Application of ¹⁸F-NaF PET/CT imaging in prognosis of fractures and treatment planning in patients with fibrous dysplasia.

Objectives: Fibrous dysplasia (FD) is an uncommon, benign skeletal disorder characterized by replacement of normal bone and normal bone marrow with abnormal fibro-osseous tissue, leading to bone deformity, fractures and significant physical impairment. FD may affect one or multiple bones and may occur in isolation or in combination with extra-skeletal manifestations termed McCune-Albright syndrome (MAS) (hyperfunctioning endocrinopathies, skin pigmentation) and Mazabraud's syndrome (intramuscular myxomas). ¹⁸F-NaF is a bone-seeking PET-agent with favorable pharmacokinetics, which can effectively target the underlying bone processes encountered in FD. Aim of the current study was to investigate potential application of ¹⁸F-NaF PET/CT imaging in prognosis of fractures and treatment planning in FD patients.

Methods: Sixteen FD patients were evaluated with whole-body ¹⁸F-NaF PET/CT scans. PET images from the vertex of the skull to the plantar surface of the feet were acquired on dedicated PET/CT scanners, 58 to 70 minutes after i.v. injection of 2.72-3.26 mCi of ¹⁸F-NaF. A non-contrast, low dose, non-diagnostic CT scan was performed for attenuation correction and co-registration purposes. FD burden was assessed by quantifying ¹⁸F-NaF activity corresponding to FD lesions using the MIM Vista workstation (version 6.5.9). A volume of interest (VOI) encompassing the entire skeleton was drawn, and subsequently a SUVmax threshold based approach customized per patient was applied in order to include all FD-related bone uptake. Separate VOIs encircling all areas above the SUVmax threshold set by the user were automatically generated and areas with physiologic or not related to the disease ¹⁸F-NaF activity were manually excluded by a nuclear medicine physician. Finally, the following parameters were automatically obtained: SUVmax, SUVmean (average SUV) and whole skeleton disease indices of total volume (TV) of all ¹⁸F-NaF avid FD lesions and total lesions activity (TA), which is determined as the summation of the activity of each individual FD lesion which is the product of each individual lesion volume multiplied by its' mean SUV respectively. Subsequently, spearman’s rank correlation test was applied to investigate potential associations between the parameters obtained from the ¹⁸F-NaF PET/CT scans for the skull and the whole-body with the number of fractures (lifetime, mean fractures per year) and the performed surgeries (craniofacial, orthopedic).

Results: TV and TA of FD lesions in the skull were very strongly associated (Spearman’s rho=0.8314, p<0.01 & rho=0.8548, p<0.01) with lifetime craniofacial surgeries, and with mean craniofacial surgeries per year (rho=0.8348, p<0.01 & rho=0.86, p<0.01) (table 1). In addition, total volume and total activity of whole-body FD lesions very strongly correlated with the lifetime fractures (rho=0.8729, p<0.01 & rho=0.8296, p<0.01) and mean fractures per year (rho=0.8721, p<0.01 & rho=0.8108, p<0.01) (table 2). Also very strong associations were found between total volume and total activity of whole-body FD lesions and lifetime orthopedic surgeries (rho=0.8803, p<0.01 & rho=0.9055, p<0.01) and mean orthopedic surgeries per year (rho=0.8774, p<0.01 & rho=0.8948, p<0.01) (table 2). Neither SUVmax nor SUVmean of FD lesions either in the skull or the torso showed any statistical significant association with fractures or surgeries in skull and body respectively.

Conclusion: Total volume and total activity of ¹⁸F-NaF avid bone lesions is of prognostic value for determination of fractures and surgeries in patients diagnosed with FD of the bone. The presented data indicate application of ¹⁸F-NaF PET/CT imaging in stratifying FD patients with higher likelihood of bone fractures and need of surgical interventions. Research Support: This project was supported by the National Institute of Dental & Craniofacial Research (NIDCR), Bethesda, MD, USA

• Download figure
• Open in new tab
• Download powerpoint