The aim of this study was to develop a geometric calibration method capable of eliminating the reconstruction artifacts of geometric misalignments in a tomosynthesis prototype with dual-axis scanning geometry. The potential scenarios of geometric misalignments were demonstrated, and their effects on reconstructed images were also evaluated. This method was a phantom-based approach with iterative optimization, and the calibration phantom was designed for specific tomosynthesis scanning geometry. The phantom was used to calculate a set of geometric parameters from each projection, and these parameters were then used to evaluate the geometric misalignments of the dual-axis scanning-geometry prototype. The simulated results revealed that the extracted geometric parameters were similar to the input values and that the artifacts of reconstructed images were minimized due to geometric calibration. Additionally, experimental chest phantom imaging results also indicated that the artifacts of the reconstructed images were suppressed and that object structures were preserved through calibration. And the quantitative analysis result also indicated that the MTF can be further improved with the geometric calibration. All the simulated and experimental results demonstrated that this method is effective for tomosynthesis with dual-axis scanning geometry. Furthermore, this geometric calibration method can also be applied to other tomography imaging systems to reduce geometric misalignments and be used for different geometric calibration phantom configurations.

This study proposes a 10-bit low-power high-color-depth LCD column driver IC with two-stage multi-channel RDACs and switch resistance compensation. The design removes intermediate buffers from two-stage RDACs and uses global reference buffers to isolate the global resistor string and output channels. Because the global resistor string is isolated from output channels, the global resistor string can use a larger resistance value to achieve lower power consumption. This study proposes a class-AB buffer for the global reference buffers to compensate for the errors caused by the voltage drop on switches connected in series with the channel resistor string. The channel resistor strings also reuse the output stage current of the global buffer to reduce power consumption. A prototype of a 200-channel column driver was fabricated using 0.18-m/0.35-m CMOS technology with the worst DNL/INL being 1.2/1.1 LSB. The proposed 10-bit DAC occupies only 66 % of the area of a conventional 8-bit RDAC using the same technology. The 200-channel column driver consumes a total static current of only 0.38 mA.

The study aims to develop a rational polynomial approximation method for improving the accuracy of the effective atomic number calculation with a dual-energy X-ray imaging system. This method is based on a multi-materials calibration model with iterative optimization, which can improve the calculation accuracy of the effective atomic number by adding a rational term without increasing the computation time. The performance of the proposed rational polynomial approximation method is demonstrated and validated by both simulated and experimental studies. The twelve reference materials are used to establish the effective atomic number calibration model, and the value of the effective atomic numbers are between 5.444 and 22. For the accuracy of the effective atomic number calculation, the relative differences between calculated and experimental values are less than 8.5%for all sample cases in this study. The average calculation accuracy of the method proposed in this study can be improved by about 40%compared with the conventional polynomial approximation method. Additionally, experimental quality assurance phantom imaging result indicates that the proposed method is compliant with the international baggage inspection standards for detecting the explosives. Moreover, the experimental imaging results reveal that the difference of color between explosives and the surrounding materials is in significant contrast for the dual-energy image with the proposed method.

F (2022) Application of tomosynthesis for vertebral compression fracture diagnosis and bone healing assessment in fracture liaison services.