Fitting the relative B1- maps derived from a B1+ shim acquisition to the Helmholtz equations allows for the calculation of absolute B1- maps. The sensitivity profiles can then be used to optimally combine coils in subsequent acquisitions. In addition, absolute B1- maps allow for the removal of the receive sensitivity from the combined images. This was validated in a GE-EPI sequence and found to produce images with lower phase standard deviation and increased temporal signal-to-noise ratios across the brain. Both of these differences were found to be statistically significant in a Student’s t-test.