Null subtraction imaging is a nonlinear beamforming technique that can improve the lateral resolution of a ultrasound imaging system by imaging with the nulls of a beam rather than the main lobe. Because the null in a beam pattern is very sharp whereas the beam falls off more slowly and is diffraction limited, null subtraction imaging can provide superior resolution. In this work we demonstrate that null subtraction imaging can be used to provide superior power Doppler images compared to traditional approaches. Figure 1 shows images of a contrast free chicken embryo brain using traditional beamforming approaches and NSI. Figure 2 shows a cross section of vessels and FWHM estimates versus DC offset values. Figure 3 shows images of a contrast enhanced chicken embryo brain using traditional beamforming approaches and NSI. Figure 4 shows a cross section of vessels and FWHM estimates versus DC offset values. (Last updated 12/19/2022).