title: Simultaneous 68Ga-DOTATOC-PET/MRI for IMRT treatment planning for meningioma: first experience.
abstract: OBJECTIVE
  To evaluate intensity-modulated radiotherapy (IMRT) treatment planning based on simultaneous positron-emission tomography and magnetic resonance imaging (PET/MRI) of meningioma.
  
  
  METHODS
  A meningioma patient was examined prior to radiotherapy with dedicated planning computed tomography (CT), MRI, PET/CT with gallium-68-labeled DOTATOC (68Ga-DOTATOC), and simultaneous 68Ga-DOTATOC-PET/MRI. The first gross target volume (GTV) was defined based on a combination of separate MR and 68Ga-DOTATOC-PET/CT imaging (GTVPET/CT+MR). Then, the simultaneous PET/MR images were used to delineate a second GTV (GTVPET/MR) by following exactly the same delineation strategy. After an isotropic expansion of those volumes by a 4-mm safety margin, the resulting planning target volumes (PTVs) were compared by calculating the intersection volume and the relative complements. A cross-evaluation of IMRT plans was performed, where the treatment plan created for the PTVPET/CT+MR was applied to the PET/MR-based PTVPET/MR.
  
  
  RESULTS
  Generally, target volumes for IMRT treatment planning did not differ between MRI plus 68Ga-DOTATOC-PET/CT and simultaneous PET/MR imaging. Only in certain regions of the GTV were differences observed. The overall volume of the PET/MR-based PTV was approximately the same as that obtained from PET/CT data. A small region of infiltrative tumor growth next to the main tumor mass was better visualized with combined PET/MR due to smaller PET voxel sizes and improved recovery. An IMRT treatment plan was optimized for the PTVPET/CT+MR. The evaluation of this plan with respect to the PTVPET/MR showed parts of the target volume that would not have received the full radiation dose after delineation of the tumor, based on simultaneous PET/MR.
  
  
  CONCLUSIONS
  This case showed that differences in target volumes delineated on the basis of separate MR and PET/CT and simultaneous PET/MR may be observed that can have significant consequences for an effectively applied radiotherapy treatment plan.
authors.affiliation: Section of Biomedical Physics, University Hospital for Radiation Oncology, Eberhard-Karls-Universität Tübingen, Tübingen, Germany. daniela.thorwarth@med.uni-tuebingen.de
authors.forename: Daniela
authors.initials: D
authors.lastname: Thorwarth
authors.forename: Guido
authors.initials: G
authors.lastname: Henke
authors.forename: Arndt-Christian
authors.initials: AC
authors.lastname: Müller
authors.forename: Matthias
authors.initials: M
authors.lastname: Reimold
authors.forename: Thomas
authors.initials: T
authors.lastname: Beyer
authors.forename: Andreas
authors.initials: A
authors.lastname: Boss
authors.forename: Armin
authors.initials: A
authors.lastname: Kolb
authors.forename: Bernd
authors.initials: B
authors.lastname: Pichler
authors.forename: Christina
authors.initials: C
authors.lastname: Pfannenberg
mesh_terms: D000368:Aged; D005260:Female; D005710:Gallium Radioisotopes; D006801:Humans; D033162:Incidental Findings; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008577:Meningeal Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D008579:Meningioma / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000473:pathology; D015282:Octreotide / Q000031:analogs & derivatives*; D009942:Organometallic Compounds; D049268:Positron-Emission Tomography / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden
chemical_list: C499142:Ga(III)-DOTATOC; D005710:Gallium Radioisotopes; D009942:Organometallic Compounds; D015282:Octreotide