Algorithm optimization of MLEM in coded aperture imaging system

Hanping LI; Feng WANG; Xianyun AI

doi:10.11889/j.0253-3219.2017.hjs.40.020404

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Algorithm optimization of MLEM in coded aperture imaging system

NUCLEAR ELECTRONICS AND INSTRUMENTATION | 更新时间：2021-05-19

- Algorithm optimization of MLEM in coded aperture imaging system
- NUCLEAR TECHNIQUES Vol. 40, Issue 2, Article number: 020404(2017)
- 作者机构：
  
  国民核生化灾害防护国家重点实验室防化研究院北京 102205
- 作者简介：
- 基金信息：
- DOI：10.11889/j.0253-3219.2017.hjs.40.020404
  CLC： TL812
- Received：20 November 2016，
  
  Revised：14 December 2016，
  
  Published：10 February 2017
- 稿件说明：
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Hanping LI, Feng WANG, Xianyun AI. Algorithm optimization of MLEM in coded aperture imaging system[J]. Nuclear techniques, 2017, 40(2): 020404
DOI：

Hanping LI, Feng WANG, Xianyun AI. Algorithm optimization of MLEM in coded aperture imaging system[J]. Nuclear techniques, 2017, 40(2): 020404 DOI： 10.11889/j.0253-3219.2017.hjs.40.020404.

摘要

为增强γ辐射编码成像系统中最大似然期望最大化（Maximum Likelihood Expectation Maximization，MLEM）算法对噪声的抑制，提高算法重建质量，基于互补编码板成像相减去除噪声的思想，对原有MLEM算法进行改进，提出了MLEM互补算法，并引入修正因子

对MLEM互补算法的收敛程度进行控制。通过模拟及实验方式验证了MLEM互补算法的有效性，给出了不同情况下MLEM互补算法达到最优值时修正因子

的拟合曲线。结果表明，MLEM互补算法可有效抑制噪声，提高重建图像质量。修正因子

的拟合曲线可以有效确定MLEM算法的最佳

值。

Abstract

Background

In gamma-ray imager

reconstruction algorithm directly affects the quality of the reconstructed image. The maximum likelihood expectation maximization (MLEM) iteration algorithm is widely used in modified uniformly redundant arrays (MURA) coded aperture for the reason of satisfactory performance of suppressing noise

improving signal noise ratio (SNR) and reducing distortion. But MLEM iteration algorithm also has shortcomings

like amplifies the noise with the increase of the iterative times.

Purpose

This study aims to improve the ability of suppressing noise for MLEM iteration algorithm

and increase precision and resolution of coded aperture imaging system.

Methods

Based on the de-noising method of complementary coded aperture

a correction factor

for MLEM algorithm modification is proposed to control the convergence rate of the complementary MLEM iteration algorithm. Both Monte Carlo simulation and experimental date are used to verify the effectiveness of the complementary MLEM iteration algorithm.

Results

The results of Monte Carlo simulation and experiment prove the complementary MLEM iteration algorithm is efficient and practicable in coded aperture image. Its efficiency is related to the modifying factor

. The fitting formula of

α-μt

in the complementary MLEM iteration algorithm is

=-0.6+0.12421

μt

-0.01252(

μt

)

Conclusions

The coded aperture gamma camera is capable of imaging gamma-rays instantly. It can form radioactive 2D-map of different radionuclides. The reconstruction algorithm is important for coded aperture gamma camera. With the development of coded aperture

more and more study of algorithm modification will focus on it.

关键词

Keywords

references

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