Rapid simultaneous estimation of relaxation rates using multi-echo, multi-contrast MRI

IF 2.1 4区 医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Elizabeth G. Keeling , Nicholas J. Sisco , Molly M. McElvogue , Aimee Borazanci , Richard D. Dortch , Ashley M. Stokes
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引用次数: 0

Abstract

Purpose

Multi-echo, multi-contrast methods are increasingly used in dynamic imaging studies to simultaneously quantify R2 and R2. To overcome the computational challenges associated with nonlinear least squares (NLSQ) fitting, we propose a generalized linear least squares (LLSQ) solution to rapidly fit R2 and R2.

Methods

Spin- and gradient-echo (SAGE) data were simulated across T2 and T2 values at high (200) and low (20) SNR. Full (four-parameter) and reduced (three-parameter) parameter fits were implemented and compared with both LLSQ and NLSQ fitting. Fit data were compared to ground truth using concordance correlation coefficient (CCC) and coefficient of variation (CV). In vivo SAGE perfusion data were acquired in 20 subjects with relapsing-remitting multiple sclerosis. LLSQ R2 and R2, as well as cerebral blood volume (CBV), were compared with the standard NLSQ approach.

Results

Across all fitting methods, T2 was well-fit at high (CCC = 1, CV = 0) and low (CCC ≥ 0.87, CV ≤ 0.08) SNR. Except for short T2 values (5–15 ms), T2 was well-fit at high (CCC = 1, CV = 0) and low (CCC ≥ 0.99, CV ≤ 0.03) SNR. In vivo, LLSQ R2 and R2 estimates were similar to NLSQ, and there were no differences in R2 across fitting methods at high SNR. However, there were some differences at low SNR and for R2 at high and low SNR. In vivo NLSQ and LLSQ three parameter fits performed similarly, as did NLSQ and LLSQ four-parameter fits. LLSQ CBV nearly matched the standard NLSQ method for R2- (0.97 ratio) and R2-CBV (0.98 ratio). Voxel-wise whole-brain fitting was faster for LLSQ (3–4 min) than NLSQ (16–18 h).

Conclusions

LLSQ reliably fit for R2 and R2 in simulated and in vivo data. Use of LLSQ methods reduced the computational demand, enabling rapid estimation of R2 and R2.

利用多回波、多对比 MRI 快速同步估算弛豫率。
目的:动态成像研究中越来越多地使用多回波、多对比度方法来同时量化 R2* 和 R2。为了克服非线性最小二乘法(NLSQ)拟合带来的计算挑战,我们提出了一种广义线性最小二乘法(LLSQ)解决方案来快速拟合 R2* 和 R2:方法:在高(200)和低(20)信噪比条件下模拟自旋和梯度回波(SAGE)数据的 T2⁎和 T2 值。采用全参数(四参数)和缩减参数(三参数)拟合,并与 LLSQ 和 NLSQ 拟合进行比较。使用一致性相关系数(CCC)和变异系数(CV)将拟合数据与地面实况进行比较。20 名复发性多发性硬化症患者获得了体内 SAGE 灌注数据。将 LLSQ R2* 和 R2 以及脑血量(CBV)与标准 NLSQ 方法进行了比较:在所有拟合方法中,T2⁎ 在高信噪比(CCC = 1,CV = 0)和低信噪比(CCC ≥ 0.87,CV ≤ 0.08)时拟合良好。除了短 T2⁎值(5-15 毫秒)外,T2 在高信噪比(CCC = 1,CV = 0)和低信噪比(CCC ≥ 0.99,CV ≤ 0.03)时拟合良好。在体内,LLSQ R2⁎和 R2 估计值与 NLSQ 相似,在高信噪比时,不同拟合方法的 R2⁎没有差异。然而,在低信噪比时,以及在高信噪比和低信噪比时,R2存在一些差异。体内 NLSQ 和 LLSQ 三参数拟合表现相似,NLSQ 和 LLSQ 四参数拟合表现也相似。LLSQ CBV 的 R2*- 比率(0.97)和 R2-CBV 比率(0.98)几乎与标准 NLSQ 方法相当。LLSQ 全脑体素拟合(3-4 分钟)比 NLSQ(16-18 小时)更快:结论:LLSQ能可靠地拟合模拟和体内数据中的R2*和R2。使用 LLSQ 方法降低了计算需求,从而能够快速估算 R2⁎和 R2。
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
Magnetic resonance imaging
Magnetic resonance imaging 医学-核医学
CiteScore
4.70
自引率
4.00%
发文量
194
审稿时长
83 days
期刊介绍: Magnetic Resonance Imaging (MRI) is the first international multidisciplinary journal encompassing physical, life, and clinical science investigations as they relate to the development and use of magnetic resonance imaging. MRI is dedicated to both basic research, technological innovation and applications, providing a single forum for communication among radiologists, physicists, chemists, biochemists, biologists, engineers, internists, pathologists, physiologists, computer scientists, and mathematicians.
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