目的探讨和比较位相对比乳腺摄影(Phase-contrast Mammography,PCM)与全数字化乳腺摄影(Full Field Digital Mammography,FFDM)的影像质量。方法选用ACR RMI-156模型,分别于PCM乳腺摄影机与FFDM乳腺摄影机拍摄,除自动曝光条件,其余选用...目的探讨和比较位相对比乳腺摄影(Phase-contrast Mammography,PCM)与全数字化乳腺摄影(Full Field Digital Mammography,FFDM)的影像质量。方法选用ACR RMI-156模型,分别于PCM乳腺摄影机与FFDM乳腺摄影机拍摄,除自动曝光条件,其余选用的曝光条件两台机器相同。拍摄好的模型图像打印成胶片,由三位放射科医师进行独立评价,以评分的方法(以观察到的模型内部细微结构为依据),比较PCM与FFDM有无差异,统计方法为配对t检验和单因素方差分析,统计软件为Stata 7.0。结果在选择的曝光条件中,每一位医师对模型的评分PCM组与FFDM组接近,差异无统计学意义(P>0.05),三位医师之间评分,无论对PCM组还是FFDM组,差异无统计学意义(P>0.05)。两组的评分已超过ACR规定的较好乳腺摄影系统的评分标准(10分)。结论 PCM与FFDM在显示RMI-156模型模拟钙化点簇数、纤维条数、模拟肿块的能力方面相当(评分接近),两种乳腺X线摄影均具较高的影像质量。展开更多
Simulation experiments were performed to investigate the characteristics of information extraction in multiple-image radiography(MIR) based on geometrical optics approximation. Different Poisson noise levels were adde...Simulation experiments were performed to investigate the characteristics of information extraction in multiple-image radiography(MIR) based on geometrical optics approximation. Different Poisson noise levels were added to the simulation, and the results show that Poisson noise deteriorates the extraction results, with the degree of refraction > USAXS > absorption. The effects of Poisson noise are negligible when the detector's photon counts are about 1000 ph/pixel. A wider sampling range allows more accurate extraction results, but a narrower sampling range has a better signal-to-noise ratio for high Poisson noise levels, e.g., PN(10). The sampling interval can be suitably increased with a minor impact on the extraction results for low Poisson noise levels(PN(10000)). The extraction results are incomplete because a portion of the samplerocking curve is beyond the sampling range. This induces artifacts in the images, especially for strong refraction and USAXS signals. The artifacts are not obvious when the refraction angle and standard deviation of the USAXS are smaller than the sampling range by an order of magnitude.In general, the absorption barely affects the extraction results. However, additional Poisson noise will be generated when the sample is made of high-Z elements or has a large size due to the strong absorption. Here, the extraction results will deteriorate, and additional exposure time is required. This simulation provides important details on practical applications of MIR, with improvements in information extraction.展开更多
文摘目的探讨和比较位相对比乳腺摄影(Phase-contrast Mammography,PCM)与全数字化乳腺摄影(Full Field Digital Mammography,FFDM)的影像质量。方法选用ACR RMI-156模型,分别于PCM乳腺摄影机与FFDM乳腺摄影机拍摄,除自动曝光条件,其余选用的曝光条件两台机器相同。拍摄好的模型图像打印成胶片,由三位放射科医师进行独立评价,以评分的方法(以观察到的模型内部细微结构为依据),比较PCM与FFDM有无差异,统计方法为配对t检验和单因素方差分析,统计软件为Stata 7.0。结果在选择的曝光条件中,每一位医师对模型的评分PCM组与FFDM组接近,差异无统计学意义(P>0.05),三位医师之间评分,无论对PCM组还是FFDM组,差异无统计学意义(P>0.05)。两组的评分已超过ACR规定的较好乳腺摄影系统的评分标准(10分)。结论 PCM与FFDM在显示RMI-156模型模拟钙化点簇数、纤维条数、模拟肿块的能力方面相当(评分接近),两种乳腺X线摄影均具较高的影像质量。
基金supported by the Fundamental Research Funds for the Central Universities of Ministry of Education of China(Nos.lzujbky-2016-208 and lzujbky-2016-32)the Lanzhou University Construction Project for Innovation and Cooperative Education Base
文摘Simulation experiments were performed to investigate the characteristics of information extraction in multiple-image radiography(MIR) based on geometrical optics approximation. Different Poisson noise levels were added to the simulation, and the results show that Poisson noise deteriorates the extraction results, with the degree of refraction > USAXS > absorption. The effects of Poisson noise are negligible when the detector's photon counts are about 1000 ph/pixel. A wider sampling range allows more accurate extraction results, but a narrower sampling range has a better signal-to-noise ratio for high Poisson noise levels, e.g., PN(10). The sampling interval can be suitably increased with a minor impact on the extraction results for low Poisson noise levels(PN(10000)). The extraction results are incomplete because a portion of the samplerocking curve is beyond the sampling range. This induces artifacts in the images, especially for strong refraction and USAXS signals. The artifacts are not obvious when the refraction angle and standard deviation of the USAXS are smaller than the sampling range by an order of magnitude.In general, the absorption barely affects the extraction results. However, additional Poisson noise will be generated when the sample is made of high-Z elements or has a large size due to the strong absorption. Here, the extraction results will deteriorate, and additional exposure time is required. This simulation provides important details on practical applications of MIR, with improvements in information extraction.
