Concurrent MR Blood Volume and Vessel Size Estimation in Tumors by Robust and Simultaneous ΔR2 and ΔR*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 Delta R-2 and Delta 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 66:144-153, 2011. (C) 2011 Wiley-Liss, Inc.