Medical Physics Program, Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, MA, USA.
Landauer Medical Physics, Glenwood, IL, USA.
J Appl Clin Med Phys. 2021 Jan;22(1):337-342. doi: 10.1002/acm2.13155. Epub 2021 Jan 5.
Gold nanoparticles (AuNPs) are visualized and quantified in a human-sized phantom with a clinical MDCT scanner.
Experiments were conducted with AuNPs between 0.00171 and 200 mgAu/mL. CT images were acquired at 80, 100, 120, and 140 kVp in a 33-cm phantom. Image contrast due to AuNPs was experimentally determined from regions of interest (ROIs) and effective linear attenuation coefficients were calculated from CT x-ray spectra with consideration of tissue attenuation.
The typical 12-bit dynamic range of CT images was exceeded for AuNPs at 150 mgAu/mL. A threshold concentration of 0.3-1.4 mgAu/mL was determined for human visualization in 1-mm images at a typical diagnostic CTDI of 23.6 mGy. Optimal image contrast was also achieved at 120 kVp and verified by calculation.
We have shown that scanners capable of reconstructing images with extended Hounsfield scales are required for distinguishing any contrast differences above 150 mgAu/mL. We have also shown that AuNPs result in optimal image contrast at 120 kVp in a human-sized phantom due to gold's 80.7 keV k-edge and the attenuation of x-rays by tissue. Typical CT contrast agents, like iodine, require the use of lower kVps for optimal visualization, but lower kVps are more difficult to implement in the clinic because of elevated noise levels, elongated scan times, and/or beam-hardening artifacts. This indicates another significant advantage of AuNPs over iodine not yet discussed in the literature.
利用临床 MDCT 扫描仪在人体大小的体模中可视化和定量金纳米颗粒（AuNPs）。
在 0.00171 至 200mgAu/mL 之间进行了 AuNP 实验。在 33cm 体模中在 80、100、120 和 140kVp 下获取 CT 图像。通过感兴趣区域（ROI）实验确定了由于 AuNP 引起的图像对比度，并考虑组织衰减从 CT 射线光谱计算了有效线性衰减系数。
对于 150mgAu/mL 的 AuNP，典型的 12 位 CT 图像动态范围已超过。在典型的诊断 CTDI 为 23.6mGy 时，在 1mm 图像中确定了人眼可见性的 0.3-1.4mgAu/mL 的阈值浓度。还在 120kVp 下实现了最佳图像对比度，并通过计算进行了验证。
我们已经表明，需要能够重建具有扩展 Hounsfield 标度的图像的扫描仪，以区分高于 150mgAu/mL 的任何对比度差异。我们还表明，由于金的 80.7keV k 边和组织对 X 射线的衰减，AuNP 在人体大小的体模中在 120kVp 下产生最佳的图像对比度。典型的 CT 造影剂，如碘，需要使用较低的 kVp 进行最佳可视化，但由于噪声水平升高、扫描时间延长和/或束硬化伪影，较低的 kVp 在临床上更难实施。这表明 AuNP 相对于碘的另一个尚未在文献中讨论的重要优势。
