Chityala R, Hoffmann K R, Bednarek D R, Rudin S
Toshiba Stroke Research Center, Rm no: 445, Biomedical Research Building, State University of New York at Buffalo, 3435, Main street, Buffalo, NY, 14214.
Proc SPIE Int Soc Opt Eng. 2004;5368(2):534-541. doi: 10.1117/12.534568.
High-resolution computed tomography (CT) reconstructions currently require either full field of view (FOV) exposure, resulting in high dose, or region of interest (ROI) exposure, resulting in artifacts. To obtain high-resolution 3D reconstruction of an ROI with minimal artifacts, we have developed a method involving a non-uniform ROI beam filter to reduce dose outside the ROI while acquiring the ROI at a higher dose. High-resolution, high-dose full-field projections of a phantom were obtained. ROIs in the images were selected and the low-dose data outside the ROI were simulated by adding various levels of noise to the projection data corresponding to a dose of 1/16 and 1/256 of the original dose. For an ROI of 30% FOV, artifacts in the reconstructed ROI were minimal for both dose reduction levels. For an ROI of 10% FOV, artifacts remained minimal only for the 1/16(th) dose case. The effect of the presence of a high contrast object outside the ROI was also studied. We found that the intensity of the artifacts increases with the contrast of the object, its size, and its distance from the axis of rotation. CT using an ROI filter provides a way to reconstruct an ROI with reduced integral dose and yet with minimal artifacts and improved spatial resolution.
目前，高分辨率计算机断层扫描（CT）重建要么需要全视野（FOV）曝光，这会导致高剂量，要么需要感兴趣区域（ROI）曝光，这会产生伪影。为了以最小的伪影获得感兴趣区域的高分辨率三维重建，我们开发了一种方法，该方法涉及使用非均匀感兴趣区域束滤波器，在以较高剂量采集感兴趣区域的同时，降低感兴趣区域之外的剂量。我们获得了一个模型的高分辨率、高剂量全视野投影。选择图像中的感兴趣区域，并通过向对应于原始剂量1/16和1/256的投影数据添加不同水平的噪声，来模拟感兴趣区域之外的低剂量数据。对于30%视野的感兴趣区域，在两种剂量降低水平下，重建的感兴趣区域中的伪影都最小。对于10%视野的感兴趣区域，仅在1/16剂量情况下，伪影仍保持最小。我们还研究了感兴趣区域之外存在高对比度物体的影响。我们发现，伪影的强度随着物体的对比度、其大小以及其与旋转轴的距离而增加。使用感兴趣区域滤波器的CT提供了一种方法，能够以降低的积分剂量重建感兴趣区域，同时具有最小的伪影并提高空间分辨率。
