Quantitative 17O imaging towards oxygen consumption study in tumor bearing mice at 7 T

17O magnetic resonance imaging (MRI) using a conventional pulse sequence was explored as a method of quantitative imaging towards regional oxygen consumption rate measurement for tumor evaluation in mice. At 7 T, fast imaging with steady state (FISP) was the best among gradient echo, fast spin echo and FISP for the purpose. The distribution of natural abundance H217O in mice was visualized under spatial resolution of 2.5 × 2.5 mm2 by FISP in 10 min. The signal intensity by FISP showed a linear relationship with 17O quantity both in phantom and mice. Following the injection of 5% 17O enriched saline, 17O re-distribution was monitored in temporal resolution down to 5 sec with an image quality sufficient to distinguish each organ. The image of labeled water produced from inhaled 17O2 gas was also obtained. The present method provides quantitative 17O images under sufficient temporal and spatial resolution for the evaluation of oxygen consumption rate in each organ. Experiments using various model compounds of R-OH type clarified that the signal contribution of body constituents other than water in the present in vivo 17O FISP image was negligible.