Fig. 2

Attenuation maps generation workflow. Both UTE images are rigidly registered to the UTE_template. Segmentation into three tissue classes (soft tissue, air, bone) is performed using first echo UTE image registered to the UTE_template. sUTE maps are then generated by assigning attenuation coefficients to all classes with respect to the masks, 3D 2-mm Gaussian smoothing and warping back to the subject space. Attenuation coefficients are fixed for soft tissue and air (0.1 cm^− 1 and 0 cm^− 1, respectively), whereas for bones can be either fixed – equal 0.151 cm^− 1(sUTE_fix) or continuous – based on R2* map (sUTE_cont)