166 Part II Chapter 6 Patients with a higher SBS showed higher BPI-scores on the domain: interference with normal work, (R2=0.518, p=0.024 with p critical=0.006; Spearman) and higher levels of FGF-23 (R2=0.567, p=0.034 with p critical=0.006; Spearman). Patients with higher TLF exhibited the same relation with this specific BPI domain (R2=0.478, p=0.036 with pcritical=0.006; Spearman). Examples of different FD burden andmeasured parameters are illustrated in Figure E. Figure E. Four illustrative patients with different FD burden: two on the left with MFD, both located in the proximal left femoral metaphysis and the two on the right with PFD (without MAS), all depicted with Na[18F]F-PET/CT and corresponding measurements: SBS, Na[18F]F-PET/CT-parameters, serum biomarkers and clinical parameters. Of the two patients with MFD, SBS using planar bone scintigraphy and serum P1NP was highest in the 17 yo female. At the same time, FD burden for the 43 yo male is determined to be higher when judged by SUVpeak on Na[ 18F]F-PET/CT, serum ALP and FGF-23 and to be clearly higher as measured with TLF on Na[18F]F-PET/CT. Note that the second patient also had degenerative disease in the lumbosacral joint, this uptake was not included in the FDdisease burden as this was clearly not related to FD in the PET/CT reconstructions.