title: Evaluation of radiation necrosis and malignant glioma in rat models using diffusion tensor MR imaging.
abstract: Standard MRI cannot distinguish between radiation necrosis and tumor progression; however, this distinction is critical in the assessment of tumor response to therapy. In this study, one delayed radiation necrosis model (dose, 40 Gy; radiation field, 10 × 10 mm(2); n = 13) and two orthotopic glioma models in rats (9L gliosarcoma, n =8; human glioma xenografts, n = 5) were compared using multiple diffusion tensor imaging (DTI) indices. A visible isotropic apparent diffusion coefficient (ADC) pattern was observed in the lesion due to radiation necrosis, which consisted of a hypointense central zone and a hyperintense peripheral zone. There were significantly lower ADC, parallel diffusivity, and perpendicular diffusivity in the necrotic central zone than in the peripheral zone (all P < 0.001). When radiation-induced necrosis was compared with viable tumor, radiation necrosis had significantly lower ADC than 9L gliosarcoma and human glioma xenografts (both P < 0.01) in the central zone, and significantly lower fractional anisotropy than 9L gliosarcoma (P = 0.005) and human glioma xenografts (P = 0.012) in the peripheral zone. Histological analysis revealed parenchymal coagulative necrosis in the central zone, and damaged vessels and reactive astrogliosis in the peripheral zone. These data suggest that qualitative and quantitative analysis of the DTI maps can provide useful information by which to distinguish between radiation necrosis and viable glioma.
authors.affiliation: Department of Radiology, Johns Hopkins University School of Medicine, 600 N. Wolfe Street, 336 Park Building, Baltimore, MD 21287, USA.
authors.forename: Silun
authors.initials: S
authors.lastname: Wang
authors.forename: Yifei
authors.initials: Y
authors.lastname: Chen
authors.forename: Bachchu
authors.initials: B
authors.lastname: Lal
authors.forename: Eric
authors.initials: E
authors.lastname: Ford
authors.forename: Erik
authors.initials: E
authors.lastname: Tryggestad
authors.forename: Michael
authors.initials: M
authors.lastname: Armour
authors.forename: Kun
authors.initials: K
authors.lastname: Yan
authors.forename: John
authors.initials: J
authors.lastname: Laterra
authors.forename: Jinyuan
authors.initials: J
authors.lastname: Zhou
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging; D056324:Diffusion Tensor Imaging; D005910:Glioma / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D011832:Radiation Injuries / Q000473:pathology*; D051381:Rats; D011916:Rats, Inbred F344; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured