Fig 1.
Scheme of VMI synthesis for MAR using projection-based MD algorithms.
Fig 2.
The error correction LUT is calculated from the MD calibration process.
The circles represent AMLE,calib, and the crosses represent Acalib. The arrows represent the error correction values δA for various material thicknesses.
Fig 3.
Image of the spectral micro-CT prototype system with PCD.
Fig 4.
TASMIP X-ray spectrum at a tube voltage of 140 kV with 2-mm thick Al filtration.
Table 1.
The parameters for data acquisition and image reconstruction for the PCD-CT imaging simulations.
Fig 5.
Representative images of the XCAT phantoms.
Each row presents various parts of the human body. Each column presents the original XCAT image, metal implant positions (indicated by the yellow regions), reconstructed CT image with metal artifacts, and reference image without metal artifacts. The display unit for the XCAT image and metal implant is cm-1. For reconstructed images and reference images, the display unit is the CT value in HU.
Table 2.
The parameters for various regions of the XCAT phantom.
Fig 6.
MD calibration phantom in the experiments.
(a) Front view of the calibration phantom. (b) Schematic of the thickness combination of the PMMA and copper.
Fig 7.
Metal artifacts evaluation (MAE) phantom in the experiments.
(a) Top view of the phantom. (b) Side view of the phantom. (c) Schematic of the cylinder diameters and positions in the phantom. (d) Schematic of the cylinder heights in the phantom.
Fig 8.
Simulated results using the XCAT phantom for evaluating the different MAR methods.
Each row corresponds to a different part of the human body. The columns represent the reference CT image; uncorrected CT image with metal artifacts; and corrected CT images obtained using LMAR, NMAR, and the projection-based VMI algorithms (VMI-poly and VMI-Atable) at 100 keV. Window width and level of the image display are 1,000 HU and 0 HU, respectively.
Fig 9.
Enlarged images of the three ROIs in Fig 8.
Each row corresponds to a different part of the human body. The columns represent the reference CT image; uncorrected CT image with metal artifacts; and corrected CT images using LMAR, NMAR and projection-based VMI algorithms (VMI-poly and VMI-Atable) at 100 keV. Window width and level of the image display are 1,000 HU and 0 HU, respectively.
Table 3.
Quantitative data of the MAR methods with XCAT phantom.
Fig 10.
Experimental results using MAE phantom for evaluating the MAR methods.
The green and orange lines denote different line-profile positions for the analysis. (a) The uncorrected CT image with 140 kV polychromatic X-ray. (b) The corrected CT images obtained using the LMAR method. (c) The corrected CT images obtained using the NMAR method. (d) The projection-based VMCT image obtained using a polynomial method (VMI-poly) at 100 keV. (e) The projection-based VMCT image obtained using the MLE and LUT method (VMI-Atable) at 100 keV. Window width and level of the image display are 11,000 HU and 4,500 HU, respectively.
Fig 11.
Line profiles of the experimental CT images with the different MAR methods, as denoted in Fig 10.
Line profiles are represented by the green and orange lines of the corresponding uncorrected CT image. (a) The uncorrected CT image with 140 kV polychromatic X-ray. (b) The corrected CT images obtained using the LMAR method. (c) The corrected CT images obtained using the NMAR method. (d) The projection-based VMCT image obtained with a polynomial method (VMI-poly) at 100 keV. (e) The projection-based VMCT image obtained with the MLE and LUT method (VMI-Atable) at 100 keV.
Fig 12.
Enlarged CT images from the experimental results using the MAE phantom with the different MAR methods.
(a) The ROI position for circularity calculations. (b) The uncorrected CT image with 140 kV polychromatic X-ray. (c) The corrected CT images obtained using the LMAR method. (d) The corrected CT images obtained using the NMAR method. (e) The projection-based VMCT image obtained using a polynomial method (VMI-poly) at 100 keV. (f) The projection-based VMCT image obtained using the MLE and LUT method (VMI-Atable) at 100 keV. Window width and level of the image display are 15,000 HU and 6,500 HU, respectively.
Table 4.
The circularity of the copper rod in the CT images obtained the different MAR methods.