Diffusion tensor imaging parameters for the early diagnosis of radiation-induced brain injury in patients with nasopharyngeal carcinoma: a meta-analysis.

Purpose: To estimate diffusion tensor imaging (DTI) parameters for early diagnosis during the stage of radiation-induced brain injury (RBI) in nasopharyngeal carcinoma (NPC) patients.PubMed, Embase, Web of Science and Cochrane Library were searched up to March 2019. Eligible studies comparing early brain injuries with controls of temporal lobe in NPC patients before and after radiotherapy which collected the DTI parameters such as apparent diffusion coefficient (ADC), fractional anisotropy (FA), axial diffusibility (λa), radial diffusibility (λr), mean diffusion (MD) were included.

Conclusion: Seven studies (N = 21) were selected from the studies in the databases. Overall, FA, λa, λr values were significant difference between early RBI and healthy control (HC) in NPC patients after radiotherapy (MD= -0.03, 95% CI= -0.05∼-0.01; p = .008 in FA, MD= -0.07, 95% CI= -0.11∼-0.02; p = .002 in λa and MD = 0.02, 95% CI = 0.00 ∼ 0.04; p = .04 in λr). The meta regression analysis about dose dependence with FA value was: -0.057 ∼ 0.0003 in 95% CI, I²=74.70%, P = 0.052 (adjust p = .029). The overall heterogeneity is p < .001, I²=91% in FA, P = 0.08, I²=61% in λa and p = .04, I²=69% in λr. DTI parameters such as the reduced FA value, the decreased λa value, and the increased λr value were significant in the early period of RBI in NPC patients after radiotherapy, which becoming a more sensitive method in diagnosing the early stage of RBI.