Yang N C, Leichner P K, Hawkins W G
Johns Hopkins Hospital, Department of Radiation Oncology, Baltimore, Maryland 21205.
Med Phys. 1987 Sep-Oct;14(5):759-66. doi: 10.1118/1.596000.
A new method is introduced in which the total photon interaction cross sections per electron of human tissues are used to define effective atomic numbers for blood, bone, brain, fat, heart, kidney, liver, lung, muscle, ovary, pancreas, spleen, and water. These effective atomic numbers are equal within 4% from 10 to 200 keV in each soft tissue, whereas for bones of different chemical compositions the variation ranges from 2.86% to 5.03%. This effective atomic number definition is less energy dependent than a previous definition based on the total photon interaction cross section per atom averaged over all elements in the tissue, from which the computed effective atomic numbers varied by as much as 50% (in bone) as a function of photon energy over the energy range from 10 to 200 keV.
本文介绍了一种新方法，即利用人体组织中每个电子的总光子相互作用截面来定义血液、骨骼、大脑、脂肪、心脏、肾脏、肝脏、肺、肌肉、卵巢、胰腺、脾脏和水的有效原子序数。在每个软组织中，这些有效原子序数在10至200keV范围内的误差在4%以内，而对于不同化学成分的骨骼，其变化范围为2.86%至5.03%。这种有效原子序数的定义比先前基于组织中所有元素平均每个原子的总光子相互作用截面的定义对能量的依赖性更小，根据先前的定义，在10至200keV的能量范围内，计算得到的有效原子序数（在骨骼中）随光子能量的变化高达50%。
