Dynamic and simultaneous MR measurement of R1 and R2* changes during respiratory challenges for the assessment of blood and tissue oxygenation

This work presents a novel method for the rapid and simultaneous measurement of R₁ and R₂* relaxation rates. It is based on a dynamic short repetition time steady‐state spoiled multigradient‐echo sequence and baseline R₁ and B₁ measurements. The accuracy of the approach was evaluated in simulations and a phantom experiment. The sensitivity and specificity of the method were demonstrated in one volunteer and in four patients with intracranial tumors during carbogen inhalation. We utilized (ΔR₂*, ΔR₁) scatter plots to analyze the multiparametric response amplitude of each voxel within an area of interest. In normal tissue R₂* decreased and R₁ increased moderately in response to the elevated blood and tissue oxygenation. A strong negative ΔR₂* and ΔR₁ response was observed in veins and some tumor areas. Moderate positive ΔR₂* and ΔR₁ response amplitudes were found in fluid‐rich tissue as in cerebrospinal fluid, peritumoral edema, and necrotic areas. The multiparametric approach was shown to increase the specificity and sensitivity of oxygen‐enhanced MRI compared to measuring ΔR₂* or ΔR₁ alone. It is thus expected to provide an optimal tool for the identification of tissue areas with low oxygenation, e.g., in tumors with compromised oxygen supply. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.