Introduction Quality in radiology images can be assessed by determining the levels of information retained or lost in an image. Information loss in images has been recently assessed via a method based on information theory and the employment of a contrast-detail (CD) phantom. In this study, the traditional CD phantom (air-Perspex) and a modified CD phantom were used. Methods Using the Agfa DX-D 600 digital flat panel system, six phantom radiographs were acquired at 70 kVp and 20 mAs. Three x-ray images were acquired for each phantom. Results Our results demonstrate that the material within the CD phantom influences total information loss (TIL) and image quality figure (IQF) measurements. The modified CD phantom provides a more realistic account of TIL and IQF for soft tissue radiology imaging. Conclusion It is recommended that a low inherent subject contrast phantom, such as this modified CD phantom, be added to the image quality assessment processes of radiology departments. In addition, use of both IQF and TIL to assess image quality will provide radiology departments with greater evidence on which to base decisions.