In this paper, we propose a new feature, Weighted Mean Frequencies (WMF), to address the difficulty of vessel segmentation due to low resolution and noise in 4D Flow MRI images. WMF represents the outline of pulsatile velocity pixels by visualizing the 3D region where the pulsatile flow has passed. Through two experiments (4D Flow MRI image segmentation using optimal thresholding and deep learning methods), we compare WMF with the conventional PC-MRA feature and show that the IoU and Dice coefficients increase by 0.12 and 0.13, respectively. This suggests that it has the potential to be applied to segmentation of other vascular regions, such as the heart and brain.