研究目的
To assess the influence of anatomic location on the relationship between computed tomography (CT) number and X-ray attenuation in limited and medium field-of-view (FOV) scans.
研究成果
There is a strong linear relationship between X-ray attenuation and CT number in CBCT scans, but this relationship is significantly influenced by the CBCT unit, FOV size, exposure settings, and anatomic location. These factors cause substantial variation in CT numbers, complicating their use for quantitative assessments like bone mineral density estimation. Clinicians should avoid direct comparisons of CT numbers from different protocols or locations, and further research is needed to develop standardized methods for reliable quantitative CBCT imaging.
研究不足
The study is limited to two specific CBCT units (Accuitomo 170 and Veraviewepocs 3De) and may not generalize to other models. The use of a phantom instead of human subjects may not fully replicate clinical conditions. Factors like scattered radiation and reconstruction algorithms could introduce variability not fully controlled. The influence of patient-specific factors (e.g., soft tissue thickness, positioning) on CT numbers was not addressed, limiting direct clinical applicability.
1：Experimental Design and Method Selection:
The study used a human head phantom with polypropylene tubes containing K2HPO4 solutions placed in tooth sockets to simulate X-ray attenuation. CBCT scans were acquired using Accuitomo 170 and Veraviewepocs 3De units with various FOV sizes and exposure settings. Linear regression analyses were performed to assess the relationship between CT number and K2HPO4 concentration, and ANOVA was used to compare slopes. The influence of anatomic location on CT numbers was examined.
2：Sample Selection and Data Sources:
A human skull phantom with soft-tissue equivalent material was used. Six teeth were extracted and replaced with tubes containing K2HPO4 solutions at concentrations of 50, 200, 400, 600, 800, 1000, and 1200 mg/mL to simulate bone attenuation.
3：List of Experimental Equipment and Materials:
Accuitomo 170 CBCT scanner, Veraviewepocs 3De CBCT scanner, human head phantom, polypropylene tubes (diameter: 5 mm), K2HPO4 solutions, i-Dixel software for reconstruction, Osirix imaging software for analysis.
4：Experimental Procedures and Operational Workflow:
CBCT scans were performed in standard resolution mode with specific FOVs, kVp, mA, rotation, and voxel sizes as per Table 1. Scans were reconstructed using the 'G001' filter in i-Dixel software and exported as DICOM files. CT numbers were measured using circular ROIs (area 0.055 cm2) on axial slices in Osirix software, averaged over five heights per tube and six anatomic locations.
5：Scans were reconstructed using the 'G001' filter in i-Dixel software and exported as DICOM files. CT numbers were measured using circular ROIs (area 055 cm2) on axial slices in Osirix software, averaged over five heights per tube and six anatomic locations.
Data Analysis Methods:
5. Data Analysis Methods: Linear regression was used to analyze the relationship between CT number and K2HPO4 concentration, with R2 calculation. One-way ANOVA compared slopes of regression lines. Variation in CT numbers by anatomic location was assessed graphically and statistically.
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