Dept. of Biomedical Engineering, College of Medicine, Catholic University, Seoul 137-701, Korea.
J Appl Clin Med Phys. 2010 Oct 7;11(4):3269. doi: 10.1120/jacmp.v11i4.3269.
A multiple-slit collimator (MSC) design was introduced for scatter reduction in cone-beam computed tomography (CBCT). Unlike most other collimators, the open and closed septa of the proposed MSC are placed in an equi-angular interval on a circular track of the central sagittal plane. Therefore, one gantry rotation provides only the half of necessary dataset and two gantry rotations are needed to obtain full information. During the first gantry rotation, the MSC position relative to the source is fixed. For the second rotation, the MSC is rotated by the equi-angle interval. We assume signals under the closed septa are totally attributed to scatter radiation. Then, scatter contributions under open septa are determined by interpolating them.Monte Carlo (MC) simulations for two virtual phantoms (one with a simple geometry and the other with two heterogeneities simulating the bone and the lung) were performed to evaluate the effectiveness of the system. Using the method developed, we could obtain images with significant scatter reduction. Contrast ratio (CR) improvement factors were 1.165 in a 2D projection view, and 1.210 and 1.223 at the central and peripheral slice of the reconstructed CBCT image of the simple geometry phantom.This preliminary study demonstrated that the proposed MSC, together with the imaging process technique, had a great potential to reduce scatter contribution in CBCT. Further studies will be performed to investigate the effect of various factors, such as reducing the detector size, increasing the number of history of MC simulation, and including many structures with different densities.
一种用于锥形束计算机断层扫描（CBCT）散射减少的多狭缝准直器（MSC）设计被引入。与大多数其他准直器不同，所提出的 MSC 的开和闭狭缝被放置在中央矢状平面的圆形轨道上的等角间隔处。因此，一个机架旋转仅提供必要数据集的一半，需要两个机架旋转才能获得完整的信息。在第一次机架旋转期间，准直器相对于源的位置是固定的。对于第二次旋转，MSC 通过等角度间隔旋转。我们假设闭狭缝下的信号完全归因于散射辐射。然后，通过插值来确定开狭缝下的散射贡献。对两个虚拟体模（一个具有简单几何形状，另一个具有模拟骨骼和肺的两个异质体）进行了蒙特卡罗（MC）模拟，以评估系统的有效性。使用所开发的方法，我们可以获得具有显着散射减少的图像。在二维投影视图中，对比度比（CR）改善因子为 1.165，在简单几何体模的重建 CBCT 图像的中央和外围切片中，CR 改善因子分别为 1.210 和 1.223。这项初步研究表明，所提出的 MSC 与成像过程技术相结合，具有在 CBCT 中减少散射贡献的巨大潜力。将进一步研究各种因素的影响，例如减小探测器尺寸、增加 MC 模拟的历史记录数量以及包括具有不同密度的许多结构。
