Multiparametric dynamic whole-body PSMA PET/CT using [68Ga]Ga-PSMA-11 and [18F]PSMA-1007

Abstract

Background: Routine prostate-specific membrane antigen (PSMA) positron emission tomography (PET) performed for primary staging or restaging of prostate cancer patients is usually done as a single static image acquisition 60 min after tracer administration. In this study, we employ dynamic whole-body (D-WB) PET imaging to compare the pharmacokinetics of [⁶⁸Ga]Ga-PSMA-11 and [¹⁸F]PSMA-1007 in various tissues and lesions, and to assess whether Patlak parametric images are quantitative and improve lesion detection and image readability.

Methods: Twenty male patients with prostate cancer were examined using a D-WB PSMA PET protocol. Ten patients were scanned with [⁶⁸Ga]Ga-PSMA-11 and ten with [¹⁸F]PSMA-1007. Kinetic analyses were made using time-activity curves (TACs) extracted from organs (liver, spleen, bone, and muscle) and lesions. For each patient, three images were produced: SUV + Patlak parametric images (K_i and DV). All images were reviewed visually to compare lesion detection, image readability was quantified using target-to-background ratios (TBR), and Ki and DV values were compared.

Results: The two PSMA tracers exhibited markedly different pharmacokinetics in organs: reversible for [⁶⁸Ga]Ga-PSMA-11 and irreversible for [¹⁸F]PSMA-1007. For both tracers, lesions kinetics were best described by an irreversible model. All parametric images were of good visual quality using both radiotracers. In general, Ki images were characterized by reduced vascular signal and increased lesion TBR compared with SUV images. No additional malignant lesions were identified on the parametric images.

Conclusion: D-WB PET/CT is feasible for both PSMA tracers allowing for direct reconstruction of parametric Ki images. The use of multiparametric PSMA images increased TBR but did not lead to the detection of more lesions. For quantitative whole-body Ki imaging, [¹⁸F]PSMA-1007 should be preferred over [⁶⁸Ga]Ga-PSMA-11 due to its irreversible kinetics in organs and lesions.

Keywords: Dynamic whole-body PET; Oncology; PSMA; Parametric imaging; Patlak; Prostate cancer.