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_vol 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.

这项工作的目的是在医学 X 射线计算机断层扫描成像中为 Hounsfield 单元 HU 提供一种与身体尺寸和管电压相关的校正方案。玻尔兹曼光子传输方程用于研究 X 射线与 CT 成像中大量水的相互作用。在 X 射线成像中推导光束强度时，采用实验测量的体模体内的 X 射线输出和水的衰减截面。西门子的 Somatom Emotion CT 扫描仪和 CIRS 的电子密度体模被用来获取不同体型和位于体表不同深度的不同组织材料的 CT 图像。从理论分析中发现管电压和深度相关的散装水有效衰减与测量的 CTDI 尺寸特定校正因子一致_vol在不同管电压下。建立了 Hounsfield 单元的尺寸和管电压相关校正方案。对于相同的组织材料，在体模测量中，体型对 CT 数变化的影响远大于体表深度的影响。通过对不同管电压和体型下实验测量的 CT 数变化应用既定的校正方案，取得了良好的结果。