Feasibility of Ultra-Low-Activity ¹⁸ F-FDG PET/CT Imaging Using a Long-Axial-Field-of-View PET/CT System.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine [J Nucl Med] 2025 Jun 02; Vol. 66 (6), pp. 961-966. Date of Electronic Publication: 2025 Jun 02.

¹⁸ F-FDG PET/CT imaging is widely used in oncology. Long-axial-field-of-view (LAFOV) PET/CT systems exhibit ultrahigh sensitivity and signal-to-noise ratios, enabling significant reductions in tracer activity and shorter acquisition times. This study aimed to evaluate the feasibility of using ultralow activities for semiquantitative measurements in ¹⁸ F-FDG PET/CT imaging performed on an LAFOV PET/CT system through a high-low activity test-retest study. Methods: Eleven oncology patients underwent 2 ¹⁸ F-FDG PET/CT scans, the first with standard activity (3.0 MBq/kg) and, within 7 d, 1 with ultralow activity (0.3 MBq/kg). List-mode data of both scans were resampled to simulate activities of 0.3 and 0.03 MBq/kg. Semiquantitative measurements (SUV mean , SUV peak , and SUV max ) and their repeatability in healthy organs and lesions were compared across different activities and reconstruction protocols. Results: SUV mean remained stable across activity reductions and reconstruction protocols, whereas SUV peak showed stability except when simulating 1% of the standard ¹⁸ F-FDG activity. SUV max significantly increased at lower ¹⁸ F-FDG activities, particularly with clinically preferred scans. Repeatability analysis showed that SUV mean and SUV peak maintained variability within acceptable limits (<15%) even at 0.03 MBq/kg, whereas SUV max variability often exceeded these limits. Lesion detection was reliable at 0.3 MBq/kg, but several lesions could not be delineated at 0.03 MBq/kg, indicating compromised image quality. Conclusion: The use of ultralow ¹⁸ F-FDG activity (0.3 MBq/kg) is feasible for PET/CT imaging on an LAFOV PET/CT system, as shown by semiquantitative measurements, repeatability analyses, lesion detectability, and semiautomated delineation methods. These findings support imaging protocols that keep radiation exposure levels as low as reasonably or practically achievable, which are particularly relevant for radiation-sensitive patients (e.g., children, pregnant women).
(© 2025 by the Society of Nuclear Medicine and Molecular Imaging.)

English

Publisher: Society of Nuclear Medicine Country of Publication: United States NLM ID: 0217410 Publication Model: Electronic Cited Medium: Internet ISSN: 1535-5667 (Electronic) Linking ISSN: 01615505 NLM ISO Abbreviation: J Nucl Med Subsets: MEDLINE

Positron Emission Tomography Computed Tomography*/methods , Positron Emission Tomography Computed Tomography*/instrumentation , Fluorodeoxyglucose F18*, Humans ; Feasibility Studies ; Female ; Male ; Middle Aged ; Aged ; Image Processing, Computer-Assisted ; Adult ; Reproducibility of Results ; Signal-To-Noise Ratio ; Radiopharmaceuticals

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