Figure 1

Five major steps for Intensity of Bone Involvement (IBI) calculation. (a) Original PET was pre-processed to clean the high intensity areas of physiological uptake and external objects. (b) Then, the image was segmented according to the Hounsfield scale (HU) of the registered CT. In this step, the skull region had to be excluded from the mask to reduce the artifacts caused by the overlapping of brain uptake (for patients with focal lesions on skull, a manual correction for IBI can be performed, see text). (c) Masked PET was transformed into a binary matrix and a morphological close was performed to achieve the final bone mask. (d) Multiplication between bone mask and subtracted PET resulted in the PET image containing only the bone and bone marrow tissues (PETbone/bm). (e) Metabolic metrics, including IBI score, were performed on PETbone/bm imaging.