Fig 1.
CEORA phantom: (A) Extension Ring M phantom used for girth simulation; (B) A set of three cylindrical calcifications; (C) The complete set-up of CEORA phantom with Cardio Calcification Insert containing nine cylindrical calcifications having different hydroxyapatite density values (800, 400 or 200 mg/cm3) within the Anthropomorphic Thorax; (D) A slice of the CT-scanned CEORA phantom with calcification locations.
Table 1.
Calcification characteristics of the CEORA and SATI phantoms.
Fig 2.
SATI phantom used together with Sim2D motion simulator: (A) Custom-built calcifications of half cylindrical shape with different height levels; (B) An artificial artery containing custom-built calcifications having one of hydroxyapatite density values (800, 400 or 200 mg/cm3) rotated ±60 degrees with respect to each other; (C) The complete set-up of the SATI phantom containing a custom-built insert placed within Anthropomorphic Thorax; (D) A slice of the large calcification insert with HA density of 200 mg/cm3 (left); Cropped slices of CT images with calcification inserts of different size and HA density (middle); Cropped slices of CT images of inserts with HA density of 800 mg/cm3 obtained at different velocity levels (right).
Table 2.
Scanner manufacturers and used reconstruction kernels.
Fig 3.
CAC segmentation using PVC-CS: Left: CT image containing calcified lesion; Right: Initial calcification volume obtained by intensity value thresholding at 130 HU (red); Refined extended calcification segmentation obtained by intensity value thresholding at 90 HU filtered with the distance transform (yellow); CAC background (blue).
Fig 4.
Left: Cropped CT slice containing CAC lesion; Middle: Segmented CAC lesion ≥ 130 HU (green); Right: Segmented region using ≥ 90 HU around the CAC lesion (red).
Fig 5.
Left: Single CT image slice showing the CEORA phantom with a large and medium lesion (98.2 and 21.2 mm3) with HA density of 400 mg/cm3; Middle: Segmentation obtained using C-CS; Right: Segmentation obtained using PVC-CS.
Fig 6.
Scatter plots of the determined calcium volumes for the total detected volume (98,2 + 21,2 = 119,4 mm3) of CACs with same HA density for the CEORA phantom using C-CS (red) and PVC-CS (blue).
Plots are grouped per ring configuration (No ring, Ring M and Ring L). Each group shows volumes determined for three HA densities of the inserts (800, 400 and 200 mg/cm3).
Table 3.
Ratios between reference CAC volumes and calculated CAC volumes determined using C-CS and PVC-CS performed on the CEORA phantom.
Results are grouped per lesion size (Large and Medium) and HA density (H-800, M-400, L-200 mg/cm3) of each calcium insert and listed per ring configuration (No ring (-), M, L). Presented values are averaged over five different acquisitions.
Table 4.
Median and range of the determined CAC volumes over five different acquisitions of the CEORA phantom.
Results are grouped per ring configuration (No Ring (-), Ring M, Ring L) and HA density (H-800, M-400, L-200 mg/cm3). Calculated values were determined using C-CS and PVC-CS. The median and range values have been rounded for easier presentation.
Fig 7.
A: A CT slice showing values in a homogeneous CAC from the CEORA phantom; B: Unexpected large differences with respect to intensities in homogeneous CAC, which led to different probabilities calculated with PVC-CS; Left: Large CAC insert with HA density of 200 mg/cm3; Middle: Segmentation obtained using C-CS; Right: Segmentation obtained using PVC-CS. Blue and red squares mark the same voxels in all images.
Fig 8.
Left: Single CT slice showing the medium sized insert of the SATI phantom with HA density of 400 mg/cm3 with the simulated motion of 30 mm/s; Middle: Segmentation obtained using C-CS; Right: Segmentation obtained using PVC-CS.
Fig 9.
Scatter plots showing the total determined calcium volumes for the SATI phantom using C-CS (red) and PVC-CS (blue).
The total detected volume ranged from 87.6-96.5 mm3. Plots are grouped for scans acquired at the same velocity (static, 10 and 30 mm/s). Each group shows determined calcification volumes per HA density (800, 400 and 200 mg/cm3).
Table 5.
Median and range of the CAC volumes over three different acquisitions of the SATI phantom for different settings, i.e. without simulated motion and with simulated velocities of 10 and 30 mm/s and with calcium insert HA densities (H-800, M-400, L-200 mg/cm3).
Results are calculated using C-CS and PVC-CS, and grouped per simulated velocity. The median and range values have been rounded for easier presentation.
Fig 10.
Bland-Altman plot for calcium volume scores calculated with C-CS by using soft vs. sharp reconstruction kernels.
Bias is -0.049 with limits of agreement [-0.185, 0.087].
Fig 11.
Bland-Altman plot for calcium volume scores calculated with PVC-CS by using soft vs. sharp reconstruction kernels.
Bias is 0.002 with limits of agreement [-0.130, 0.134].
Table 6.
ICC with 95% confidence interval and Bland-Altman with bias and limits of agreemnts of the CAC volumes over three different vendors (GE, Siemens, Philips) calculated for C-CS and PVC-CS.