title: Investigation of prolonged hypobaric hypoxia-induced change in rat brain using T2 relaxometry and diffusion tensor imaging at 7T.
abstract: The present study examines the change in water diffusion properties of the corpus callosum (CC) and the hippocampus, in response to prolonged hypobaric hypoxia (HH) stress, using in vivo magnetic resonance imaging (MRI) modalities such as T2 relaxometry and diffusion tensor imaging (DTI). Three groups of rats (n=7/group) were exposed to a simulated altitude of 6700m above sea level for the duration of 7, 14 and 21days, respectively. Data were acquired pre-exposure, post-exposure and after 1week of normoxic follow-up in each group. The increment in T2 values with no apparent diffusion coefficient (ADC) change in the CC after 7 and 14days of HH exposure indicated mixed (vasogenic and cytotoxic) edema formation. After 1week of normoxia, 7-day HH-exposed rats showed a decrease in ADC values in the CC, probably due to cytotoxic edema. A delayed decrease in ADC values was observed in the hippocampus after 1week normoxic follow-up in 7- and 14-day HH groups giving an insight of cytotoxic edema formation. Interestingly, 21-day HH-exposed rats did not show change in ADC values. The decrease in T2 values after 14 and 21days in the hippocampal region depicts iron deposition, which was confirmed by histopathology. This study successfully demonstrated the use of MRI modality to trace water diffusion changes in the brain due to prolonged HH exposure.
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), Lucknow Road, Timarpur, Delhi 110054, India; Department of Biophysics, Panjab University, Chandigarh 160014, India.
authors.forename: S
authors.initials: S
authors.lastname: Koundal
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), Lucknow Road, Timarpur, Delhi 110054, India.
authors.forename: S
authors.initials: S
authors.lastname: Gandhi
authors.affiliation: Department of Biophysics, Panjab University, Chandigarh 160014, India.
authors.forename: T
authors.initials: T
authors.lastname: Kaur
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), Lucknow Road, Timarpur, Delhi 110054, India.
authors.forename: R
authors.initials: R
authors.lastname: Trivedi
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), Lucknow Road, Timarpur, Delhi 110054, India. Electronic address: skhushu@inmas.drdo.in.
authors.forename: S
authors.initials: S
authors.lastname: Khushu
mesh_terms: D000532:Altitude Sickness; D000818:Animals; D001929:Brain Edema / Q000378:metabolism / Q000473:pathology; D003337:Corpus Callosum / Q000378:metabolism / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D005295:Ferrocyanides; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology*; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology*; D007501:Iron / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D008297:Male; D010784:Photomicrography; D011312:Pressure; D017207:Rats, Sprague-Dawley
chemical_list: D005295:Ferrocyanides; D007501:Iron; C000170:ferric ferrocyanide
keywords: T2-weighted imaging (T2WI); corpus callosum (CC); diffusion tensor imaging (DTI); hippocampus; hypobaric hypoxia (HH); rat brain