Comparison of parametric imaging and SUV imaging with [⁶⁸ Ga]Ga-PSMA-11 using dynamic total-body PET/CT in prostate...

Standardized uptake value (SUV) has been prevalently used to measure [⁶⁸ Ga]Ga-PSMA-11 activity in prostate cancer, but it is susceptible to multiple factors. Parametric imaging allows for absolute quantification of tracer uptake and provides a better diagnostic accuracy that is crucial for lesion detection. However, the clinical significance of total-body parametric imaging of [⁶⁸ Ga]Ga-PSMA-11 remains to be fully assessed. Therefore, the aim of our study is to delve into the diagnostic implications of total-body parametric imaging of [⁶⁸ Ga]Ga-PSMA-11 PET/CT for patients with prostate cancer.

Twenty prostate cancer patients were included and underwent a dynamic total-body [⁶⁸ Ga]Ga-PSMA-11 PET/CT scan. An irreversible two-tissue compartment model (2T3k) was fitted for each tissue time-to-activity curve, and the net influx rate (K_i) was obtained. The image quality and semi-quantitative analysis of lesion-to-background ratio (LBR), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were compared between parametric images and SUV images.

Kinetic modeling using 2T3k demonstrated favorable model fitting in both normal organs and lesions. All of the lesions detected on SUV images (55-60 min) could be detected on K_i images. The correlation between K_i, SUV_mean, and SUV_max in both normal organs and pathological lesions was found to be positive and statistically significant. Conversely, a moderate positive correlations were found between K_i and K₁ (R = 0.69, P < 0.001; R = 0.61, P < 0.001) and K_i and k₃ (R = 0.69, P < 0.001; R = 0.62, P < 0.001), in normal organs and pathological lesions, respectively. Visual assessment in K_i images showed less image noise and higher lesions conspicuity compared to SUV images. K_i image-derived LBR, SNR, and CBR of pathological lesions including primary tumors (PTs), lymph node metastases (LNMs) and bone metastases (BMs), exhibited remarkably higher folds (1.4-3.6 folds) compared to those derived from SUV of corresponding lesions.

Total-body parametric imaging of [⁶⁸ Ga]Ga-PSMA-11 enhanced lesion contrast and improved lesion detectability compared to SUV images. This may potentially serve as an imaging biomarker and theranostic tool for precise diagnosis and treatment evaluation in prostate cancer patients.