title: Quantitative analysis of whole-tumor Gd enhancement histograms predicts malignant transformation in low-grade gliomas.
abstract: OBJECTIVE
  To quantify subtle gadolinium (Gd) enhancement (signal increase) in whole-tumor histograms and optimize their ability to predict subsequent malignant transformation in low-grade gliomas (LGGs).
  
  
  METHODS
  We analyzed histograms from 21 adult subjects with LGGs (eight nontransformers and 13 transformers) who had been imaged every six months for periods of two to five years. Before transformation these tumors were reported as radiologically non-enhancing. Imaging included a T(1)-weighted volume sequence before and after a double dose of Gd-DTPA contrast agent. Image data sets were spatially registered and subtracted to obtain maps of percent enhancement (%E). Tumor outlines were defined on fluid-attenuated inversion recovery (FLAIR) images, and the volumes were calculated. Histogram tails were analyzed to obtain the volume (mL) of subtly enhancing tissue (%E > 10%).
  
  
  RESULTS
  Baseline enhancing volumes were higher for Ts than for NTs (P < 0.005). Kaplan-Meier survival curves for a threshold of 4 mL showed clear differences at five years (P < 0.04). Pretransformation examinations predicted transformation (corrected threshold = 3.0 mL, P = 0.011).
  
  
  CONCLUSIONS
  Clear histogram differences at presentation suggest that the process of transformation starts very early. It is now possible to identify individuals at high risk for transformation at baseline by quantifying the volume of subtly enhancing tumor tissue, and such findings could have an impact on patient management.
authors.affiliation: Institute of Neurology, University College London, London, United Kingdom.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Tofts
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Benton
authors.forename: Rimona S
authors.initials: RS
authors.lastname: Weil
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Tozer
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Altmann
authors.forename: H Rolf
authors.initials: HR
authors.lastname: Jäger
authors.forename: Adam D
authors.initials: AD
authors.lastname: Waldman
authors.forename: Jeremy H
authors.initials: JH
authors.lastname: Rees
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000473:pathology*; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D005910:Glioma / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA