The objective of the work is to assess the clinical value of 18F-FDG images with a dual head coincidence SPECT ( DHC SPECT ) in the diagnosis of tumors and compare the diagnostic accuracy obtained with a DHC SPECT with those obtained with CT and ultrasound (US). Total 109 patents with known or suspected malignancies underwent 18F-FDG images 40-50min after injection of 222—296 MBq 18F-FDG. The images were reconstructed using iterative algorithms after attenuation correction with a CT map. 89 of 109 patients were proven to have malignancies. There were 87 patients with positive images including 3 cases of false positive

the sensitivity was 94.38% ( 84/89 ) with positive predict value of 96.55% ( 84/87 ) . The specificity was 90% ( 18/20 ) with negative predict value of 81.81% ( 18/22 ) . There were 26 patients with 18F-FDG coincidence images matched with CT or US

and 73 cases mis- matched with CT or US. 52 patients had more lesions on 18F-FDG imaging than on CT or US

only 5 patients less than on CT or US. The 18F-FDG coincidence imaging is therefore a valuable tool for diagnosis of tumors with higher sensitivity and specificity. Combined FDG image with CT will facilitate the precise localization of tumors. It is useful for differentiating malignancy from benign tumor;for tumor staging and restaging;for detecting recurrence or re- sidual tumor;for monitoring the response to treatment including surgery

chemotherapy or radiotherapy; and for pre- dicting the prognosis. With accumulation of clinical experience and improvement of technology

18F-FDG coincidence imaging will be popularized. But due to the limitation of SPECT’s resolution and the false positive from various in- flammation

a correct diagnosis must be based on the combination of SPECT imaging with clinical and other imaging data.