Dual-head gamma camera 2-[fluorine-18]-fluoro-2-deoxy-D-glucose positron emission tomography in oncological patients: effects of non-uniform attenuation correction on lesion detection

The purpose of this study was to evaluate a dual head coincidence gamma cam era (DH-PET) equipped with single-photon transmission for 2-[fluorine-18]-f luoro-2-deoxy-D-glucose (FDG) imaging in oncological patients. Forty-five p atients with known or suspected malignancies, scheduled for a positron emis sion tomography (PET) scan, were first studied with a dedicated ring PET an d subsequently with DH-PET. All patients underwent measured attenuation cor rection using germanium-68 rod sources for ring PET and caesium-137 sources for DH-PET. Ring PET emission scan was started 64+/-17 min after intraveno us administration of 235+/-42 MBq FDG, DH-PET emission followed 160+/-32 mi n after i.v. FDG. Attenuation-corrected and non-attenuation-corrected image s were reconstructed for ring PET and DH-PET. The image sets were evaluated independently by three observers blinded to clinical data and to results o f conventional imaging. Attenuation-corrected ring PET as the standard of r eference depicted 118 lesions, non-attenuation-corrected ring PET 113 (96%) lesions, and attenuation-corrected DH-PET and non-attenuation-corrected DH -PET, 101 (86%) and 84 (71%) lesions, respectively (P<0.05). The lesion det ection rate of attenuation-corrected and non-attenuation-corrected DH-PET w as almost similar for lesions >20 mm, whereas attenuation correction increa sed the detection rate from 60% to 80% for lesions less than or equal to 20 mm (P<0.01). A patient-based analysis revealed concordant results relative to attenuation-corrected ring PET for non-attenuation-corrected ring PET, attenuation-corrected DH-PET and non-attenuation-corrected DH-PET in 42 (93 %), 36 (80%) and 31 (69%) patients, respectively. Differences might have in fluenced patient management in two (4%), six (13%) and ten (22%) patients, respectively. In conclusion, measured attenuation correction markedly impro ves the lesion detection capability of DH-PET. With measured attenuation co rrection the diagnostic performance of DH-PET is closer to that of dedicate d ring PET.