Concurrent MR blood volume and vessel size estimation in tumors by robust and simultaneous Δ R 2 and Δ R 2 * quantification

This work presents a novel method for concurrent estimation of the fractional blood volume and the mean vessel size of tumors based on a multi‐gradient‐echo‐multi‐spin‐echo sequence and the injection of a super‐paramagnetic blood‐pool agent. The approach further comprises a post‐processing technique for simultaneous estimation of changes in the transverse relaxation rates R 2 and R   2 * , which is robust against global B 0 and B 1 field inhomogeneities and slice imperfections. The accuracy of the simultaneous Δ R 2 and Δ R   2 *quantification approach is evaluated in a phantom. The simultaneous blood volume and vessel size estimates, obtained with MR, compare well to the immunohistological findings in a preclinical experiment (HT1080 cells, implanted in nude mice). Clinical translation is achieved in a patient with a pleomorphic sarcoma in the left pubic bone. The latter demonstrates the robustness of the technique against changes in the contrast agent concentration in blood during washout. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.