Influence of proton T sub(1) on oxymetry using Overhauser enhanced magnetic resonance imaging

• Published in: Magnetic resonance in medicine 2005-07, Vol.54 (1), p.213-217
• Main Authors: Matsumoto, Shingo, Utsumi, Hideo, Aravalluvan, Thirumaran, Matsumoto, Ken-Ichiro, Matsumoto, Atsuko, Devasahayam, Nallathamby, Sowers, Anastasia L, Mitchell, James B, Subramanian, Sankaran, Krishna, Murali C
• Format: Article
• Language: English
• ISSN: 0740-3194
• DOI: 10.1002/mrm.20564

In Overhauser enhanced magnetic resonance imaging (OMRI) for in vivo measurement of oxygen partial pressure (pO sub(2)), a paramagnetic contrast agent is introduced to enhance the proton signal through dynamic nuclear polarization. A uniform proton T sub(1) is generally assumed for the entire region of interest for the computation of pO sub(2) using OMRI. It is demonstrated here, by both phantom and in vivo (mice) imaging, that such an assumption may cause erroneous estimate of pO sub(2). A direct estimate of pixel-wise T sub(1) is hampered by the poor native MR intensities, owing to the very low Zeeman field (15-20 mT) in OMRI. To circumvent this problem, a simple method for the pixel-wise mapping of proton T sub(1) using the OMRI scanner is described. A proton T sub(1) image of a slice through the center of an SCC tumor in a mouse clearly shows a range of T sub(1) distribution (0.2 similar to 1.6 s). Computation of pO sub(2) images using pixel-wise T sub(1) values promises oximetry with minimal artifacts by OMRI.