采用脂肪激励稳态进动快速成像序列的磁共振血氧测定法

MR-oximetry with fat DESPOT.

作者信息

Fortier Véronique, Levesque Ives R

机构信息

Medical Physics Unit, McGill University, Montréal, QC, Canada; Biomedical Engineering, McGill University, Montréal, QC, Canada; Medical Imaging, McGill University Health Centre, Montréal, QC, Canada; Department of Diagnostic Radiology, McGill University, Montréal, QC, Canada; Gerald Bronfman Department of Oncology, McGill University, Montréal, QC, Canada.

Medical Physics Unit, McGill University, Montréal, QC, Canada; Biomedical Engineering, McGill University, Montréal, QC, Canada; Gerald Bronfman Department of Oncology, McGill University, Montréal, QC, Canada; Research Institute of the McGill University Health Centre, Montréal, QC, Canada.

出版信息

Magn Reson Imaging. 2023 Apr;97:112-121. doi: 10.1016/j.mri.2022.12.023. Epub 2023 Jan 3.

DOI:10.1016/j.mri.2022.12.023

PMID:36608912

Abstract

PURPOSE

The R relaxation rate of fat is a promising marker of tissue oxygenation. Existing techniques to map fat R in MR-oximetry offer limited spatial coverage, require long scan times, or pulse sequences that are not readily available on clinical scanners. This work addresses these limitations with a 3D voxel-wise fat R mapping technique for MR-oximetry based on a variable flip angle (VFA) approach at 3 T.

METHODS

Varying levels of dissolved oxygen (O) were generated in a phantom consisting of vials of safflower oil emulsion, used to approximate human fat. Joint voxel-wise mapping of fat and water R was performed with a two-compartment VFA model fitted to multi-echo gradient-echo magnitude data acquired at four flip angles, referred to as Fat DESPOT. Global R was also calculated. Variations of fat, water, and global R were investigated as a function of the partial pressure of O (pO). Inversion-prepared stimulated echo magnetic resonance spectroscopy was used as the reference technique for R measurements.

RESULTS

Fat R from Fat DESPOT was more sensitive than water R and global R to variations in pO, consistent with previous studies performed with different R mapping techniques. Fat R sensitivity to pO variations with Fat DESPOT (median O relaxivity r = 1.57× 10 s mmHg) was comparable to spectroscopy-based measurements for methylene, the main fat resonance (median r= 1.80 × 10 s mmHg).

CONCLUSION

Fat and water R can be measured on a voxel-wise basis using a two-component fit to multi-echo 3D VFA magnitude data in a clinically acceptable scan time. Fat and water R measured with Fat DESPOT were sensitive to variations in pO. These observations suggest an approach to 3D in vivo MR oximetry.

摘要

目的

脂肪的R弛豫率是一种很有前景的组织氧合标记物。磁共振血氧测定法中用于绘制脂肪R值的现有技术，空间覆盖范围有限，需要较长的扫描时间，或者需要临床扫描仪上不易获得的脉冲序列。本研究基于3T时的可变翻转角（VFA）方法，采用三维体素级脂肪R值映射技术解决了这些局限性。

方法

在由红花油乳液小瓶组成的模型中产生不同水平的溶解氧（O），用于模拟人体脂肪。使用两室VFA模型对在四个翻转角采集的多回波梯度回波幅度数据进行拟合，对脂肪和水的R值进行联合体素级映射，即脂肪DESPOT。还计算了全局R值。研究了脂肪、水和全局R值随O分压（pO）的变化。采用反转预脉冲刺激回波磁共振波谱作为R值测量的参考技术。