Gallium-68 DOTATATE PET/CT in Neuroendocrine Tumors




You, Helena Ningna

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BACKGROUND: Ga-68 DOTATATE PET/CT has been increasingly used for diagnosis and therapy response assessment of patients with neuroendocrine tumors (NETs). Point spread function (PSF) modeling is a partial volume correction method that can be used within PET imaging reconstruction. However, little is known about the effects of PSF reconstruction on quantitative measurements of Ga-68 DOTATATE PET/CT. OBJECTIVE: The objective is to investigate the impact of PSF reconstruction and lesion size on Ga-68 DOTATATE PET/CT quantitative parameters. METHODS: A total of 38 patients with 42 Ga-68 DOTATATE PET/CT scans and 125 lesions were included. Scans were reconstructed with and without PSF modulation. For each lesion, maximum and peak standardized uptake value (SUVmax, SUVpeak), metabolic tumor volume (MTV), total lesion somatostatin avidity (TLS), and tumor somatostatin receptor expression heterogeneity (TH) using area under the curve method were measured. Intraclass correlation coefficients (ICC) and Bland-Altman analyses were used to compare PSF and non-PSF values. Subgroup analysis was performed to determine the impact of lesion size. RESULTS: Of the 125 lesions, 51 were in the liver, 31 in lymph nodes, 17 in bone, 8 in pancreas, 4 in lung, and 14 in other sites. ICC between PSF and non-PSF values were excellent for SUVmax, SUVpeak, MTV, and TLS (0.97-0.99), and was good for TH (0.81). Comparison of PSF with non-PSF values showed a bias (mean percent change ± standard deviation) of +27.5 ± 14.7% for SUVmax, +15.5 ± 9.5% for SUVpeak, -18.6 ± 37.6% for MTV, +0.8 ± 28.1% for TLS, and -7.1 ± 11.0% for TH. For lesions less than 2 cm in size (n=75), comparison of PSF with non-PSF values showed corresponding biases larger than for lesions greater than 2 cm. CONCLUSION: PSF reconstruction effected higher values for SUVmax and SUVpeak, lower values for TH, and had a variable effect on MTV and TLS depending on lesion size. Clinical readers of Ga-68 DOTATATE PET/CT should be aware of such effects, as comparison between baseline and post-treatment follow-up scans can result in spurious artifact without any true change if different reconstruction methods are used between two time points.

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