Abstract：
OBJECTIVE: To demonstrate the potential of low-dose ultra-high-resolution CT (UHRCT) images to generate high-quality radiographic images on extremity phantoms and to estimate the radiation dose required for this.
METHODS: A hand and knee phantom containing real human bones was imaged on an UHRCT scanner at full-dose, half-dose, and quarter-dose levels using a high-resolution extremity protocol. The raw data was reconstructed using both filtered back projection (FBP) and an iterative reconstruction algorithm (AIDR3D). Using custom designed software, each CT volume data set was converted to attenuation coefficients, and then a synthesized radiograph (synDX) was generated by forward projecting the volume data sets from a point source onto a 2D synthetic detector. The signal-to-noise ratio (SNR) was measured in the synDXs across all dose levels and the root-mean-squared error (RMSE) was computed with the FD synDXs as the reference.
RESULTS: The proposed workflow generates high-quality synDXs at any arbitrary angle. For FBP, the SNR largely tracked with the radiation dose levels for both the knee and hand phantoms. For the knee phantom, iterative reconstruction provided a 6.1% higher SNR when compared to FBP. The RMSE was overall higher for the lowest dose levels and monotonically decreased with increasing dose. No substantial differences were observed qualitatively in the visualization of skeletal detail of the phantoms.
CONCLUSIONS: The fine detail provided by UHRCT acquisitions of extremities facilitates the ability to generate quality radiographs, potentially eliminating the need for additional scanning on a conventional digital radiography system.
METHODS: A hand and knee phantom containing real human bones was imaged on an UHRCT scanner at full-dose, half-dose, and quarter-dose levels using a high-resolution extremity protocol. The raw data was reconstructed using both filtered back projection (FBP) and an iterative reconstruction algorithm (AIDR3D). Using custom designed software, each CT volume data set was converted to attenuation coefficients, and then a synthesized radiograph (synDX) was generated by forward projecting the volume data sets from a point source onto a 2D synthetic detector. The signal-to-noise ratio (SNR) was measured in the synDXs across all dose levels and the root-mean-squared error (RMSE) was computed with the FD synDXs as the reference.
RESULTS: The proposed workflow generates high-quality synDXs at any arbitrary angle. For FBP, the SNR largely tracked with the radiation dose levels for both the knee and hand phantoms. For the knee phantom, iterative reconstruction provided a 6.1% higher SNR when compared to FBP. The RMSE was overall higher for the lowest dose levels and monotonically decreased with increasing dose. No substantial differences were observed qualitatively in the visualization of skeletal detail of the phantoms.
CONCLUSIONS: The fine detail provided by UHRCT acquisitions of extremities facilitates the ability to generate quality radiographs, potentially eliminating the need for additional scanning on a conventional digital radiography system.
摘要：
目的：证明低剂量超高分辨率CT（UHRCT）图像在四肢体模上生成高质量射线照相图像的潜力，并估算为此所需的辐射剂量。
方法：在UHRCT扫描仪上以全剂量对包含真实人体骨骼的手和膝盖模型进行成像，半剂量，和四分之一剂量水平使用高分辨率四肢协议。使用滤波反投影(FBP)和迭代重建算法(AIDR3D)重建原始数据。使用定制设计的软件，每个CT体积数据集被转换为衰减系数，然后通过将来自点源的体积数据集正向投影到2D合成检测器上来生成合成射线照片(synDX)。在所有剂量水平的synDX中测量信噪比（SNR），并以FDsynDX为参考计算均方根误差（RMSE）。
结果：建议的工作流程以任意角度生成高质量的synDX。对于FBP，SNR在很大程度上跟踪了膝盖和手体模的辐射剂量水平。对于膝盖幻影，与FBP相比,迭代重建提供了6.1%的高SNR。对于最低剂量水平，RMSE总体较高，并且随着剂量的增加而单调降低。在体模骨骼细节的可视化中没有观察到实质性差异。
结论：UHRCT采集四肢提供的精细细节有助于产生高质量的射线照片，潜在地消除了对常规数字射线照相系统的额外扫描的需要。
方法：在UHRCT扫描仪上以全剂量对包含真实人体骨骼的手和膝盖模型进行成像，半剂量，和四分之一剂量水平使用高分辨率四肢协议。使用滤波反投影(FBP)和迭代重建算法(AIDR3D)重建原始数据。使用定制设计的软件，每个CT体积数据集被转换为衰减系数，然后通过将来自点源的体积数据集正向投影到2D合成检测器上来生成合成射线照片(synDX)。在所有剂量水平的synDX中测量信噪比（SNR），并以FDsynDX为参考计算均方根误差（RMSE）。
结果：建议的工作流程以任意角度生成高质量的synDX。对于FBP，SNR在很大程度上跟踪了膝盖和手体模的辐射剂量水平。对于膝盖幻影，与FBP相比,迭代重建提供了6.1%的高SNR。对于最低剂量水平，RMSE总体较高，并且随着剂量的增加而单调降低。在体模骨骼细节的可视化中没有观察到实质性差异。
结论：UHRCT采集四肢提供的精细细节有助于产生高质量的射线照片，潜在地消除了对常规数字射线照相系统的额外扫描的需要。
