Potential values of uEXPLORER total-body PET/CT in nasopharyngeal carcinoma: dynamic imaging and kinetic parameters

Objectives

To explore the dynamic imaging and kinetic parameters of total-body positron-emission tomography/computed tomography (TB-PET/CT) in nasopharyngeal carcinoma (NPC).

Methods

Fifty-six NPC patients were prospectively enrolled and underwent pretreatment 1-hour dynamic TB-PET/CT (uEXPLORER) acquisition. Standardized uptake values (SUVs) and Patlak-based quantitative kinetic parameters, including glucose metabolic rate (Ki), glucose transport rate of flow-in and flow-out between blood and tissues (K₁ and k₂), and tissue glucosamine-6-phosphatization rate (k₃) were assessed. The suspected metastatic small lymph nodes with mild-to-moderate [¹⁸F] FDG uptake and those important for the N staging of tumor underwent ultrasound-guided biopsy, and the lesion-to-background ratio (LBR) in TB-PET images and K_i images were compared.

Results

In total, 97 frame of SUVmean images were collected in each patient. The time‒activity curves (TAC) of primary lesions showed a continuous upward trend. The SUVmean dispersion among primary lesions increased gradually. SUV_max correlated strongly with K_i and k₃ (r = 0.903 and 0.660, P = 0.001 and < 0.001, respectively) in primary lesions. Out of the 34 cervical lymph nodes biopsied using ultrasound, 10 were confirmed as metastases, and 24 involved inflammations. SUV_max, K_i, k_2, and k₃ were significantly different (p < 0.0001, p < 0.01, p < 0.01, and p < 0.0001 respectively) between metastatic lymph nodes and inflamed lymph nodes, while K₁ had no significant difference. K_i images had higher LBR than PET images in metastatic lymph nodes conspicuity (p < 0.05).

Conclusion

TB-PET/CT uncovered tumor heterogeneity and metabolic characteristics via [¹⁸F] FDG uptake during the first hour after injection. Kinetic parameters and K_i images may help in discriminating between malignant and inflammatory lymph nodes in Nasopharyngeal Carcinoma.