title: Recognition of anaplastic foci within low-grade gliomas using MR spectroscopy.
abstract: BACKGROUND
  The recognition of anaplastic foci within low-grade gliomas is of extreme importance in patients under follow-up for Grade II gliomas. We present the algorithm of MR spectroscopy (MRS)-guided brain biopsy and its correlation with tumour histology.
  
  
  METHODS
  Twenty-seven patients harbouring suspected Grade II/III glioma were examined on our 3T MR. 2D PRESS-CSI metabolite images of Choline/Creatine, Creatine/N-acetylaspartate and Choline/N-acetylaspartate were calculated and exported to the DICOM format. According to these maps, a stereobiopsy was performed at the point of maximum Choline/Creatine ratio prior to tumour resection. In the case of enhancing tumour, a subsequent biopsy was performed from the point of enhancement. Comparisons were made between the histology of the biopsied specimens and the resected tumours.
  
  
  RESULTS
  Eleven tumours were diagnosed as high-grade and sixteen as low-grade lesions. The correlation between main spectroscopic ratios (Cho/Cr and Cho/NAA) was strongly positive at the points of maximum Cho/Cr. Similar results were obtained at the points of contrast enhancement. Comparison of histological parameters of biopsy samples at the points of maximum Cho/Cr and histological examination of the completely resected tumours gives a strong correlation of tumour grade, number of mitoses and Ki-67 expression. The diagnostic accuracy of MRS-guided biopsy was 84%. The absolute value of Cho/NAA was higher in high-grade compared to that of low-grade lesions. The value of Cho/NAA ratio of 0.9 using MRS produced a sensitivity and specificity of 78% in the differentiation between low-grade and high-grade lesions. Combining MRS with structural MR, the sensitivity increased to 86% and the specificity to 80%.
  
  
  CONCLUSIONS
  Strong correlation was demonstrated between Cho/Cr and Ch/NAA ratios. Strong correlation was demonstrated between histological parameters of biopsy samples taken using Cho/Cr ratio and those from total tumour examination. Diagnostic accuracy of MRS-guided biopsy was 84%. Sensitivity and specificity of MRS combined with structural MR reaches 86% and 80%.
authors.affiliation: Department of Neurosurgery, First Faculty of Medicine, Charles University in Prague and Military University Hospital Prague , Czech Republic.
authors.forename: Ondrej
authors.initials: O
authors.lastname: Bradac
authors.forename: Jiri
authors.initials: J
authors.lastname: Vrana
authors.forename: Filip
authors.initials: F
authors.lastname: Jiru
authors.forename: Filip
authors.initials: F
authors.lastname: Kramar
authors.forename: David
authors.initials: D
authors.lastname: Netuka
authors.forename: Petr
authors.initials: P
authors.lastname: Hrabal
authors.forename: Daniel
authors.initials: D
authors.lastname: Horinek
authors.forename: Patricia
authors.initials: P
authors.lastname: de Lacy
authors.forename: Vladimir
authors.initials: V
authors.lastname: Benes
mesh_terms: D000328:Adult; D000368:Aged; D001706:Biopsy; D001932:Brain Neoplasms / Q000175:diagnosis / Q000473:pathology*; D003401:Creatine / Q000378:metabolism; D005910:Glioma / Q000175:diagnosis / Q000473:pathology*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008875:Middle Aged; D060787:Neoplasm Grading
chemical_list: D003401:Creatine
keywords: MR imaging; MR spectroscopy; anaplastic focus; brain tumour; low-grade glioma; stereotactic biopsy