Impact of 18F-FDG PET/CT Dual Time Point Imaging in Lymphoma Patients with Lung Lesions.

The aim of: this prospective study was to assess the role of dual time imaging PET/CT study in characterization of the lung lesions in lymphoma patients with lung lesion. Patients and methods: The study was conducted on 28 lymphoma patients. Scan 1 (early image) was performed at 50 min and scan 2 (delayed image) at 110 min after FDG IV injection. The majority of final decisions were reached based on clinical and radiological follow up and the minority was pathologically based. SUV max was calculated at early and delayed images. The difference between early and delayed SUV max (D-SUV max) and the retention index (RI-SUV max) were estimated. Then their cut-off values were evaluated using area under the curve (AUC) from receiver operating characteristic (ROC) analysis. Also, the median quantitative analysis for these parameters was used. Results: Thedelayed SUV max cut-off value of 4.9 giving sensitivity of 90% and specificity of 72% (P=0.004). The cut-off value of D-SUV max of 0.55 yielding a sensitivity of 90% and specificity of 78% (P=0.001). Using 7.5% as a cut-off value of RI-SUV max had sensitivity of 80% and specificity of 67% (P=0.04). The delayed SUV max and D-SUV max had AUCs (0.825 & 0.894 respectively) which is statistically greater than of early SUV max (0.789). The D-SUV max has the largest AUC between the four indices. The median quantitative analysis for Delayed-SUV max was 4.9 (P=0.003), D-SUV max was 0.50 (P=0.001), RI-SUV max was 0.75 (P=0.01). Conclusion: The delayed time point PET/CT imaging is additive technique with higher sensitivity and specificity to characterize lung lesions in lymphoma patients.