Abstract
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Introduction: The world’s first 2-meter-long total-body PET scanner (uEXPLORER) provides a versatile platform for biomedical research and opens a new venue for lesion detection throughout the body. Our study aims to explore the value of multi-parametric total-body dynamic PET/CT imaging in distinguishing benign and malignant lymph nodes of the whole body. Materials and Methods: A total number of 40 patients with lymph node lesions were recruited in this study, including 25 males and 15 females, with a median age of 55.13 (range 31-79), a median height of 1.68m (range 1.55-1.85m), and a median weight of 69.61kg (range43-110kg). We conducted total body kinetic analysis on each patient using the uEXPLORER. The patients were told to fast for at least 6 hours prior to the study. The leg was chosen as the injection site due to easier access. A low dose CT with a slice thickness of 5mm and slice increment of 5mm was applied to provide the attenuation information for the PET image reconstruction. A dynamic PET scan of 60 minutes was acquired subsequently. The FDG is given on a dosage of 3.7MBq/kg (0.1mCi/kg) and is to be injected right after the PET scan starts. An image-derived input function is acquired from the dynamic images using a region-of-interest placed on the descending aorta. A set of parametric images were produced using two methods. The net flux rate Ki images were generated by the uKinetics software (United Imaging Healthcare) using the linear Patlak model. The K1, k2, plasma fraction (VB), and the time delay (TD) were estimated jointly via a non-linear 1-tissue compartment model using early phase data (5 minutes post-injection). SUVmax was measured from PET image.The Mann-Whitney U test and receiver operating characteristic (ROC) analysis were performed for all dynamic PET/CT parameters to compare their diagnosis performance in distinguishing benign and malignant lymph nodes.
Results: Ninety-five lymph nodes (including 42 benign lymph nodes in 16 cases and 53 malignant lymph nodes in 24 cases) confirmed by pathological diagnosis or clinical follow-up were included in the study.Both Ki and SUVmax values of benign lymph nodes were lower than those of malignant lymph nodes (0.66×10-2 vs 2.64×10-2 ml/g/min and 2.43 vs 5.46), and there was a statistically significant difference between them (all P < 0.001). But there was no statistically significant difference between K1values of benign lymph nodes and malignant lymph nodes (3.83×10-3 vs 3.99×10-3ml/g/s), between k2 values of benign lymph nodes and malignant lymph nodes (1.54×10-2 vs 1.7×10-2s-1), between TD values of benign lymph nodes and malignant lymph nodes (0.482vs 0.128 s), between VB values of benign lymph nodes and malignant lymph nodes (4.66×10-2 vs 8.43×10-2) (all P > 0.05). The area under the ROC curve (AUC) of Ki (AUC=0.945) was significantly higher than that of SUVmax (AUC=0.881) in discriminating malignant and benign lymph nodes (P < 0.05).
Conclusions: Among all different kinetic parameters and traditional SUVmax, Ki was shown to provide the highest diagnostic efficiency and was an promising indicator in the differential diagnosis of benign and malignant lymph nodes.
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