Open AccessIn Vivo Quantification of Cerebral R2*-Response to Graded Hyperoxia at 3 Tesla
Author(s) -
Grigorios Gotzamanis,
Roman Kocián,
Pinar Senay Özbay,
Manuel Redle,
Spyridon Kollias,
Christian Eberhardt,
Andreas Boss,
Daniel Nanz,
Cristina Rossi
Publication year - 2015
Publication title -
journal of clinical imaging science
Language(s) - English
Resource type - Journals
eISSN - 2156-7514
pISSN - 2156-5597
DOI - 10.4103/2156-7514.150439
Subject(s) - hyperoxia , analysis of variance , medicine , nuclear magnetic resonance , white matter , magnetic resonance imaging , in vivo , respiratory rate , nuclear medicine , oxygen saturation , heart rate , respiratory system , repeated measures design , oxygen , anesthesia , cardiology , blood pressure , chemistry , lung , biology , mathematics , radiology , physics , microbiology and biotechnology , organic chemistry , statistics
Objectives: This study aims to quantify the response of the transverse relaxation rate of the magnetic resonance (MR) signal of the cerebral tissue in healthy volunteers to the administration of air with step-wise increasing percentage of oxygen. Materials and Methods: The transverse relaxation rate (R2FNx01) of the MR signal was quantified in seven volunteers under respiratory intake of normobaric gas mixtures containing 21, 50, 75, and 100% oxygen, respectively. End-tidal breath composition, arterial blood saturation (SaO 2 ), and heart pulse rate were monitored during the challenge. R2FNx01 maps were computed from multi-echo, gradient-echo magnetic resonance imaging (MRI) data, acquired at 3.0T. The average values in the segmented white matter (WM) and gray matter (GM) were tested by the analysis of variance (ANOVA), with Bonferroni post-hoc correction. The GM R2FNx01-reactivity to hyperoxia was modeled using the Hill′s equation. Results: Graded hyperoxia resulted in a progressive and significant (P < 0.05) decrease of the R2FNx01 in GM. Under normoxia the GM-R2FNx01 was 17.2 ± 1.1 s -1 . At 75% O 2 supply, the R2FNx01 had reached a saturation level, with 16.4 ± 0.7 s -1 (P = 0.02), without a significant further decrease for 100% O 2 . The R2FNx01-response of GM correlated positively with CO 2 partial pressure (R = 0.69 ± 0.19) and negatively with SaO 2 (R = -0.74 ± 0.17). The WM showed a similar progressive, but non-significant, decrease in the relaxation rates, with an increase in oxygen intake (P = 0.055). The Hill′s model predicted a maximum R2FNx01 response of the GM, of 3.5%, with half the maximum at 68% oxygen concentration. Conclusions: The GM-R2FNx01 responds to hyperoxia in a concentration-dependent manner, suggesting that monitoring and modeling of the R2FNx01-response may provide new oxygenation biomarkers for tumor therapy or assessment of cerebrovascular reactivity in patients