title: Magnetic resonance spectroscopy guided brain tumor resection: differentiation between recurrent glioma and radiation change in two diagnostically difficult cases.
abstract: BACKGROUND
  It is often difficult to differentiate a recurrent glioma from the effects of post-operative radiotherapy by means of conventional neurodiagnostic imaging. Proton magnetic resonance spectroscopic imaging (1H-MRSI), that allows in vivo measurements of the concentration of brain metabolites such as choline-containing phospholipids (Cho), may provide in vivo biochemical information helpful in distinguishing areas of tumor recurrence from areas of radiation effect.
  
  
  METHODS
  Two patients who had undergone resection and post-operative radiotherapy for a cerebral glioma became newly symptomatic. Computed tomographic (CT) and magnetic resonance imaging (MRI) performed after the intravenous infusion of contrast material, and in one case, [18F]fluorodeoxyglucose positron emission tomography (PET), could not differentiate between the possibilities of recurrent glioma and radiation effect. The patients underwent 1H-MRSI prior to reoperation and the 1H-MRSI results were compared to histological findings originating from the same locations.
  
  
  RESULTS
  A high Cho signal measured by 1H-MRSI was seen in areas of histologically-proven dense tumor recurrence, while low Cho signal was present where radiation changes predominated.
  
  
  CONCLUSIONS
  The differentiation between the recurrence of a cerebral glioma and the effects of post-operative irradiation was achieved using 1H-MRSI in these two patients whose conventional neurodiagnostic imaging was equivocal for such a distinction. Where these two conditions are present, metabolite images from 1H-MRSI, such as that based on Cho, can be co-registered with other imaging modalities such as MRI and may also be integrated with functional MRI or functional PET within a multimodal imaging-guided surgical navigation system to assure maximal resection of recurrent tumor while minimizing the risk of added neurological damage.
authors.affiliation: Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, Quebec, Canada.
authors.forename: M C
authors.initials: MC
authors.lastname: Preul
authors.forename: R
authors.initials: R
authors.lastname: Leblanc
authors.forename: Z
authors.initials: Z
authors.lastname: Caramanos
authors.forename: R
authors.initials: R
authors.lastname: Kasrai
authors.forename: S
authors.initials: S
authors.lastname: Narayanan
authors.forename: D L
authors.initials: DL
authors.lastname: Arnold
mesh_terms: D000328:Adult; D001921:Brain / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy / Q000601:surgery*; D002794:Choline / Q000378:metabolism; D003131:Combined Modality Therapy; D003937:Diagnosis, Differential; D005910:Glioma / Q000175:diagnosis* / Q000532:radiotherapy / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis*; D010743:Phospholipids / Q000378:metabolism; D011832:Radiation Injuries / Q000175:diagnosis*; D013238:Stereotaxic Techniques; D014055:Tomography, Emission-Computed
chemical_list: D010743:Phospholipids; D002794:Choline