Evaluation of pulmonary nodules: comparison of a prototype dual crystal (LSO/NAI) dual head coincidence camera and full ring positron emission tomography (PET)

Abstract

Purpose: To determine the concordance of a prototype dual head coincidence camera (LSO-PS) and full ring PET (BGO-PET) using 18F-fluorodeoxyglucose (FDG) in the evaluation of pulmonary nodules (PNs). Materials and methods: Patients referred for evaluation of ≤3 PNs (≤3 cm diameter) were prospectively studied on the same day with both BGO-PET and LSO-PS. Imaging was performed at 60 and 120 min after injection of 370 MBq FDG, respectively. Images were independently interpreted by four observers with each observer blinded to the other modality for the same patient. Lesions were scored in terms of relative intensity versus background. Non-attenuation corrected (nonAC) BGO-PET was used as the reference test. Results: Forty-seven patients with 54 PNs (mean diameter 1.7 cm, S.D. 0.7) were included. Twelve nodules were in the ≤1.0 cm – 27 in the 1.1–2.0 cm – and 15 in the 2.1–3.0 cm range. Interobserver agreement was similar for both FDG imaging modalities. Using a sensitive assessment strategy with LSO-PS (≥ faint intensity deemed positive), there was a 97% (38/39, 95%CI 87–100%) concordance with BGO-PET and one false positive case with LSO-PS. Conservative reading (moderate or intense intensity deemed positive) resulted in a 92% (36/39, 95%CI 80–97%) concordance with BGO-PET, without false positives. The only lesion missed by LSO-PS using both assessment strategies involved a nodule 1.5 cm diameter that demonstrated moderate increased FDG uptake on BGO-PET. Conclusion: Depending on the test positivity criteria, LSO-PS demonstrates a high concordance (92–97%) with nonAC BGO-PET for the characterization of pulmonary nodules.