title: Volumetric spectroscopic imaging of glioblastoma multiforme radiation treatment volumes.
abstract: OBJECTIVE
  Magnetic resonance (MR) imaging and computed tomography (CT) are used almost exclusively in radiation therapy planning of glioblastoma multiforme (GBM), despite their well-recognized limitations. MR spectroscopic imaging (MRSI) can identify biochemical patterns associated with normal brain and tumor, predominantly by observation of choline (Cho) and N-acetylaspartate (NAA) distributions. In this study, volumetric 3-dimensional MRSI was used to map these compounds over a wide region of the brain and to evaluate metabolite-defined treatment targets (metabolic tumor volumes [MTV]).
  
  
  METHODS
  Volumetric MRSI with effective voxel size of ∼1.0 mL and standard clinical MR images were obtained from 19 GBM patients. Gross tumor volumes and edema were manually outlined, and clinical target volumes (CTVs) receiving 46 and 60 Gy were defined (CTV46 and CTV60, respectively). MTVCho and MTVNAA were constructed based on volumes with high Cho and low NAA relative to values estimated from normal-appearing tissue.
  
  
  RESULTS
  The MRSI coverage of the brain was between 70% and 76%. The MTVNAA were almost entirely contained within the edema, and the correlation between the 2 volumes was significant (r=0.68, P=.001). In contrast, a considerable fraction of MTVCho was outside of the edema (median, 33%) and for some patients it was also outside of the CTV46 and CTV60. These untreated volumes were greater than 10% for 7 patients (37%) in the study, and on average more than one-third (34.3%) of the MTVCho for these patients were outside of CTV60.
  
  
  CONCLUSIONS
  This study demonstrates the potential usefulness of whole-brain MRSI for radiation therapy planning of GBM and revealed that areas of metabolically active tumor are not covered by standard RT volumes. The described integration of MTV into the RT system will pave the way to future clinical trials investigating outcomes in patients treated based on metabolic information.
authors: Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, Florida.
authors: N Andres
authors: NA
authors: Parra
authors: Department of Radiology, University of Miami Miller School of Medicine, Miami, Florida.
authors: Andrew A
authors: AA
authors: Maudsley
authors: Department of Radiology & Imaging, Fortis Memorial Research Institute, Gurgaon, Haryana, India.
authors: Rakesh K
authors: RK
authors: Gupta
authors: Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, Florida.
authors: Fazilat
authors: F
authors: Ishkanian
authors: Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, Florida.
authors: Kris
authors: K
authors: Huang
authors: Biostatistics and Bioinformatics Core Resource, Sylvester Cancer Center, University of Miami Miller School of Medicine, Miami, Florida.
authors: Gail R
authors: GR
authors: Walker
authors: Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, Florida; Department of Radiology, University of Miami Miller School of Medicine, Miami, Florida.
authors: Kyle
authors: K
authors: Padgett
authors: Department of Radiology & Imaging, Fortis Memorial Research Institute, Gurgaon, Haryana, India.
authors: Bhaswati
authors: B
authors: Roy
authors: Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, Florida.
authors: Joseph
authors: J
authors: Panoff
authors: Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, Florida.
authors: Arnold
authors: A
authors: Markoe
authors: Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, Florida. Electronic address: RStoyanova@med.miami.edu.
authors: Radka
authors: R
authors: Stoyanova
mesh_terms: D000328:Adult; D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D001929:Brain Edema / Q000378:metabolism*; D001931:Brain Mapping; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy; D002794:Choline / Q000378:metabolism*; D003401:Creatine / Q000378:metabolism; D005260:Female; D005909:Glioblastoma / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D047368:Tumor Burden
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline