The BOLD-sensitivity of balanced SSFP at very high fields is similar to GE-EPI but more selective to small vessels

The excellent sensitivity and stability of BOLD-imaging with balanced SSFP (bSSFP) on humans at 9.4T has been demonstrated in a recent paper. Here, we analyze the signal change of bSSFP for different vessel (spheres) sizes and susceptibility differences for different repetition times and flip angles using Monte Carlo simulations and experiments on micro spheres, and compare it to gradient echo EPI. Simulated and measured signal changes (using values of susceptibility changes and vessel sized comparable to a typical BOLD experiment at 9.4T) of bSSFP are in the range of 10 to 15 with a peak sensitivity to the vessel (sphere) size at about 3 mm, and a decreased sensitivity for larger vessels (spheres). For GE-EPI, signal changes are similar to bSSFP, however, no selectivity to small vessels is visibl