Differentiation of recurrent brain tumor versus radiation injury using diffusion tensor imaging in patients with new contrast-enhancing lesions This study was presented at the American Society of Neuroradiology, Toronto, Canada, 2005

Background and Purpose The purpose of this study was to assess the use of diffusion tensor imaging (DTI) in the evaluation of new contrast-enhancing lesions and perilesional edema in patients previously treated for brain neoplasm in the differentiation of recurrent neoplasm from treatment-related injury. Methods Twenty-eight patients with new contrast-enhancing lesions and perilesional edema at the site of previously treated brain neoplasms were retrospectively reviewed. Nine directional echoplanar DTIs with b=1000 s/mm super(2) were obtained using a single-shot spin-echo echoplanar imaging. Standardized regions of interest were manually drawn in several regions. Mean apparent diffusion coefficient (ADC), fractional anisotropy (FA) and eigenvalue indices ( lambda sub() and lambda sub()) and their ratios relative to the contralateral side were compared in patients with recurrent neoplasm versus patients with radiation injury, as established by histological examination or by clinical course, including long-term imaging studies and magnetic resonance spectroscopy. Results The ADC values in the contrast-enhancing lesions were significantly higher (P=.01) for the recurrence group (range=1.01x10 super(-3) to 1.66x10 super(-3) mm super(2)/s; mean+/-S.D.=1.27+/-0.15) than for the nonrecurrence group (range=0.9x10 super(-3) to 1.31x10 super(-3) mm super(2)/s; mean+/-S.D.=1.12+/-0.14). The ADC ratios in the white matter tracts in perilesional edema trended higher (P=.09) in treatment-related injury than in recurrent neoplasm (mean+/- S.D.=1.85+/-0.30 vs. 1.60+/-0.27, respectively). FA ratios were significantly higher in normal-appearing white matter (NAWM) tracts adjacent to the edema in the nonrecurrence group (mean+/-S.D.=0.89+/-0.15) than in those in the recurrence group (mean+/-S.D.=0.74+/-0.14; P=.03). Both eigenvalue indices lambda sub() and lambda sub() were significantly higher in contrast-enhancing lesions in the recurrence group than in those in the nonrecurrence group (P=.02). As well, both eigenvalue indices lambda sub() and lambda sub() were significantly higher in perilesional edema than in normal white matter (P