使用微型计算机断层扫描的时间和光谱成像。
Temporal and spectral imaging with micro-CT.
作者信息
Johnston Samuel M, Johnson G Allan, Badea Cristian T
机构信息
Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina 27710, USA.
出版信息
Med Phys. 2012 Aug;39(8):4943-58. doi: 10.1118/1.4736809.
PURPOSE
Micro-CT is widely used for small animal imaging in preclinical studies of cardiopulmonary disease, but further development is needed to improve spatial resolution, temporal resolution, and material contrast. We present a technique for visualizing the changing distribution of iodine in the cardiac cycle with dual source micro-CT.
METHODS
The approach entails a retrospectively gated dual energy scan with optimized filters and voltages, and a series of computational operations to reconstruct the data. Projection interpolation and five-dimensional bilateral filtration (three spatial dimensions + time + energy) are used to reduce noise and artifacts associated with retrospective gating. We reconstruct separate volumes corresponding to different cardiac phases and apply a linear transformation to decompose these volumes into components representing concentrations of water and iodine. Since the resulting material images are still compromised by noise, we improve their quality in an iterative process that minimizes the discrepancy between the original acquired projections and the projections predicted by the reconstructed volumes. The values in the voxels of each of the reconstructed volumes represent the coefficients of linear combinations of basis functions over time and energy. We have implemented the reconstruction algorithm on a graphics processing unit (GPU) with CUDA. We tested the utility of the technique in simulations and applied the technique in an in vivo scan of a C57BL∕6 mouse injected with blood pool contrast agent at a dose of 0.01 ml∕g body weight. Postreconstruction, at each cardiac phase in the iodine images, we segmented the left ventricle and computed its volume. Using the maximum and minimum volumes in the left ventricle, we calculated the stroke volume, the ejection fraction, and the cardiac output.
RESULTS
Our proposed method produces five-dimensional volumetric images that distinguish different materials at different points in time, and can be used to segment regions containing iodinated blood and compute measures of cardiac function.
CONCLUSIONS
We believe this combined spectral and temporal imaging technique will be useful for future studies of cardiopulmonary disease in small animals.
目的
微型计算机断层扫描（Micro-CT）广泛应用于心肺疾病临床前研究中的小动物成像，但仍需进一步改进以提高空间分辨率、时间分辨率和物质对比度。我们提出了一种利用双源微型计算机断层扫描技术观察心动周期中碘分布变化的方法。
方法
该方法包括使用优化的滤过器和电压进行回顾性门控双能量扫描，以及一系列用于重建数据的计算操作。采用投影插值和五维双边滤波（三个空间维度+时间+能量）来减少与回顾性门控相关的噪声和伪影。我们重建对应于不同心动周期的单独容积，并应用线性变换将这些容积分解为代表水和碘浓度的成分。由于所得的物质图像仍受噪声影响，我们通过一个迭代过程来提高其质量，该过程可使原始采集的投影与重建容积预测的投影之间的差异最小化。每个重建容积体素中的值代表基函数随时间和能量的线性组合系数。我们已使用计算统一设备架构（CUDA）在图形处理单元（GPU）上实现了重建算法。我们在模拟中测试了该技术的实用性，并将该技术应用于对一只体重为0.01 ml/g的C57BL∕6小鼠注射血池造影剂后的体内扫描。重建后，在碘图像的每个心动周期阶段，我们分割左心室并计算其容积。利用左心室的最大和最小容积，我们计算了每搏输出量、射血分数和心输出量。
结果
我们提出的方法产生了五维容积图像，可在不同时间点区分不同物质，并可用于分割含碘化血液的区域并计算心功能指标。
结论
我们相信这种光谱和时间成像相结合的技术将对未来小动物心肺疾病的研究有用。
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