Abstract: There is provided a method for reconstructing a 3D image, comprising: obtaining Doppler ultrasound images depicting a blood vessel and measurement of blood flow in the blood vessel, and 2D camera images captured by a camera depicting fiducial objects randomly distributed within a viscous material and spaced apart by random distances on a surface of the individual, computing 3D coordinates within a world coordinate system for pixels of the Doppler images using an external reference of an ultrasound transducer pose computed by analysis of relative changes in locations of the fiducial objects within sequential camera images, and computing a respective estimated blood flow for pixels of the Doppler images at locations within the blood vessel, reconstructing a 3D image from 3D voxels computed from the 3D coordinates of pixels of the Doppler images, including respective estimated blood flow, wherein the 3D image depicts the blood vessel and blood flow.