Small Animal SPECT Using a Skew-Slit Collimator

描述(申请人提供)：该项目的主要目标是开发和评估使用斜缝准直器的小动物SPECT(单光子发射计算机断层扫描)。最先进的小动物SPECT成像配置使用针孔或多针孔准直器。我们建议使用斜缝准直器来代替针孔或多针孔准直器，以显著减少图像伪影并提高轴向分辨率。针孔形成锥形波束成像几何体。如果准直器在圆形轨道上围绕对象(例如，小动物)旋转，则锥束成像几何体获取的投影测量是不完整的，并且不足以进行无伪影图像重建。伪影的严重程度与针孔在旋转轴方向上的锥角成正比。通过将针孔转换为一对斜缝，成像锥角可以通过两个狭缝到探测器的距离来控制。我们可以在横轴方向使用较大的圆锥角来增加图像的放大率，而在旋转轴方向使用较小的圆锥角来减少数据不足的伪影。这是通过在靠近对象的位置放置垂直狭缝(即，狭缝平行于旋转轴)并将水平狭缝放置在更远的位置来实现的。多针孔准直器能够显著减少锥束伪影，并通过将多个锥束图像拼接在探测器上来提高检测灵敏度。为了尽可能避免多路复用，多针孔准直器中的锥束图像放大倍数比单针孔中的小。图像放大倍数越小，空间分辨率越差。因此，我们提出了一种具有一个垂直缝和几个水平缝的多斜缝准直器。与多针孔系统相比，多斜缝系统在轴向具有更大的图像放大倍数，因此具有更好的图像分辨率。这项拨款申请促进了小动物成像领域非常新的技术的发展。虽然我们在理论上展示了斜缝系统的巨大潜力，但需要进一步开发重建算法以及构建和测试实际的物理系统，才能将这一想法转移到适合R01型资金的较低风险类别。一个关键目标是从物理斜缝系统中产生初步数据。这些目标的成功将提供证据，证明斜缝SPECT系统为小动物的应用提供了实质性的改进。这些成果将自然形成R01的基础，进行严格的评估和进一步的优化和改进。 与公共健康相关：该项目提出了一种新的SPECT成像系统，该系统具有超越最先进的针孔成像系统的潜力。我们的系统使用垂直缝隙来代替针孔。结果，提高了图像的分辨率。这意味着我们可以看到更小的物体。这一新系统将在小动物成像中发挥重要作用。

DESCRIPTION (provided by applicant): The main objective of this project is the development and evaluation of small animal SPECT (single photon emission computed tomography) using skew-slit collimators. The state-of-the-art configuration for small animal SPECT imaging uses a pinhole or a multi-pinhole collimator. We propose the use of a skew-slit collimator to replace the pinhole or multi-pinhole collimator, in order to significantly reduce image artifacts and increase transaxial resolution. A pinhole forms a cone-beam imaging geometry. If the collimator rotates around the object (e.g., a small animal) in a circular orbit, the projection measurements acquired by the cone-beam imaging geometry are incomplete and not enough for an artifact-free image reconstruction. The severity of the artifact is proportional to the cone-angle of the pinhole in the direction of the axis of rotation. By transforming a pinhole into a pair of skew slits, the imaging cone-angle can be controlled by the distances of the two slits to the detector. We are able to use a large cone-angle in the transaxial direction to increase image magnification, and a small cone-angle in the direction of axis of rotation in order to reduce the data-insufficiency artifacts. This is achieved by placing a vertical slit (that is, the slit is parallel to the axis of rotation) close to the object and placing a horizontal slit farther out. The multi-pinhole collimator is able to significantly reduce the cone-beam artifacts and to increase the detection sensitivity by tiling the detector with multiple cone-beam images. To avoid multiplexing as much as possible, the cone-beam image magnification in the multi-pinhole collimator is smaller than that in the single- pinhole. The smaller image magnification could result in poorer spatial resolution. We therefore propose a multiple-skew-slit collimator that has one vertical slit and several horizontal slits. Compared with the multi- pinhole system, the multi-skew-slit system has a larger image magnification in the transaxial direction, and thus has better image resolution. This grant application promotes the development of very novel technologies in small animal imaging. While we show great potential for the skew-slit system in theory, further development of reconstruction algorithms and construction and testing of an actual physical system are required to move this idea into a lower risk category suitable for R01 type funding. A key goal is to generate preliminary data from a physical skew-slit system. Success in the aims here will provide evidence that skew-slit SPECT systems offer substantial improvements for small animal applications. The achievements will naturally form the basis for an R01 for rigorous evaluation and further optimization and improvements. PUBLIC HEALTH RELEVANCE: This project proposes a novel SPECT imaging system that has the potential to outperform the state-of-the-art pinhole imaging system. Our system uses perpendicular slits to replace the pinholes. As a result, the image resolution is improved. It means that we can see smaller objects. This new system will be very important in small animal imaging.