F-18-FDG positron imaging in oncological patients: Gamma camera coincidence detection versus dedicated PET

Aim of the present study was to investigate the feasibility of 2-[fluorine1 8]-fluoro-2-deoxy-D-glucose (FDG) imaging in oncological patients with a du al head gamma camera modified for coincidence detection (MCD). Methods: Pha ntom studies were done to determine lesion detection at various lesion-to-b ackground ratios, system sensitivity and spatial resolution. Thirty-two pat ients with suspected or known malignant disease were first studied with a d edicated full-ring PET system (DPET) applying measured attenuation correcti on and subsequently with an MCD system without attenuation correction. MCD images were first interpreted without knowledge of the DPET findings. In a second reading, MCD and DPET were evaluated simultaneously. Results: The ph antom studies revealed a comparable spatial resolution for DPET and MCD (5. 9 x 6.3 x 4.2 mm vs. 5.9 x 6.5 x 6.0 mm). System sensitivity of MCD was les s compared to DPET (91 cps/Bq/ml/cm(FOV) vs. 231 cps/Bq/ml/cm(FOV)). At a l esion-to-background ratio of 4:1, DPET depicted a minimal phantom lesion of 1.0 cm in diameter, MCD a minimal lesion of 1.6 cm. With DPET, a total of 91 lesions in 27 patients were classified as malignant. MCD without knowled ge of DPET results revealed increased FDG uptake in all patients with posit ive DPET findings. MCD detected 72 out of 91 DPET lesions (79.1%). With kno wledge of the DPET findings, 11 additional lesions were detected (+12%). MC D missed lesions in six patients with relevance for staging in two patients . Ali lesions with a diameter above 18 mm were detected. Conclusion: MCD FD G imaging yielded results comparable to dedicated PET in most patients. How ever, a considerable number of small lesions clearly delectable with DPET w ere not detected by MCD alone. Therefore, MCD cannot yet replace dedicated PET in all oncological FDG studies. Further technical refinement of this ne w method is needed to improve image quality (e.g. attenuation correction).