document: Oxygen-enhanced MRI of the brain Blood oxygenation level-dependent -LRB- BOLD -RRB- contrast MRI is a potential method for a physiological characterization of tissue beyond mere morphological representation . The purpose of this study was to develop evaluation techniques for such examinations using a hyperoxia challenge . Administration of pure oxygen was applied to test these techniques , as pure oxygen can be expected to induce relatively small signal intensity -LRB- SI -RRB- changes compared to CO/sub 2 / - containing gases and thus requires very sensitive evaluation methods . Fourteen volunteers were investigated by alternating between breathing 100 % O/sub 2 / and normal air , using two different paradigms of administration . Changes ranged from > 30 % in large veins to 1.71 % + or-0 .14 % in basal ganglia and 0.82 % + or-0 .08 % in white matter . To account for a slow physiological response function , a reference for correlation analysis was derived from the venous reaction . An objective method is presented that allows the adaptation of the significance threshold to the complexity of the paradigm used . Reference signal characteristics in representative brain tissue regions were established . As the presented evaluation scheme proved its applicability to small SI changes induced by pure oxygen , it can readily be used for similar experiments with other gases
doc_bio_tags: O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O B I O O O O B I O O O O O O O O O O O O B I O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
extractive_keyphrases: hyperoxia brain physiological response function correlation analysis venous reaction significance threshold
abstractive_keyphrases: bold contrast mri oxygen-enhanced mri oxygen breathing normal air breathing paradigm complexity mri contrast agent functional imaging fourier transform analysis