title: The effect of prior surgery on blood oxygen level-dependent functional MR imaging in the preoperative assessment of brain tumors.
abstract: OBJECTIVE
  Blood oxygen level-dependent functional MR imaging (BOLD fMRI) is a clinically useful technique for preoperative mapping of eloquent cortices in patients with brain tumors. The purpose of this study was to determine the effect on BOLD fMRI accuracy of susceptibility artifacts caused by prior surgery by comparing volumes of activation in the primary motor cortex (PMC) of patients with and without prior brain surgery.
  
  
  METHODS
  The volumes of fMRI activation of the PMC were measured for the tumor and nontumor sides in patients with (n = 13) and without (n = 30) prior neurosurgery. Statistical comparisons of the volumes were performed by using paired t tests and linear regression analysis. The location and degree of susceptibility artifact were subjectively assessed.
  
  
  RESULTS
  No significant difference was found between the mean tumor and nontumor volumes of fMRI activations in patients without prior surgery (P = .51). In patients who had prior surgery, the volume of activation was significantly smaller on the side of the prior operation when compared with the contralateral side (P = .001). The volume of activation on the side of the tumor was also significantly smaller in the patients with prior surgery compared with those without prior surgery (P < .001). Nevertheless, the PMC was identified in all cases, and its location was confirmed intraoperatively.
  
  
  CONCLUSIONS
  Prior surgery is associated with a decrease in the volume of fMRI activation in patients with prior surgery; however, by examining the T2 images, an astute radiologist can recognize this phenomenon, draw the appropriate conclusions, and correctly identify the PMC.
authors.affiliation: Department of Radiology, Functional MRI Laboratory, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
authors.forename: Michael J J
authors.initials: MJ
authors.lastname: Kim
authors.forename: Andrei I
authors.initials: AI
authors.lastname: Holodny
authors.forename: Bob L
authors.initials: BL
authors.lastname: Hou
authors.forename: Kyung K
authors.initials: KK
authors.lastname: Peck
authors.forename: Chaya S
authors.initials: CS
authors.lastname: Moskowitz
authors.forename: Dmitry L
authors.initials: DL
authors.lastname: Bogomolny
authors.forename: Philip H
authors.initials: PH
authors.lastname: Gutin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D001932:Brain Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000601:surgery*; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008499:Medical Records; D008875:Middle Aged; D019635:Neurosurgical Procedures; D010100:Oxygen / Q000097:blood*; D011300:Preoperative Care
chemical_list: D010100:Oxygen