Abstract
Our purpose was to establish proof of principle case study for the use of dynamic 18F-NaF PET-CT in the assessment of knee and hip prostheses. Approval was granted by the research ethics committee and informed<br />consent was obtained. This is a case study investigating the role of dynamic 18F NaF PET-CT in a patient with ilateral knee prostheses (1 symptomatic/painful and 1 asymptomatic). Both knees were studied with dynamic 18F-NaF PET-CT technique to demonstrate the different pattern of uptake in normal/asymptomatic joint as well as painful joints with aseptic loosening. In addition, a knee aspirate was obtained from the symptomatic knee and serum C-reactive protein and erythrocyte sediment rate levels as well as a peripheral white cell count were<br />obtained in addition to 12 month clinical follow up. Images were obtained with multi-sequential dynamic image acquisition in list mode using GE Healthcare® volume imaging protocol (ViP) after an intravenous injection of 250 MBq 18F-NaF. The images were interpreted as normal, loosening or septic loosening based on the graphical pattern of tracer uptake produced at the bone-prosthesis interface. A final diagnosis was made by a combination of joint aspiration microbiology and clinical follow-up for 1 year; in addition to C-reactive protein and erythrocyte sediment rate levels as well as peripheral white cell count. NaF PET results were compared with 3-phase dynamic bone scan results and plain radiographs. The degree of uptake in the symptomatic joint exceeded background<br />levels and also levels of uptake in the asymptomatic knee. The pattern of uptake and curve slope in both the asymptomatic and symptomatic joints matched the pattern of uptake in our hypothesis. Dynamic 18F-NaF PET-CT is a useful imaging modality for assessing painful joint prosthesis. It can differentiate between asymptomatic joints and aseptic loosening. However, more work is required for the detection of septic loosening.
Highlights
As the population ages and the average body mass index rises, lower limb arthroplasty will become more common [1]
When an area of increased uptake was detected in the bone-prosthesis interface of the knee arthroplasty in comparison with adjacent bone and soft tissue, the region of interest was assessed using time-activity curves with simple standardized uptake value (SUV) analysis and background subtraction [3]
Arthroplasties were considered aseptic if the preceding investigations were negative and this was backed by normal C-reactive protein and erythrocyte sediment rate levels as well as a normal peripheral white cell count
Summary
Our patient was a 72 year old female with a painful left knee total knee replacement studied with dynamic 18F-NaF PET-CT. She had underwent routine clinical and laboratory studies for the evaluation of painful prostheses, in addition to the dynamic NaF PET-CT scan. 18F-NaF PET-CT - Dynamic 18F-NaF PET-CT images were acquired using a GE Discovery ST with 16 slice CT (GE Healthcare®) volume imaging protocol (ViP) [2]. CT images of the joints were acquired, followed by dynamic PET image acquisition in list mode from the time of injection till 30 to 40 minutes after bolus intravenous administration of 250 MBq 18F NaF [2]. The images were reconstructed using ordered-subset expectation maximization, and images were corrected for attenuation
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