Table II.

List of designations, densities and electron densities relative to water for the tissue-equivalent objects examined in this study (Tissue Characterization phantom, Gammex 467, Gammex rmi, Middleton, WI). Note that there are two entries for solid water material: one for the material of the main body of the contrast phantom and the other for the tissue-equivalent object inserted in that body. The inclusion of this solid water object in the study was motivated by the fact that it provided the lowest electron density difference relative to the solid water of the main body (2.76%) – offering a challenging test for visualization of low contrast objects at the lowest available dose. The last column in the table gives the percentage difference in electron density between the tissue-equivalent objects and the solid water of the main body of the contrast phantom.

Designation of Tissue- equivalent Object	Physical Density (g/cm3)	Electron Density Relative to Water	Electron density difference (%)
Lung (LN-300)	0.29	0.280	72.44
Lung (LN-450)	0.44	0.429	57.78
Adipose (AP6)	0.94	0.925	8.96
Breast	0.98	0.954	6.10
Solid Water (Object)	1.017	0.988	2.76
Solid Water (Phantom)	1.046	1.016	0.00
Brain	1.053	1.049	3.25
Liver (LV1)	1.097	1.065	4.82
Inner Bone	1.143	1.096	7.87
Bone (B200)	1.154	1.106	8.86
Bone (CB2-30% Mineral)	1.335	1.280	25.98
Bone (CB2-50% Mineral)	1.56	1.470	44.69
SB3 Cortical Bone	1.825	1.697	67.03