title: Re-examine tumor-induced alterations in hemodynamic responses of BOLD fMRI: implications in presurgical brain mapping.
abstract: BACKGROUND
  Blood oxygenation level dependent (BOLD) fMRI is used for presurgical functional mapping of brain tumor patients. Abnormal tumor blood supply may affect hemodynamic responses and BOLD fMRI signals.
  
  
  OBJECTIVE
  To perform a multivariate and quantitative investigation of the effect of brain tumors on the hemodynamic responses and its impact on BOLD MRI signal time course, data analysis in order to better understand tumor-induced alterations in hemodynamic responses, and accurately mapping cortical regions in brain tumor patients.
  
  
  METHODS
  BOLD fMRI data from 42 glioma patients who underwent presurgical mapping of the primary motor cortex (PMC) with a block designed finger tapping paradigm were analyzed, retrospectively. Cases were divided into high grade (n = 24) and low grade (n = 18) groups based on pathology. The tumor volume and distance to the activated PMCs were measured. BOLD signal time courses from selected regions of interest (ROIs) in the PMCs of tumor affected and contralateral unaffected hemispheres were obtained from each patient. Tumor-induced changes of BOLD signal intensity and time to peak (TTP) of BOLD signal time courses were analyzed statistically.
  
  
  RESULTS
  The BOLD signal intensity and TTP in the tumor-affected PMCs are altered when compared to that of the unaffected hemisphere. The average BOLD signal level is statistically significant lower in the affected PMCs. The average TTP in the affected PMCs is shorter in the high grade group, but longer in the low grade tumor group compared to the contralateral unaffected hemisphere. Degrees of alterations in BOLD signal time courses are related to both the distance to activated foci and tumor volume with the stronger effect in tumor distance to activated PMC.
  
  
  CONCLUSIONS
  Alterations in BOLD signal time courses are strongly related to the tumor grade, the tumor volume, and the distance to the activated foci. Such alterations may impair accurate mapping of tumor-affected functional areas when using conventional fixed models.
authors: Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia,  USA.
authors: Liya
authors: L
authors: Wang
authors: Dandan
authors: D
authors: Chen
authors: Jeffrey
authors: J
authors: Olson
authors: Shazia
authors: S
authors: Ali
authors: Tianning
authors: T
authors: Fan
authors: Hui
authors: H
authors: Mao
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery*; D005260:Female; D005910:Glioma / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery*; D006439:Hemodynamics; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007430:Intraoperative Care; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D012044:Regression Analysis; D012189:Retrospective Studies