A hybrid, nonlinear programming approach for optimizing passive shimming in MRI

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

Medical physics Pub Date : 2024-09-13 DOI:10.1002/mp.17403

Jie Zhao, Minhua Zhu, Ling Xia, Yifeng Fan, Feng Liu

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引用次数: 0

Abstract

Background

In magnetic resonance imaging (MRI), maintaining a highly uniform main magnetic field (B₀) is essential for producing detailed images of human anatomy. Passive shimming (PS) is a technique used to enhance B₀ uniformity by strategically arranging shimming iron pieces inside the magnet bore. Traditionally, PS optimization has been implemented using linear programming (LP), posing challenges in balancing field quality with the quantity of iron used for shimming.

Purpose

In this work, we aimed to improve the efficacy of passive shimming that has the advantages of balancing field quality, iron usage, and harmonics in an optimal manner and leads to a smoother field profile.

Methods

This study introduces a hybrid algorithm that combines particle swarm optimization with sequential quadratic programming (PSO-SQP) to enhance shimming performance. Additionally, a regularization method is employed to reduce the iron pieces' weight effectively.

Results

The simulation study demonstrated that the magnetic field was improved from 462 to 3.6 ppm, utilizing merely 1.2 kg of iron in a 40 cm diameter spherical volume (DSV) of a 7T MRI magnet. Compared to traditional optimization techniques, this method notably enhanced magnetic field uniformity by 96.7% and reduced the iron weight requirement by 81.8%.

Conclusion

The results indicated that the proposed method is expected to be effective for passive shimming.

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优化磁共振成像中被动垫片的混合非线性编程方法

背景在磁共振成像（MRI）中，保持高度均匀的主磁场（B0）对于生成详细的人体解剖图像至关重要。被动垫片（Passive shimming，PS）是一种通过在磁体孔内战略性地布置垫片铁片来增强 B0 均匀性的技术。传统上，PS 优化是通过线性规划（LP）来实现的，在平衡磁场质量与垫片所用铁片数量方面存在挑战。目的在这项工作中，我们旨在提高被动垫片的功效，它具有以最佳方式平衡磁场质量、铁片使用量和谐波的优点，并能带来更平滑的磁场轮廓。结果模拟研究表明，在 7T 磁共振成像磁体直径为 40 厘米的球形体积（DSV）中，仅使用了 1.2 千克的铁片，磁场就从 462 ppm 提高到了 3.6 ppm。与传统优化技术相比，该方法显著提高了 96.7% 的磁场均匀性，并减少了 81.8% 的铁重量需求。

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.