PDF(Pubmed)
Abstract：
BACKGROUND: Computer-aided modeling and design (CAM/CAD) of patient anatomy from computed tomography (CT) imaging and 3D printing technology enable the creation of tangible, patient-specific anatomic models that can be used for surgical guidance. These models have been associated with better patient outcomes; however, a lack of CT imaging guidelines risks the capture of unsuitable imaging for patient-specific modeling. This study aims to investigate how CT image pixel size (X-Y) and slice thickness (Z) impact the accuracy of mandibular models.
METHODS: Six cadaver heads were CT scanned at varying slice thicknesses and pixel sizes and turned into CAD models of the mandible for each scan. The cadaveric mandibles were then dissected and surface scanned, producing a CAD model of the true anatomy to be used as the gold standard for digital comparison. The root mean square (RMS) value of these comparisons, and the percentage of points that deviated from the true cadaveric anatomy by over 2.00 mm were used to evaluate accuracy. Two-way ANOVA and Tukey-Kramer post-hoc tests were used to determine significant differences in accuracy.
RESULTS: Two-way ANOVA demonstrated significant difference in RMS for slice thickness but not pixel size while post-hoc testing showed a significant difference in pixel size only between pixels of 0.32 mm and 1.32 mm. For slice thickness, post-hoc testing revealed significantly smaller RMS values for scans with slice thicknesses of 0.67 mm, 1.25 mm, and 3.00 mm compared to those with a slice thickness of 5.00 mm. No significant differences were found between 0.67 mm, 1.25 mm, and 3.00 mm slice thicknesses. Results for the percentage of points deviating from cadaveric anatomy greater than 2.00 mm agreed with those for RMS except when comparing pixel sizes of 0.75 mm and 0.818 mm against 1.32 mm in post-hoc testing, which showed a significant difference as well.
CONCLUSIONS: This study suggests that slice thickness has a more significant impact on 3D model accuracy than pixel size, providing objective validation for guidelines favoring rigorous standards for slice thickness while recommending isotropic voxels. Additionally, our results indicate that CT scans up to 3.00 mm in slice thickness may provide an adequate 3D model for facial bony anatomy, such as the mandible, depending on the clinical indication.
METHODS: Six cadaver heads were CT scanned at varying slice thicknesses and pixel sizes and turned into CAD models of the mandible for each scan. The cadaveric mandibles were then dissected and surface scanned, producing a CAD model of the true anatomy to be used as the gold standard for digital comparison. The root mean square (RMS) value of these comparisons, and the percentage of points that deviated from the true cadaveric anatomy by over 2.00 mm were used to evaluate accuracy. Two-way ANOVA and Tukey-Kramer post-hoc tests were used to determine significant differences in accuracy.
RESULTS: Two-way ANOVA demonstrated significant difference in RMS for slice thickness but not pixel size while post-hoc testing showed a significant difference in pixel size only between pixels of 0.32 mm and 1.32 mm. For slice thickness, post-hoc testing revealed significantly smaller RMS values for scans with slice thicknesses of 0.67 mm, 1.25 mm, and 3.00 mm compared to those with a slice thickness of 5.00 mm. No significant differences were found between 0.67 mm, 1.25 mm, and 3.00 mm slice thicknesses. Results for the percentage of points deviating from cadaveric anatomy greater than 2.00 mm agreed with those for RMS except when comparing pixel sizes of 0.75 mm and 0.818 mm against 1.32 mm in post-hoc testing, which showed a significant difference as well.
CONCLUSIONS: This study suggests that slice thickness has a more significant impact on 3D model accuracy than pixel size, providing objective validation for guidelines favoring rigorous standards for slice thickness while recommending isotropic voxels. Additionally, our results indicate that CT scans up to 3.00 mm in slice thickness may provide an adequate 3D model for facial bony anatomy, such as the mandible, depending on the clinical indication.
摘要：
背景：通过计算机断层扫描（CT）成像和3D打印技术对患者解剖结构进行计算机辅助建模和设计（CAM/CAD），可用于手术指导的患者特定解剖模型。这些模型与更好的患者预后相关；然而，缺乏CT成像指南的风险是捕获不适合患者特定建模的成像.本研究旨在探讨CT图像像素大小（X-Y）和切片厚度（Z）如何影响下颌模型的准确性。
方法：以不同的切片厚度和像素大小对六个尸体头部进行CT扫描，每次扫描都将其转换为下颌骨的CAD模型。然后解剖尸体下颌骨并进行表面扫描，制作真实解剖的CAD模型，用作数字比较的黄金标准。这些比较的均方根(RMS)值，并使用偏离真实尸体解剖结构超过2.00mm的点的百分比来评估准确性。使用双向ANOVA和Tukey-Kramer事后检验来确定准确性的显着差异。
结果：双向方差分析显示，切片厚度的RMS存在显着差异，而像素尺寸则没有差异，而事后测试显示，像素尺寸仅在0.32mm和1.32mm之间存在显着差异。对于切片厚度，事后测试显示，对于切片厚度为0.67mm的扫描，RMS值明显较小，1.25mm,与切片厚度为5.00毫米的那些相比，还有3.00毫米。在0.67mm之间没有发现显着差异，1.25mm,和3.00毫米的切片厚度。偏离尸体解剖结构大于2.00mm的点的百分比与RMS的结果一致，除了在事后测试中比较像素大小为0.75mm和0.818mm与1.32mm时，这也显示出显著的差异。
结论：这项研究表明，与像素大小相比，切片厚度对3D模型精度的影响更大，为支持切片厚度严格标准的指南提供客观验证，同时推荐各向同性体素。此外,我们的结果表明，CT扫描层厚达3.00毫米可以为面部骨解剖提供足够的3D模型，比如下颌骨，取决于临床适应症。
方法：以不同的切片厚度和像素大小对六个尸体头部进行CT扫描，每次扫描都将其转换为下颌骨的CAD模型。然后解剖尸体下颌骨并进行表面扫描，制作真实解剖的CAD模型，用作数字比较的黄金标准。这些比较的均方根(RMS)值，并使用偏离真实尸体解剖结构超过2.00mm的点的百分比来评估准确性。使用双向ANOVA和Tukey-Kramer事后检验来确定准确性的显着差异。
结果：双向方差分析显示，切片厚度的RMS存在显着差异，而像素尺寸则没有差异，而事后测试显示，像素尺寸仅在0.32mm和1.32mm之间存在显着差异。对于切片厚度，事后测试显示，对于切片厚度为0.67mm的扫描，RMS值明显较小，1.25mm,与切片厚度为5.00毫米的那些相比，还有3.00毫米。在0.67mm之间没有发现显着差异，1.25mm,和3.00毫米的切片厚度。偏离尸体解剖结构大于2.00mm的点的百分比与RMS的结果一致，除了在事后测试中比较像素大小为0.75mm和0.818mm与1.32mm时，这也显示出显著的差异。
结论：这项研究表明，与像素大小相比，切片厚度对3D模型精度的影响更大，为支持切片厚度严格标准的指南提供客观验证，同时推荐各向同性体素。此外,我们的结果表明，CT扫描层厚达3.00毫米可以为面部骨解剖提供足够的3D模型，比如下颌骨，取决于临床适应症。
