Fig. 1

X-ray (a), CT scan (b), MRI scan (c) and ¹⁸F-Fluoride PET-MR (d) images of a 58-year-old female patient (patient no. 13). In the lateral X-ray (a) of the ankle region, neither acute stress fractures, nor degenerative lesions can be diagnosed. Sagittal CT images (b) show sclerotic lesions in the dorsal calcaneus (red arrow) and degenerative changes in the talonavicular region, no acute stress fractures are shown. Sagittal MRI images (c) show a fracture line in the dorsal calcaneus with little oedema (red arrow), due to an older stress fracture, coming along with a higher fluoride uptake in the ¹⁸F-Fluoride PET-MR (d, red arrow). Another stress fracture is shown in the mediodorsal parts of the cuboid with bone marrow oedema in the MRI scan (c, dotted arrow) and a higher fluoride uptake in the ¹⁸F-Fluoride PET-MR (d, dotted arrow)