Department of Radiological Sciences, University of California, Irvine, CA, 92697, USA.
Med Phys. 2017 Aug;44(8):3939-3951. doi: 10.1002/mp.12296. Epub 2017 Jun 28.
To investigate the feasibility of accurate quantification of iodine mass thickness in contrast-enhanced spectral mammography.
A computer simulation model was developed to evaluate the performance of a photon-counting spectral mammography system in the application of contrast-enhanced spectral mammography. A figure-of-merit (FOM), which was defined as the decomposed iodine signal-to-noise ratio (SNR) with respect to the square root of the mean glandular dose (MGD), was chosen to optimize the imaging parameters, in terms of beam energy, splitting energy, and prefiltrations for breasts of various thicknesses and densities. Experimental phantom studies were also performed using a beam energy of 40 kVp and a splitting energy of 34 keV with 3 mm Al prefiltration. A two-step calibration method was investigated to quantify the iodine mass thickness, and was validated using phantoms composed of a mixture of glandular and adipose materials, for various breast thicknesses and densities. Finally, the traditional dual-energy log-weighted subtraction method was also studied as a comparison. The measured iodine signal from both methods was compared to the known value to characterize the quantification accuracy and precision.
The optimal imaging parameters, which lead to the highest FOM, were found at a beam energy between 42 and 46 kVp with a splitting energy at 34 keV. The optimal tube voltage decreased as the breast thickness or the Al prefiltration increased. The proposed quantification method was able to measure iodine mass thickness on phantoms of various thicknesses and densities with high accuracy. The root-mean-square (RMS) error for cm-scale lesion phantoms was estimated to be 0.20 mg/cm . The precision of the technique, characterized by the standard deviation of the measurements, was estimated to be 0.18 mg/cm . The traditional weighted subtraction method also predicted a linear correlation between the measured signal and the known iodine mass thickness. However, the correlation slope and offset values were strongly dependent on the total breast thickness and density.
The results of this study suggest that iodine mass thickness for cm-scale lesions can be accurately quantified with contrast-enhanced spectral mammography. The quantitative information can potentially improve the differential power for malignancy.
研究在对比增强光谱乳腺摄影中准确量化碘质量厚度的可行性。
开发了一个计算机模拟模型，用于评估光子计数光谱乳腺摄影系统在对比增强光谱乳腺摄影中的应用性能。选择了一种性能指标（FOM），它被定义为分解后的碘信噪比（SNR）与平均腺体剂量（MGD）的平方根之比，用于优化成像参数，包括光束能量、分裂能量以及针对不同厚度和密度的乳房的预过滤。还使用 40 kVp 的光束能量和 34 keV 的分裂能量以及 3 mm Al 预过滤进行了实验体模研究。研究了一种两步校准方法来量化碘质量厚度，并使用由腺体和脂肪材料混合组成的体模进行了验证，这些体模具有各种厚度和密度。最后，还研究了传统的双能对数加权减法方法作为比较。通过比较两种方法测量的碘信号与已知值来表征定量精度和准确性。
在 42 至 46 kVp 之间的光束能量和 34 keV 的分裂能量下，找到了导致最高 FOM 的最佳成像参数。最佳管电压随着乳房厚度或 Al 预过滤的增加而降低。所提出的量化方法能够在各种厚度和密度的体模上准确测量碘质量厚度。对于厘米级病变体模，均方根（RMS）误差估计为 0.20 mg/cm。该技术的精度，由测量值的标准偏差来表示，估计为 0.18 mg/cm。传统的加权减法方法也预测了测量信号与已知碘质量厚度之间的线性相关性。然而，相关斜率和偏移值强烈依赖于乳房的总厚度和密度。
这项研究的结果表明，在对比增强光谱乳腺摄影中可以准确量化厘米级病变的碘质量厚度。定量信息有可能提高恶性肿瘤的鉴别能力。
