Table 2. Tabulated compositions and calculated ρ_e by imaging for synthetic tissue phantoms.

Tissue Type	Water (%)	Lipid (%)	Protein (%)	Minerals (%)	ρ (g/cc)	ρe	ρ(kV1)	ρe(kV1)	ρ(kV5)	ρe(kV5)	ρ(MV1)	ρe(MV1)	ρ(MV5)	ρe(MV5)
Skin	75	0	25	0	1.060 ± 0.002	1.048 ± 0.002	1.052	1.033	1.053	1.042	1.065	1.045	1.068	1.057
							(-0.7%)	(-1.4%)	(-0.6%)	(-0.5%)	(0.5%)	(-0.3%)	(0.8%)	(0.8%)
Muscle	75	5	20	0	1.045 ± 0.002	1.036 ± 0.002	1.034	1.017	1.035	1.027	1.051	1.032	1.051	1.042
							(-1.0%)	(-1.9%)	(-0.9%)	(-0.9%)	(0.6%)	(-0.4%)	(0.6%)	(0.6%)
Adipose	47	49	4	0	0.953 ± 0.002	0.955 ± 0.002	0.941	0.931	0.946	0.947	0.970	0.958	0.960	0.961
							(-1.2%)	(-2.5%)	(-0.7%)	(-0.9%)	(1.8%)	(0.3%)	(0.7%)	(0.6%)
Spongiosa	27	47	13	13	1.060 ± 0.002	1.044 ± 0.002	1.099	1.071	1.065	1.046	1.055	1.036	1.059	1.041
							(3.6%)	(2.6%)	(0.4%)	(0.2%)	(-0.4%)	(-0.8%)	(-0.1%)	(-0.3%)

Ground truth ρ and ρ_e values were calculated with noted uncertainties and used as a basis of comparison for the two other methods of calculating ρ and ρ_e by imaging. For ρ and ρ_e by imaging (either kV or MV CT), two methods were used in its determination: 1) piecewise linear (1-dimensional) direct interpolation of HU from CIRS tissue surrogate phantom imaging data (kV₁/MV₁) and 2) calculation by HU and known molecular composition (water, lipid, protein, and minerals) (kV₅/MV₅). Errors compared with ground truth for each imaging determined value of ρ and ρ_e are shown in parentheses.