Abstract
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Purpose: To evaluate the diagnostic performance of standardized quantitative 99mTc-DPD-SPECT/CT with and without use of anatomical bone segmentation as well as with and without mitigation for CT metal artefact reduction in patients with painful knee and hip joint prostheses suspicious for loosening.
Methods: Thirteen patients with a total of 22 prostheses (13 hip and 9 knee prostheses) underwent 99mTc-Dicarboxypropandiphosphate(DPD)-SPECT/CT 3h after injection of 99mTc-DPD (mean dose 697MBq). Quantitative reconstruction was performed with Siemens xSPECT-Quant and xSPECT-Bone, with and without iMAR-reconstruction of CT data which show high Z-material streak artefacts. SUVmax means were correlated to intraoperative findings or clinical outcome after 1 year (standard of comparison). Cut-off values and accuracy of the different reconstructions were calculated using receiver operator characteristics (ROC) and compared to the accuracy of visual SPECT/CT readings by a senior physician and a trainee blinded for the quantitative data and clinical outcome. Results: SUVmax were significantly higher in loose prostheses compared to stable prostheses, with all methods of quantification used (p=0.018-0.001). For xSPECT Bone quantification, diagnostic accuracy was 91% without iMAR (cut-off SUVmax 13.4, sensitivity 88%, specificity 93%). With iMAR, accuracy of xSPECT Bone was 95% (Cut-off SUVmax 13.8, sensitivity 100%, specificity 93%). For xSPECT Quant without iMAR, accuracy was 85% (Cut-off SUVmax 10.3, sensitivity 100%, specificity 83%). With with iMAR, accuracy was 83% (Cut-off SUVmax 11.1, sensitivity 88%, specificity 86%). Diagnostic accuracies of blind-readers were 79% for an experienced reader, and 71% for a trainee. Conclusion: This interims analysis provides first evidence that quantitative uptake values of periprosthetic bone metabolism using 99mDPD-SPECT/CT with xSPECT Quant and Bone reconstructions has a higher accuracy compared to conventional scan reading underlining the high potential of quantification as a biomarker for the diagnosis of prosthetic loosening. The use of iMAR reconstructed CT in the xSPECT Quant and xSPECT Bone reconstruction only mildly impacts attenuation correction but improves image quality of CT and xSPECT Bone.