Quantitative Analysis of Multimodal Skeletal SPECT/CT Reconstructions in Diagnosing Medication-related Osteonecrosis of the Jaw.

Aim: Our goal was to assess visual and quantitative aspects of multimodal skeletal SPECT/CT reconstructions (recon) in differentiating necrotic and healthy bone of patients with suspected MRONJ.

Methods: Prior to surgery, 20 patients with suspected MRONJ underwent SPECT/CT of the jaw 3-4 hours after injection of Tc-99m-DPD (622±112.4 MBq). SPECT/CT data were reconstructed using the multimodal xSPECT Bone and xSPECT Quant algorithms as well as the OSEM-algorithm FLASH 3D. For analysis, we divided the jaw into 12 separate regions. Both xSPECT Bone and FLASH 3D datasets were scored on a four-point scale (VIS xSPECT; VIS F3D), based on the intensity of localized tracer uptake. In F3D and xSPECT Quant datasets, local tracer uptake of each region was recorded as semi-quantitative uptake ratio (SQR F3D) or SUVs, respectively. ROC analysis was performed. Postoperative histologic results served as gold standard.

Results: VIS F3D, VIS xSPECT and SQR F3D did not differ significantly in diagnostic accuracy (VIS xSPECT sensitivity=0.64; specificity=0.89). Of the quantitative parameters, SUVpeak yielded the best interobserver reproducibility. SUVpeak was 9.9±7.1 (95%CI: 7.84-11.95) in MRONJ regions, as opposed 3.6±1.8 (95% CI:3.36-3.88) elsewhere, with a cutpoint of 4.5 (sensitivity=0.83; specificity=0.80). Absolute quantitation significantly surpassed VIS and SQR (p<0.05) in accuracy and interobserver agreement (SUVpeak: κ=0.92; VIS xSPECT: κ=0.61; SQR F3D κ=0.66).

Conclusion: Absolute quantitation proved significantly more accurate than visual and semi-quantitative assessment in diagnosing MRONJ, with higher interobserver agreement.