Fig 1.
Calculated mass density normalized HU, HU⍴, were plotted against mass density normalized electron density, ρe/ρ.
For biologically relevant molecules (A) kVCT and (B) MVCT energies. For human tissues at (C) kVCT and (D) MVCT. Molecule types are indicated by symbols, colors, and with labels in panels A and B. For panels C and D, tissue types contained a wide range of molecules although trends towards higher lipid, water, and protein content are labelled with text in the figure.
Fig 2.
Workflow for the two proposed methods to determine values for αi parameters needed to calculate HU⍴.
In method 1 (left), an energy spectrum must be explicitly determined a priori whereas in method 2 (right) these parameters are obtained by imaging a phantom.
Fig 3.
For (A) kVCT, (B) MVCT, and HU⍴ plotted against ρe/ρ for (C) kVCT, (D) MVCT for a CIRS tissue surrogate phantom with various tissue mimicking materials and liquid water. Circles (o) represent lung mimicking materials while plus signs (+) represent other tissue mimicking materials (including synthetic soft tissue, liquid water, and synthetic bone).
Table 1.
Tabulated assumed molecular compositions, manufacturer provided ρ, and calculated ρe for the calibration phantom.
Table 2.
Tabulated compositions and calculated ρe by imaging for synthetic tissue phantoms.
Table 3.
Sensitivity analysis of the HU and molecular composition to ρ and ρe conversion process for kVCT using αi values determined by method 2 (CT calibration phantom).