Article Figures & Data
Figures
- FIGURE 1.
Gyroid structures used in this work. (Top) Gyroid cubes (edge length, 2a) for a period of a = 12.56 mm and different wall thicknesses (G1, 0.40 mm; G2, 1.29 mm; G3, 2.65 mm). (Bottom) Corresponding cross-sections (only a single period is depicted) to illustrate the gyroid features (period, wall thickness) and the spatial volume filled by gyroid.
- FIGURE 2.
Cuboid phantom. (A) Model components (3 gyroid cubes of different volume fraction ratios and shell consisting of 2 parts). (B) Cross-section through CAD model. (C) Cross-section through CT (gray scale) superimposed by CAD model (different colors). (D) Cross-section of SPECT reconstruction (48 iterations, 1 subset, and 10-mm postprocessing filter).
- FIGURE 3.
Design of patient-specific 2-compartment kidney phantom. (A) Boolean operations necessary to generate kidney CAD model out of patient-specific kidney VOIs, different gyroid and filling structures (example: G1 and G3 for cortex and medulla, respectively), attachment and filling ports, and patient-specific kidney shell. (B) 3D printed 1:7.5 kidney phantom. ∧ = Boolean “and”; ∨ = Boolean “or.”
- FIGURE 4.
Quantitative analysis of cuboid. Depicted is the mean activity concentration in square regions of interest plotted in axial direction for different reconstruction parameters (number of iterations and postfilters). Positioning of axial regions of interest is illustrated at the top right by red boxes in the SPECT reconstruction. Solid black vertical lines represent borders between different gyroid cubes. Dashed black rectangles indicate axial position of 2 × 2 × 2 cm3 cubes used for the quantitative analysis (height of each box = HPGe-based activity concentration).
- FIGURE 5.
Design and validation of patient-specific kidney phantoms. (Top, left to right) Coronal contrast-enhanced CT slice of patient kidney; segmented cortex (red) and medulla (green); and 3D model of segmentation. (Center) Cross-sections through CAD models (green arrows: top sections without internal structure) for all 3 phantom designs (grid dimension, 1 cm). (Bottom) Contrast-enhanced patient CT (grayscale) overlaid with CT of phantom kidney (yellow) for all 3 phantom designs. CE = contrast-enhanced.
- FIGURE 6.
SPECT/CT fusions of patient acquisition and 3 phantoms (resin fraction ratios of 1:1, 1:3.5, and 1:7.5) for different postfilters (left to right: 0, 10, and 20 mm). Green arrows indicate overestimation of activity concentration in medulla for resin fraction ratio 1:1. Blue arrows indicate surface tension–related air bubbles.
- FIGURE 7.
Activity concentration–voxel histograms for patient (black) and 3 phantoms (red, 1:7.5; blue, 1:3.5; green, 1:1) for 48 iterations, 1 subset, and gaussian postfilters of 0 mm (A), 10 mm (B), and 20 mm (C) in full width at half maximum. While solid curves depict number of voxels containing certain activity concentration, vertical dashed lines indicate HPGe-based activity concentrations in medulla and cortex (values are presented in Table 2).
Tables
- TABLE 1
Calculation of Resin Fraction and Fillable Fraction for 3 Cuboid Structures, and Resin Fraction Ratio of G2 and G3 with Respect to G1
Gyroid Wall thickness (mm) Resin fraction Fillable fraction Resin fraction ratio G1 0.40 0.078 0.922 1:1 G2 1.29 0.277 0.723 1:3.55 G3 2.65 0.580 0.420 1:7.44 - TABLE 2
Activities and Activity Concentrations Measured with Regard to Patient-Specific Kidney Phantom Measurements
HPGe-based SPECT-based Ratio V (mL) Target, c (MBq/mL) c (MBq/mL) A (MBq) cMedulla (MBq/mL) cCortex (MBq/mL) A0 mm (MBq) A10 mm (MBq) A20 mm (MBq) 1:1 149.8 0.63 0.65 97.4 0.60 0.60 103.8 103.7 103.6 1:3.5 140.2 0.67 0.63 88.3 0.46 0.58 93.6 93.5 93.5 1:7.5 131.5 0.72 0.68 89.4 0.29 0.63 87.8 87.7 87.7 Shown are filling volume (V) as well as target, HPGe-based, and SPECT-based activity concentrations (c) and total kidney activities (A). Medulla and cortex concentrations were calculated on basis of the fillable fractions (Table 1). The SPECT-based target total activity for the patient kidney was 94.9 MBq.
Iterations No postprocessing filter 10-mm gaussian 20-mm gaussian Activity concentration G1 (1:1) gyroid (HPGe-based): 0.64 12 0.81 0.74 0.58 24 0.79 0.74 0.58 48 0.76 0.71 0.57 Activity concentration G2 (1:3.5) gyroid (HPGe-based): 0.50 12 0.59 0.55 0.46 24 0.57 0.55 0.46 48 0.54 0.52 0.45 Activity concentration G3 (1:7.5) gyroid (HPGe-based): 0.29 12 0.33 0.31 0.26 24 0.32 0.31 0.26 48 0.29 0.29 0.25 Vertically are shown different numbers of iterations; horizontally are shown postfilters of different full widths at half maximum. All activity concentrations are given in MBq/mL.
