On the origin of MTF reduction in grating-based x-ray differential phase contrast CT imaging

IF 3.2 2区医学 Q1 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Medical physics Pub Date : 2024-12-20 DOI:10.1002/mp.17593

Yuhang Tan, Jiecheng Yang, Hairong Zheng, Dong Liang, Peiping Zhu, Yongshuai Ge

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引用次数: 0

Abstract

Background

The complementary absorption contrast CT (ACT) and differential phase contrast CT (DPCT) can be generated simultaneously from an x-ray computed tomography (CT) imaging system incorporated with grating interferometer. However, it has been reported that ACT images exhibit better spatial resolution than DPCT images. By far, the primary cause of such discrepancy remains unclear.

Purpose

The purpose of this study is to investigate the underlying cause of the resolution discrepancy between ACT and DPCT in a grating interferometer CT imaging system.

Methods

In this study, theoretical derivations were performed with a $π$ -phase Talbot–Lau grating interferometer system to model the signal formation mechanism of absorption imaging and phase imaging, respectively. In addition, physical, and numerical experiments were conducted to verify the theoretical findings and assess the resolution discrepancy between ACT and DPCT under various conditions. Herein, the ACT and DPCT images were reconstructed from the filtered-back-projection algorithm using a standard Ramp filter and a standard Hilbert filter, respectively.

Results

Experiments demonstrated that the spatial resolution of ACT and DPCT images are primarily impacted by the beam diffraction induced signal splitting. In particular, lower modulation transfer function (MTF) was observed for DPCT than ACT due to the opposite-superposition of phase signals. In addition, factors such as focal spot size, beam spectra, object composition, sample size, and detector pixel size were found to have minor impacts on the MTFs of both ACT and DPCT.

Conclusions

In conclusion, this study reveals that the opposite-superposition of split phase signals causes the spatial resolution reduction in DPCT imaging.

查看原文本刊更多论文

基于光栅的x射线差相衬CT成像中MTF降低的原因。

背景：结合光栅干涉仪的x射线计算机断层扫描（CT）成像系统可以同时产生互补吸收对比CT （ACT）和差分相位对比CT （DPCT）。然而，有报道称ACT图像比DPCT图像具有更好的空间分辨率。到目前为止，造成这种差异的主要原因尚不清楚。目的：探讨光栅干涉仪CT成像系统中ACT和DPCT分辨率差异的根本原因。方法：利用π $\pi$相位Talbot-Lau光栅干涉仪系统进行理论推导，分别模拟了吸收成像和相位成像的信号形成机制。此外，通过物理和数值实验验证了理论结果，并评估了ACT和DPCT在不同条件下的分辨率差异。在此，ACT和DPCT图像分别使用标准斜坡滤波器和标准希尔伯特滤波器从滤波后的反投影算法重建。结果：实验表明，ACT和DPCT图像的空间分辨率主要受到光束衍射引起的信号分裂的影响。特别是，由于相位信号的反向叠加，DPCT的调制传递函数（MTF）比ACT低。此外，焦点光斑大小、光束光谱、物体组成、样本量和探测器像素大小等因素对ACT和DPCT的mtf影响较小。结论：综上所述，本研究揭示了分裂相位信号的反向叠加导致DPCT成像空间分辨率降低。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Medical physics 医学-核医学

CiteScore

6.80

自引率

15.80%

发文量

660

审稿时长

1.7 months

期刊介绍： Medical Physics publishes original, high impact physics, imaging science, and engineering research that advances patient diagnosis and therapy through contributions in 1) Basic science developments with high potential for clinical translation 2) Clinical applications of cutting edge engineering and physics innovations 3) Broadly applicable and innovative clinical physics developments Medical Physics is a journal of global scope and reach. By publishing in Medical Physics your research will reach an international, multidisciplinary audience including practicing medical physicists as well as physics- and engineering based translational scientists. We work closely with authors of promising articles to improve their quality.