Pato Lara R V, Vandenberghe Stefaan, Zedda Tiziana, Van Holen Roel
Department of Electronics and Information Systems, MEDISIP, Ghent University-iMinds-IBiTech, De Pintelaan 185 Blok B-5, B-9000 Ghent, Belgium.
Phys Med Biol. 2015 Nov 21;60(22):8791-807. doi: 10.1088/0031-9155/60/22/8791. Epub 2015 Nov 3.
Parallel-hole SPECT collimators have traditionally been manufactured by stacking sheets of lead foil or by casting. These techniques significantly restrict our options in terms of collimator geometry. However, recent developments in metal additive manufacturing are making novel collimator designs possible, giving rise to new opportunities in SPECT imaging. In this paper we propose an innovative type of collimator for stationary SPECT, using parallel-holes whose collimation direction depends on their axial position. Its main advantage compared to current stationary SPECT systems (which are based on pinholes) is that, using only axial bed translations, we can achieve complete angular sampling of an increased portion of the transaxial area of the collimator bore. This allows the system to be much more compact than current stationary SPECT systems that image objects of the same size. We describe three possible designs, for full-body, brain and small-animal imaging, respectively, and test their feasibility using simulations. The system modeling method is validated against realistic Monte Carlo simulations, and then used in the evaluation of the systems' performances and reconstructions. The simulations show that the system is able to reconstruct objects occupying the predicted field of view ([Formula: see text] of the transaxial area of the bore) without sampling artifacts. In particular, we perform reconstructions from noisy projection data obtained for an activity and scanning time similar to standard protocols for the three applications, and the resulting images indicate the possibility of using the proposed systems in practice.
传统上，平行孔单光子发射计算机断层扫描（SPECT）准直器是通过堆叠铅箔片或铸造来制造的。这些技术在准直器几何形状方面极大地限制了我们的选择。然而，金属增材制造的最新进展使新颖的准直器设计成为可能，为SPECT成像带来了新机遇。在本文中，我们提出了一种用于固定式SPECT的创新型准直器，它使用平行孔，其准直方向取决于它们的轴向位置。与当前的固定式SPECT系统（基于针孔）相比，其主要优点在于，仅通过轴向床平移，我们就可以对准直器孔的跨轴区域的更大一部分实现完整的角度采样。这使得该系统比成像相同尺寸物体的当前固定式SPECT系统更加紧凑。我们分别描述了用于全身、脑部和小动物成像的三种可能设计，并通过模拟测试它们的可行性。该系统建模方法针对实际的蒙特卡洛模拟进行了验证，然后用于评估系统的性能和重建。模拟结果表明，该系统能够重建占据预测视野（孔径跨轴区域的[公式：见原文]）的物体，而不会出现采样伪影。特别是，我们从类似于这三种应用的标准协议的活动和扫描时间获得的噪声投影数据进行重建，所得图像表明了在实际中使用所提出系统的可能性。
