Respiratory-gated ¹⁸F-FDG PET/CT for the diagnosis of liver metastasis

To ascertain the role of respiratory-gated PET/CT with (18)F-fluorodeoxyglucose ((18)F-FDG) for accurate diagnosis of liver metastasis.

Forty patients with suspected liver metastasis underwent conventional whole-body PET/CT scan initially, followed by respiratory-gated PET/CT scan covering the liver. Visual detectability (using a 5-point confidence scale), maximum standardized uptake value (SUVmax) and metabolic tumor volume (MTV) of hepatic metastatic lesions were assessed for three data sets including ordinary whole-body (WB) scan, and non-respiratory-gated (nRG) and respiratory-gated (RG) scans. Results of enhanced CT and/or MRI, or clinical and radiological follow-up were used for reference.

Sixteen of the patients were found to have 53 metastatic lesions in the liver. Patient-based accuracy of WB, nRG, and RG was 92.5%, 95.0%, and 97.5%, respectively, with a lesion-based detection rate of 67.9%, 73.6%, and 73.6%, respectively. The average SUVmax of 34 liver metastatic lesions for WB, nRG, and RG was 6.60 ± 2.34, 7.19 ± 2.66, and 8.08 ± 3.24, respectively. SUVmax for RG was significantly higher than that for WB (p=0.0069). The average MTV of these 40 lesions for the three protocols was 5.32 ± 4.78 cm(3), 5.07 ± 4.73 cm(3), and 4.73 ± 4.67 cm(3), respectively. Among the three protocols, RG showed the best visual and quantitative evaluation for diagnosis of liver metastasis.

Respiratory-gated PET/CT allows more accurate identification of liver metastases than non-respiratory-gated PET/CT.