title: Volumetric quantification of brain swelling after hypobaric hypoxia exposure.
abstract: We applied a novel MR imaging technique to investigate the effect of acute mountain sickness on cerebral tissue water. Nine volunteers were exposed to hypobaric hypoxia corresponding to 4572 m altitude for 32 h. Such an exposure may cause acute mountain sickness. We imaged the brains of the volunteers before and at 32 h of hypobaric exposure with two different MRI techniques with subsequent data processing. (1) Brain volumes were calculated from 3D MRI data sets by applying a computerized brain segmentation algorithm. For this specific purpose a novel adaptive 3D segmentation program was used with an automatic correction algorithm for RF field inhomogeneity. (2) T(2) decay rates were analyzed in the white matter. The results demonstrated that a significant brain swelling of 36.2 +/- 19.6 ml (2.77 +/- 1.47%, n = 9, P < 0.001) developed after the 32-h hypobaric hypoxia exposure with a maximal observed volume increase of 5.8% (71.3 ml). These volume changes were significant only for the gray matter structures in contrast to the unremarkable changes seen in the white matter. The same study repeated 3 weeks later in 6 of 9 original subjects demonstrated that the brains recovered and returned approximately to the initially determined sea-level brain volume while hypobaric hypoxia exposure once again led to a significant new brain swelling (24.1 +/- 12.1 ml, 1.92 +/- 0.96%, n = 6, P < 0.005). On the contrary, the T(2) mapping technique did not reveal any significant effect of hypobaria on white matter. We present here a technique which is able to detect reversible brain volume changes as they may occur in patients with diffuse brain edema or increased cerebral blood volume, and which may represent a useful noninvasive tool for future evaluations of antiedematous drugs.
authors.affiliation: Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA. morocz.istvan@weizmann.ac.il
authors.forename: I A
authors.initials: IA
authors.lastname: Mórocz
authors.forename: G P
authors.initials: GP
authors.lastname: Zientara
authors.forename: H
authors.initials: H
authors.lastname: Gudbjartsson
authors.forename: S
authors.initials: S
authors.lastname: Muza
authors.forename: T
authors.initials: T
authors.lastname: Lyons
authors.forename: P B
authors.initials: PB
authors.lastname: Rock
authors.forename: R
authors.initials: R
authors.lastname: Kikinis
authors.forename: F A
authors.initials: FA
authors.lastname: Jólesz
mesh_terms: D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000473:pathology*; D000818:Animals; D001921:Brain / Q000033:anatomy & histology* / Q000473:pathology; D001929:Brain Edema / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D002534:Hypoxia, Brain / Q000473:pathology* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D013997:Time Factors