Artificial intelligence-based 68 Ga-DOTATOC PET denoising for optimizing 68 Ge/ 68 Ga generator use throughout its lifetime.

Introduction: The yield per elution of a ⁶⁸ Ge/ ⁶⁸ Ga generator decreases during its lifespan. This affects the number of patients injected per elution or the injected dose per patient, thereby negatively affecting the cost of examinations and the quality of PET images due to increased image noise. We aimed to investigate whether AI-based PET denoising can offset this decrease in image quality parameters.
Methods: All patients addressed to our PET unit for a ⁶⁸ Ga-DOTATOC PET/CT from April 2020 to February 2021 were enrolled. Forty-four patients underwent their PET scans according to Protocol_FixedDose (150 MBq) and 32 according to Protocol_WeightDose (1.5 MBq/kg). Protocol_WeightDose examinations were processed using the Subtle PET software (Protocol_WeightDose ^AI ). Liver and vascular SUV mean were recorded as well as SUVmax, SUVmean and metabolic tumour volume (MTV) of the most intense tumoural lesion and its background SUVmean. Liver and vascular coefficients of variation (CV), tumour-to-background and tumour-to-liver ratios were calculated.
Results: The mean injected dose of 2.1 (0.4) MBq/kg per patient was significantly higher in the Protocol&#95;FixedDose group as compared to 1.5 (0.1) MBq/kg for the Protocol&#95;WeightDose group. Protocol&#95;WeightDose led to noisier images than Protocol&#95;FixedDose with higher CVs for liver (15.57% ± 4.32 vs. 13.04% ± 3.51, p = 0.018) and blood-pool (28.67% ± 8.65 vs. 22.25% ± 10.37, p = 0.0003). Protocol&#95;WeightDose ^AI led to less noisy images than Protocol&#95;WeightDose with lower liver CVs (11.42% ± 3.05 vs. 15.57% ± 4.32, p < 0.0001) and vascular CVs (16.62% ± 6.40 vs. 28.67% ± 8.65, p < 0.0001). Tumour-to-background and tumour-to-liver ratios were lower for protocol&#95;WeightDose ^AI : 6.78 ± 3.49 vs. 7.57 ± 4.73 ( p = 0.01) and 5.96 ± 5.43 vs. 6.77 ± 6.19 ( p < 0.0001), respectively. MTVs were higher after denoising whereas tumour SUVmax were lower: the mean% differences in MTV and SUVmax were + 11.14% (95% CI = 4.84-17.43) and -3.92% (95% CI = -6.25 to -1.59).
Conclusion: The degradation of PET image quality due to a reduction in injected dose at the end of the ⁶⁸ Ge/ ⁶⁸ Ga generator lifespan can be effectively counterbalanced by using AI-based PET denoising.
Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2023 Quak, Weyts, Jaudet, Prigent, Foucras and Lasnon.)