A study has been made of threshold detection of disks in Computerized Tomography (CT) images. Low contrast objects with and without sharp edges (polystyrene cylinders and cones) have been constructed and placed in a phantom. The phantom is filled with various water/alcohol mixtures to vary contrast, and imaged with a modern CT Scanner. The scan dose, slice thickness, reconstruction algorithm and display parameters have been varied to demonstrate their effect, on delectability and to understand how low contrast detestability might be optimized. Preliminary results of detection experiments are presented.