Mao Yanfei, Yu Zhicong, Zeng Gengsheng L
Department of Radiology, Utah Center for Advanced Imaging Research (UCAIR), University of Utah, Salt Lake City, Utah 84108 and Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112.
Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905.
Med Phys. 2015 Sep;42(9):5426-34. doi: 10.1118/1.4928484.
This work is a preliminary study of a stationary cardiac SPECT system. The goal of this research is to propose a stationary cardiac SPECT system using segmented slant-hole collimators and to perform computer simulations to test the feasibility. Compared to the rotational SPECT, a stationary system has a benefit of acquiring temporally consistent projections. The most challenging issue in building a stationary system is to provide sufficient projection view-angles.
A GATE (GEANT4 application for tomographic emission) Monte Carlo model was developed to simulate a two-detector stationary cardiac SPECT that uses segmented slant-hole collimators. Each detector contains seven segmented slant-hole sections that slant to a common volume at the rotation center. Consequently, 14 view-angles over 180° were acquired without any gantry rotation. The NCAT phantom was used for data generation and a tailored maximum-likelihood expectation-maximization algorithm was used for image reconstruction. Effects of limited number of view-angles and data truncation were carefully evaluated in the paper.
Simulation results indicated that the proposed segmented slant-hole stationary cardiac SPECT system is able to acquire sufficient data for cardiac imaging without a loss of image quality, even when the uptakes in the liver and kidneys are high. Seven views are acquired simultaneously at each detector, leading to 5-fold sensitivity gain over the conventional dual-head system at the same total acquisition time, which in turn increases the signal-to-noise ratio by 19%. The segmented slant-hole SPECT system also showed a good performance in lesion detection. In our prototype system, a short hole-length was used to reduce the dead zone between neighboring collimator segments. The measured sensitivity gain is about 17-fold over the conventional dual-head system.
The gate Monte Carlo simulations confirm the feasibility of the proposed stationary cardiac SPECT system with segmented slant-hole collimators. The proposed collimator consists of combined parallel and slant holes, and the image on the detector is not reduced in size.
本研究是对固定式心脏单光子发射计算机断层扫描（SPECT）系统的初步探索。本研究的目标是提出一种使用分段斜孔准直器的固定式心脏SPECT系统，并通过计算机模拟来测试其可行性。与旋转式SPECT相比，固定式系统具有获取时间上一致投影的优势。构建固定式系统最具挑战性的问题是提供足够的投影视角。
开发了一个GATE（用于断层发射的GEANT4应用程序）蒙特卡罗模型，以模拟使用分段斜孔准直器的双探测器固定式心脏SPECT。每个探测器包含七个分段斜孔部分，这些部分向旋转中心的一个公共体积倾斜。因此，无需任何机架旋转即可在180°范围内获取14个视角。使用NCAT体模生成数据，并使用定制的最大似然期望最大化算法进行图像重建。本文仔细评估了有限视角数量和数据截断的影响。
模拟结果表明，所提出的分段斜孔固定式心脏SPECT系统即使在肝脏和肾脏摄取量较高的情况下，也能够获取足够的心脏成像数据而不损失图像质量。每个探测器同时获取七个视角，在相同的总采集时间内，与传统双头系统相比，灵敏度提高了5倍，进而使信噪比提高了19%。分段斜孔SPECT系统在病变检测方面也表现出良好的性能。在我们的原型系统中，使用了较短的孔长度来减少相邻准直器段之间的死区。测量得到的灵敏度增益比传统双头系统高约17倍。
GATE蒙特卡罗模拟证实了所提出的带有分段斜孔准直器的固定式心脏SPECT系统的可行性。所提出的准直器由平行孔和斜孔组合而成，探测器上的图像尺寸不会减小。
