Medical Radiation Sciences, School of Dentistry and Health Sciences, Faculty of Science, Charles Sturt University, Wagga Wagga, NSW, 2678, Australia.
Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, 130033, Jilin, China.
Sci Rep. 2020 Sep 24;10(1):15696. doi: 10.1038/s41598-020-72707-y.
The purpose of this work is to present a body size and tube voltage dependent correction scheme for the Hounsfield Unit, HU, in medical X-ray Computed Tomography imaging. Boltzmann photon transport equation was employed to study X-ray interaction with bulk water in CT imaging. Experimentally measured X-ray output in body of phantoms and attenuation cross sections of water were employed in the derivation of beam intensity in X-ray imaging. A Somatom Emotion CT scanner from Siemens and electron density phantoms from CIRS were employed to acquire CT images of different body sizes and different tissue materials located at different depths from body's surface. Tube voltage and depth dependent effective attenuation of bulk water was found from theoretical analysis in agreement with measured size-specific correction factors for CTDI under different tube voltages. A size and tube voltage dependent correction scheme for the Hounsfield Unit is established. For the same tissue material, body size has much larger impact on the CT number variations than that of depth from the body surface in phantom measurements. Good results were achieved by applying the established correction scheme on the experimentally measured CT number variations under different tube voltages and body sizes.
本工作旨在提出一种与体模尺寸和管电压相关的亨氏单位（HU）校正方案，用于医学 X 射线计算机断层摄影成像。采用玻尔兹曼光子输运方程研究 X 射线与 CT 成像中块状水中的相互作用。在推导 X 射线成像中的束强度时，使用了在体模中测量的 X 射线输出和水的衰减截面。采用西门子的 Somatom Emotion CT 扫描仪和 CIRS 的电子密度体模，获取不同体模尺寸和位于距体表不同深度的不同组织材料的 CT 图像。从理论分析中发现了与不同管电压下 CTDI 的实测尺寸特异性校正因子一致的体模中与管电压和深度相关的水的有效衰减。建立了一种与体模尺寸和管电压相关的亨氏单位校正方案。对于相同的组织材料，体模测量中体模尺寸对 CT 值变化的影响远大于距体表的深度。通过在不同管电压和体模尺寸下应用所建立的校正方案，对实验测量的 CT 值变化进行了很好的校正。
