Multistatic synthetic aperture (SA) imaging allows for dynamic focusing for all points in the image, in contrast to conventional beamforming techniques. As further improvement of image quality the use of frequency modulated continuous wave (FMCW) systems could be considered. However, algorithms need to be adapted to handle imaging in these settings efficiently. In this paper, the use of a Fourier-based imaging (FBI) method from microwave radar technology is proposed for an ultrasound system suitable for FMCW operation. The FBI method is compared to the delay-and-sum (DAS) method regarding the theoretical time complexity using the random access machine computer model. Run-time measurements using C++ implementations as well as the comparison of image quality using the array performance index are conducted. It could be shown, that the FBI method has an overall better time complexity than DAS within FMCW settings. Moreover, the FBI method consistently outperforms DAS regarding its image quality.