Ga-DOTATOC-PET resulted in more than 10% modification of the size of the GTVfinal in 32 (67%) meningiomas
  
  
  CONCLUSIONS
  68Ga-DOTATOC-PET/CT seems to improve the target volume delineation in skull base meningiomas, often leading to a reduction of GTV compared with results from conventional imaging (MRI and CT).
authors.affiliation: Department of Radiation Oncology, Charité Universitätsmedizin Berlin, Berlin, Germany. reinhold.graf@charite.de
authors.forename: Reinhold
authors.initials: R
authors.lastname: Graf
authors.forename: Fonyuy
authors.initials: F
authors.lastname: Nyuyki
authors.forename: Ingo G
authors.initials: IG
authors.lastname: Steffen
authors.forename: Roger
authors.initials: R
authors.lastname: Michel
authors.forename: Daniel
authors.initials: D
authors.lastname: Fahdt
authors.forename: Peter
authors.initials: P
authors.lastname: Wust
authors.forename: Winfried
authors.initials: W
authors.lastname: Brenner
authors.forename: Volker
authors.initials: V
authors.lastname: Budach
authors.forename: Reinhard
authors.initials: R
authors.lastname: Wurm
authors.forename: Michail
authors.initials: M
authors.lastname: Plotkin
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005710:Gallium Radioisotopes; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008577:Meningeal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D008579:Meningioma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D015282:Octreotide / Q000031:analogs & derivatives*; D009942:Organometallic Compounds; D049268:Positron-Emission Tomography; D016634:Radiosurgery; D012189:Retrospective Studies; D019292:Skull Base Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden; D055815:Young Adult
chemical_list: C499142:Ga(III)-DOTATOC; D005710:Gallium Radioisotopes; D009942:Organometallic Compounds; D015282:Octreotide