Dependence of blood R2 relaxivity on CPMG echo-spacing at 2.35 and 7 T

The transverse relaxation rate (R(2)) of fresh human blood has been investigated at high and ultrahigh field, to characterize the R(2) dependency on blood sample oxygenation, hematocrit, and Carr-Purcell Meiboom-Gill sequence inter-echo spacing. Data were fitted to chemical exchange and diffusion models to assess their performance at different field strengths. The diffusion model gave a slightly superior fit at both field strengths, but the difference is unlikely to be relevant for the signal to noise ratio achieved in most in vivo experiments. Fitted model parameters were similar to those found in literature.