Department of Physics, Ryerson University, Toronto, M5B 2K3, Canada.
Physiol Meas. 2017 Sep 21;38(10):1848-1858. doi: 10.1088/1361-6579/aa87f0.
Recent evidence of gadolinium (Gd) deposition in bones of healthy individuals who have previously received Gd-based contrast agents (GBCAs) for MRI has led to a demand for in vivo measurement techniques. The technique of x-ray fluorescence provides a low risk and painless method to assess Gd deposition in bone, and has the potential to be a useful clinical tool. However, interpatient variability creates a challenge while performing in vivo measurements.
We explored the use of coherent normalization, which involves normalizing the Gd K x-rays to the coherent scattered γ-ray from the excitation source, for bone Gd measurements through a series of phantom-based experiments and Monte Carlo simulations.
We found coherent normalization is able to correct for variation in overlying tissue thickness over a wide range (0-12.2 mm). The Gd signal to coherent signal ratio is independent of tissue thickness for both experiments and Monte Carlo simulations.
Coherent normalization has been demonstrated to be used in practice with normal healthy adults to improve in vivo bone Gd measurements.
最近有证据表明，先前曾接受过基于钆的磁共振成像对比剂（GBCA）的健康个体的骨骼中出现了钆沉积，这导致人们对体内测量技术产生了需求。X 射线荧光技术为评估骨骼中的 Gd 沉积提供了一种低风险、无痛苦的方法，并且有可能成为一种有用的临床工具。然而，在进行体内测量时，患者间的差异会带来挑战。
我们通过一系列基于体模的实验和蒙特卡罗模拟，探讨了使用相干归一化的方法，即将 Gd K X 射线与激发源的相干散射γ射线进行归一化，用于骨骼 Gd 测量。
我们发现，相干归一化能够在较宽的范围内（0-12.2mm）校正覆盖组织厚度的变化。实验和蒙特卡罗模拟均表明，Gd 信号与相干信号的比值与组织厚度无关。
相干归一化已被证明可用于对正常健康成年人进行体内骨骼 Gd 测量，以提高测量的准确性。
