Dynamic and simultaneous MR measurement of R sub(1) and R sub(2) 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 R sub(1) and R sub(2)* relaxation rates. It is based on a dynamic short repetition time steady-state spoiled multigradient-echo sequence and baseline R sub(1) and B sub(1) 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 ( Delta R sub(2)*, Delta R sub(1)) scatter plots to analyze the multiparametric response amplitude of each voxel within an area of interest. In normal tissue R sub(2)* decreased and R sub(1) increased moderately in response to the elevated blood and tissue oxygenation. A strong negative Delta R sub(2)* and Delta R sub(1) response was observed in veins and some tumor areas. Moderate positive Delta R sub(2)* and Delta R sub(1) 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 Delta R sub(2)* or Delta R sub(1) 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. [copy 2012 Wiley Periodicals, Inc.