Characterizing the MTF in 3D for a Quantized SPECT Camera Having Arbitrary Trajectories.
Characterizing the MTF in 3D for a Quantized SPECT Camera Having Arbitrary Trajectories.
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DOI：
10.1109/tns.2009.2013464
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发表时间：
2009-06-01
影响因子：
1.8
通讯作者：
Tornai MP
中科院分区：
文献类型：
--
作者：
Madhav P;Bowsher JE;Cutler SJ;Tornai MP
特定应用的3D断层扫描小动物和专用乳房成像系统的出现刺激了简单方法的发展，以量化系统的三维空间分辨率或调制传递函数(MTF)。从特定位置的线源测量获得的本地确定的MTF可以表征系统分辨率的空间变化，并有助于校正这种变化。在这项研究中，描述了一种用于紧凑型SPECT系统的三维MTF测量方法，该系统使用基于16×20cm2 CZT的紧凑型伽马相机和能够沿不同轨迹移动的三维定位台架。采集由三根充满放射性的毛细管组成的新型体模的图像数据，这些毛细管彼此几乎垂直放置。这些图像提供了沿着重建的成像体积的三维的局部MTF的同时测量。通过使用不同的(1)能量窗口；(2)迭代重建参数，包括迭代次数、体素大小和投影视图数目；(3)简单和复杂的3D轨道轨迹，包括简单的垂直旋转轴、简单的倾斜、复杂的圆加圆弧和投影到半球上的复杂正弦曲线；以及(4)相机视野中的对象形状，来表征重建的3D体积中不同位置的MTF。结果表明，该方法可以提供由系统设计、采样、能量窗、重建参数、新的三维轨道轨迹和物体形状引起的空间分辨率影响的信息。基于这些对专用乳腺断层成像有用的测量，结果表明，对于不同的能量窗和重建参数，3D中的MTF有微小的变化。然而，定量地表明，对感兴趣的乳房体积进行均匀采样的复杂轨迹比更简单的轨迹具有略好的空间分辨率性能。
The emergence of application-specific 3D tomographic small animal and dedicated breast imaging systems has stimulated the development of simple methods to quantify the spatial resolution or Modulation Transfer Function (MTF) of the system in three dimensions. Locally determined MTFs, obtained from line source measurements at specific locations, can characterize spatial variations in the system resolution and can help correct for such variations. In this study, a method is described to measure the MTF in 3D for a compact SPECT system that uses a 16 × 20 cm2 CZT-based compact gamma camera and 3D positioning gantry capable of moving in different trajectories. Image data are acquired for a novel phantom consisting of three radioactivity-filled capillary tubes, positioned nearly orthogonally to each other. These images provide simultaneous measurements of the local MTF along three dimensions of the reconstructed imaged volume. The usefulness of this approach is shown by characterizing the MTF at different locations in the reconstructed imaged 3D volume using various (1) energy windows; (2) iterative reconstruction parameters including number of iterations, voxel size, and number of projection views; (3) simple and complex 3D orbital trajectories including simple vertical axis of rotation, simple tilt, complex circle-plus-arc, and complex sinusoids projected onto a hemisphere; and (4) object shapes in the camera’s field of view. Results indicate that the method using the novel phantom can provide information on spatial resolution effects caused by system design, sampling, energy windows, reconstruction parameters, novel 3D orbital trajectories, and object shapes. Based on these measurements that are useful for dedicated tomographic breast imaging, it was shown that there were small variations in the MTF in 3D for various energy windows and reconstruction parameters. However, complex trajectories that uniformly sample the breast volume of interest were quantitatively shown to have slightly better spatial resolution performance than more simple orbits.