Comparison of driven equilibrium and standard spin-echo sequence in MR microscopy : analysis of signal dependence on RF pulse imperfection and diffusion

Serša, Igor (author)

Rapid MR imaging of slowly relaxing samples is often challenging. The most commonly used solutions are found in multi spin-echo (RARE) sequences or gradient-echo (GE) sequences, which allow faster imaging of such samples with multiple acquisitions of k-space lines per excitation or imaging with very short repetition times (TRs). Another solution is the use of a spin-echo (SE) sequence superimposed with a driven equilibrium Fourier transform (DEFT) method. Such a (DE-SE) imaging sequence has two refocusing RF pulses that produce two spin-echoes. In the first echo, the signal is acquired from the k-space line, and in the second echo, a 90° RF pulse is applied, typically 180° out of phase with respect to the excitation RF pulse. This last RF pulse allows almost complete magnetization reversal back to the longitudinal orientation with minimal magnetization loss. The DE-SE sequence and its RARE variant are widely used in clinical imaging, but its use in MR microscopy has some peculiarities related to the usually less perfect RF pulse flip angles and diffusion. In this study, their effects are first theoretically analyzed and later verified by experiments on test samples performed on a 9.4 T system for MR microscopy. Experiments on a water-filled tube for TE = 3.4 ms and TR = 25–200 ms showed that the DE-SE sequence produces about 10 times more signal than the SE sequence in this TR range. Finally, the performance of the DE-SE sequence compared to the SE sequence was demonstrated on a biological sample. The presented DE-SE sequence has been shown to be effective for rapid imaging of samples with long T$_1$ relaxation times in MR microscopy and can also be considered as a suitable method for rapid proton density weighed imaging of materials.

• Language: English
• Keywords: MRI sequences, spin-echo, image contrast, magnetization reversal, diffusion
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: MF - Faculty of Medicine
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: 11 str.
• Numbering: Vol. 359, art. 107624
• PID: 20.500.12556/RUL-156201
• UDC: 53
• ISSN on article: 1096-0856
• DOI: 10.1016/j.jmr.2024.107624
• COBISS.SI-ID: 181658627
• Publication date in RUL: 14.05.2024

Record is a part of a journal

• Title: Journal of magnetic resonance
• Shortened title: J. magn. res.
• Publisher: Elsevier
• ISSN: 1096-0856
• COBISS.SI-ID: 18272295

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: magnetna resonanca, slikanje z magnetno resonanco

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P1-0060
• Name: Eksperimentalna biofizika kompleksnih sistemov in slikanje v biomedicini