Low-Contrast Detail Phantom: Proof of Concept

To investigate the concept of filling the air gaps of the conventional contrast detail phantom (CDP) with various concentrations of contrast media, and to develop a variable level of attenuation-level differential phantoms that could be more appropriate for contrast measurements in some radiology cases.

Images were acquired using the digital radiography system of the traditional CDP (Perspex/air hole phantom) and the novel form of CDP where the air holes were replaced with attenuating material. In this study, two different attenuating materials were introduced, water and a 30% concentration of iodine-based contrast medium. Image quality was assessed using automated processing to calculate the image quality factor (IQF)_inv.

Phantom studies indicate that lower contrast levels are obtained when CDP holes are filled with water and a 30% concentration of iodine contrast media than those observed for air/Perspex or traditional CDP. As an example, when a 5-mAs beam is used the IQF_inv values are 5.32 in the case of air filling the holes; however, when these holes are filled with water under the same conditions, the value of the IQF_inv drops to 2.55, and to 2.83 when 30% of contrast media is used. Other concentrations were also tested. These results indicate that it is possible to extend the contrast scale in these phantoms to include ranges that are more realistic for a patient's body than just air and tissue-equivalent material.

These findings indicate that the proposed extension of the contrast scales allows smaller changes in contrast to be discerned. This is due to the small attenuation differences of the subject materials (e.g, 30% contrast liquid and wax) from the traditional form of CDP (material/air). This suggests that the low form of the CDP may have a useful role in assessing image quality in planar radiology as an evaluation tool to better represent low-subject contrast imaging requirements.