Capabilities of two- and three-dimensional FDG-PET for detecting small lesions and lymph nodes in the upper torso: a dynamic phantom study

The capabilities and limitations of two-(2D) and three-dimensional (3D) flu orine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) in detec ting small tumors and lymph nodes were studied in a phantom modeling the hu man chest and axilla. Multiple dual-radionuclide phantom studies were perfo rmed. Five hollow spheres ranging in diameter from 3 mm to 15 mm were fille d with carbon-11 and placed in the axillary and mediastinal regions of an a nthropomorphic phantom containing hollow organs filled with F-18 to simulat e FDG uptake 1 h after injection. Dynamic imaging was performed to acquire PET images with varying target-to-background ratios. Imaging was performed in 2D and 3D acquisition modes, with and without attenuation correction, on a modern PET scanner. Lesion detectability was visually and quantitatively assessed. For objects larger than 9 mm in diameter, target-to-background r atios ranging from similar to 3:1 to similar to 10:1 were detectable. Objec ts <9 mm in diameter required a target-to-background ratio of greater than or equal to 18:1. Target-to-background ratios required for lesion detectabi lity were equivalent for 2D and 3D PET images with and without attenuation correction. In conclusion, 2D and 3D PET with attenuation correction consis tently detected "tumors" greater than or equal to 9 mm. Lesions <9 mm could be detected if there was high enough tumor uptake. No statistically signif icant differences in lesion detection were found for 2D versus 3D PET, or f or attenuation-corrected versus non-attenuation-corrected images.