Table 1.
Imaging parameters of the CBCT and MDCT systems.
Fig 1.
(a) Illustration of the calibration step wedge setup in relation to the geometry of CBCT to forward project axial images into projections. (b) Axial images of the calibration step wedge acquired using MDCT (left) and the corresponding projections obtained via forward projection (right). (c) Illustration of the calibration step wedge setup relative to the projection.
Fig 2.
Workflow of VMCT images synthesized using CBCT + MDCT.
Fig 3.
The bilinear scaling functions used to convert 120-kVp MDCT to 90-kVp MDCT.
The R2 is the coefficient of determination.
Fig 4.
Illustration of the electron density phantom.
Fig 5.
Axial image of the electron density phantom without (top row) and with (bottom row) titanium inserts acquired using (a) CBCT, (b) low-energy MDCT and (c) standard MDCT.
Fig 6.
Illustration of the anthropomorphic chest phantom which consists of the phantom body and the extension ring.
Fig 7.
(a) Wedge thickness versus image intensity in low energy projection, (b) decomposed projections from basis material decomposition and (c) the corresponding illustrations for aluminum (top row) and acrylic (bottom row) step wedges.
Fig 8.
CT numbers of MDCT, original CBCT and shading corrected CBCT for the electron density phantom without titanium inserts.
Fig 9.
(a) Difference image between VMCT images synthesized using low-energy MDCT + standard MDCT and CBCT + MDCT at 45–50 keV for the electron density phantom without titanium inserts. (b) Total intensity of the difference image at different energies.
Fig 10.
Axial image and intensity profile through the red line of (a) CBCT, (b) shading corrected CBCT and (c) VMCT at 48 keV synthesized using CBCT + MDCT for the electron density phantom without titanium inserts. (d) The mean CT number of the rod insert simulating trabecular bone in different axial slices.
Fig 11.
Axial image and intensity profile through the red line of (a) CBCT, (b) shading corrected CBCT and (c) VMCT at 48 keV synthesized using CBCT + MDCT for the electron density phantom with titanium inserts. (d) The mean CT number of the rod insert simulating trabecular bone in different axial slices.
Fig 12.
(a) CNR and (b) %Diff in CBCT, shading corrected CBCT and VMCT for the electron density phantom without and with titanium inserts.
Fig 13.
Axial image and intensity profile through the red line of (a) CBCT, (b) shading corrected CBCT and (c) VMCT at 48 keV synthesized using CBCT + MDCT for the chest phantom. (d) A phantom plan study (left) and the corresponding MU (right) for 6 MV photon beam irradiated bilaterally from the left side (field 1) and the right side (field 2).