Value of BOLD-fMRI in the protection of visual function during postoperative intensity-modulated radiotherapy for cerebral gliomas

Objective To investigate the clinical value of blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) in the protection of visual function during postoperative radiotherapy for occipital lobe gliomas. Methods Twenty-eight patients with occipital lobe gliomas receiving postoperative radiotherapy from 2014 to 2016 were enrolled as subjects. All patients underwent computed tomography (CT) simulation, conventional MRI, and BOLD-fMRI before radiotherapy. The location and scope of the visual cortex on 3DT1 anatomical images were used to guide the labeling of the visual cortex on simulated CT images. A visual cortex protective radiotherapy plan and a conventional radiotherapy plan were made by intensity-modulated radiotherapy. The feasibility of the visual cortex protective radiotherapy plan was evaluated using conformity index (CI), homogeneity index (HI), Dmax, and Dmean for planning target volume (PTV) and Dmax and Dmean to the visual cortex. Results For the two plans, if the effective dose to target volume was guaranteed and the doses to conventional organs at risk were acceptable, there were no significant differences in CI or HI for PTV between them (P=0.874, P=0.602). Compared with the conventional radiotherapy plan, the Dmax and Dmean to the ipsilateral visual cortex were reduced by 8.40% and 9.25%, respectively, while the Dmax and Dmean to the contralateral visual cortex were reduced by 13.26% and 14.77%, respectively, in the protective radiotherapy plan. Conclusions With a guaranteed prescribed dose to target volume and BOLD-fMRI used as a guide, the visual cortex protective radiotherapy, compared with the conventional plan, can reduce the dose to the visual cortex and protect the corresponding functional areas. Key words: Blood oxygen level-dependent functional magnetic resonance imaging; Visual cortex; Cerebral gliomas/intensity-modulated radiotherapy