Comparison between Gallium-68 citrate PET-CT and Gallium-67 citrate scintigraphy for infection imaging: Gallium-68 citrate PET-CT for infection

Background Preliminary studies have reported promising results for the utility of gallium-68 (Ga-68) citrate positron emission tomography-computed tomography (PET-CT) for infection imaging. This technique offers reduced radiation dose to patients, shorter time between injection and imaging and reduced time for image acquisition compared to the 'gold standard' nuclear imaging technique: gallium-67 (Ga-67) citrate scintigraphy. Aims To compare the two imaging modalities to ascertain whether Ga-68 citrate PET-CT is of equivalent diagnostic efficacy for bone and joint infection or pyrexia of unknown origin (PUO) and to assess image quality and reporter confidence. Methods Patients with PUO and suspected bone or joint infection underwent Ga-67 citrate scintigraphy and Ga-68 citrate PET-CT. Participants were followed up for 3 months to record subsequent treatment, investigations and outcome. Results 60 patients were recruited to this multicentre prospective study: 32 for bone and joint infection, 28 for PUO. The results show a sensitivity of 81% for Ga-67 citrate scintigraphy and 69% for Ga-68 citrate PET-CT, a specificity of 79% for Ga-67 citrate and 67% for Ga-68 citrate and were concordant for 76% of the participants. The reporting physician confidence was significantly lower for Ga-68 citrate (P < 0.05), frequently due to prominent physiologic blood pool activity adjacent to the site of infection. Conclusion The sensitivity and specificity of Ga-68 citrate PET-CT were found to be consistently lower than Ga-67 citrate scintigraphy. Additionally, due to the insufficient level of confidence of the reporting physicians for the Ga-68 citrate PET-CT, this modality could not currently be recommended to replace Ga-67 citrate scintigraphy for routine clinical use.