title: Fever of unknown origin: prospective comparison of [18F]FDG imaging with a double-head coincidence camera and gallium-67 citrate SPET.
abstract: Gallium-67 citrate is currently considered as the tracer of first choice in the diagnostic workup of fever of unknown origin (FUO). Fluorine-18 2'-deoxy-2-fluoro-D-glucose (FDG) has been shown to accumulate in malignant tumours but also in inflammatory processes. The aim of this study was to prospectively evaluate FDG imaging with a double-head coincidence camera (DHCC) in patients with FUO in comparison with planar and single-photon emission tomography (SPET) 67Ga citrate scanning. Twenty FUO patients underwent FDG imaging with a DHCC which included transaxial and longitudinal whole-body tomography. In 18 of these subjects, 67Ga citrate whole-body and SPET imaging was performed. The 67Ga citrate and FDG images were interpreted by two investigators, both blinded to the results of other diagnostic modalities. Forty percent (8/20) of the patients had infection, 25% (5/20) had auto-immune diseases, 10% (2/20) had neoplasms and 15% (3/20) had other diseases. Fever remained unexplained in 10% (2/20) of the patients. Of the 20 patients studied, FDG imaging was positive and essentially contributed to the final diagnosis in 11 (55%). The sensitivity of transaxial FDG tomography in detecting the focus of fever was 84% and the specificity, 86%. Positive and negative predictive values were 92% and 75%, respectively. If the analysis was restricted to the 18 patients who were investigated both with 67Ga citrate and FDG, sensitivity was 81% and specificity, 86%. Positive and negative predictive values were 90% and 75%, respectively. The diagnostic accuracy of whole-body FDG tomography (again restricted to the aforementioned 18 patients) was lower (sensitivity, 36%; specificity, 86%; positive and negative predictive values, 80% and 46%, respectively). 67Ga citrate SPET yielded a sensitivity of 67% in detecting the focus of fever and a specificity of 78%. Positive and negative predictive values were 75% and 70%, respectively. A low sensitivity (45%), but combined with a high specificity (100%), was found in planar 67Ga imaging. Positive and negative predictive values were 100% and 54%, respectively. It is concluded that in the context of FUO, transaxial FDG tomography performed with a DHCC is superior to 67Ga citrate SPET. This seems to be the consequence of superior tracer kinetics of FDG compared with those of 67Ga citrate and of a better spatial resolution of a DHCC system compared with SPET imaging. In patients with FUO, FDG imaging with either dedicated PET or DHCC should be considered the procedure of choice.
authors: Department of Nuclear Medicine, Georg August University, Göttingen, Germany.
authors: J
authors: J
authors: Meller
authors: G
authors: G
authors: Altenvoerde
authors: U
authors: U
authors: Munzel
authors: A
authors: A
authors: Jauho
authors: M
authors: M
authors: Behe
authors: S
authors: S
authors: Gratz
authors: H
authors: H
authors: Luig
authors: W
authors: W
authors: Becker
mesh_terms: D000328:Adult; D000368:Aged; D002951:Citrates; D005260:Female; D005335:Fever of Unknown Origin / Q000000981:diagnostic imaging*; D019788:Fluorodeoxyglucose F18; D005708:Gallium; D005710:Gallium Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D002951:Citrates; D005710:Gallium Radioisotopes; D019788:Fluorodeoxyglucose F18; D005708:Gallium; C103850:gallium citrate