三种新颖的精确像素驱动的 2D CT 和 3D EPR 成像投影方法。

Three novel accurate pixel-driven projection methods for 2D CT and 3D EPR imaging.

机构信息

School of Computer and Information Technology, Shanxi University, Taiyuan, Shanxi, China.

Department of Radiation and Cellular Oncology, The University of Chicago, Chicago, IL, USA.

出版信息

J Xray Sci Technol. 2018;26(1):83-102. doi: 10.3233/XST-17284.

DOI:10.3233/XST-17284

PMID:29036875

Abstract

OBJECTIVES

This work aims to explore more accurate pixel-driven projection methods for iterative image reconstructions in order to reduce high-frequency artifacts in the generated projection image.

METHODS

Three new pixel-driven projection methods namely, small-pixel-large-detector (SPLD), linear interpolation based (LIB) and distance anterpolation based (DAB), were proposed and applied to reconstruct images. The performance of these methods was evaluated in both two-dimensional (2D) computed tomography (CT) images via the modified FORBILD phantom and three-dimensional (3D) electron paramagnetic resonance (EPR) images via the 6-spheres phantom. Specifically, two evaluations based on projection generation and image reconstruction were performed. For projection generation, evaluation was using a 2D disc phantom, the modified FORBILD phantom and the 6-spheres phantom. For image reconstruction, evaluations were performed using the FORBILD and 6-spheres phantom. During evaluation, 2 quantitative indices of root-mean-square-error (RMSE) and contrast-to-noise-ratio (CNR) were used.

RESULTS

Comparing to the use of ordinary pixel-driven projection method, RMSE of the SPLD based least-square algorithm was reduced from 0.0701 to 0.0384 and CNR was increased from 5.6 to 19.47 for 2D FORBILD phantom reconstruction. For 3D EPRI, RMSE of SPLD was also reduced from 0.0594 to 0.0498 and CNR was increased from 3.88 to 11.58. In addition, visual evaluation showed that images reconstructed in both 2D and 3D images suffered from high-frequency line-shape artifacts when using the ordinary pixel-driven projection method. However, using 3 new methods all suppressed the artifacts significantly and yielded more accurate reconstructions.

CONCLUSIONS

Three proposed pixel-driven projection methods achieved more accurate iterative image reconstruction results. These new and more accurate methods can also be easily extended to other imaging modalities. Among them, SPLD method should be recommended to 3D and four dimensional (4D) EPR imaging.

摘要

目的

本研究旨在探索更精确的像素驱动投影方法，用于迭代图像重建，以减少生成投影图像中的高频伪影。

方法

提出了三种新的像素驱动投影方法，即小像素大探测器（SPLD）、基于线性插值的（LIB）和基于距离前插的（DAB），并将其应用于图像重建。通过改进的 FORBILD 体模的二维（2D）计算机断层扫描（CT）图像和六球体模的三维（3D）电子顺磁共振（EPR）图像对这些方法的性能进行了评估。具体来说，进行了基于投影生成和图像重建的两项评估。对于投影生成，使用二维圆盘体模、改进的 FORBILD 体模和六球体模进行评估。对于图像重建，使用 FORBILD 和六球体模进行评估。在评估过程中，使用了两个定量指标，即均方根误差（RMSE）和对比噪声比（CNR）。

结果

与使用普通像素驱动投影方法相比，基于 SPLD 的最小二乘算法的 RMSE 从 2D FORBILD 体模重建的 0.0701 降低到 0.0384，CNR 从 5.6 增加到 19.47。对于 3D EPRI，SPLD 的 RMSE 也从 0.0594 降低到 0.0498，CNR 从 3.88 增加到 11.58。此外，视觉评估表明，在使用普通像素驱动投影方法时，2D 和 3D 图像重建的图像都受到高频线状伪影的影响。然而，使用这三种新方法都显著抑制了伪影，得到了更准确的重建结果。