Impact of Point-Spread Function Reconstruction on ⁶⁸Ga-DOTATATE PET/CT Quantitative Imaging Parameters

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Imaging
• Oncology

Background:

• Gallium-68 tetraazacyclododecanetetraacetic acid-DPhe1-Tyr3-octreotate (⁶⁸Ga-DOTATATE) Positron Emission Tomography/Computed Tomography (PET/CT) is crucial for diagnosing and monitoring neuroendocrine tumors.
• Accurate quantitative parameters derived from PET/CT are essential for treatment response assessment.
• Point-spread function (PSF) reconstruction is a technique that can potentially improve image resolution and quantitative accuracy.

Purpose of the Study:

• To evaluate the impact of PSF reconstruction on quantitative parameters in ⁶⁸Ga-DOTATATE PET/CT.
• To assess how lesion size influences the quantitative differences observed with PSF reconstruction.

Main Methods:

• Retrospective analysis of 42 ⁶⁸Ga-DOTATATE PET/CT studies from 38 patients, including 125 lesions.
• Scans were reconstructed both with and without PSF modulation.
• Quantitative parameters measured included SUVmax, SUVpeak, metabolic tumor volume (MTV), total lesion somatostatin avidity, and tumor somatostatin receptor expression heterogeneity. Intraclass correlation coefficient (ICC) and Bland-Altman analyses were used for comparisons, with subgroup analysis based on lesion size (<2 cm vs. ≥2 cm).

Main Results:

• Excellent ICCs (0.97-0.99) were observed for SUVmax, SUVpeak, MTV, and total lesion somatostatin avidity between PSF and non-PSF reconstructions.
• PSF reconstruction resulted in significantly higher SUVmax (27.5% ± 14.7%) and SUVpeak (15.5% ± 9.5%) values.
• PSF reconstruction led to decreased tumor somatostatin receptor expression heterogeneity (-7.1% ± 11.0%) and showed variable effects on MTV (-18.6% ± 37.6%) and total lesion somatostatin avidity (0.8% ± 28.1%), particularly influenced by lesion size. Smaller lesions (<2 cm) exhibited greater biases compared to larger lesions (≥2 cm).

Conclusions:

• PSF reconstruction in ⁶⁸Ga-DOTATATE PET/CT significantly increases SUVmax and SUVpeak values.
• PSF reconstruction decreases tumor somatostatin receptor expression heterogeneity and variably affects MTV and total lesion somatostatin avidity, with lesion size being a critical factor.
• These findings highlight the need to consider reconstruction methods and lesion size when interpreting quantitative ⁶⁸Ga-DOTATATE PET/CT parameters.