Zeng Gengsheng L
Department of Radiology, Utah Center for Advanced Imaging Research (UCAIR), University of Utah, Salt Lake City, Utah 84108, USA.
J Nucl Med Technol. 2008 Dec;36(4):207-12. doi: 10.2967/jnmt.108.055582. Epub 2008 Nov 13.
The main objective of this work was the development of a skew-slit collimator for small-animal SPECT to replace the state-of-the-art multipinhole collimator.
A pinhole forms a cone-beam imaging geometry. If the collimator rotates around the object in a circular orbit, the projection measurements acquired by the cone-beam imaging geometry are incomplete and not enough for 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. Multipinhole geometry can greatly reduce the data-insufficiency artifacts; however, image magnification is sacrificed. By transforming a pinhole into a pair of skewed slits, 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 the axis of rotation to reduce data-insufficiency artifacts. This transformation is achieved by placing a vertical slit (i.e., the slit is parallel to the axis of rotation) close to the object and placing a horizontal slit farther out. Similar to the multipinhole collimator, we also propose a multiple-skew-slit collimator that has a single vertical slit and several horizontal slits.
Computer simulations were performed to verify the working principle of the skew-slit collimator. A prototype multiple-skew-slit collimator was fabricated, and phantom experiments were performed on a SPECT system. The smallest channels (of 0.75-mm diameter) in the phantom were clearly separated in the reconstructed image.
This study suggests a novel technology in small-animal SPECT to replace the multipinhole collimator, resulting in significantly reduced image artifacts and increased transaxial resolution. A physical multiple-skew-slit system was built and tested. Compared with the multipinhole system, the multiple-skew-slit system has a larger image magnification in the transaxial direction and thus has better image resolution.
本研究的主要目的是开发一种用于小动物单光子发射计算机断层显像（SPECT）的斜缝准直器，以取代当前的先进多针孔准直器。
针孔形成锥束成像几何结构。如果准直器绕物体在圆形轨道上旋转，由锥束成像几何结构获取的投影测量数据是不完整的，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。多针孔几何结构可大大减少数据不足伪影；然而，会牺牲图像放大率。通过将针孔转换为一对倾斜狭缝，我们能够在横向方向上使用大锥角来增加图像放大率，并在旋转轴方向上使用小锥角来减少数据不足伪影。这种转换是通过在靠近物体处放置一个垂直狭缝（即狭缝平行于旋转轴）并在更远位置放置一个水平狭缝来实现的。与多针孔准直器类似，我们还提出了一种具有单个垂直狭缝和多个水平狭缝的多斜缝准直器。
进行了计算机模拟以验证斜缝准直器的工作原理。制作了一个多斜缝准直器原型，并在SPECT系统上进行了体模实验。体模中最小直径为0.75毫米的通道在重建图像中清晰可辨。
本研究提出了一种用于小动物SPECT的新技术，以取代多针孔准直器，从而显著减少图像伪影并提高横向分辨率。构建并测试了一个物理多斜缝系统。与多针孔系统相比，多斜缝系统在横向方向上具有更大的图像放大率，因此具有更好的图像分辨率。
