Multimodality imaging in characterization of postoperative changes after tumor resection: role of PET/CT, Fused MRI

Abstract Background Distinguishing postoperative inflammatory alterations from residual or recurrent neoplastic tissue remains a significant diagnostic obstacle when relying solely on conventional imaging techniques. 18F-FDG PET/CT provides metabolic insight but is prone to false-positive results attributable to inflammatory processes during the early postoperative phase. MRI delivers superior soft tissue resolution yet lacks functional or metabolic assessment capabilities. The integration of metabolic data from 18 F-FDG PET with MRI’s detailed anatomical imaging enhance diagnostic precision. Aim This research aimed to assess the diagnostic utility of MRI in characterizing postoperative changes, compared to 18F-FDG PET/CT. Additionally it evaluated the impact of integrating MRI & PET/CT data for improved characterization of postoperative changes. Methods This prospective investigation involved 50 patients (30 females, 20 males; mean age 52.3 ± 9.9 years) who underwent 18 F-FDG PET/CECT and MRI at least six weeks following tumor resection. Imaging datasets from PET and MRI were analyzed. Interpretations were correlated with histopathology and/or follow-up data. Sensitivity, specificity, positive and negative predictive values, and overall accuracy were determined for 18 F-FDG PET/CECT, MRI, and combined data from PET/CT & MRI. Results Confirmatory histopathology and/or follow-up demonstrated tumor tissue in 24 (48%) patients and postoperative inflammatory changes in 26 (52%) patients. For detection of residual/recurrent tumor tissue, 18 F-FDG PET/CECT achieved a sensitivity of 83.3%, specificity of 76.9%, PPV of 76.9%, NPV of 83.3%, and accuracy of 80% (AUC = 0.801). MRI alone exhibited 100% sensitivity, 69.2% specificity, 75% PPV, 100% NPV, and 84% accuracy (AUC = 0.846). The combined data from PET/CT and MRI significantly improved diagnostic performance with 100% specificity, 100% PPV, 86.7% NPV, and 92% accuracy (AUC = 0.917). An ADC cutoff value 1.5 × 10⁻ 3 mm 2 /s yielded superior diagnostic efficacy (AUC = 0.84) compared to SUVmax cutoff 5.5 (AUC = 0.67). Conclusions Fusion of data from 18F-FDG PET/CT and MRI markedly enhances diagnostic accuracy in differentiating postoperative inflammatory changes from tumor recurrence relative to 18F-FDG PET/CECT or MRI independently. This represents a valuable diagnostic tool in the post-surgical management of oncologic patients.