Department of Radiologic Sciences, Kuwait University, Sulaibikhat 90805, Kuwait.
Department of Radiology, Al Sabah Hospital, Ministry of Health, Kuwait.
Radiography (Lond). 2021 Feb;27(1):95-100. doi: 10.1016/j.radi.2020.06.017. Epub 2020 Jul 12.
Computed tomography (CT) numbers are used in radiological diagnosis, attenuation correction and radiotherapy treatment planning. Modern CT scanners use iterative reconstruction methods instead of the traditional filtered back projection (FBP). Hence, the investigation of CT number accuracy with image reconstruction techniques and X-ray tube potential (kVp) used in CT is warranted. The aim of this study is to evaluate the effect of Sinogram Affirmed Iterative Reconstruction (SAFIRE) Technique and image acquisition at different tube potentials on CT numbers of different tissue equivalent materials.
Images of the Computerised Imaging Reference System Model 062M Electron Density Phantom were acquired at different tube potentials and reconstructed using FBP and different strengths of SAFIRE. Average CT numbers, in circular regions of interest, and their standard deviations were used to investigate any dependence of CT numbers on tube potentials and/or image reconstruction technique using non-parametric statistical tests with p-values set at 0.05.
Statistically significant differences in CT numbers were not observed (p > 0.091) between the different image reconstruction techniques. CT number of bone equivalent materials increased significantly (p < 0.015), by up to 400 Hounsfield Units, when tube potential was decreased. Such extent of CT number change over the tube potentials range used in this study may influence diagnostic outcomes in lung nodule, contrast enhanced and calcium score studies. For all other tissue equivalent materials, the CT number did not change significantly for different tube potentials. Linear relationship was observed between CT numbers and electron densities.
The study concludes that the CT numbers of all tissues did not change significantly with image reconstruction methods. However, the CT numbers of bone equivalent materials increased with decreasing tube potentials, which may result in misrepresentation of clinical information obtained.
When CT images are used to extract quantitative parameters such as calcium score, to characterise lung nodules and contrast enhanced structures, the kVp used for image acquisition should be carefully selected to avoid any misrepresentation of clinical information.
计算机断层扫描（CT）数值用于放射诊断、衰减校正和放射治疗计划。现代 CT 扫描仪使用迭代重建方法，而不是传统的滤波反投影（FBP）。因此，有必要研究图像重建技术和 CT 中使用的 X 射线管电压（kVp）对 CT 数值的准确性的影响。本研究旨在评估 Sinogram Affirmed Iterative Reconstruction（SAFIRE）技术和不同管电压下的图像采集对不同组织等效材料 CT 数值的影响。
使用不同的管电压和 FBP 以及不同强度的 SAFIRE 对 Computerised Imaging Reference System Model 062M 电子密度体模的图像进行采集。使用圆形感兴趣区域中的平均 CT 值及其标准差，使用非参数统计检验（p 值设为 0.05）来研究 CT 值是否取决于管电压和/或图像重建技术。
不同图像重建技术之间的 CT 值没有观察到统计学上的显著差异（p>0.091）。当管电压降低时，骨等效材料的 CT 值显著增加（p<0.015），最高可达 400 个 Hounsfield 单位。在本研究中使用的管电压范围内，CT 值的这种变化程度可能会影响肺结节、对比增强和钙评分研究中的诊断结果。对于所有其他组织等效材料，不同管电压下的 CT 值没有明显变化。观察到 CT 值与电子密度之间存在线性关系。
研究得出结论，所有组织的 CT 值与图像重建方法没有显著变化。然而，骨等效材料的 CT 值随管电压的降低而增加，这可能导致对所获得的临床信息的错误表示。
当使用 CT 图像提取定量参数（如钙评分、特征化肺结节和对比增强结构）时，应仔细选择用于图像采集的 kVp，以避免对临床信息的任何错误表示。
