Small Animal SPECT Using a Skew-Slit Collimator

项目描述（申请人提供）：本项目主要目的是使用斜缝准直器开发和评估小动物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取代针孔或多针孔准直器，以显着减少图像伪影并提高跨轴分辨率。针孔形成锥束成像几何形状。如果准直器围绕物体（如小动物）在圆形轨道上旋转，则锥束成像几何结构获得的投影测量是不完整的，不足以进行无伪影图像重建。工件的严重程度与针孔在旋转轴方向上的锥角成正比。通过将针孔转换成一对斜缝，成像锥角可以由两个斜缝到探测器的距离来控制。我们可以在横轴方向上使用较大的锥角来增加图像的放大倍率，在旋转轴方向上使用较小的锥角来减少数据不足的伪影。这是通过在物体附近放置一个垂直狭缝（即，狭缝平行于旋转轴）和在更远的地方放置一个水平狭缝实现的。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平铺在检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像放大倍率小于单针孔准直器中的放大倍率。较小的图像放大倍数可能导致较差的空间分辨率。因此，我们提出了一种具有一个垂直狭缝和几个水平狭缝的多斜缝准直器。与多针孔系统相比，多斜缝系统在跨轴方向上具有更大的图像放大倍率，从而具有更好的图像分辨率。这项拨款申请促进了小动物成像新技术的发展。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实际物理系统的构建和测试，才能将这一想法转移到适合R01类型资助的较低风险类别。一个关键目标是从物理斜缝系统生成初步数据。成功的目标将提供证据，证明斜缝SPECT系统为小动物应用提供了实质性的改进。这些成果自然会成为R01严格评估和进一步优化改进的基础。

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.